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  • Chemistry  (861)
  • mercury  (63)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Environmental monitoring and assessment 64 (2000), S. 409-419 
    ISSN: 1573-2959
    Keywords: monitoring ; assessment ; water ; sediment ; bioaccumulation ; toxicity ; pesticides ; mercury ; PCB
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The San Francisco Estuary Regional Monitoring Program for Trace Substances (RMP) began in 1993 and is sponsored by 74 local, state, and federal agencies and companies through their discharge or Bay use permits. The RMP monitors water, sediment, toxicity, and bivalve bioaccumulation at 25 sites in the Bay that are considered to represent "background" conditions. Several major environmental issues have been identified by the RMP. Polychlorinated biphenyls and mercury were often above water quality guidelines, and often occurred in fish tissues above U.S. Environmental Protection Agency (U.S. EPA) screening values. Concentrations do not appear to be decreasing, suggesting continuing inputs. Episodes of aquatic toxicity often occurred following runoff events that transport contaminants into the Bay from urbanized and agricultural portions of the watershed. Sediment toxicity occurred throughout the Bay, and has been correlated with concentrations of specific contaminants (chlordanes, polynuclear aromatic hydrocarbons) at some locations; mixtures of contaminants were probably also important. Since the RMP does not monitor all ecosystem components, assessments of the overall condition of the Bay cannot be made. However, in terms of contamination, the RMP samples suggest that the South Bay, and North Bay sites are moderately contaminated.
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  • 2
    ISSN: 1573-2959
    Keywords: bioaccumulation ; mercury ; methylmercury ; remediation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Approximately 250 000 kg of mercury was lost towater and soils at the U.S. Dept. of Energy Y-12 Plantin Oak Ridge, Tennessee in the 1950s and early 1960s. A creek originating within the plant receivedcontinuous inputs of waterborne mercury, predominantlyas dissolved inorganic mercury, from groundwater,streambed contamination, and sump and process waterdischarges to the contaminated storm sewer network.These produce aqueous total mercury concentrations of1–2 μg L-1 in the upper reaches of the stream,decreasing to about 0.1–0.2 μg L-1 in its lowerreaches. A program to reduce mercury concentrationsin the creek identified specific sources (buildingsumps, contaminated springwater seeps, foundationdrains, and contaminated piping) and rerouted wateraround contaminated portions of the drain system orcollected and treated mercury-contaminated waterbefore discharging it. As a result, waterbornemercury concentrations in the creek and total mercuryloading were reduced from 1.8 μg L-1 to0.6 μg L-1 and 100 to 20 g d-1, respectively, in the last 5 yr.Mean mercury concentrations in fish nearest sourceareas in the creek headwaters decreased at roughly thesame rate as waterborne total mercury concentrationsover the past five years, but at the facility boundarydownstream the decline in mercury bioaccumulation wasmuch less. At sites 5–15 km farther downstream, nodecrease was evident. Dissolved methylmercury tendedto increase with distance downstream in a patterninverse to that noted for its dissolved inorganicmercury precursor.Improvements in water quality and modification ofweirs to allow the passage of fish have resulted inthe establishment of large populations of fish inmercury-contaminated headwater areas previously devoidof fish. It may be that the accumulation, retention,and eventual downstream transport of this reservoir ofbiologically incorporated methylmercury has acted tobuffer against expected reductions in mercury in fishat downstream sites.
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  • 3
    ISSN: 1573-2959
    Keywords: mercury ; mining ; monitoring ; aquatic ; acid mine drainage ; floc ; Clear Lake ; remediation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Mercury (Hg) in the aquatic ecosystem of Clear Lake has been documented since the 1970s when fishes were found to have elevated levels of toxic methyl mercury (meHg). Mining practices at the Sulphur Bank Mercury Mine (active intermittently from 1872–1957) along the shoreline of Clear Lake included the bulldozing of waste rock and overburden ore into the shallow nearshore regions of the lake and the creation of steeply sloped piles of waste rock at the water's edge. This process, plus erosion of the waste rock piles, resulted in the accumulation of an estimated 100 metric tons of Hg in Clear Lake. A monitoring program to assess Hg in Clear Lake was established in 1992, and conducted continuously from 1994. Drought conditions in California had persisted for ca. 6 yrs prior to 1992, when the U.S. Environmental Protection Agency (USEPA) remediated the steeply sloped eroding waste rock piles, which appeared to reduce sediment Hg concentrations significantly. In April 1995, a white flocculent material was observed in Clear Lake adjacent to the mine and has been observed every year since, leading to the discovery of ongoing acid mine drainage (AMD), low pH fluids high in Hg and extremely high in sulfate. AMD is now believed to be the most likely cause of elevated meHg in Clear Lake. The discovery of this source of meHg production in Clear Lake, which will significantly influence remedial options, was only made possible by implementation of a diligent monitoring program.
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  • 4
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    Water, air & soil pollution 117 (2000), S. 353-369 
    ISSN: 1573-2932
    Keywords: hydrogeochemistry ; Kejimkujik ; lake water quality ; mercury ; principal component analysis ; regression modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Distribution and sources of total mercury were evaluated in sixty lakes in Nova Scotia and Newfoundland. The concentration of total mercury in the lake water samples was similar to those observed in other natural water systems. Mercury concentration in the lakes correlated positively with aluminum, total organic carbon, color, iron, and total nitrogens and inversely with pH and sulfate. The lake water quality parameters were placed in three distinct groups using principal component and cluster analyses. The chemical constituents in the groups were identified as being associated with lake watershed geology, atmospheric washouts of long range transported acidic pollutants and dust particles, and a marine source. Stepwise multiple regression applied to the variables in the same principal component and strongly correlating with mercury identified total organic carbon, total nitrogen, pH, aluminum and iron as the best predictors for total mercury concentrations in the study lakes.
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  • 5
    ISSN: 1573-2932
    Keywords: mercury ; mercury fluxes ; solar radiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Mercury flux measurements were conducted at two lakes and three soil sites in Kejimkujik National Park, located in the eastern Canadian province of Nova Scotia. One of the lakes had high levels of both mercury and Dissolved Organic Carbon (DOC). Two of the soil sites were located under the forestcanopy, while the other was in a small clearing surrounded by forest. Flux measurements were performed using the dynamic chamber method. Mercury concentrations in the air were measured with a TEKRAN mercury analyzer. Mercury fluxes over the two lakes were most strongly correlated with solar radiation, although the flux was also significantly correlated with water temperature, air temperature, and negatively correlated with relative humidity. The flux from the high DOC lake (Big Dam West) was especially high when the conditions were both sunny and windy (wind speed greater than 1.3 m s-1) and the average flux measured was 5.4 ng m-2 h-1. The mercury flux from this lake was wellparameterized in terms of a simple expression involving solar radiation and a nonlinear dependence on wind speed. The flux measured from the low DOC lake (North Cranberry) tended to be lower than from the high DOC lake. The averageflux measured was 1.1 ng m-2 h-1, but was again strongly correlated with solar radiation. The flux was low during windy conditions in the absence of sunlight, suggesting that wind enhances mercury evasion from lakes only in the presence of solar radiation. Mercury fluxes measured over the soil sites tended to be smaller than those over water (a range of –1.4–4.3 ng m-2 h-1). At one of the forest sites, mercury flux was very strongly correlated with 0.5 cm soil temperature, and this dependence was well described by an Arrhenius-typeexpression with an activation energy of 14.6 kcal-1 mole, quite close to the heat of vaporization of mercury (14.5 kcal-1 mol-1 at 20 °C). At the clearing, where there was direct exposure to the sun, the mercury flux was most strongly correlated with solar radiation.
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  • 6
    ISSN: 1573-2932
    Keywords: mercury ; particle movement ; sediments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The Lahontan Reservoir in western Nevada has among the highest mercury (Hg) concentrations recorded in water, sediments and biota. The QWASI fugacity/aquivalence multispecies model was applied to examine Hg dynamics through a steady-state analysis of high loading conditions. The analysis indicated that the Carson River supplies most Hg in the water and upper sediments, with minimal inputs from the atmosphere and the Truckee Canal. Model estimates suggest that more than 90% of Hg entering the system from the Carson River at high flow is retained in the sediment of the reservoir, with export removing the remainder. Losses due to volatilization are negligible. The amount of methylmercury (MeHg) in the reservoir can be accounted for by inputs from the Carson River with minimal methylation occurring in the reservoir. The lack of species conversion and high retention rate appear to be due to the unreactive mineralogy of particulate Hg. Thus, we suggest that Hg dynamics are similar to that of other highly particle-reactive metals where fate is determined by particle movement. Finally, model results suggest an additional source of Hg to the system, which we hypothesize is from deep contaminated sediment that enters the system through sediment mixing caused by seasonal wet and dry cycles and sediment resuspension.
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  • 7
    ISSN: 1573-2932
    Keywords: Everglades ; mercury ; mobility ; peat ; phosphorus ; soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Soils in the southern half of Water Conservation Area3A are mostly peats with some organic-rich marls. Mercury contents of 64 surface samples over a500 km2 area average 28.7 ng cc-1 (209 ppb drysediment), which is typical of organic-rich soils. High Hg contents in Everglades fish are therefore notcaused by anomalously high soil Hg. Hg contents showno systematic lateral variation, consistent withdeposition from well-mixed atmospheric sources ratherthan nearby point sources or runoff from canals.Cores from 9 sites contain more Hg and P at or nearthe surface than at 20–30 cm depth. Hg and P contentsof individual cores correlate well and define separatebackground and anomalous populations. The subsurfacedistribution of P is determined largely by uptake bysawgrass and other plants. The correlation between Pand Hg suggests that, although atmospheric Hgdeposition has undoubtedly increased in recentdecades, postdepositional mobilization of Hg may beimportant in Everglades soils. This finding, togetherwith recent direct measurements of atmospheric Hgdeposition, indicates that previous estimates of Hgdeposition rates based on Everglades peat cores, whichassumed that Hg is immobile in peat after deposition,have yielded large overestimates.
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  • 8
    ISSN: 1573-2932
    Keywords: fish ; French Guiana ; mercury ; stream
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This study examines the level of mercury contamination for different components of the biosphere in French Guiana. The spatial variability of the contamination of the waters, soils and sediments in the catchment area of the Sinnamary River is studied. The contamination of the trophic chain isdiscussed by analysis of the flesh of fish for the principal species represented in nine Guianese rivers, especially species consumed by human populations. The mercury contamination of sediments and soils, is extremely heterogeneous and that of fish is generalised. For carnivorous fish, the average mercury content is 0.48 μg g-1 (±0.28) (fresh weight) and for non-carnivorous species, 0.05 μg g-1 (±0.07). The concentrationsmeasured are greater than the European standards forconsumption for 4.7% of the carnivorous individuals.
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  • 9
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    Water, air & soil pollution 124 (2000), S. 301-317 
    ISSN: 1573-2932
    Keywords: fish ; lakes ; mercury ; model ; predictions ; regressions ; remedial measures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This work presents a new regression model for mercuryin lake fish, which provides the highest r 2-valueso far reported for a predictive model for Hg in lakefish. A new method to transform static regressionmodels to dynamic (time-dependent) models is alsopresented. The method to mathematically transformregression models to dynamic model uses the ecologicalhalflife concept and two differential equations, onefor the target organism (the predator) and one for theprey. This method is generic and can be applied inanalogous cases. The practical use of the dynamicmodel is illustrated in two case studies involvinglake liming and fertilization as methods to reduce Hgin lake fish. The dynamic model is a tool to obtainrealistic expectations of the recovery process, whichis slow because Hg in lake fish has a relatively longecological halflife (about 3 yr).
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  • 10
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    Water resources management 13 (1999), S. 383-407 
    ISSN: 1573-1650
    Keywords: critical period ; reliability ; resilience ; surface water reservoirs ; within-year and over-year behaviours
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract Surface water reservoirs can beclassified as either within-year or over-year based onthe duration of their critical period (CP). Ingeneral, within-year systems are those which willrefill and spill several times in a year, whereasover-year systems have much longer critical periods,usually of the order of years. If the duration of thecritical period, and hence the precise mode ofbehaviour, of a reservoir were to be known apriori, then advantage could be taken of this toselect the level of detail required for reservoiranalysis. For example, if the reservoir system ispurely over-year, i.e. the CP is much longer than 12months, then only annual streamflow data are requiredfor analysis. On the contrary, systems which exhibitdual within-year and over-year behaviours will requiretime series data of a finer resolution to capture boththe seasonal and annual discrepancies between thedemand and inflow. Such a consideration often resultsin a phenomenal increase in the analysis time overthat required for annual data. Finally, if the systemis purely within-year, then the analysis effort can besignificantly reduced by concentrating on the criticalor driest year of the record. In this paper, weexamine the properties of the test in current use fordistinguishing between within-year and over-yearbehaviours. In particular we investigate how theparameter of the test is related to the CP, and weargue that knowing the CP is a more complete test. Wethen develop predictive equations for the CP and weoffer suggestions for extending the study.
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  • 11
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    Ecotoxicology 8 (1999), S. 49-56 
    ISSN: 1573-3017
    Keywords: mercury ; methylmercury ; fish ; acidification ; biomagnification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Two small drainage lakes of similar surface area (0.4–0.6 km 2 ) and depth, and situated in close proximity to one another (about 9 km apart) in the Muskoka-Haliburton district of rural Ontario, Canada were chosen to investigate the effects of differing pH on Hg accumulation in fish and other biota. Blue Chalk Lake is circumneutral (pH = 6.3–6.9) with an average dissolved organic carbon (DOC) concentration of 2.69 mg/L; Plastic Lake is acidic (pH = 5.2–5.6) with a similar DOC level (2.72 mg/L). Neither lake is an impoundment, and neither receives inputs from point-source urban or industrial waste emissions. Surficial (top 4 cm) sediments and various aquatic biota, including crayfish (Orconectes virilis)], and 5 species of fish [brown bullhead (Ictalurus nebulosus), creek chub (Semotilus atromaculatus), pumpkinseed sunfish (Lepomis gibbosus), yellow perch (Perca flavenscens) and rock bass (Ambloplites rupestris)] were sampled for Hg analysis. Only creek chub and pumpkinseed occurred in both lakes. Significant size (length) vs. Hg-concentration relationships were observed for brown bullhead, pumpkinseed, yellow perch and rock bass, but not for crayfish nor for creek chub in either lake. Rock bass had the highest mean Hg concentration (1.02 ± 0.98 μg/g dry wt.). Pumpkinseed from Plastic Lake had the highest overall rate of accumulation with increasing size. Several individual pumpkinseed and rock bass sampled from the acidic Plastic Lake had Hg concentrations equal to or greater than levels reported to be hazardous to breeding piscivorous birds, such as common loons (Gavia immer), whereas no fish from Blue Chalk approached this threshold (0.3 μg/g wet wt). This study illustrates the importance of within-lake parameters, particularly pH, and species trophic level, in determining Hg accumulation in fish in lakes of similar size that receive similar atmospheric Hg inputs.
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  • 12
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    Environmental monitoring and assessment 57 (1999), S. 85-107 
    ISSN: 1573-2959
    Keywords: Kissimmee River ; mercury ; nutrients ; restoration ; water quality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The planned restoration of the Kissimmee River ecocystem will backfill approximately 35 km of flood control canal (C-38) that cuts through the meandering river channel, re-establish natural flow patterns, and restore the river/floodplain ecosystem. Water quality monitoring, including nutrients, total suspended solids (TSS), turbidity, dissolved oxygen (DO), and mercury, was conducted during a pilot `test fill' project to determine if soil disturbance during canal backfilling would negatively impact these water quality constituents. Surface water nutrient concentrations varied little between sites. Generally, highest concentrations occurred prior to construction, with lowest concentrations occurring during and after construction. During construction, TSS concentrations increased at sites immediately upstream, downstream, and adjacent to the construction area. Increased turbidity was generally restricted to areas immediately upstream and downstream of the test plug, with maximum levels occurring during the initial construction phase. Some downstream increases in turbidity were observed; however, impacts were short-term, lasting less than 24 h. Depresssed DO levels (〈2 mg/l) were observed upstream of the test plug following completion of the initial plug across C-38. Dissolved oxygen levels remained low for approximately 6 weeks, with no apparent ecological impacts. Total mercury (HgT) within canal sediment ranged from 9.2–180 ng/g and methylmercury concentrations ranged from 0.037–0.708 ng/g. Concentration of total mercury and total methylmercury (MeHgT) in the backfill material were much lower than concentrations in the canal sediment. No significant change in aqueous HgT concentrations occurred over the sampling period, although construction-induced turbidity could have temporarily caused a slightly elevated concentration immediately downstream of the construction site. Methylmercury concentrations in the water column ranged from 0.033–0.518 ng/l. No significant differences in mean MeHgT concentrations occured between sites or between sampling dates, except at one downstream site where MeHgT declined significantly over the sampling period.
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  • 13
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    Water, air & soil pollution 112 (1999), S. 151-162 
    ISSN: 1573-2932
    Keywords: exposure assessment ; mercury ; uncertainty analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A modeling system has been developed to simulate regional environmental exposure to mercury due to atmospheric deposition of mercury to watersheds. The atmospheric fate and transport of mercury is simulated using a comprehensive three-dimensional Eulerian model, the Trace Element Atmospheric Model (TEAM). The aquatic chemistry and bioaccumulation of mercury in fish are simulated using a model of mercury cycling in a lake/watershed system, the Regional Mercury Cycling Model (R-MCM). Fish consumption was derived from a review of available surveys. Previous work focused on an assessment of the environmental and inter-individual variability in key input data (Seigneur et al., 1997a). We address here the uncertainties associated with critical model input variables (e.g., atmospheric deposition velocities, precipitation rate, limnological characteristics). A probabilistic assessment is conducted to propagate the uncertainties in the input data through the modeling system and develop a probability distribution of the human mercury dose that reflects these uncertainties. The standard deviation of the distribution of the calculated human dose is about 50% of the mean value. For the example considered here (i.e., Park Lake in Michigan, U.S.A.), 80% of the uncertainty in the human dose was due to uncertainties in the speciation of mercury air emissions, pH and temperature of the lake, burial velocity of the sediments, and rate of fish consumption.
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  • 14
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    Water, air & soil pollution 110 (1999), S. 313-333 
    ISSN: 1573-2932
    Keywords: Florida Everglades ; Lake Erie ; mercury ; paleoecology ; sediment cores ; uncertainty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Increased recognition of the ecological damage of mercury (Hg) has focused attention on quantifying spatial and temporal patterns of Hg deposition. Studies are commonly based on core chronologies and use a combination of techniques to measure parameters such as bulk density, percent solids, Hg concentration, and radionuclide activity. Little attention is generally devoted to the propagated error associated with these measurements. We identified the impact of sources of uncertainty on stratigraphic Hg determinations for Florida Everglades and Lake Erie cores. Large errors may be introduced by converting wet sample Hg content to dry-weight concentrations. Drying of sediments at 55 °C caused Hg losses of 18%. Samples, air-dried at room temperature, retained considerable moisture and required corrections for remaining water content. Frozen sediments did not lose Hg during a 72-day storage. Random error in radionuclide analysis of cores resulted in dating uncertainty of ±1.2 yr in 10 yr old deposits. This error increased to ±20 yr in 100 yr old sediments. Propagation of small errors in each step of the analysis (while adhering to strict QA/QC criteria) produced compounded uncertainties of ±11 and ±29% in Hg concentrations under different analytical rigor, and errors of up to ±73% in Hg accumulation rates in older sediments. Enrichment factors, comparing uncertain recent and historic Hg accumulation rates, differed by as much as ±48%. Uncertainty in paleoecological studies of mercury needs to be documented in order to correctly evaluate trends and remediation efforts.
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  • 15
    ISSN: 1573-2932
    Keywords: bioaccumulation ; mercury ; methyl mercury ; tropic levels ; trout
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Methyl mercury (Hg) was determined in rainbow trout (Oncorhynchus mykiss) and organisms in the lower tropic levels: smelts (Retropinna retropinna), bullies (Gobiomorphus cotidianus), koura (Paranephrops planifrons); and zooplankton (Daphnia carinata and Calamoecia lucasi) in Lakes Okareka, Okaro, Tarawera, Rotorua and Rotomahana, New Zealand. Water concentrations of total Hg (HgT) and methyl Hg were also measured. Mean methyl Hg concentrations in the trout, the prey species (smelts, bullies and koura) and zooplankton increased linearly with mean HgT and methyl Hg chloride (CH3HgCl) concentrations in water. Most of the bio-magnification of methyl Hg occurred in the lower trophic levels of the trout food web (104.72) between the zooplankton and water. The bioaccumulation factors between the forage fish and zooplankton were 100.73 for bullies and 101.06 for smelt. Methyl Hg was 100.41 to 100.95 times greater in the trout then their prey.
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  • 16
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    Water, air & soil pollution 111 (1999), S. 287-295 
    ISSN: 1573-2932
    Keywords: analysis ; atomic fluorescence ; geological ; mercury ; water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The Tekran 2537A mercury vapour analyser, designed to measure Hg in air by cold vapour atomic fluorescence spectrometry, has been modified to determine Hg in solution. The new ‘front-end’, required to generate Hg° vapour from acidified waters or acid leachates, is described. Using 1% NaBH4 as reducing agent, a 12 mL water sample can be analysed, at a rate of 1 every 6 min, for Hg to a detection limit of 0.8 ppt (ng L-1). Instrumental precision is typically 1% relative standard deviation (RSD) at levels of Hg from 10 to 200 ppt. Results for 10 analyses of the international water standard, NIST 1642b, are 1530±20 ppt Hg, agreeing well with the certified value of 1480±130 ppt. Nineteen geological standard reference materials (soils, sediments and tills) were used to assess accuracy. Results for these samples, digested in aqua regia in triplicate, showed good agreement with recommended values for all but two, SO-3 and TILL-1. However, results by this method for these two standards were confirmed by an independent method, direct atomic absorption spectrometry. Average method precision was shown to be 5% RSD over the range 10 ng g- 1 to 35 μg g-1 Hg.
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  • 17
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    Water, air & soil pollution 112 (1999), S. 279-295 
    ISSN: 1573-2932
    Keywords: ambient air ; chemical analysis ; mercury ; particulatemercury ; speciation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Total particulate mercury (TPM) may constitute, in general, a small percentage by mass of total atmospheric mercury, but under certain conditions it can be a very significant form of atmospheric Hg, and play an important role in the deposition of mercury to terrestrial and aquatic cosystems. To understand the cycling and distribution of mercury in the environment, accurate determination of the total concentration and speciation of TPM are necessary. This article provides a review of scientific and technical literature published in the past 5 yr pertaining to sampling and analytical methodologies for the determination and chemical speciation of TPM in ambient air. Sampling methods discussed include the conventional filtration method and the diffusion denuder-based technique. Analytical techniques, such as gold-amalgamation/cold-vapor spectrometry, and nuclear methods, are summarized.
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  • 18
    ISSN: 1573-2932
    Keywords: Amazonia ; mercury ; soil erosion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Three Hg sources were characterised and mass balance calculations were used to determine their relative contributions to the contamination of the Amazonian environment. About an order of magnitude more Hg is emitted to the atmosphere by goldmining activity than by the burning of forest biomass. However, anthropogenic atmospheric Hg cannot account for the high Hg burdens found in terrestrial ecosystems: deposition of Hg from goldmining sources is estimated to account for less than 3% of the Hg present in the surface horizons of soils. We propose that erosion of deforested soils following human colonization constitutes a major disturbance of the natural Hg cycle. Deforestation thus increases soil Hg mobilisation by runoff, which may explain the increase of Hg burdens in Amazonian aquatic ecosystems in newly colonized watersheds.
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  • 19
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    Water, air & soil pollution 113 (1999), S. 141-154 
    ISSN: 1573-2932
    Keywords: forest soils ; mercury ; methylmercury ; runoff ; soil solution ; wetland
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Mercury (Hg) and methylmercury (CH3Hg+) are global pollutants, but little information is available on their distribution and mobility in soils and catchments of Central Europe. The objective of this study was to investigate the pools and mobility of Hg and CH3Hg+ in different forest soils. Upland and wetland forest soils, soil solutions and runoff were sampled. In upland soils the highest contents of total-Hg were found in the Oh layer of the forest floor (〉400 ng g-1) and the storage of non geogenic total-Hg (calculated for 60 cm depth) was about 120 mg/m2. The storage of total-Hg was one order of magnitude lower in wetland soils as compared to the upland soils. By far the largest proportion of total-Hg in soils was bound in immobile fractions. The depth gradients of CH3Hg+ did not correspond to those of total-Hg and the highest contents of CH3Hg+ in upland soils were observed in the litter layer of the forest floor and in the Bsv horizon. The CH3Hg+ content of the wetland soils was generally much higher in comparison with upland soils. CH3Hg+ in solution was found in the forest floor percolates of upland soils and in wetland soils, but not in soil solutions from mineral soil horizons. Gaseous losses of Hg as well as methylation of Hg are likely in wetland soils. The latter might be highly relevant for CH3Hg+ levels in runoff.
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  • 20
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    Water, air & soil pollution 113 (1999), S. 273-294 
    ISSN: 1573-2932
    Keywords: atmospheric deposition ; dissolved organic carbon ; mercury ; stemflow ; throughfall
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Inputs of mercury (Hg) and dissolved organic carbon (DOC) in throughfall and stemflow waters were measured for an upland/bog watershed in northern Minnesota, and were compared to the deposition in a nearby opening to determine the influence of tree canopies on Hg and DOC deposition. Twice as much Hg and seven times as much DOC was deposited in the forested watershed compared to the opening. Mass balance studies that are based on wet-only deposition in openings severely underestimate atmospheric deposition of Hg in forests. Conifer canopies are more efficient filters of airborne particulates than are deciduous canopies as indicated by much higher Hg concentrations and total deposition in throughfall and stemflow waters under conifers. Significant positive relationships existed between Hg and DOC in both throughfall (36–57% of the variation) and stemflow waters (55–88% of the variation). Hg complexation by DOC appears to be related to the contact time between precipitation and carbon sources.
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  • 21
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    Water, air & soil pollution 114 (1999), S. 339-346 
    ISSN: 1573-2932
    Keywords: biomonitoring indices ; germination ; heavy metals ; lead ; mercury ; rice ; seedling growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Treatment of seeds of two rice (Oryza sativa L.) cultivars (Ratna and IR36) separately with 10-5and 10-4M PbCl2and HgCl2decreased germination percentage, germination index (GI), shoot and root length, tolerance index (TI), vigour index (VI) and dry mass of shoot and root but increased percentage difference from control (% DFC) of germination and percentage phytotoxicity in both the cultivars. It was observed from these indices that the phytotoxic effect of mercury was greater than lead at identical concentrations and that IR36 appeared more tolerant than Ratna to these metals. Among the monitoring indices examined, TI, VI, and % phytotoxicity seemed to serve as good biological monitoring methods for evaluating the relative toxicity of lead and mercury to rice cultivars.
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    Water, air & soil pollution 111 (1999), S. 337-357 
    ISSN: 1573-2932
    Keywords: mass balance model ; mercury ; temperature lake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A simple, mechanistic model of mercury (Hg) dynamics in a lake has been developed, based on the fugacity/aquivalence approach of Mackay (1991) and Mackay and Diamond (1989) and its extension to treat several interconverting chemical species (Diamond et al., 1992). The model considers the distribution of inorganic (HgII), elemental (Hg°) and methyl (MeHg) mercury species between dissolved and particle-sorbed phases, and fate and transport in a system consisting of a well-mixed water column and an active sediment layer. Hg can enter the lake from watershed runoff and by atmospheric deposition directly to the lake surface. Once in the lake, Hg exchanges between water and air, and water and sediments, and exits by sediment burial, advective flow and volatilization. The model was applied to a hypothetical drainage lake on the Canadian Shield. Model estimates of water and sediment concentrations compare well with measured values. The results suggest that the three Hg species experience significantly different fates and persistence, with overall Hg dynamics dominated by the fate of HgII (the predominant species). A sensitivity analysis illustrates the importance of physical/chemical properties and lake characteristics on the total amount and behavior of Hg in the lake.
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  • 23
    ISSN: 1539-6924
    Keywords: Benchmark ; mercury ; risk assessment ; epidemiology
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    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This paper presents benchmark (BMD) calculations and additional regression analyses of data from a study in which scores from 26 scholastic and psychological tests administered to 237 6- and 7-year-old New Zealand children were correlated with the mercury concentration in their mothers' hair during pregnancy. The original analyses of five test scores found an association between high prenatal mercury exposure and decreased test performance, using category variables for mercury exposure. Our regression analyses, which utilized the actual hair mercury level, did not find significant associations between mercury and children's test scores. However, this finding was highly influenced by a single child whose mother's mercury hair level (86 mg/kg) was more than four times that of any other mother. When that child was omitted, results were more indicative of a mercury effect and scores on six tests were significantly associated with the mothers' hair mercury level. BMDs calculated from five tests ranged from 32 to 73 mg/kg hair mercury, and corresponding BMDLs (95% lower limits on BMDs) ranged from 17 to 24 mg/kg. When the child with the highest mercury level was omitted, BMDs ranged from 13 to 21 mg/kg, and corresponding BMDLs ranged from 7.4 to 10 mg/kg.
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  • 24
    ISSN: 1573-3017
    Keywords: fish ; mercury ; natural selection ; allozyme ; population
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    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Measurements of the differential tolerance between enzyme genotypes and shifts in allozyme frequencies in populations from contaminated habitats have prompted the use of allozymes as markers of population-level toxicant effects. However, such studies often do not consider other factors that influence allele frequencies, including natural clines, migration, the intensity and specificity of selection and toxicant-induced genetic bottlenecks. In addition, selection components other than survival are not included. Consequently, the associated conclusions remain speculative. To assess this approach rigorously, a simulation study was conducted with the mosquitofish (Gambusia holbrooki) GPI-2 locus. Laboratory studies have shown the GPI-238/38 homozygote at this locus to be less tolerant than other genotypes during acute exposure to mercury. The GPI-2100/100 genotype has also been shown to have a reproductive disadvantage at lower mercury concentrations. Simple and then more complex models were used to quantify the relative effects of viability selection, random genetic drift and migration on the GPI-238 allele frequency. Simulations were also performed to assess the contribution of sexual and fecundity selection. A simple population model suggested that viability selection plays a greater role than does mortality-driven, genetic drift in the decrease of the sensitive allele under the conditions of this study. A more complex, stochastic model indicated that no significant mortality-driven drift was taking place in this system. In both models, migration mitigated the effect of selection. Sexual and fecundity selection had little effect on the allele frequencies in these simulations. We conclude that, provided the system under study is clearly understood, shifts in allele frequency can indicate the population-level effects of pollutants.
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  • 25
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    Water resources management 12 (1998), S. 13-30 
    ISSN: 1573-1650
    Keywords: risk ; reliability ; resiliency ; vulnerability ; drought risk index ; drought damage index ; simulation ; water supply ; reservoir operation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract In this study, simulation is used to evaluate the performance of the municipal water system in Fukuoka city. In combination with daily simulation model, a kind of risk model incorporating water demand prediction is presented. This model applies five risk indices: reliability, resiliency, vulnerability, drought risk index (DRI) and drought damage index (DDI). They aid in the identification of operation policies for the municipal water system, and the planning and operational policies obtained are aimed at achieving minimum risk for a given scenario of operation. In this paper, the performance risk of the municipal water system is investigated under three alternatives: (1) the existing system operation when available supply from the Chikugo river is decreased; (2) water restrictions for different percentages of reduction are implemented; and (3) available water supply increases when desalination of sea water is implemented. The results obtained show that savings of between 5 and 12% of water consumption from May 1, or increasing of daily desalination of sea water about 30 000 m3 or more, may efficiently decrease the performance risk of the Fukuoka water supply system. Potentials also exist for further increase of reservoir storage by more rational operation. The measure that more attention should be paid to increasing the water supply from stable sources is recommended as well.
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    Water resources management 12 (1998), S. 95-120 
    ISSN: 1573-1650
    Keywords: reliability ; resilience ; vulnerability ; reservoirhedging
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    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract Based on a detailed Monte-Carlo simulation, the effects of hedging parameters namely, starting water availability (SWA), ending water availability (EWA) and hedging factor (HF) on reservoir storage performance indicators have been investigated within the storage-yield plane of over-year reservoirs. Also, trade-off relationships between the various storage performance indicators are developed and selection of reasonable compromising hedging policies based on performance criteria is attempted for over-year reservoirs. Regions within the storage-yield plane of over-year reservoirs where hedging would be effective are identified. This would help the reservoir managers in mitigating the severity during long stretched critical drought periods.
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  • 27
    ISSN: 1573-3017
    Keywords: radiocaesium ; mercury ; lead ; fish ; Chernobyl
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Samples of fish and sediments collected from waters within 10 km of the Chernobyl Nuclear Power Plant were analysed for radiocaesium and other atmospherically transported pollutants (lead (Pb) and mercury (Hg)) were measured in fish tissues. For comparison, fish muscle was also sampled from a less-contaminated area of the Kiev Reservoir and from a hatchery in Kiev. In sediments, 137Cs was the major gamma-emitting isotope, with concentrations of over 100 Bq g−1 in canals adjacent to the reactor and in ponds that were downwind during the accident. The radiocaesium distributions appeared non-normal, were very patchy and could vary by over 100% in samples collected metres to tens of metres apart. Fish muscle radiocaesium from ponds within 10 km of the power plant was in the range of 6–192 Bq g−1. The fish muscle radiocaesium concentrations were highest in ponds from the downwind sites and were correlated with the sediment radiocaesium concentrations. The lead and mercury concentrations in fish were relatively low (medians 〈0.8 μg Hg per g dry mass and 〈150 ng Pb per g dry mass), suggesting little contamination from lead applied to the burning reactor after the accident. The radiocaesium levels in fish in areas close to the reactor continue to be high enough to cause health concerns to humans that might utilize these resources.
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    Water, air & soil pollution 101 (1998), S. 309-321 
    ISSN: 1573-2932
    Keywords: Arctic ; atmospheric deposition ; contaminants ; lead-210 ; mercury ; sediment ; sewage ; subarctic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The history of atmosheric mercury inputs to remote arctic regions can be measured in lake sediment cores using lead-210 chronology. In this investigation, total mercury deposition is measured in sediments from Imitavik and Annak Lakes on the Belcher Islands in southeastern Hudson Bay, an area in the southern Canadian Arctic with no history of local industrial or agricultural sources of contamination. Both lakes received background and atmospheric inputs of mercury while Annak also received mercury from raw domestic sewage from the Hamlet of Sanikiluaq, a growing Inuit community of about 550 established in the late 1960's. Results from Imitavik show that anthropogenic mercury inputs, apparently transported through the atmosphere, began to appear in the mid-eighteenth century, and continued to the 1990's. Annak had a similar mercury history until the late 1960's when disposal of domestic sewage led to increased sediment and contaminant accumulation. The high input of mercury to Annak confirms that Sanikiluaq residents are exposed to mercury through native food sources.
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  • 29
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    Environmental monitoring and assessment 53 (1998), S. 259-277 
    ISSN: 1573-2959
    Keywords: air quality model ; dispersion model ; industrial source complex model ; mercury ; model evaluation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The goal of this paper is to compare and evaluate the performance of three air quality regulatory models for mercury releases. The models include Industrial Source Complex Short Term model (ISCST2), Industrial Source Complex Long Term model (ISCLT2), and SCREEN2. The evaluation is conducted in multiple point source urban environment using meteorological data, emission inventory and monitoring data for eight stations for the year 1990 to 1992. The performance of the models is evaluated using eight statistical parameters. The comparison of models results for both quarterly and annual averaging periods shows that ISCST2 predictions qualitatively match the observed concentrations; whereas SCREEN2 predicts highest concentrations and ISCLT2 the lowest concentrations. The summary of statistical analysis obtained by using three different methods of observed concentration (Co) and predicted concentrations (Cp) comparison show that the ISCST2 has a better overall performance than ISCLT2 and SCREEN2 models. However, none of the models met the criteria for a reasonable model. Summaries of 95% confidence limits on normalize mean square error (NMSE), geometric mean variance (VG) and geometric mean bias (MG) for each and among model indicate that of the three models, ISCST2 has the best overall performance indicators. Improved model performance may be achieved by incorporating different types of mercury forms into emission rate and air dispersion calculations.
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  • 30
    ISSN: 1573-2932
    Keywords: aquatic ; Clear Lake ; mercury ; mining ; pollution ; sediments ; water
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    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Mining operations conducted at the Sulphur Bank Mercury Mine at Clear Lake, California, from 1872–1957, together with acid mine drainage since abandonment, deposited ca. 100 metric tons of mercury (Hg) in the sediments of Clear Lake. In 1992 Hg in surficial sediments (up to 183 mg kg-1 total Hg and 15.9 μg kg-1 methyl Hg) exhibited a classic point source distribution with maximum concentrations adjacent to the mine. However, the ratio of methyl:total Hg in sediments increased with distance from the mine, suggesting either differential transport of methyl Hg or a non-linear relationship between sediment inorganic Hg concentrations and methylation. Water exhibited an even more gradual decline in total Hg concentrations with distance from the mine, in both unfiltered bottom water (max. ca. 70 ng L-1) and filtered surface water (max. ca. 7 ng L-1). In comparison with other studies, Clear Lake exhibits high total Hg in sediment and water, yet relatively low methyl Hg concentrations. Our findings indicate a non-linearity between total and methyl Hg concentrations in sediments. The ratio of methyl:inorganic Hg is approximately 2 orders of magnitude higher in the water column than in the sediments, making the methyl fraction much more available for down-gradient transport away from the mine. Particulate Hg comprises ca. 33–94% of the total Hg and ca. 25–78% of the methyl Hg in the water column. Geothermal springs do not appear to represent a significant source of Hg to Clear Lake. The present pattern of Hg distribution in Clear Lake shows that water column transport plays some role in the lake-wide contamination of methyl Hg, but high methylation at relatively low inorganic Hg concentrations cannot be ruled out. No quantitative estimate of the area of sediments requiring remediation is possible from these descriptive data alone.
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    Water, air & soil pollution 101 (1998), S. 289-308 
    ISSN: 1573-2932
    Keywords: emission factor ; emissions ; inventory ; mercury ; operating rate ; sources ; uncertainty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Estimates of mercury emissions from individual sources and source categories are needed to understand relationships between the emissions and resulting deposition and to evaluate possible approaches to reducing those emissions. We have developed geographically-resolved estimates of annual average mercury emission rates from current anthropogenic sources in the 48 contiguous United States. These estimates were made by applying emission factors to individual facility operating data and to county-wide source activity levels. We apportioned the emissions to an Eulerian modeling grid system using point source coordinates and the fractions of county areas in each grid cell. Point sources account for about 89% of the 48-state total mercury emissions of 146.4 Mg/yr. Most of the emissions in the inventory are from combustion of mercury-containing fossil fuels and municipal waste, located primarily in the mid-Atlantic and Great Lakes states as well as in the Southeast. The major uncertainties in the emission estimates are caused by uncertainties in the emission factors used to develop the estimates. This uncertainty is likely a result of variability in the mercury content of the combusted materials and in the removal of mercury by air pollution control devices. The greatest research need to reduce uncertainties in mercury emission estimates is additional measurements to improve emission factors.
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  • 32
    ISSN: 1573-2932
    Keywords: bioavailability ; copper ; dredge spoil ; Eisenia fetida (brandling worm) ; mercury ; sequential extractions ; Urtica dioica (common nettle)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The contaminants Hg and Cu, as well as Fe, Mn and K were sequentially extracted from upland disposed dredge spoil using DTPA and 10% nitric acid. Concentrations of these metals in aerial plant tissue and roots of Urtica dioica growing on the dredge spoil were also determined and used to correlate the biological absorption coefficients (BACs) and mobile element absorption coefficients (MACs) with soil extractable metals. DTPA extractions were most suitable for prediction of aerial plant tissue uptake of Cu, Mn and K whilst total Hg and Fe soil concentrations were correlated with plant root BACs and MACs. A laboratory bioassay using Eisenia fetida was also used to assess the potential biological uptake of the contaminants. Both Hg and Cu were accumulated by the worms, but interpretation of the results was hampered by the inherent difficulties of such active biomonitoring.
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    Water, air & soil pollution 102 (1998), S. 427-436 
    ISSN: 1573-2932
    Keywords: chlor-alkali plant ; Hypogymnia physodes ; lichens ; mercury
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Emissions of mercury from a chlor-alkali plant in central Wisconsin have raised concern about possible effects on biota in the area. Samples of the lichen Hypogymnia physodes, which no longer grows in the area, were transplanted from a site in northeastern Wisconsin and positioned on plastic stands at varying distances up to 1250 m from the plant and sampled for Hg quarterly for one year to test the hypothesis that Hg would be taken up by the lichens and would decline with distance. Average tissue concentrations were elevated when first sampled at three months and continued to increase at the nearest sites until the study ended after one year. Average concentrations after a year of exposure ranged from 4418 ppb at 250 m from the plant to 403 ppb at 1250 m from the plant. The decrease over distance followed a negative exponential pattern. Background concentrations at a control site in northern Wisconsin averaged 155 ppb.
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    Water, air & soil pollution 105 (1998), S. 427-438 
    ISSN: 1573-2932
    Keywords: biogeochemistry ; catchment ; input/output budget ; Lake Champlain watershed ; mercury ; forest ; stream
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Total mercury (Hg) deposition and input/output relationships were investigated in an 11-ha deciduous forested catchment in northern Vermont as part of ongoing evaluations of Hg cycling and transport in the Lake Champlain basin. Atmospheric Hg deposition (precipitation + modeled vapor phase downward flux) was 425 mg ha-1 during the one-year period March 1994 through February 1995 and 463 mg ha-1 from March 1995 through February 1996. In the same periods, stream export of total Hg was 32 mg ha-1, respectively. Thus, there was a net retention of Hg by the catchment of 92% the first year and 95% the second year. In the first year, 16.9 mg ha-1 or about half of the annual stream export, occurred on the single day of peak spring snowmelt in April. In contrast, the maximum daily export in the second year, when peak stream flow was somewhat lower, was 3.5 mg ha-1 during a January thaw. The fate of the Hg retained by this forested catchment is not known. Dissolved (〈 0.22 µm) Hg concentrations in stream water ranged from 0.5-2.6 ng L-1, even when total (unfiltered) concentrations were greater than 10 ng L-1 during high flow events. Total Hg concentrations in stream water were correlated with the total organic fraction of suspended sediment, suggesting the importance of organic material in Hg transport within the catchment. High flow events and transport with organic material may be especially important mechanisms for the movement of Hg through forested ecosystems.
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    Water, air & soil pollution 103 (1998), S. 129-136 
    ISSN: 1573-2932
    Keywords: coastal pollution ; mercury ; methylation ; methyl mercury ; sediment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Concentrations of total mercury (Hg), methyl Hg and Hg(II) were determined in coastal marine sediments collected from the Baltic, South China and the Bering Seas. Methyl Hg concentrations in sediments were between 0.01 and 2 ng g-1 on a dry weight basis, accounting for only 〈1% of the total Hg concentrations. The percentage of Hg(II) (i.e. available Hg) in total Hg was between 5 and 13 suggesting that most of the Hg in sediments was bound as HgS and/or Hg-humic complexes. Relatively larger proportion of methyl Hg was found in less polluted freshwater sediments than in marine sediments. Methyl Hg concentrations in marine sediments were not found to be correlated with total Hg and/or Hg (II) concentrations.
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    Water, air & soil pollution 107 (1998), S. 277-288 
    ISSN: 1573-2932
    Keywords: freezing ; lyophilisation ; mercury ; methylmercury ; sediment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Estuarine and riverine sediments from fourlocations showing different sediment structures wereanalysed as fresh, thawed and lyophilised samples fortotal mercury (TotHg) and methylmercury (MeHg)concentrations, and results were compared to addresseffects of sample preservation on Hg speciation. TotHg was measured by cold vapour atomic absorptionspectrometry (CVAAS). MeHg was isolated bydistillation and ion-exchange and analysed by coldvapour atomic fluorescence spectrometry (CVAFS) afterpreconcentration on a gold trap. No loss of TotHg norMeHg due to lyophilisation was found. Concentrationsof TotHg and MeHg respectively ranged from 92 to 267ng g-1 dw and 1.1 to 2.9 ng g-1 dw in freshsamples, from 94 to 215 ng g-1 dw and 1.1 to 2.8ng g-1 dw in thawed samples, and from 100 to 256ng g-1 dw and 1.2 to 3.1 ng g-1 dw inlyophilised samples. Lyophilised samples showedbetter homogeneity and better MeHg analysisreproducibility compared with wet samples.
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  • 37
    ISSN: 1573-2932
    Keywords: budget ; mass balance ; mercury ; regional model ; Onondaga Lake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Onondaga Lake exhibits elevated concentrations of total mercury (HgT) and methyl-mercury (MeHg) in the water column, sediments and fish tissue due to industrial inputs, wastewater discharge and urban runoff. The steady-state Regional Mercury Cycling Model (RMCM) was calibrated to Onondaga Lake and applied to evaluate various remediation scenarios. Because of detailed data available for Onondaga Lake, the RMCM was effectively calibrated. Model predictions of water column and fish concentrations of Hg generally agreed with measured values. The model underestimated concentrations of Hg in sediments. Mass balance calculations show that inputs of HgT largely originate from tributary and wastewater inflows to the lake. In contrast, MeHg is largely derived from internal production. Model calculations suggest that elimination of Hg inputs from wastewater effluent and of drainage from a former chlor-alkali facility could greatly decrease Hg concentrations in fish tissue.
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    Fire and Materials 22 (1998), S. 43-43 
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Fire and Materials 22 (1998), S. 44-44 
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Fire and Materials 22 (1998), S. 39-42 
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: Heat Release Rates of organic materials are studied in many countries, but there is no mathematical formula to represent their shape. We considered a mathematical expression of the Heat Release Rate Curve by a simple equation. And we also derived the index of degree of combustibility, named ‘Burning Index (BI)’. The Heat Release Rate Curve is expressed by the derivative of a probability function of maximum value and has three parameters; an amplitude coefficient, a time width coefficient and an ignition index. BI is in proportion to an amplitude and a time width and in inverse proportion to an ignition index. BI values of cable plastic compounds with flame-retardant material had good relations with the quantity of non-organic ingredients. © 1998 John Wiley & Sons, Ltd.
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    Fire and Materials 22 (1998), S. 47-54 
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: High-temperature pyrolysis of various classes of polymers have been discussed. For the non-carbonizing polymers it was shown that polymer structure can affect the pyrolysis characteristics. Data on the high-temperature pyrolysis of some polypropylene samples with different crystallinity have been presented. Modification of the standard method allowing one to obtain kinetic data from the single experiment was discussed. A kinetic model for the degradation of char-forming polymers in conditions of high-temperature pyrolysis has been suggested. It has been supposed that pyrolysis of carbonizing polymers proceeds in some (two in present work) parallel stages with different activation energies, temperatures and pyrolysis rates. Questions of the applicability of the suggested model to describe the various types of charring systems have been discussed. High-temperature pyrolysis for a number of epoxy resin-based polymeric compositions have been investigated. Kinetic parameters of the pyrolysis have been computed. © 1998 John Wiley & Sons Ltd.
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    Fire and Materials 22 (1998), S. 77-83 
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Fire-retardant wood treatment with fire-retardant chemicals consisting of basic nitrogen compounds and phosphoric acid have been thoroughly examined. The fire retardance and endurance of wood were influenced by the treatment method. Here two treatment methods were compared, heat-pressed treatment method improved these qualities more than heat-dried treatment method. Furthermore, to gain lasting fire retardance, it was considered necessary to react basic nitrogen compounds and phosphoric acid with formaldehyde as in the dicyandiamide-formaldehyde-phosphoric acid or melamine-dicyandiamide-formaldehyde-phosphoric acid system. In the treated wood, the concentration of chemicals gradually decreased as it approached the center. The functional fire retardance could be graded in accordance with the chemical content. © 1998 John Wiley & Sons, Ltd.
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    Fire and Materials 22 (1998), S. 103-108 
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: The thermal decomposition of six different samples of wood and leaves in nitrogen has been studied by using dynamic thermogravimetry. In the experiments two main weight loss processes took place and the total weight loss at 500°C was over 95% in all six cases. By means of the Doyle method, the two processes were found to fit most closely the plot for the second-order equation in the form dα/dt=k(1-α)2, and each of the weight loss processes was found to be controlled, respectively, by two dominant reactions as the temperature increases. It was inferred that competing reactions occur during the overall temperature interval for all the six samples. By comparing the activation energies using this model with those by the method of Moll et al., and by comparing the experimental and theoretical thermogravimetric curves, the ‘second-order’ model was tested to be able to predict the weight loss processes of the samples with very good accuracy. It can be concluded that the ‘second-order’ kinetic model acts much better than the conventionally adopted first-order model. © 1998 John Wiley & Sons, Ltd.
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    Keywords: Chemistry ; Polymer and Materials Science
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    Fire and Materials 22 (1998), S. 119-128 
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This work compares the fire degradation of ethylene-vinyl acetate 8% copolymer (EVA8) with two flame-retarded formulations, using the cone calorimeter. The first one, EVA8/ammonium polyphosphate (APP) leads to the protection of the material, in the conditions of a fire, by means of blowing up and weak carbonization. The addition of polyamide-6 (PA-6) in EVA8/APP improves the protection by forming an intumescent carbonaceous shield. The fire hazard of the virgin polymer and of the FR systems are quantified, in terms of rate of heat release, weight loss, effective heat of combustion, volume of smoke production and CO and CO2 production. It assesses the effectiveness of the fire retardant additives APP and APP/PA-6 in EVA8-based materials under simulated real fire test conditions.The respective temperatures of the degradation front are deduced from the weight loss data recorded in the course of the cone calorimeter experiments and the results of the invariant kinetic parameters method applied to the different specimens. The addition of APP/PA-6 in EVA8 leads to a superficial phenomenon; the degradation zone is thus located on the upper volume of the specimen during all the exposure to the heat flux. © 1998 John Wiley & Sons, Ltd.
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    Fire and Materials 22 (1998), S. 155-165 
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A set of small-scale experiments was carried out to study the effects of material structural properties on the re-ignition characteristics of solid fuels. The influence of other key parameters, such as the incident heat flux and pre-burn, was also carefully investigated. The experiments were conducted on specimens of wood and PMMA using a cone calorimeter. As expected, the effect of water on the re-ignition time was found to be significant. It was also found that the re-ignition characteristics of charring materials, such as wood, are quite different from non-charring materials, mainly due to the structural differences. Based on the experimental observations two different mathematical models were developed to analyse the data for both wood and PMMA samples. Calculations of the re-ignition time made using these models agree generally well with the measurements and confirm that the material structure plays a vital role in its re-ignition behaviour. © 1998 John Wiley & Sons, Ltd.
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    Fire and Materials 22 (1998), S. 44-44 
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Fire and Materials 22 (1998), S. 25-37 
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: An analysis has been made to compare the repeatability and reproducibility of three tests for cigarette ignition of upholstered furniture composites: ASTM E1352, ASTM E1353 and NIST 851 mock-up. The first two of these tests are traditional methods designed to assess the potential of upholstered furniture components to being ignited by cigarettes while the last one, NIST 851 mock-up, is a new method designed to assess the propensity of cigarettes to ignite upholstered furniture composites. The traditional methods, ASTM E1352 and ASTM E1353 use a single cigarette for each determination and can be run in two ways: to obtain a numerical output of char length on the substrate (following the standard) or to obtain a pass/fail result for the substrate (practical use); the precision was analysed in both fashions. The new method, NIST 851 mock-up, uses 144 cigarettes for each determination (48 each on three substrate composites), and assesses the fraction of substrates that have been ignited (char length exceeding 10 mm), i.e. by a combination of pass/fail data. The analysis for actual char length was made according to ASTM E691 guidelines, while the analysis of the pass/fail was made according to a modification applicable to binary data. The precision of the test methods was as follows (in descending order):NIST 851〉ASTM E1353 P/F〉ASTM E1352 P/F〉ASTM E1353〉ASTM E1352© 1998 John Wiley & Sons, Ltd.
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    Fire and Materials 22 (1998), S. 149-154 
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Ion exchangers prepared from beech sawdust by introduction of weak and strong basic ion-exchanging groups were analysed with thermogravimetry, differential scanning calorimetry and limited oxygen index methods to evaluate their thermal stability and flame-retarding properties. By cross-linking with epichlorohydrin in the presence of NH4OH, ion exchangers in free form or in H3BO3 or H3PO4 form were obtained with increased thermal stability in comparison to the starting material. By cross-linking and quaternization of sawdust in one step with 1,3-bis(3-chloro-2-hydroxypropyl)imidazolium hydrogen sulfate, a material with better thermal stability and flame-retarding properties was obtained than by the previous procedure. This resulted in greater residues at higher temperatures as measured by dynamic thermogravimetry. The values of rate constants and activation energies of gasification calculated from isothermal thermogravimetric measurements decreased with improved thermal resistance similar to heat effects observed with differential scanning calorimetry. Limited oxygen index values up to 35.6% were obtained. © 1998 John Wiley & Sons, Ltd.
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    Fire and Materials 22 (1998), S. 179-185 
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Silicones comprise a wide variety of materials such as fluids, elastomers, resins, and foams. This paper reports the ignitability of some typical silicones under various external radiant heat fluxes. The ignitability of silicones was studied using a cone calorimeter under radiant heat flux levels of 0.5-60 kW m-2. The time to ignition of the silicones was found to be proportional to a power of the incident heat flux that varies from -1.33 to -2.84. For silicone fluids, viscosity (or molecular size) is the key variable in controlling the ignitability. For silicone elastomers, the fillers play an important role in controlling the ignitability, especially at incident heat fluxes lower than 35 kW m-2. The ignitability of silicone resins depends on the chemical structure of the resins: the pure trifunctional resin has the lowest ignitability. The ignitability of the silicone foams having the same density depends on the foam thickness, especially at incident heat fluxes lower than 30 kW m-2. © 1998 John Wiley & Sons, Ltd.
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    Fire and Materials 22 (1998), S. 199-206 
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The behaviour of wood with the heat-compressed treatment method was evaluated. Fire retardance and endurance of wood treated with basic nitrogen compounds and phosphoric acid were much improved by the compressed method using a hot press. In this way, the concentration of chemical contents and the density of wood were raised at the surface of the treated wood and it increased the specific gravity of the treated wood as a whole. It was recognized that the increase of specific gravity improved fire retardance and endurance, and fire endurance of wood was indicated by the equation of addition of chemicals and specific gravity. It is more effective to increase the specific gravity of wood at the surface to improve fire endurance. Wood treated with chemicals showed a high limiting oxygen index in proportion to the increase in the addition of chemicals regardless of the treatment method, and high fire endurance was not always accompanied by a high limiting oxygen index. © 1998 John Wiley & Sons, Ltd.
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    Notes: Fire retardant fast-growing wood product was developed by coating with fire retardant and densifying the surface of wood. Trimethylol melamineformaldehyde resin mixed with phosphoric acid was coated on the wood surface, preheated and followed by hot pressing. Effects of the amount of coating, preheating temperature, and densifying ratio on the fire retardancy of sugi (Cryptomeria japonica D. Don) wood, and pressing temperature and pressing time on that of albizia (Paraserianthes falcataria Becker) wood were discussed. Bending strength, creep performance under fire and fire retardancy were evaluated. The results showed that the treatments improved the fire retardancy of woods without reduction in the bending strength. © 1998 John Wiley & Sons, Ltd.
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    Fire and Materials 22 (1998), S. 1-6 
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The measurements of effective heat of combustion obtained from the Cone Calorimeter test for several wood composites (different types of plywood and particle board) at horizontal configuration are presented. Comparison of the average effective heat of combustion at different irradiation shows no correlation to gross heat of combustion measured in the oxygen bomb calorimeter. It was also found, that for the materials studied, there is no statistically significant correlation of heat of combustion to lignin content, but on the other hand, there is an evidence of correlation to the burning weight loss of the samples, but further investigation is necessary. Additionally, the effective heat of combustion is shown as a function of time for different external radiant heat-flux level for the chosen materials. Similar profiles have been found for remaining samples. Two different types of such curves can be distinguished. © 1998 John Wiley & Sons, Ltd.
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    Notes: The oxygen index (OI) of poly(butylene terephthalate) (PBT) tends to decrease when it is combined with milled-glass fibres either with or without the sizing treatment. This shows that the previously found apparent increase of flammability of PBT glass fibre composites (GFPBT) as compared to PBT is not due to the introduction of the flammable sizing together with the glass fibres in the polymer which was one suggested explanation in the literature, but rather to the wick and anti-dripping effects of glass fibres. The effectiveness of a typical brominated organic compound-antimony trioxide fire retardant system (FR), as measured by OI, is found to be larger in GFPBT as compared to PBT. A linear increase of the temperature index (TI) of PBT and of GFPBT is observed with increasing concentration of the FR. The fire retardant increases the time to ignite while it decreases the maximum rate of heat release and increases the smoke optical density and CO evolution on burning in the cone calorimeter. The dependence of fire risk and hazard assessement on the combustion model of the combustion test method is discussed for OI and cone calorimeter in the case of PBT, GFPBT and FR corresponding materials. © 1998 John Wiley & Sons, Ltd.
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    Fire and Materials 22 (1998), S. 129-130 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Fire and Materials 22 (1998), S. 141-148 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The fire retardance of wood treated with basic nitrogen compounds and phosphoric acid is improved. It was investigated which chemicals were suitable for the fire retardant treatment of wood and how chemicals influenced fire retardance and endurance from the perspective of chemical reaction and also it was investigated how chemicals and treatment methods influenced fire retardance and endurance from a thermal perspective. Although the fire endurance was improved by a heat-pressed treatment method, the chemical reaction was carried out by heat irrespective of the pressing or drying method. The wood structure would become complex as the cross-linked structure occurred by chemicals and pressure. Its structure would be maintained at combustion. Fire endurance of wood is shown to be related to a cross-linked structure created by a chemical and/or physical reaction rather than thermal factors related to the carbonized product. © 1998 John Wiley & Sons, Ltd.
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    Fire and Materials 22 (1998), S. 167-173 
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A thorough review was recently conducted to verify the correctness of equations being used to calculate heat release rate in standard test methods. The review incorporated 17 different standard test methods from American Society of Testing and Materials (ASTM), National Fire Protection Association (NFPA), Uniform Building Code (UBC), California Technical Bulletin (CA TB), International Standards Organization (ISO), and British Standards (BS). The standard test methods reviewed were ASTM D5424, ASTM D5537, ASTM E1354, ASTM E1537, ASTM E1590, ASTM E1623, ASTM E1822, NFPA 264, NFPA 265, NFPA 266, NFPA 267, CA TB 129, CA TB 133, UBC 8-2, UBC 26-8, ISO 5660, BS 476. Through this review, incorrect equations were found in 12 of the 17 standards with a total of 22 incorrect equations overall. The following paper provides the correct heat release rate equations and a summary of the review. © 1998 John Wiley & Sons, Ltd.
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    Fire and Materials 22 (1998), S. 175-178 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: In the paper entitled ‘Comparison of the Propensity of Cigarettes to Ignite Upholstered Furniture Fabrics and Cotton Ducks (500-Fabric Study)’ (Fire Mater. 21, 123-141 (1997)) Marcelo M. Hirschler addresses the validity of a test method, proposed by NIST, for smoldering cigarette ignition propensity of upholstery fabrics. The thrust of the study is to establish similarities ‘between the ignition propensity of cigarettes assessed by (1) a set of 500-upholstery fabrics (chosen at random among typical upholstery fabrics) and (2) a test method proposed by NIST (NIST 851) and based on “cotton duck” fabrics’. The conclusion of Hirschler's study is that ‘the overall results obtained from the 500-upholstery fabric study correlate well with those of the “cotton duck” study.’ In addition, the author states that ‘the “cotton duck” can be considered, as a whole, to behave similarly to the majority (estimated at perhaps 80%) of the upholstery fabrics available at the time of the study, and the test is valid’. In an attempt to validate these statements, the ignition patterns generated by the five test cigarettes on each of the 500-upholstery fabrics were compared with the NIST “cotton duck” pattern. Only 6.6% were found to generate a pattern similar to the NIST pattern and 94% of this group were heavyweight (greater than 14 oz/sq yd.) fabrics. Assessment of the test results fails to substantiate Hirschler's statements. © 1998 John Wiley & Sons, Ltd.
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    Fire and Materials 22 (1998), S. 219-220 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Fire and Materials 22 (1998), S. 187-197 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: This work reports one-dimensional predictions of methane/air fuel combustion in inert porous media using four combustion models: full mechanism (FM, 49 species and 227 elemental reactions), skeletal mechanism (SM, 26 species and 77 elemental reactions), 4-step reduced mechanism (4RM, 9 species) and 1-step global mechanism (1GM). The effects of these models on temperature, species, burning speeds and pollutant emissions are examined. The calculations are compared with available experimental data. It is concluded that the already known limitation of the 1-step global mechanism can be partially eliminated by the present 4-step reduced mechanism. This 4RM model compares very satisfactorily with the full mechanism in the simulation of combustion in porous media. This conclusion is encouraging for the simulation of practical porous media burners because the 4RM model improves the stability of the calculation process and can be used with reduced computational resources and cost. © 1998 John Wiley & Sons, Ltd.
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    Fire and Materials 22 (1998), S. 213-218 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The paper describes results of investigations of conveyor belt flammability in full scale, using the large-scale gallery method and using cone calorimeter. On the basis of oxygen consumption calorimetry, the amounts of heat release during burning of conveyor belts were calculated. A correlation was found between results of conveyor belt flammability obtained using both methods. Criteria for conveyor belt flammability assessment were established for the cone calorimeter method, which define a level that would be equivalent to that for the large-scale gallery test. © 1998 John Wiley & Sons, Ltd.
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    Notes: Smoke evolution [in NBS chamber by the ASTM E-622-(1983) method] and ignitability (by the oxygen-index method) was investigated for glass-reinforced polyester (GRP) laminates obtained with unsaturated polyester (UP) resins containing chlorine and bromine in the chain. In these studies, the effect on the properties of such additives as Sb2O3, Al (OH)3, MoO3, Mg(OH)2 and melamine diphosphate in an amount up to 30 mass-% was determined. The most efficient ignition and smoke-evolution retarder of the investigated compounds was Mg(OH)2, whereas an essential reduction in smoke evolution was observed also with MoO3. GRP laminates with these additives meet the fire-safety recommendations concerning smoke evolution from materials used in transportation means and in the building industry. © 1998 John Wiley & Sons, Ltd.
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    Fire and Materials 22 (1998), S. 55-60 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The charring of wood studs has been studied in the cone calorimeter at constant heat flux 50 kW/m2 and compared to data from full-scale furnace wall tests. The wood studs were unprotected or protected by gypsum plasterboards on the exposed side. Similar charring depths were found and the data analysed mainly in terms of fire exposure. A simple small-scale technique was developed to measure the heat transfer through protective boards and the charring depth of wood studs. These properties are essential for the load bearing capacity of wood frame structures. © 1998 John Wiley & Sons, Ltd.
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    Notes: We report here on the results of our continuing effort to study the flame-retardant mechanism of silica gel and potassium carbonate. These additives reduce the flammability of a wide variety of common polymers such as polypropylene, nylon, polymethylmethacrylate, poly(vinyl alcohol), and cellulose. In an effort to determine how these additives reduce polymer flammability, we have used electron paramagnetic resonance spectroscopy and solid-state 13C and 29Si nuclear magnetic resonance spectroscopy to characterize the combustion chars or residues. These data indicate that, in the case of poly(vinyl alcohol), the additives do not change the type of char formed, but they do change the rate of char formation relative to the rate of fuel generation. We also found that, using only CP/MAS 13C NMR, there can be significant intensity distortions which complicate interpretation, if the char is hydrogen depleted and contains paramagnetic centres. © 1998 John Wiley & Sons, Ltd.
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    Fire and Materials 22 (1998), S. 89-94 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Although the fire resistance of wood depends on its dimensions, it needs a lot of time and energy to fire retard thick wood. On the other hand, it is easier and takes less time and energy to treat thin materials. The fire resistance of wood was improved by compressed treatment, even untreated wood, and moreover compressed wood loaded with chemicals was improved more. Fire resistance of a laminated board was the same as a solid compressed board, and also fire resistance of a laminated board which was arranged with compressed thin wood on two sides of untreated wood showed similar fire endurance. A laminated lathe veneer board showed better fire resistance than solid untreated wood and a laminated board with treated veneers arranged concentratively showed better fire resistance than it did when arranged dispersively.So it was judged that it was important to retard fire ignition and to form a carbonized layer effectively in a fire by physical and chemical treatment, especially on the surface of a material. © 1998 John Wiley & Sons Ltd.
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    Notes: Transient gasification rates and fluid temperatures were measured for polydimethylsiloxane fluids ranging in viscosity from 0.65 cS to 60 000 cS in a nitrogen atmosphere at external radiant fluxes from 20 kW/m2 to 70 kW/m2. A detailed energy balance for each fluid sample was conducted to determine its global heat of vaporization. Two major energy loss corrections were identified and quantified. The absorption of incident radiation by the volatile products from short chain oligomers was measured and found to substantially reduce the incident flux to the sample surface; the energy loss due to re-radiation was determined to be a substantial factor in reducing the net heat flux to the sample for long chain length fluids. Other energy losses, e.g. heat loss to the substrate, were observed but were less significant. The average gasification rate for each fluid increased linearly with increasing external radiant flux. The global heat of gasification increases with an increase in the chain length (molecular weight) for the siloxane oligomers. These agreed well with calculated values. The global heat of gasification for 50 cS fluid is about 1200 kJ/kg and its value remains nearly constant for all higher molecular weight dimethylsiloxanes. Pyrolysis rates for siloxane fluids are very sensitive to trace catalysts. Measurements of the global heat of gasification for ultra-clean polymers resulted in significantly higher values (3000 kJ/kg). The gasification of siloxanes occurs via two modes or combinations thereof: (1) volatilization of molecular species native to the polymer, and (2) volatilization of thermal degradation products. The former process dominates for low molecular weight siloxanes (η〈10 cS) and the latter process dominates for high molecular weight siloxanes (η〉1000 cS). For the intermediate molecular weight siloxanes, both volatilization and degradation processes occur. © 1998 John Wiley & Sons, Ltd.
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    Fire and Materials 22 (1998), S. 239-252 
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: The gasification behavior for a wide range of polydimethylsiloxane fluids in a nitrogen atmosphere was investigated. Part 1 of this study addressed the measurement of the energy (global heat of gasification) required for the gasification of a wide range of dimenthylsiloxanes. Several significant corrections were required to reconcile measured gasification energy(s) with calculated heat(s) of gasification based on fundamental thermochemical data. The identification of the dominant mode(s) of gasification via the characterization of pyrolysis products provided a firm basis and rationale for understanding and directing efforts at quantifying these correction factors. In Part 2, the gasification products were identified and quantified at various stages of the gasification process corresponding to ignition, fire growth, and steady-state burning. Pyrolysis of methylated siloxanes occurs via two modes: (1) the volatilization of short chain and intermediate chain length species native to the polymer, and (2) the volatilization of short chain and intermediate chain length species resulting from thermal degradation via siloxane rearrangement. The former process is the dominant gasification mechanism for short chain oligomers and low viscosity fluids (η〈10 cS) and the latter process is dominant in all higher molecular weight polymers (η〉100 cS). Both gasification mechanisms are evident in all polymers (η〉20 cS); the dominant mechanism is dependent upon polymer size and distribution thereof, the gasification stage, and the presence of trace catalysts in the polymer. Because of their structural similarity, the combustion of all gasification products emanating from PDMS regardless of the stage of the pyrolysis process or the dominant mode of gasification will result in virtually identical combustion products, i.e. SiO2, CO2, and H2O. Copyright © 1998 John Wiley & Sons, Ltd. This paper was written under the auspices of the US Government and is therefore not subject to copyright in the US.
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  • 69
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    Fire and Materials 22 (1998), S. 43-43 
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 70
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The study presented addresses the fire behaviour of polypropylene compounded with six classes of flame retardants. The application of cone calorimetry for the assessment of the thermal characteristics of the tested materials and their comparison with thermogravimetry are the central point of this research. This study only presents data for 25 kW/m2 of incident heat flux exposure and includes five tests for polypropylene with no additives and five tests for polypropylene with flame retardants based on triglycidylisocyanurate and lignin. The data collected include the rate of heat release, mass loss rate, char yield, time to ignition and time of total combustion. Results represent meaningful comparison between the behaviour of the materials under simulated fire conditions, using the cone calorimeter, and in the slow dynamic environment utilized in thermogravimetric analysis. © 1998 John Wiley & Sons Ltd.
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  • 71
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    Fire and Materials 22 (1998), S. 19-23 
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This paper describes how a standard polyester cloth was irradiated in the presence of a cross-linking reagent to produce a fabric whose thermoplastic melt-drip behaviour had been modified to that of a charring thermoset material. British Crown Copyright 1998/MoD.
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  • 72
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 73
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    Fire and Materials 22 (1998), S. 69-76 
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This study demonstrates the shielding effects of a silica-ash layer on the combustion of silicones and their possible applications on the fire retardancy of organic materials. The deposited silica-ash layer, formed on the surface of silicone materials during combustion, has shielding effects on the combustion of silicones. It insulates the burning surface from the radiant heat of flame, as well as from the radiant heat produced from the burning of adjacent materials. It also restricts the diffusion of fuels into the combustion zone and the access of oxygen to the unburned fuels. The shielding effects provide some of the fundamentals for the development of silicone-based fire retardants. © 1998 John Wiley & Sons, Ltd.
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  • 74
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    Fire and Materials 22 (1998), S. 95-101 
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The dynamics of microgravity concurrent flame spread over thin cellulosic sheets are theoretically investigated. The mathematical model is based on the laminar, reactive Navier-Stokes equations coupled to solid-phase enthalpy and mass conservation equations. Simulations have been made for forced flow velocities in the range 0.25-15 cm/s, by decreasing the oxygen mass fraction of the concurrent flow below the ambient value and by increasing the solid charring rate (fire-retarded cellulose). For air, non-retarded cellulose and flow velocites larger than 5 cm/s, the dynamics of concurrent flame spread are qualitatively similar to those of normal gravity. As the concurrent flow is decreased below 5 cm/s, after short transients, a transition from fast flame spread to slow solid burning and then to flame quenching is predicted. Flame quenching is also observed, for relatively high flow velocities, in vitiated air or for fire-retarded cellulose. Finally, blow-off at the highest velocity considered (15 cm/s) is predicted only for sufficiently low oxygen concentrations. © 1998 John Wiley & Sons, Ltd.
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  • 75
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    Fire and Materials 22 (1998), S. 109-118 
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A theory for approximately steady thermal degradation of solids is developed from a superset of nonlinear integral-differential equations. The theory extends previous work, using a degradation model that is more consistent than previously published models and fully accounts for surface radiation losses. The thermal decomposition of the solid is assumed to follow a single-step first-order Arrhenius reaction. A quasi-steady regime is identified and approximate solutions are compared with experimental results for PMMA and numerical results obtained by integrating the full model. The numerical solutions are found to compare well with experimental results and the approximate solutions compare well with the numerics. Furthermore, it is found that the quasi-steady mass loss rate gives a good estimate of the average mass loss rate even during thermally thin degradation. To simplify interpretation and to aid the analysis, the degradation kinetics are re-cast in terms of a critical temperature and a critical temperature range. Application of the theory to practical situations and other modelling approaches is also discussed. © 1998 John Wiley & Sons, Ltd.
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  • 76
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    Fire and Materials 22 (1998), S. 133-140 
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: WALL2D, a two-dimensional computer model for predicting heat transfer through uninsulated wood-stud walls protected by gypsum board, has been under development at Forintek for several years. This paper describes major revisions which improve the description of heat transfer through the entire assembly, but, most notably, across the cavity. WALL2D's predictions for time-dependent temperature profiles in wood-stud walls are in very good agreement with the results of both small- and full-scale fire resistance tests. Although further refinement of WALL2D will continue, the model, in its current form, is suitable for application to fire safety engineering design. © 1998 John Wiley & Sons, Ltd.
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  • 77
    ISSN: 1573-2932
    Keywords: acid rain ; batch experiment ; Freundlich isotherm ; lysimeter experiment ; mercury ; simulation model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Increasing mercury contents are reported from freshwater systems and fish in northern Europe and North America. Mercury input from soils is a major source with the leaching being affected by increased atmospheric mercury deposition compared to pre-industrial times and by other environmental conditions such as acid rain. The results of a mathematical model-calculation of vertical inorganic Hg(II) leaching in a Scandinavian iron-humus podzol under different atmospheric input rates of mercury are presented. Leaching under background rain conditions was calculated to be considerably stronger than under acid rain conditions. Increasing fractions of deposited soluble or solute atmospheric mercury were leached from the O f(h)-horizon with decreasing soil content of soluble mercury under acid rain conditions; this effect was less pronounced under background rain conditions. The steady state concentrations of soluble mercury of the upper soil horizons were calculated and compared with the actual concentrations of total (= soluble + insoluble mercury) and extractable (= estimate of soluble) mercury measured in these horizons. The results indicate that even if the deposition of airborne mercury to soil is strongly reduced, the total mercury content of the soil decreases only slowly. It may take decades or even centuries before a new steady state concentration of total mercury is established in the soil. The decrease of the mercury concentration in the O f(h)-horizon is probably largely dependent on the turnover of organic matter, binding most of the deposited airborne mercury in an insoluble form. Hence, present day mercury leaching is likely to be dominated by mercury deposited during former times and temporarily retained in an insoluble form in the organic matter.
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  • 78
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    Water, air & soil pollution 97 (1997), S. 205-207 
    ISSN: 1573-2932
    Keywords: mercury ; gold mining ; ecosystems ; methyl-Hg ; cycling ; global sources
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract As described by Jemelov and Ramel (1995), the Scientific Committee on Problems of the Environment (SCOPE) sponsored an investigation of Hg in ecosystems with special emphasis on tropical regions. In these regions small-scale gold mining activities have occupied about 10 million people worldwide who use Hg for extracting gold.
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  • 79
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    Water, air & soil pollution 97 (1997), S. 257-263 
    ISSN: 1573-2932
    Keywords: mercury ; atmosphere ; rainwater ; marine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Total gaseous mercury (TGM) and rainwater were collected on board of two research vessels (F. S. ALKOR and R.V. BELGICA) positioned 200 km apart in the center of the North Sea during the North Sea Experiment, September 1991. On the F. S. ALKOR (up-wind ship) TGM concentrations ranged from 0.7 to 2.6 ng·m−3 with an average of 1.5 ng m−3 and on the R. V. BELGICA (down-wind ship) TGM ranged from 0.7 to 1.9 ng·m−3 with an average of 1.2 ng·m−3. An average 20% decrease is observed from the up-wind to the down wind ship. which may largely be affected by entrainment into the free troposphere. An overall removal (entrainment) velocity of 0.95 cm·s−1 was calculated for the whole experiment. The average removal velocity was 0.5 cm·s−1 for dry periods and varied between 1 to 5 cm·s−1 during rain events. Rainwater concentrations varied between 5 and 25 ng·1−1. Based on these data an annual wet deposition flux of 1.08 ng Hg cm−2 yr1− was estimated for the North Sea.
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  • 80
    ISSN: 1573-2932
    Keywords: mercury ; methylmercury ; sediment ; polychaete ; Nereis diversicolor ; methylation ; bioaccumulation ; Scheldt estuary
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Total mercury (Hg) and methylmercury (MeHg) concentrations were determined in sediments and in the polychaete worm Nereis diversicolor at 13 stations of a brackish water intertidal mudflat of the Scheldt estuary. Hg and MeHg concentrations in sediments ranged from 144 to 1192 ng g−1 dw and from 0.8 to 6 ng g−1 dw, respectively. Both Hg and MeHg concentrations increased with an increase of organic matter (OM) content and fine grain fraction. In contrast, Hg accumulation by N. diversicolor was significantly (p 〈 0.05) higher at stations with sandy sediments (mean value: 125 ng g−1 dw) than at stations with muddy sediments (mean value, 80 ng g−1), probably because Hg availability for bioaccumulation at muddy stations was reduced by high OM content of the muddy sediments. MeHg accounted for an average of 0.7% of the total Hg in sediments and 18% of the total Hg in N. diversicolor. Seasonal variations significantly affected Hg concentrations in sediments and MeHg in N. diversicolor. Total Hg concentrations in sediments were significantly (p 〈 0.05) higher in autumn and winter than in spring and summer whereas MeHg concentrations were lowest in winter compared to the other seasons. On the other hand, total Hg concentrations in the worms were lowest in spring whereas MeHg concentrations were significantly (p 〈 0.01) higher in spring and summer than in autumn and winter.
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  • 81
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    Water, air & soil pollution 99 (1997), S. 217-223 
    ISSN: 1573-2932
    Keywords: selective leach ; organic ; humic ; fulvic ; analysis ; mercury ; zinc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The international reference lake sediment, LKSD-4, was used to compare Hg, organic C and Zn extracted from its ‘soluble organic’ phase by two commonly used reagents: 0.1 M Na4P2O7 solution at pH 10 and 0.5 M NaOH solution at pH 12. While recoveries of Hg and Zn by 0.1 M Na4P2O7 are not affected by changes in sample weight to reagent volume ratio (W/V) or contact time, those by NaOH show a marked dependency. In general, the NaOH leach extracts more organic C and Hg from LKSD-4 but less Zn. Over the range of conditions studied, the NaOH-based method extracted 4.7–9.8% C, 27–103 ng g−1 Hg and 19–69 μg g−1 Zn from LKSD-4, compared to 2.3–2.8% C, 17–24 ng g−1 Hg and 64–72 μg g−1 Zn by the Na4P2O7 leach. Clearly, different groups of organic substances are being dissolved by these two reagents and therefore a comparison of data from different laboratories becomes meaningless. This paper suggests that more research is needed into the exactNature of metal-organic associations extracted by selective leaches and into associated artifacts of extraction such as readsorption phenomena.
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  • 82
    ISSN: 1573-2932
    Keywords: acid rain ; batch experiment ; Freundlich isotherm ; lysimeter experiment ; mercury ; simulation model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Increasing mercury contents are reported from freshwater systems and fish in northern Europe and North America. Mercury input from soils is a major source with the leaching being affected by increased atmospheric mercury deposition compared to pre-industrial times and by other environmental conditions such as acid rain. The results of a mathematical model-calculation of vertical inorganic Hg(II) leaching in a Scandinavian iron-humus podzol under different atmospheric input rates of mercury are presented. Leaching under background rain conditions was calculated to be considerably stronger than under acid rain conditions. Increasing fractions of deposited soluble or solute atmospheric mercury were leached from the O f(h)-horizon with decreasing soil content of soluble mercury under acid rain conditions; this effect was less pronounced under background rain conditions. The steady state concentrations of soluble mercury of the upper soil horizons were calculated and compared with the actual concentrations of total (= soluble + insoluble mercury) and extractable (= estimate of soluble) mercury measured in these horizons. The results indicate that even if the deposition of airborne mercury to soil is strongly reduced, the total mercury content of the soil decreases only slowly. It may take decades or even centuries before a new steady state concentration of total mercury is established in the soil. The decrease of the mercury concentration in the O f(h)-horizon is probably largely dependent on the turnover of organic matter, binding most of the deposited airborne mercury in an insoluble form. Hence, present day mercury leaching is likely to be dominated by mercury deposited during former times and temporarily retained in an insoluble form in the organic matter.
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  • 83
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    Water, air & soil pollution 98 (1997), S. 241-254 
    ISSN: 1573-2932
    Keywords: coal ; deposition ; emission ; mercury ; municipal solidwaste
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Different species of mercury have different physical/chemical properties and thus behave quite differently in air pollution control equipment and in the atmosphere. In general, emissions of mercury from coal combustion sources are approximately 20–50% elemental mercury (Hg°) and 50–80% divalent mercury (Hg(II)), which may be predominantly HgCl2. Emissions of mercury from waste incinerators are approximately 10–20% Hg° and 75–85% Hg(II). The partitioning of mercury in flue gas between the elemental and divalent forms may be dependent on the concentration of particulate carbon, HCl and other pollutants in the stack emissions. The emission of mercury from combustion facilities depends on the species in the exhaust stream and the type of air pollution control equipment used at the source. Air pollution control equipment for mercury removal at combustion facilities includes activated carbon injection, sodium sulfide injection and wet lime/limestone flue gas desulfurization. While Hg(II) is water-soluble and may be removed from the atmosphere by wet and dry deposition close to combustion sources, the combination of a high vapor pressure and low water-solubility facilitate the long-range transport of Hg° in the atmosphere. Background mercury in the atmosphere is predominantly Hg°. Elemental mercury is eventually removed from the atmosphere by dry deposition onto surfaces and by wet deposition after oxidation to water- soluble, divalent mercury.
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  • 84
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    Water, air & soil pollution 98 (1997), S. 241-254 
    ISSN: 1573-2932
    Keywords: coal ; deposition ; emission ; mercury ; municipal solid waste
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Different species of mercury have different physical/chemical properties and thus behave quite differently in air pollution control equipment and in the atmosphere. In general, emissions of mercury from coal combustion sources are approximately 20–50% elemental mercury (Hg°) and 50–80% divalent mercury (Hg(II)), which may be predominantly HgCl2. Emissions of mercury from waste incinerators are approximately 10–20% Hg° and 75–85% Hg(II). The partitioning of mercury in flue gas between the elemental and divalent forms may be dependent on the concentration of particulate carbon, HCl and other pollutants in the stack emissions. The emission of mercury from combustion facilities depends on the species in the exhaust stream and the type of air pollution control equipment used at the source. Air pollution control equipment for mercury removal at combustion facilities includes activated carbon injection, sodium sulfide infection and wet lime/limestone flue gas desulfurization. While Hg(II) is water-soluble and may be removed from the atmosphere by wet and dry deposition close to combustion sources, the combination of a high vapor pressure and low water-solubility facilitate the long-range transport of Hg° in the atmosphere. Background mercury in the atmosphere is predominantly Hg°. Elemental mercury is eventually removed from the atmosphere by dry deposition onto surfaces and by wet deposition after oxidation to water-soluble, divalent mercury.
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  • 85
    ISSN: 1573-2932
    Keywords: mercury ; mercury accumulation ; mercury deposition ; North Dakota ; saline lakes ; sediment cores
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Sediment cores were collected from lakes in the Devils Lake Basin in North Dakota to determine if mercury (Hg) accumulation chronologies from sediment-core data are good indicators of variations in Hg accumulation rates in saline lakes. Sediment cores from Creel Bay and Main Bay, Devils Lake were selected for detailed analysis and interpretation. The maximum Hg concentration in the Creel Bay core was 0.15 micrograms per gram at 8 to 9 centimeters. The maximum Hg concentration in the Main Bay core was 0.07 micrograms per gram at 5 to 7 centimeters. The general decreases in Hg concentrations with depth are attributed to historic variations in atmospheric Hg deposition rate. Hg stratigraphies combined with210 Pb and 137Cs dating analyses yield Hg chronologies that indicate a general increase in Hg accumulation rates in Devils Lake since the middle of the 19th century. Mean modern Hg accumulation rates in Creel Bay were 4.9 nanograms per square centimeter per year, and rates in Main Bay were 1.8 nanograms per square centimeter per year. Mean preindustrial Hg accumulation rates in Creel Bay were 1.2 nanograms per square centimeter per year, and rates in Main Bay were 1.6 nanograms per square centimeter per year. Relatively low Hg concentrations in recent sediments in the Devils Lake Basin, along with similarities in Hg accumulation rates between lakes in the Devils Lake Basin and other lakes in the northern interior of North America, indicate that local sources of Hg are not important sources of Hg. Results of the study indicate that accurate Hg chronologies are discernible in sediment cores collected from saline lakes. However, spatial and temporal variations in lake level and water chemistry common to saline lakes make interpretation of radioisotopic and geochemical chronologies difficult. Hg geochemistry in Devils Lake, and presumably in other saline lakes, is dynamic. The results of this study indicate that the absolute amount of sediment transported to Devils Lake, along with the associated Hg and total organic carbon, and the distribution of sedimentation patterns in Devils Lake may be affected by changing lake levels.
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  • 86
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    Water, air & soil pollution 95 (1997), S. 35-43 
    ISSN: 1573-2932
    Keywords: humic acid ; mercury ; transport ; transformation ; soil-plant system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The influence of humic acid (HA) on the transport and transformation of mercury (Hg) in soil was studied. No available Hg could be detected (〈2.5 μg kg−1) in alluvial soil when the content of HA-carbon (HA-C) was higher than 0.2 g kg−1 although a large amount of Hg (8 μg kg−1) was applied to the soil. The available Hg decreased with the increase of HA in purple soil (r=0.735). There are significant correlations between HA concentration and organic Hg in the tested soils (r=0.974 for the purple soil and r=0.979 for the alluvial soil). The increase of HA results in decrease of Hg absorbed by plant from the soil. A loss of Hg from soil caused by microbes was observed.
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  • 87
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    Water, air & soil pollution 95 (1997), S. 35-43 
    ISSN: 1573-2932
    Keywords: humic acid ; mercury ; transport ; transformation ; soil-plant system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The influence of humic acid (HA) on the transport and transformation of mercury (Hg) in soil was studied. No available Hg could be detected (〈2.5 μg kg-1) in alluvial soil when the content of HA-carbon (HA-C) was higher than 0.2 g kg-1 although a large amount of Hg (8 μg kg-1) was applied to the soil. The available Hg decreased with the increase of HA in purple soil (r=0.735). There are significant correlations between HA concentration and organic Hg in the tested soils (r=0.974 for the purple soil and r=0.979 for the alluvial soil). The increase of HA results in decrease of Hg absorbed by plant from the soil. A loss of Hg from soil caused by microbes was observed.
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  • 88
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    Water, air & soil pollution 97 (1997), S. 205-207 
    ISSN: 1573-2932
    Keywords: mercury ; gold mining ; ecosystems ; methyl-Hg ; cycling ; global sources
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract As described by Jernelov and Ramel (1995), the Scientific Committee on Problems of the Environment (SCOPE) sponsored an investigation of Hg in ecosystems with special emphasis on tropical regions. In these regions small-scale gold mining activities have occupied about 10 million people worldwide who use Hg for extracting gold.
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  • 89
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    Water, air & soil pollution 97 (1997), S. 257-263 
    ISSN: 1573-2932
    Keywords: mercury ; atmosphere ; rainwater ; marine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Total gaseous mercury (TGM) and rainwater were collected on board of two research vessels (F. S. ALKOR and R.V. BELGICA) positioned 200 km apart in the center of the North Sea Experiment, September 1991. On the F.S. ALKOR (up-wind ship) TGM concentrations ranged from 0.7 to 2.6 ng·m-3 with an average of 1.5 ng·m-3 and on the R. V. BELGICA (down-wind ship) TGM ranged from 0.7 to 1.9 ng·m-3 with an average of 1.2 ng·m-3. An average 20% decrease is observed from the up-wind to the downwind ship, which may largely be affected by entrainment into the free troposphere. An overall removal was 0.5 cm·s-1 for dry periods and varied between 1 to 5 cm·s-1 during rain events. Rainwater concentrations varied between 5 and 25 ng·l-1. Based on these data an annual wet deposition flux of 1.08 ng Hg cm-2 yr1- was estimated for the North Sea.
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  • 90
    ISSN: 1573-2932
    Keywords: mercury ; mercury accumulation ; mercury deposition ; North Dakota ; saline lakes ; sediment cores
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Sediment cores were collected from lakes in the Devils Lake Basin in North Dakota to determine if mercury (Hg) accumulation chronologies from sediment-core data are good indicators of variations in Hg accumulation rates in saline lakes. Sediment cores from Creel Bay and Main Bay, Devils Lake were selected for detailed analysis and interpretation. The maximum Hg concentration in the Creel Bay core was 0.15 micrograms per gram at 8 to 9 centimeters. The maximum Hg concentration in the Main Bay core was 0.07 micrograms per gram at 5 to 7 centimeters. The general decreases in Hg concentrations with depth are attributed to historic variations in atmospheric Hg deposition rate. Hg stratigraphies combined with210Pb and137Cs dating analyses yield Hg chronologies that indicate a general increase in Hg accumulation rates in Devils Lake since the middle of the 19th century. Mean modern Hg accumulation rates in Creel Bay were 4.9 nanograms per square centimeter per year, and rates in Main Bay were 1.8 nanograms per square centimeter per year. Mean preindustrial Hg accumulation rates in Creel Bay were 1.2 nanograms per square centimeter per year, and rates in Main Bay were 1.6 nanograms per square centimeter per year. Relatively low Hg concentrations in recent sediments in the Devils Lake Basin, along with similarities in Hg accumulation rates between lakes in the Devils Lake Basin and other lakes in the northern interior of North America, indicate that local sources of Hg are not important sources of Hg. Results of the study indicate that accurate Hg chronologies are discernible in sediment cores collected from saline lakes. However, spatial and temporal variations in lake level and water chemistry common to saline lakes make interpretation of radioisotopic and geochemical chronologies difficult. Hg geochemistry in Devils Lake, and presumably in other saline lakes, is dynamic. The results of this study indicate that the absolute amount of sediment transported to Devils Lake, along with the associated Hg and total organic carbon, and the distribution of sedimentation patterns in Devils Lake may be affected by changing lake levels.
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  • 91
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    Water, air & soil pollution 99 (1997), S. 217-223 
    ISSN: 1573-2932
    Keywords: selective leach ; organic ; humic ; fulvic ; analysis ; mercury ; zinc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The international reference lake sediment, LKSD-4, was used to compare Hg, organic C and Zn extracted from its 'soluble organic' phase by two commonly used reagents: 0.1 M Na4P2O7 solution at pH 10 and 0.5 M NaOH solution at pH 12. While recoveries of Hg and Zn by 0.1 M Na4P2O7 are not affected by changes in sample weight to reagent volume ratio (W/V) or contact time, those by NaOH show a marked dependency. In general, the NaOH leach extracts more organic C and Hg from LKSD-4 but less Zn. Over the range of conditions studied, the NaOH-based method extracted 4.7-9.8% C, 27-103 ng g-1 Hg and 19-69 µg g-1 Zn from LKSD-4, compared to 2.3-2.8% C, 17-24 ng g-1 Hg and 64-72 µg g-1 Zn by the Na4P2O7 leach. Clearly, different groups of organic substances are being dissolved by these two reagents and therefore a comparison of data from different laboratories becomes meaningless. This paper suggests that more research is needed into the exact nature of metal-organic associations extracted by selective leaches and into associated artifacts of extraction such as readsorption phenomena.
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  • 92
    ISSN: 1573-2932
    Keywords: mercury ; methylmercury ; sediment ; polychaete ; Nereis diversicolor ; methylation ; bioaccumulation ; Scheldt estuary
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Total mercury (Hg) and methylmercury (MeHg) concentrations were determined in sediments and in the polychaete wormNereis diversicolor at 13 stations of a brackish water intertidal mudflat of the Scheldt estuary. Hg and MeHg concentrations in sediments ranged from 144 to 1192 ng g−1 dw and from 0.8 to 6 ng g−1 dw, respectively. Both Hg and MeHg concentrations increased with an increase of organic matter (OM) content and fine grain fraction. In contrast, Hg accumulation byN. diversicolor was significantly (p〈0.05) higher at stations with sandy sediments (mean value: 125 ng g−1 dw) than at stations with muddy sediments (mean value, 80 ng g−1), probably because Hg availability for bioaccumulation at muddy stations was reduced by high OM content of the muddy sediments. MeHg accounted for an average of 0.7% of the total Hg in sediments and 18% of the total Hg inN. diversicolor. Seasonal variations significantly affected Hg concentrations in sediments and MeHg inN. diversicolor. Total Hg concentrations in sediments were significantly (p〈0.05) higher in autumn and winter than in spring and summer whereas MeHg concentrations were lowest in winter compared to the other seasons. On the other hand, total Hg concentrations in the worms were lowest in spring whereas MeHg concentrations were significantly (p〈0.01) higher in spring and summer than in autumn and winter.
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  • 93
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    Environmental monitoring and assessment 48 (1997), S. 285-296 
    ISSN: 1573-2959
    Keywords: herring gulls ; heavy metals ; selenium ; feathers ; bioindicator ; mercury ; lead ; cadmium ; chromium ; manganese
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract With increasing interest in assessing the health or well-being ofcommunities and ecosystems, birds are being used asbioindicators. Coloniallynesting species breed mainly in coastal areas that are alsopreferred for humandevelopment, exposing the birds to various pollutants. Inthis paper concentrations of heavy metal and selenium in the feathers ofHerring Gulls(Larus argentatus) nesting in several colonies fromMassachusetts toDelaware are reported. There were significant differencesamong colonies forall metals, with metal concentrations being two to nearly fivetimes higher atsome colonies than others. Selenium showed the leastdifference, and cadmium showed the greatest difference among sites. Concentrations of lead werehighest at Prall‘s Island; mercury was highest at Shinnecock,Huckleberry andHarvey, and manganese was highest at Captree.
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  • 94
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    Environmental monitoring and assessment 47 (1997), S. 79-87 
    ISSN: 1573-2959
    Keywords: air emissions ; Canada ; mercury ; Ontario ; sources
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Mercury is released to the environment from various anthropogenic and natural sources. This work is a compilation of mercury emissions from anthropogenic sources in Ontario, Canada. The goal of our study was to identify all sources of mercury, and develop an emission inventory of anthropogenic mercury in Ontario. The result of our investigation revealed that combustion of fossil fuels and emissions from landfill sites are two primary sources of mercury to the atmosphere. Other sources of significance are emissions from waste incinerators, various industrial activities, and cement production. Total mercury emission in Ontario is estimated as 4100 kg per year.
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  • 95
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    Fire and Materials 21 (1997), S. 7-16 
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The modelling of the spread of fire and its extinguishment still represents a significant challenge. As part of a combined experimental and computational study of fires we have developed a general Computational Fluid Dynamics (CFD) model of fire spread and extinguishment. The primary objective was to produce a flexible computational tool which can be used by engineers and scientists for design or research purposes. The present paper deals with the description and validation of a solid pyrolysis model which has been applied, as a sub-model, in this general computer fire code. The pyrolysis model has been formulated using the heat-balance integral method. The model can be applied to slabs of char forming solids, such as wood, as well as non-charring thermoplastic materials, such as PMMA. Results are compared with analytical solutions, numerical simulations and experimental data. In all cases the integral model performs well. © 1997 by John Wiley & Sons, Ltd.
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  • 96
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    Fire and Materials 21 (1997), S. 17-22 
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: An investigation of cone calorimeter test procedures was performed using two types of mattress composites with various specimen preparations and equipment configurations. The objective was to discover suitable procedures for testing mattress composites. Concurrent with this work a much larger and more sophisticated project known as CBUF was underway in Europe. One of CBUF's secondary objectives was to provide an appropriate test protocol for testing upholstered furniture composites, including mattresses. Most of the CBUF protocol was available at the time of this study and a modified form of the specimen preparation technique was used in this investigation. Preliminary tests found unacceptable test performance with some configurations. Subsequent testing examined variations of the established test protocols and other test procedures. The data sample was small, but observations of the data indicate trends that might be attributable to the use of the different procedures. Significantly it was determined that the edge frame used to hold specimens in place during the test does affect the test results. A modified CBUF protocol proved to be the best procedure, but it requires extensive experience with the CBUF specimen preparation method in order to be able to produce satisfactory specimens. © 1997 by John Wiley & Sons, Ltd.
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  • 97
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    Fire and Materials 21 (1997), S. 1-6 
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The effect of melting behaviour on upward flame spread of thermoplastic materials when subjected to small ignition sources and considered to suffer no external flux was studied using large-scale tests. For moderate fire conditions the cone calorimeter was utilized, with the sample set in a vertical orientation to study the melting behaviour of the specimens. Under these conditions the results indicate that the melting behaviour significantly affects upward flame spread behaviour. A pool of the melt which formed at the base of the vertically oriented sample tested creates a pool fire which then controls the fire growth and flame spread. In contrast, it was found that some thermoplastic materials which have higher glass transition temperatures or undergo a special pyrolysis process such as depolymerization, intumescing or charring do not experience significant melting behaviour when exposed to the same thermal insult. As a result, they behave very differently in terms of upward flame spread. The study also indicates that the melting behaviour of thermoplastic materials is an important characteristic in fires which should be taken into account in the development of modelling, in particular for upward flame spread models. © 1997 by John Wiley & Sons, Ltd.
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  • 98
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    Fire and Materials 21 (1997), S. 51-51 
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: No Abstract
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  • 99
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    Fire and Materials 21 (1997), S. 33-39 
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A series of 37 cigarettes were analysed to develop a model, based on cigarette physical properties, to predict the ignition propensity of the cigarettes towards cellulosic fabrics. The properties used were: cigarette circumference (in mm), tobacco packing density (in g cm-2), paper permeability (in CORESTA units) and the presence or absence of citrate additives in the paper (used independent of concentration, although typical additions range from 0.5 to 0.8 wt%). Two empirical models were developed, one for low and medium paper permeabilities, and one for very high paper permeabilities (above 50 CORESTA units). The latter exceed the paper permeability of most commercial cigarettes, and have medium to high ignition propensities. Thus, they are probably only of interest from the point of view of a mathematical curiosity. The former model, however, addresses cigarettes in the range where commercial cigarettes are potentially viable. The resulting ignition propensities exhibited cover the entire feasible range, from 0% to 100%. Both models predicted the ignition propensities of the tested cigarettes quite well, within an error range which did not exceed 30% for any cigarette. Physical rationales are presented for the effects of the variables used. However, the rationale for the discontinuity in ignition propensity found for the cigarettes with extremely high paper permeability is less clear. One explanation is that there is probably excess oxygen present so that a fuel/oxygen mixture is obtained with a ratio which is less than the lower flammability limits and is too lean to support combustion. However, further analysis of this issue is warranted. The empirical model for low and medium paper permeability cigarettes is potentially useful for developing cigarettes with lower ignition propensity, since it is a practical way of combining the individual properties that most heavily affect cigarette ignition propensity. © 1997 by John Wiley & Sons, Ltd.
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  • 100
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    Fire and Materials 21 (1997), S. 53-65 
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Fire hazard assessments must be primarily driven by life safety variables. Concern is often highly focused on toxicity issues, since fire deaths, in the majority of cases, are found (in whole or in part) to be due to toxic gas inhalation. Procedures have recently been published by ISO, wherein the toxicity assessment of fire products is focused primarily on bench-scale testing for toxic potency (the ‘per-gram toxicity’). Yet hazards of products with regards to fire toxicity may be determined much more by their differences in burning rates than by any differences in toxic potency. Burning rates are not assessed in the pertinent standards (ISO 13344 and ISO TR 9122). For most product categories, techniques for predicting full-scale burning rates from bench-scale data are not yet in hand. Thus, today the best means of comparing actual, full-scale toxic fire hazards is the full-scale fire test, equipped with additional gas measuring instrumentation. Such an approach is not among the recommended methods of the international standards, yet it is the only one with innate validity. In the present work, a series of sandwich panel products were tested in a full-scale room configuration. Bench-scale comparison was made to the ISO 5660 Cone Calorimeter and the DIN 53436 tube furnace. The toxic gases were quantified in all cases by chemical analysis. The product which showed the best performance in the full-scale tests (rock wool insulated sandwich panel) did not achieve a good fire toxicity performance due to minimization of toxic potency. Instead, the successful performance was attributed wholly to reduction of burning rate. Bench-scale measurements of toxic potency were shown to lack relevance to reality in such cases where even the full-scale toxic potency is not a determining factor. © 1997 John Wiley & Sons, Ltd.
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