ALBERT

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.

Notes: Summary Due to the international importance of the Wadden Sea for waders and waterfowl a long-term programme to monitor contamination of birds breeding in the Wadden Sea has been established in the early 1980s. One of the species selected is the Oystercatcher. Comparatively little is known about contamination of birds breeding inland. Therefore, we collected eight eggs of Oystercatchers breeding at the Lower Rhine (district of Kleve) and analysed their contamination with biocides (DDT, DDE, HCH) and industrial chemicals (PCB, HCB, Hg) in comparison to birds breeding on the Wadden Sea islands of Griend (NL) and Mellum (D), where ten eggs were collected in 1994/95. We found distinctive differences between inland and Wadden Sea breeding Oystercatchers. Eggs from the Lower Rhine had significantly higher residues of all organochlorines, whereas concentration of mercury was significantly lower than in those from birds breeding on the Wadden Sea islands. In general, eggs collected on Griend held lower concentrations than those collected on Mellum island, except pp'-DDT and Σ PCB. The high PCB contamination in Ostercatcher eggs from the Lower Rhine nowadays reflects the extreme pollution in the past. However, concentrations of the parameters studied obviously had no embryotoxic effects in Oystercatchers.

Notes: Abstract The nuclear phenotypes and survival of the hemipteran,Triatoma infestans (Hemiptera, Reduviidae), were studied in specimens treated with copper sulfate and methylmercury. The objective was to determine whether changes in chromatin supraorganization and insect survival similar to those promoted by other stressing agents could also be induced by heavy metals. At the concentrations used, copper sulfate and methylmercury were toxic to the cells, mainly inducing nuclear degenrration in the Malpighian tubules and being lethal to a large part of the insect population. Although some individual resistance was found, especially in fasted specimens, heavy metals were found to be much more lethal than was, for instance, a thermal shock at 0°C for 12 h. The nuclear phenotypes detected after heavy metal treatment were similar to those reported under other stressing conditions. However, the frequency at which nuclei exhibited aspects of heterochromatin unraveling was much higher than that found in fasted and thermal-shocked specimens, and was independent of the heavy metal type used. If this phenotype represents an attempt to improve opportunities for extensive cell and insect survival, it was not sufficiently effective. In 5th instar nymphs, the effect of CuSO4 on chromatin supraorganization was detected at early steps of spermatogenesis but not in the cells which were at late spermiogenesis when the metal was administered. This is probably due to changes in nuclear protein composition and to the tightly packed state of the DNA-protein complexes occurring at spermiogenesis, which may protect chromatin from damages. However, when CuSO4 was supplied to 4th instar nymphs, it slowed down the spermiogenesis process, possibly due to several factors including Cu2+ binding to DNA phosphates.

Notes: Abstract Effects of some metals on the growth of cultured human erythroleukemia K-562 cells were investigated when grown in two different types of media based upon RPMI-1640 or Ham's F-10. The study on proliferation, using RPMI-1640 supplemented with sodium selenite, selenomethionine, mercuric chloride, methylmercuric chloride and cadmium nitrate showed no inhibition of growth at concentrations of 2.5, 25, 25, 2.5 and 25 μM, while at 75, 250, 50, 5 and 50 μM toxicity was apparent. Selenite at 5–50 μM and selenomethionine at 50–100 μM inhibited the growth. In Ham's F-10 supplemented with the same compounds no inhibition was found at concentrations of 5, 10, 25, 1 and 50 μM, while at 50, 100, 50, 5 and 75 μM toxic effects were noted. Selenite 10 μM and selenomethionine 25-50 μM inhibited the proliferation. Measurements of trace element levels in pellets of K-562 cells grown in RPMI-1640 or Ham's F-10 unveiled higher cell contents of cadmium and selenium in cells grown in RPMI-1640, being consistent with higher concentrations of these elements in that medium. Manganese and mercury concentrations were higher in cells grown in Ham's F-10 correlating with a higher medium concentration of these elements. The growth responses and cellular uptake differed between the metals and the selenocompounds and although extrapolating the results to humans is difficult the selenium exposures were in approximately the same order of magnitude as in human exposures. The compounds could be ranked according to decreasing toxicity as: methylmercuric chloride 〉 mercuric chloride, cadmium nitrate, sodium selenite 〉 selenomethionine.

Notes: Abstract We have shown that mercury affects energy transfer in Spirulina platensis. It inhibits energy transfer from phycocyanin to chlorophyll a by specifically bleaching the β-84 chromophore of the chromo protein, phycocyanin (PC), in the cyanobacterium. This effect is observed during short-term exposure of cells to Hg2+ ions. Upon long-term (12 h) exposure, mercury at low concentrations (1–2.5 μm) causes the gradual degradation of the β polypeptide (22 kDa) of the PC of phycobilisomes in this cyanobacterium. The effect of mercury on this polypeptide is significant compared with the other phycobiliproteins.

Notes: Abstract Specific binding of Hg to ouabain-sensitive Na-K-ATPase of rat liver plasma membrane was demonstrated with a K of 2.64¥10 and B of 1.6nmole mg protein. The binding of mercury to the enzyme also causes significant inhibition of the enzyme, which is greater than its ouabain sensitivity. In the cytosol Hg binding to reduced glutathione (GSH) is stimulated by GSH-S-transferase (GST), the activity of which was found to be significantly enhanced by 15mM Na and 10mM Hg. It is proposed that the transport of Hg2 inside the cell takes place by increased dissociation of Hg from the membrane due to greater avidity of Hg towards cytosolar GSH binding. The GSH-Hg complex enters the nucleus where it dissociates to bind the metal response element (MRE) of the metallothionein (MT) gene to induce MT transcription.

Notes: Abstract Effects of Pb2+, Ni2+, Hg2+ and Se4+ on cultured human glioma U-343MG cells were investigated considering uptake, toxicity and, in combination with radiation, clonogenic cell survival. The cells were exposed to 0-100 μm of the metals for a week before the evaluation. The tests showed a tendency to toxicity with 10 μm nickel although not significant (P 〉 0.05). Selenium, lead and mercury exerted a significant toxicity (P 〈 0.05) at 2.5 μm, 10 μm and 1 μm, respectively. To challenge the clonogenic cell survival capacity, the cells were irradiated with60Co photons after being exposed to the highest nontoxic concentration of the different metals. The clonogenic cell survival tests, after irradiation, showed no significant change if the cells were exposed to 5 μm nickel, 0.5 μm selenium or 5 μm lead compared with those not exposed. Mercury, 0.1 μm, gave a relative reduction in survival compared with only irradiated cells of 58 ± 17%. Thus, only mercury affected the radiation-induced damage and/or repair. When exposed to the highest nontoxic concentrations of the different metals, the cultures did not display a significant uptake ratio (metal concentration ratio of exposed cells to control cells) of nickel (3.1 ± 3.3), only a small uptake ratio of selenium (4.0 ± 0.4), while there was a large uptake ratio of both lead (2.6 ± 1.7) x 102 and mercury (1.5 ± 0.2) x 101. The results indicated that nickel was neither especially toxic nor influenced the clonogenic cell survival after irradiation. Mercury was more toxic and also influenced the radiation sensitivity. Lead was taken up strongly but did not influence the radiation sensitivity. Selenium accumulated but gave no detectable effect on the radiation sensitivity.

Notes: Abstract Both in vitro and in vivo HgCl treatment demonstrated a remarkably high rate of progesterone synthesis accompanied by a low rate of conversion to 17β-estradiol in the oocyte of Channa punctatus. On depuration, however, there was a reversal of the steroidogenic scenario with a low progesterone and high estradiol level. The accumulation of progesterone was positively correlated with the significant increase in 3β-hydroxysteroid dehydrogenase activity in the Hg-treated fish. Thus, it was clear that at the early stage of intoxication Hg does play a role in the induction of 3β-hydroxysteroid dehydrogenase in the oocyte of fish at the spawning stage. The induction of this enzyme was found to be mediated by specific binding of Hg to the plasma membrane Na-K-ATPase (B: 14 nmoles mg protein; K 1.14 x 108 moles) and increase in the specific messenger RNA translating 3β-hydroxysteroid dehydrogenase. It is concluded that inorganic mercury is able to initiate translatable messenger RNA synthesis in fish oocyte at a low degree of intoxication.

Notes: Abstract The excretion of mercury, copper and zinc in urine, and mercury in whole blood andplasma, was determined in 40 chloralkali workers exposed to mercury vapour and 40age-matched referents. The Hg concentrations in whole blood, plasma and urine werehigher in the exposed group (35 nmol l, 30 nmol l,and 11.5 nmol mmol creatinine, respectively) in comparison with thereference group (15 nmol l, 6.3 nmol l, and 1.8nmol mmol creatinine, respectively). The urinary copper excretionwas similar in the two groups, while U-Zn excretion was significantly higher (P = 0.04)in the exposed group, median 0.83 mmol mmol creatinine versus 0.76mnmol mmol creatinine in the reference group. In a subgroup of exposedworkers with current U-Hg above 11.5 nmol lmmolcreatinine (20 mg g creatinine) the medianU-Zn was 1.1 mmol mmol creatinine. In both groups smokers had highU-Zn levels than non smokers. When both U-Hg and smoking were taken into account in alinear regression model, there was a significant association between U-Hg and U-Zn inthe combined group of exposed and referents (P = 0.002). This study indicates thatmercury exposure in humans, as in animals, causes increased urinary excretion of zinc.The mechanisms may be induced synthesis of metallothionein in the kidneys, displacementof Zn from preexisting metallothionein by Hg, or a decreased reabsorption of zinc in thekidneys owing to a slight tubular dysfunction.

Notes: Abstract Mercury concentrations were determined in muscles and feathers of 58 cock pheasants. Birds were collected from seven different polluted sites in southern Poland in 1987. The mercury concentrations in the muscle ranged from 0.010 to 0.026 mug g dry mass. The significantly highest values were found in muscle samples from Przylasek and Przemysl. The levels found in the flight feathers were higher than in breast feathers. Average concentrations in flight feathers ranged from 0.050 mug g (Przemysl) to 0.240 mug g dry mass (Przylasek). © Rapid Science 1998

Notes: Abstract Escherichia coli K1 secretes a homopolymer capsular polysaccharide (CPS) consisting of alpha 2,8 linked N-acetylneuraminic acid (poly α2,8NeuNAc). Typically poly α2,8NeuNAc is arranged in low and high order alpha helices with carboxyl and hydroxyl groups extending from the helices. Several properties of CPS such as antigenicity and metal binding can be influenced by its structural conformation. We examined the influences of metal ions and temperature on the secondary structure of polyαa2,8NeuNAc. Conformation alteration was detected by ultraviolet (UV) spectroscopy and circular dichroism (CD). The majority of metal ions tested had no detectable influence on poly a2,8NeuNAc structure. In contrast, Yb3+., Hg2+, and Cu2+ ions greatly altered the UV and CD spectra, which suggests that these ions had disrupted the alpha helical structure of poly α2,8NeuNAc. These changes were influenced by the metal ion concentration. When poly α2,8NeuNAc was incubated at temperatures ranging from 20 - 60°C, alterations in its UV absorption spectra were also seen. The most significant change occurred between 35 and 40°C. In summary, this study suggests that the higher order structure and function of bacterial CPS may be influenced by environmental factors

Notes: Abstract An amalgam filling was inserted into the first upper molar of 12 rats and the animals were killed after 3–9 months. Tissue sections from the trigeminal ganglia and the brain stem were then investigated with a sensitive histochemical technique to trace mercury deposits. Within the trigeminal ganglia, nerve cells with mercury deposits were observed in seven out of 12 rats, whereas no mercury was detected in sections from the brain stem. The mechanism responsible for the accumulation of mercury in neurons of the trigeminal ganglia is discussed.

Notes: Abstract The effects of long-term daily intake of mercury on its urinary and fecal excretion, whole-body retention, and blood concentration in male rats were observed. The animals were exposed to mercuric chloride labeled with 203Hg via drinking water for 8 weeks (5, 50 and 500 μ m Hg). 203Hg in urine, feces and blood was quantified. The blood mercury concentration did not keep a linear relationship with the increasing dose. The percentage of the total amount of mercury intake which is excreted by the fecal route in rats exposed to 500 μ m Hg was significantly lower than in those exposed to 5 and 50 μ m. The daily dose percentage of mercury excreted in urine increased with dose size. The results show that the absorption fraction of mercury through the gastrointestinal tract (30–40%) was higher than values previously reported.

Notes: Abstract The effects of long-term daily intake of low and high levels of mercury on its organ distribution and binding to renal metallothionein (MT) in male rats were studied. The animals were exposed to mercuric chloride labelled with203Hg via drinking water for 8 weeks (5, 50 and 500μ m Hg). The greatest concentration of mercury was found in the kidneys. Similar levels of radioactivity in the buccal cavity and oesophagus were also observed by whole-body autoradiography. In the kidneys, the mercury was accumulated in the outer stripe of the outer zone of the medulla and, to a minor degree, in the renal cortex. Almost 50% the total renal mercury was associated to MT. The binding capacity of the renal MT for mercury tends to saturate with increasing doses, thus this means that the capacity of the kidneys to accumulate mercury is limited.

Notes: Abstract The aim of this study was to measure the distribution of mercury, in tissues of rats exposed to amalgam over a two months period. Possible interaction of mercury with copper and zinc in organs was also evaluated. Rats were either exposed to mercury from 4 dental amalgams, or fed the diet containing powdered amalgam during two months. Mercury was measured in the kidney, liver and brain, copper in kidney and brain and zinc in kidney. The results showed significantly higher concentrations of mercury in the kidneys and the brains of rats in both exposed groups compared to control. Even after two months of exposure to mercury brain mercury concentration in rats with amalgam fillings was 8 times higher than in the control and 2 times higher than in rats exposed to amalgam supplemented diet. The highest mercury concentration in the latter group was found in the kidneys and it was 5 times higher than in the control group. We found no significant differences between mercury levels in exposed and control rat's liver. Exposure to mercury from dental amalgams did not alter the concentrations of copper and zinc in the tissues. Histopathological analyses of rats tissues did not show any pathological changes. These results support previously proposed nose-brain transport of mercury released from dental amalgam fillings.

Notes: Abstract The effects of HgCl2 on urinary excretion of Zn, Cu and metallothionein at different time intervals were observed in male Wistar rats. The rats were given a daily intraperitoneal injection of203HgCl2 (0.5 or 1.0 mg Hg kg−1) for 2 days.203Hg, Zn, Cu and metallothionein in urine, kidney and liver were analyzed. Significant increases in urinary Zn and Cu concentrations were found in HgCl2-dosed groups. Elevated urinary Zn and Cu concentrations were accompanied by an increased metallothionein excretion in urine at different time periods. Zn concentration in urine remained elevated during the entire observation period of 7 days. There were also increased concentrations of Cu and Zn in the renal cortex in one of the two exposed groups. The results indicate that urinary Cu and Zn are related to the manifestation of renal toxicity and/or the synthesis of metallothionein in kidney induced by mercury.

Notes: Abstract Pseudomonas sp isolated from the Bay of Bengal (Madras coast) contained a single large plasmid (pMR1) of 146 kb. Plasmid curing was not successful with mitomycin C, sodium dodecyl sulfate, acridine orange, nalidixic acid or heat. Transfer of mercury resistance from marinePseudomonas toEscherichia coli occurred during mixed culture incubation in liquid broth at 10−4 to 10−5 ml−1. However, transconjugants lacked the plasmid pMR1 and lost their ability to resist mercury. Transformation of pMR1 intoE. coli competent cells was successful; however, the efficiency of transformation (1.49×102 Hgr transformants μg−1 pMR1 DNA) was low.E. coli transformants containing the plasmid pMR1 conferred inducible resistance to mercury, arsenic and cadmium compounds similar to the parental strain, but with increased expression. The mercury resistant transformants exhibited mercury volatilization activity. A correlation existed between metal and antibiotic resistance in the plasmid pMR1.

Notes: Abstract Several cores were compared to elucidate the grade of mercury retention in sediments of the Baltic Sea near Oulu, Finland. The known history of the mercury discharge to waste water from a chlor-alkali plant, the primary pollution source, was compared to that in the sedimentary record. One core was dated by lead-210 and varve counts. During the past thirty years, the rate of sedimentation was up to 10 mm per year corresponding to a dry matter accumulation rate of about 3 kg m−2a−1. Under these conditions, most of the mercury reaching the sediment was retained. Correspondingly, the mercury levels in fish were considerably lower, with a delay of some five years. The present mercury content of the upper layers is some 1/4 or 1/5 that of the late 1970's, but it is still some twentyfold compared to levels at the beginning of the century. The extent to which the present mercury level in the sediment represents the various phases of industrial emission remains unsolved due to the origin of mercury in this sea area from several other sources and due to difficulties in exact core correlations from different years.

Notes: Abstract Susceptibility to inorganic mercuric ions and to organomercurials of 237 Pseudomonas aeruginosa clinical strains isolated in Mexico was determined by agar dilution tests. Resistant strains fell into two classes: i) narrow-spectrum resistant strains (27% of total isolates) resistant only to mercuric ions and to merbromin, and most grouped in pyocin type 1; and ii) broad-spectrum resistant strains (5%) with additional resistances to thimerosal, phenylmercury, methylmercury and p-hydroxymercuribenzoate, that belonged mostly to pyocin type 10. Mercurial resistant isolates showed a higher proportion of resistance to antibiotics and metals than did mercurial sensitive isolates, and broad-spectrum resistant strains had the highest frequency of resistance to antibiotics and to tellurite and arsenate.

Notes: Summary The C-reactive proteins (CRP) from both rat andLimulus were found to bind mercury (Hg) in both in vivo and in vitro conditions. CRP has high-affinity binding sites for Hg as evidenced by the loss of free sulfhydryl groups, arrested mobility in polyacrylamide gel electrophoresis, and the consumption of CRP in the serum after Hg administration. The binding was tight as it could not be inhibited either by the addition of cysteine or EDTA. By using a direct titration method it was shown that binding of Hg to CRP was saturable at a molar ratio of Hg/CRP=13.11. The possibility that CRP may act as a scavenger for Hg is discussed.

Notes: Abstract Mono-ADP-ribosylation is a protein modification that occurs at a number of different amino acids, dictated by the specificity of the individual ADP-ribosyltransferases. A specific cysteine in several guanine nucleotide-binding regulatory proteins is ADP-ribosylated by the bacterial protein pertussis toxin. Recent purification of an ADP-ribosylcysteine hydrolase and NAD:cysteine ADP-ribosyltransferase, and detection of ADP-ribose-cysteine linkages in tissue samples has raised hope that an endogenous regulatory cysteine-specific ADP-ribosylation pathway exists. A current goal is the identification of such a pathway for ADP-ribosylation of cysteine within animal cells. Interpretation of the data in this field has been complicated by recent reports that revealed several unforeseen chemical reactions of NAD and its metabolites with free cysteine and cysteine in proteins. This mini-review covers the latest understanding of the ADP-ribosylation reactions associated with cysteine, and provides a set of criteria for future research to establish positively the existence of an endogenous cysteine-specific mono-ADP-ribosyltransferase.

Notes: Abstract We determined mercury in fish (perch Perca fluviatilis) from 26 Russian lakes in three regions over four years. The lakes ranged in size from 2 to 395,000 ha, in pH from 4.5 to 10.0, and in color from 3 to 190 hazen. Sixteen lakes were drainage lakes, with permanent outlets, and 10 were seepage lakes, with no permanent inlets or outlets. The lakes were generally located in forested regions with little or no human habitation in the watershed. The three regions were geologically distinct: Precambrian Shield granitic bedrock covered with thin soil; Triassic bedrock covered with thick glacial tills; and Triassic bedrock covered with thin sediments. At each lake water samples were collected and analyzed for pH, add neutralizing capacity (ANC), major cations, and anions. Dissolved mercury species were estimated with a thermodynamic equilibrium model (MINTEQA2). Mercury content of dorsal muscle varied from 0.04 to 1.0 μg/g wet weight, and was linearly related to calculated HgCH3Cl (r20.68, p〈0.001). Lake HgCH3Cl, in turn, was related to lake pH (r2=0.86, p〈0.001). Stepwise multiple regression selected lake HgCH3Cl and color as the factors most highly related to fish mercury content, with the model accounting for 75% of the variation.

Notes: Abstract A reactive plume model that includes atmospheric chemical reactions of mercury was developed. The model simulates advective transport with the mean wind flow; horizontal and vertical turbulent diffusion; gas phase; aqueous-phase and particulate chemistry; cloud microphysics; wet deposition and dry deposition. The model was applied to the simulation of clear sky, non-precipitating cloud and precipitating cloud scenarios. No significant mercury chemistry occurs in the absence of droplets. In clouds, Hg(II) is reduced to Hg(0) with more reduction taking place in precipitating clouds than in non-precipitating clouds.

Notes: Abstract A denuder-based method for sampling and separating gaseous and participate mercury in the air is described. Two different denuder configurations developed in Vilnius, Lithuania (silver) and in Gothenburg, Sweden (gold) are compared. Data were acquired at different sampling locations around the cities of Vilnius and Gothenburg. The concentration of particulate Hg was found to be 0.04 to 0.40 ng m−3 in the Vilnius region, and 0.11 to 0.57 ng m−3 in the Gothenburg region. Intel-calibration results for the silver and gold denuders are presented. The results obtained by the two different denuder configurations and sampling set-ups display satisfactory agreement.

Notes: Abstract The concentration of mercury has been determined in assimilation organs of forest trees from 10 main industrial regions of Slovakia, four mountain forests and one military area and compared with concentration of mercury from 1356 permanent monitoring plots of Slovakia. The mercury concentration ranges for 2 yr old needles of Picea abies Karst. were (in mg kg−1): 1.249–4.402 (Rudnany iron ore mines), 0.013–0.749 (nine other industrial regions), 0.021–0.737 (four mountain forests) and 0.053–0.538 (military area). The mercury content in the soil (0–5 cm) from a mercury smelting plant ranged from 9.9 to 130 mg kg−1, and the moss Pleurozium schreberi contained 3.8–9.1 mg kg−1. The values obtained were compared with the available literature data.

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.

Notes: Abstract The water-mobilizability of mercury from contaminated floodplain soils of the river Elbe in Northern Germany was evaluated by batch extraction experiments. It was shown that only a small amount of the total mercury present (about 1% per extraction) can be mobilized by water. This mercury is transported entirely in the form of a complex bound to humic acids (HA); particulates and fulvic acids (FA) did not seem to contribute to the process. It could not be removed from the HA even at pH 1, indicating an extremely strong complexation e.g. by sulfur-containing ligands. Furthermore, the influence of pH on the mobilization was investigated. It was found that in the range of natural pH-values, there was no observable effect of pH on the mobilization of either mercury or dissolved organic carbon (DOC). This surprising finding is explained by an unexpectedly high buffering capacity of the humics, both in the acidic and in the alkaline region. Only at extreme pH-values there was deviation from this behaviour. In contrast to other heavy metals, the amount of mobilized mercury decreases at pH 〈 3; and at pH 〉 12, an increased mobilization of mercury was observed because the humics are mobilized completely, accompanied by the total amount of mercury bound to them.

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.

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.

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.

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.

Notes: We studied mercury concentrations and amounts in tissues of 19 starved young Common Tern chicks (median age 4 days) and in eggs from the same colony. Concentrations and burden were similar between eggs and newly hatched chicks. Mercury concentrations were highest in down, which contained at least 38% of the body mercury. The mercury burden of the whole body and of the tissues as well as the concentration in down increased with age and body mass, indicating the importance of down as an elimination pathway. Conversion ratios between mercury concentrations in tissues and the whole chick body varied according to the contamination level.

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.

Notes: Abstract The effects of Hg(II) on bioenergetic and oxidative status of rat renal cortex mitochondria were evaluated both in vitro, and in vivo 1 and 24 h after treatment of animals with 5 mg HgCl2/kg ip. The parameters assessed were mitochondrial respiration, ATP synthesis and hydrolysis, glutathione content, lipid peroxidation, protein oxidation, and activity of antioxidant enzymes. At low concentration (5 µM) and during a short incubation time, Hg(II) uncoupled oxidative phosphorylation while at slightly higher concentration or longer incubation time the ion impaired the respiratory chain. The rate of ATP synthesis and the phosphorylation potential of mitochondria were depressed, although inhibition of ATP synthesis did not exceed 50%. In vivo, respiration and ATP synthesis were not affected 1 h post-treatment, but were markedly depressed 24 h later. ATP hydrolysis by submitochondrial particle FoF1-ATPase was inhibited (also by no more than 50%) both in vitro, and in vivo 1 and 24 h post-treatment. Hg(II) induced maximum ATPase inhibition at about 1 uM concentration but did not have a strong inhibitory effect in the presence of Triton X-100. Oxidative stress was not observed in mitochondria 1 h post-treatment. However, 24 h later Hg(II) reduced the GSH/GSSG ratio and increased mitochondrial lipid peroxidation and protein oxidation, as well as inhibited GSH-peroxidase and GSSG-reductase activities. These results suggest that the following sequence of events may be involved in Hg(II) toxicity in the kidney: (1) inhibition of FoFl-ATPase, (2) uncoupling of oxidative phosphorylation, (3) oxidative stress-associated impairment of the respiratory chain, and (4) inhibition of ATP synthesis.

Notes: Summary The cellular mechanisms by which nephrotoxic heavy metals injure the proximal tubule are incompletely defined. We used extracellular electrodes to measure the early effects of heavy metals and other sulfhydryl reagents on net K+ and Ca2+ transport and respiration (QO2) of proximal tubule suspensions. Hg2+, Cu2+, and Au3+ (10−4 m) each caused a rapid net K+ efflux and a delayed inhibition of QO2. The Hg2+-induced net K+ release represented passive K+ transport and was not inhibited by barium, tetraethylammonium, or furosemide. Both Hg2+ and Ag+ promoted a net Ca2+ uptake that was nearly coincident with the onset of the net K+ efflux. A delayed inhibition of ouabainsensitive QO2 and nystatin-stimulated QO2, indicative of Na+, K+-ATPase inhibition, was observed after 30 sec of exposure to Hg2+. More prolonged treatment (2 min) of the tubules with Hg2+ resulted in a 40% reduction in the CCCP-uncoupled QO2, indicating delayed injury to the mitochondria. The net K+ efflux was mimicked by the sulfhydryl reagents pCMBS and N-ethylmaleimide (10−4 m) and prevented by dithiothreitol (DTT) or reduced glutathione (GSH) (10−4 m). In addition, both DTT and GSH immediately reversed the Ag+-induced net Ca2+ uptake. Thus, sulfhydryl-reactive heavy metals cause rapid, dramatic changes in the membrane ionic permeability of the proximal tubule before disrupting Na+, K+-ATPase activity or mitochondrial function. These alterations appear to be the result of an interaction of the metal ions with sulfhydryl groups of cell membrane proteins responsible for the modulation of cation permeability.

Notes: Abstract Sediments were sampled on the ‘Groot Buitenschoor’, an intertidal flat located at about 60 km from the Scheldt's river mouth. Hg concentrations ranged from 30 to 1756 ng g−1. The concentrations were strongly correlated with fine grain fraction, organic matter content and sulphide concentrations. Incubation experiments were performed in order to determine the potential methylation rate of Hg as well as biotic and abiotic factors influencing this transformation. About 1 to 2% of the added inorganic Hg is converted into methylmercury. This conversion rate points to the same equilibrium ratio as was observed in natural sediments, indicating an equilibrium between methylation and demethylation reactions in the sediments. Incubation of a sterilised sediment sample significantly decreased the methylation rate, but the methylmercury concentrations observed are still ten times higher than the natural (unspiked) sediment. This result could be due to a chemical (non-enzymatic) methylation of mercury. Sulphate reducing bacteria are the main species responsible for the methylation of Hg at this site. Addition of Na2MoO4, a specific inhibitor of sulphate reducing bacteria, decreased the methylation rate to the abiotic level (sterilised sediment). High sulphate reduction rates, however, lead to lower methylation rates. Increased formation of sulphides due to microbial sulphate reduction leads to enhanced HgS formation and this reaction competes with the methylation process. HgS is in fact the major product formed by the reaction of sulphate reducing bacteria with Hg species. About 50% of the Hg spiked to the sediments is transformed into HgS during the incubation experiments, and that compound is practically unavailable for methylation in contrast to other bound forms of Hg.

Notes: Abstract The growth ofAzolla was stimulated in different water bodies in Burdwan. It depended on the PO4−P contents of the media. Biomass, chlorophyll and tissue phosphorus content ofAzolla were positively correlated with PO4−P of the different water bodies while chlorophyll content of the fern was positively correlated with conductivity. We concluded that the water bodies of Burdwan can be utilised as sites for large scale multiplication ofAzolla for fertilization purposes in rice cultivation, despite the presence of mercury.

Notes: Abstract Water, suspended particulate matter (SPM) and sediments were collected from the Esteiro de Estarreja (Ria de Aveiro, Portugal), which receives considerable quantities of waste mercury from a chlor-alkali plant. Dissolved and particulate Hg concentrations in the effluent ranged between 4 –167 μg I−1 and 141–3144 μg g−1, respectively, at pH values of 〉10. The effluent plume undergoes significant chemical changes during advection downestuary. The evidence suggested that adsorption of dissolved Hg onto organic-rich SPM was an important process. A maximum sediment Hg concentration of 500 μg g−1 was found about 1.5 km from the discharge, as a result of the settling of Hg-rich SPM. Downestuary Hg concentrations in sediments decline to about 100 μg g−1 at the mouth of the Esteiro. The particle-water interactions are discussed in terms of the transport of dissolved and particulate Hg into the Ria de Aveiro.

Notes: Abstract The accumulation and volatilization of mercury by non-immobilized and immobilizedChlorella emersonii have been studied in batch culture systems. Reduction in the mercury concentration in the growth medium by non-immobilized cells was highly dependent on inoculum density, whilst reduction in mercury concentration by immobilized cells was rapid at all inoculum densities. Mercury accumulation by immobilized cell biomass was significantly greater than by non-immobilized cells with 106 and 105 cells bead−1 or ml−1. Volatilization of mercury by non-immobilized cell systems was greatest at higher inoculum densities, whereas more mercury was volatilized from immobilized cell systems at lower inoculum densities, and was greatest with unstocked alginate beads. Thus, in immobilized systems, mercury removal from solution is complex and involves mercury accumulation by the cells and volatilization by the matrix and cells. Further studies of mercury accumulation and volatilization by unstocked immobilization matrices revealed that agarose volatilized much less mercury than alginate or agar. The precise mechanism of mercury volatilization by alginate remains unclear, though it is thought to be a chemical effect.

Notes: Abstract Mercuric compound toxicity is well documented in animals and man for practically all organs. The recent development of cell culture techniques appeared as a novel fruitful tool in toxicology, especially in renal toxicology. Heavy metal induced renal cell alterations can be evaluated by membrane permeability damages. The present study evaluates mercuric chloride nephrotoxic effect in human kidney epithelial cells by measuring the release of two specific nephrotoxicity marker enzymes, Gamma Glutamyl Transferase (GGT) and Alkaline Phosphatase (ALP) in the culture medium. Cultured kidney epithelial cells were exposed to different HgCl2 concentrations (5, 10, 20, and 50 μg). Cultures were examined after 6 and 24 hours exposure. A good correlation between mercury dose and toxic effect, and exposure time and toxic effect was found. Enzymes were significantly released into the culture medium for 5 μg and 10 μg HgCl2/ml after 6 hours exposure; and after 24 hours exposure, enzymes were released for 5 μg/ml only. It appears that the specific tubular enzyme release in the culture medium is a good in vitro test for quantification of specific tubular damage.

Notes: Abstract Total mercury was measured in different compartments of Lake Xolotlán's (Managua) ecosystemviz., sediments, water, fish and men. Sediments from 18 localities at 5 depths inside the sediment (5, 10, 15, 20 and 25 cm) contained an average concentration of 0.62 μg Hg.g−1±0.46 at the surface, with extreme values of 0.16 and 1.8 μg.g−1. The highest concentration was observed at 25 cm depth in front of the chlor-alkaly factory (ELPESA). This maximum is associated with the period of highest production of this factory. The highest mercury concentrations in water were also measured close to the discharge of ELPESA,viz. 787 μg.Hg−1 in January and 506 μg.g−1 in April. The mean mercury concentrations measured in the muscles of the most consumed fish were 0.63 μg.g−1±0.22 (extreme values 0.22 and 1.45) inCichlasoma managuense, and 0.07 μg.g−1±0.14 (extreme values 0.004 and 0.63) inC. citrinellum. The concentration in the liver was 0.79 μg.g−1±1.29 inC. managuense and 0.62 μg.g−1±0.44 inC. citrinellum. Human hairs (n=98) of fishermen and their families contained 5.03 μg.g−1±6.2 (extreme values 0.02 and 38.22). The mean concentration measured in men was 6.22 μg.g−1±6.34 (n=58), and in women 3.39 μg.g−1±5.7 (n=40). The average mercury concentration of hairs of workers of ELPESA was 91.24 μg.g−1±156.9 (extreme values 0.46 and 724.53; n=32). We conclude that total mercury levels in the various ecosystem compartments are very high and mercury contamination in the lake may be considered as dangerous for human health.

Notes: Abstract The environmental factors governing the distribution and behaviour of total and methylmercury within mercury contaminated shallow lakes, associated with the River Yare, Norfolk, UK, have been assessed in situ through the use of sediment cores. These were analysed for microbial and chemical changes on both a temporal and spatial scale. The distribution of total mercury proved to be site dependent and related to the hydrology, sediment transport dynamics, the degree of sediment disturbance and distance from the contamination source. The core profiles revealed a subsurface peak in total mercury with maximum concentrations residing at depths of 12 and 36 cm, depending upon location, with enrichment extending down to depths in excess of 88 cm. This vertical distribution was deemed to reflect historical emission in the late 1960s and early 1970s rather than post depositional migration effects. The distribution of methylmercury was distinct from that of its inorganic counterpart since it also displayed temporal variability with highest concentrations occurring in the spring and summer. Maximum concentrations also prevailed in the uppermost 12 cm of sediment, with peak loadings at or just below the sediment/water interface and detectable levels being restricted to the upper 36 cm. The temporal and spatial behaviour of methylmercury appeared to reflect variations in redox potential, the availability of the Hg2+ ion and the nature of microbial populations.

Notes: Abstract Some results of a 2-year study of mercury pollution of the Katun river (Siberia) are summarised. Measurements of water flow, sediment transport and mercury concentrations were made and used to calculate the amount of mercury transported by the river. The distribution of transport between water phase and suspended material is calculated. It is concluded that suspended sediments play the main role in this process. The significance of different fractions of suspended sediment is also discussed.

Notes: Abstract Zinc, lead and mercury accumulation in the amphipod Hyalella azteca increases with increasing exposure to metals. During 10 week chronic toxicity tests, metal accumulated at the highest non-toxic/lowest toxic concentration was 126/136 µg Zn g−1, 7.1/16 µg Pb g−1 and 56/90 µg Hg g−1 dry weight. Concentrations of lead and mercyry in control animals were substantially lower (1.3 µg Pb g−1 and 0.4 µg Hg g−1), but concentrations of zinc in controls (74 µg g−1) were about one half those of the lowest toxic concentration. Copper was completely regulated. Accumulated copper concentrations after 10 weeks exposure to all waterborne copper concentrations resulting in less than 100% mortality were not significantly different from controls (79 µg g−1). Lead and mercury concentrations in wild H. azteca should be useful indicators of potential toxicity. Zinc accumulation may also be a useful indicator of zinc toxicity, but careful comparison with control or reference animals is necessary because of the small differences between toxic and control concentrations. Copper is not accumulated by H. azteca under chronic exposure conditions and body burdens of field animals cannot be used as an indicator of exposure or potential toxic effects. Short term exposures to copper, however, result in elevated copper concentrations in H. azteca, even at concentrations below those causing chronic toxicity. Short term bioaccumulation studies might, therefore, provide a useful indication of potential chronic copper toxicity.

Notes: Abstract The floodplain of the river Ill in the Alsace Rhine valley is used as a model to study river-groundwater exchange process. Groundwater-fed streams located in the Ill floodplain are analysed using three methods: an analytical method based on hydrochemical variables (Cl− NO3 −, PO 4 3− and NH4 +), a phytosociological one based on surveys of aquatic macrophyte communities and a biological method based on the accumulation of mercury in the moss Fontinalis antipyretica. The results show that the eutrophicated and polluted river Ill (660 µg l−1 N-NH4 +, 500 µg l−1 P-PO 4 3− , 0.3–0.4 mg Hg kg− dry weight of moss) has a negative effect on the groundwater via the bed, depending on the level of the river bed in relation to the groundwater table level. Upstream of Colmar in the south of the Alsace floodplain, the Ill waters infiltrate and contaminate the groundwater, but this is not the case further downstream. Along a stretch of the Ill (40 km) annual floods provide eutrophicated and polluted waters to the aquifer. However these waters are purified during their transfer through the soil-vegetation system. Thus in the groundwater-fed streams the water is characterised by a low level of phosphate, ammonium nitrogen and mercury (10–20 µg l−1 N-NH4 + and P-PO 4 3− , 〈 0.05 mg Hg kg−1 dry weight of moss). We demonstrate the importance of a functional floodplain in replenishing the aquifer with poor-nutrient waters. The aquatic vegetation of groundwater-fed streams reflects the water quality and thus can be used as a bioindicator and descriptor of river-groundwater exchange process.

Notes: Abstract Tubificid worms of the species Pomatothrix hammoniensis with characteristic, but hitherto unknown, deformities are described from four bays and fjords of Lake Vänern, Southern Sweden. These worms are easily recognized, since their chaetae are grotesquely enlarged distally, others are strongly serrated or deeply split, etc. These deformities are clearly associated with pollutants, since the limited areas of the lake in which they occur have long been under severe stress from industrial and municipal wastes, especially from nearby pulp mild and chlor-alkaline industries from which mercury compounds are known to emanate. Lake Vänern belongs to the most mercury-polluted major lakes of the world (Håkansson, 1976) with sediment concentrations of up to 10 000 ng Hg g−1 dry weight (natural back-ground value about 30 ng g−1 dry weight). The Kendall Rank statistical test showed a highly significant correlation (τ = 0.87; S = 14) between the incidence of deformities and mercury deposits in the lake. Zinc and cadmium are also deposited in large concentrations in the lake and there are also a variety of chlorinated organic compounds in the waste water about which we know little at present. It is speculated that synergistic effects between contaminants may be responsible for the deformities. It is likely that the observed deformities are mainly of phenotypic origin, since aberrant young specimens are uncommon.

Notes: Abstract The sediments and aquatic life of Tokuyama Bay, Japan, have been polluted by mercury effluent from chloro-alkali plants. In total, about 380 tons mercury were released from these plants and 6.64 tons of mercury were discharged into the bay in waste waters between 1952 and 1975, when mercury cells were employed. A number of surveys to study mercury pollution and the effectiveness of control measures in this area were conducted in the early 1970's by our laboroatory and other agencies. Analysis of human hair from Tokuyama Bay residents contained less mercury than those in Minamata and Agano districts, Japan, where serious mercury poisoning had occurred, but were contaminated with more mercury than those in other unpolluted areas. No occurrence of Minamata disease has been reported in the Tokuyama district. Reclamation of mercury contaminated sediments began in 1975; dredging of the bay continued until 1977. Since then, the levels of mercury contamination in sediments and aquatic life have gradually decreased. Today there are no problems with respect to mercury pollution. In this paper, we describe and discuss mercury pollution in Tokuyama Bay with regard to the following aspects of research and pollution control: the history of mercury pollution; mercury discharge and its accumulation in sediments; behaviour of mercury in sediments; mercury contamination of fish; mercury and the health of local residents; and remedial actions.

Notes: Abstract An account is given of the use of Enteromorpha to monitor zinc, cadmium, mercury and lead pollution in six estuaries and the British North Sea coast. The ranges for each element were: Zn, 19–437 µg g−1; µg g−1 Cd, 0.07–4.8 µg g−1; Hg, 0.02–0.23 µg g−1. It is suggested that tissue analysis of Enteromorpha is one of the most useful biological techniques available in estuaries for pin-pointing aqueous (as opposed to sediment) metal contamination, and also for providing data suitable for world-wide comparisons. Provisional values are given for concentrations corresponding to ‘moderate’ and ‘high’ pollution.

Notes: Abstract Seasonal and regional variations in the speciation, sediment-water partitioning, and dynamics of mercury (Hg) were studied at selected sites along the Hg-polluted Wabigoon River, and at unpolluted headwater and tributary sites, during April–September, 1979. ‘Dissolved’ and ‘particulate’ forms of Hg in the water were separated by continuous-flow centrifugation in the field. The Hg and other pollutants such as wood chips and salt had been discharged from a chlor-alkali plant and paper mill at Dryden, Ontario. Concentrations and loadings of particulate methyl mercury (CH3Hg+) and total particulate Hg (and loadings of total ‘dissolved’ Hg) were greatest during the spring flood (April-May) owing to accelerated resuspension and transport of sediments. Concentrations of ‘dissolved’ CH3Hg+, however, were highest in the summer (July–September), probably reflecting stimulation of microbial methylating activity by elevated temperatures, together with factors such as reduced levels of metal-scavenging particulates and minimal dilution by runoff. Total dissolved Hg concentrations were relatively high in September at polluted sites only, possibly because of desorption from sediments due to elevated concentrations of Cl− ions. Loadings of dissolved CH3Hg+ tended to be high in the summer but were generally depressed (suggesting sorption by suspended particles) during the major spring-flood episode in May. During July–August dissolved CH3Hg+ was a function of total dissolved Hg, suggesting rapid biomethylation of desorbed inorganic Hg; but in general dissolved and suspended CH3Hg+ levels depended on environmental variables and were unrelated to total Hg concentrations. In the summer only, total dissolved Hg was a function of dissolved Cl−. Hg species in particulates were associated with sulfides, hydrated Fe and Mn oxides, organic matter (notably high molecular weight humic and humic-Fe components), and selenium (Se); but CH3Hg+ and total Hg differed in their specific preferences for binding agents, implying that binding sites discriminate between CH3Hg+ and Hg2+ ions. CH3Hg+ was associated with sulfide and (in the spring only) with Fe oxides, whereas total Hg was associated with organic matter and Se and with DTPA- and NaOH-extractable Fe in the spring but with Mn oxide and NaOH-extractable organics in the summer. Sulfides were most abundant in May, indicating that they were eroded from bottom sediments, but Fe and Mn oxides were most abundant in the summer, probably owing to activities of filamentous iron bacteria and other micro-organisms. Particulate Hg was 98–100% nonextractable by mild solvents such as Ca acetate, CaCl2, dilute acetic acid, and (at polluted sites only) DTPA solutions, suggesting that the particulate Hg mobilized in the spring may not be readily available to organisms; association with Se and high molecular weight humic matter also supports this hypothesis. Hg probably becomes more bio-available in the summer, as suggested by the upsurge in dissolved CH3Hg+ and total dissolved Hg levels, and by increases in the solubility of particulate Hg in acetic acid, DTPA, H2O2, and NaOH solutions, as well as an increase in the relative importance of lower molecular weight fractions of NaOH-extractable Hg (in September). Regional variations in Hg speciation and partitioning reflected a gradient in sediment composition from wood chips near Dryden to silt-clay mud further downstream. Hg in silt-clay mud relatively far (〉 35 km) downstream from the source of pollution or in unpolluted areas appeared to be more readily solubilized by Cl− ions or chelators such as DTPA, more readily methylated (as indicated by downstream increases in dissolved CH3Hg+ levels and CH3Hg+/total Hg ratios), and was to a greater degree organically bound (H2O2-extractable), and thus was probably more bio-available, than Hg in wood-chip deposits. Possible explanations include weaker binding of Hg by the mud, the more finely divided state of the mud, and improved microbial growth at lower concentrations of toxic pollutants. Owing to enrichment in sulfides and Fe oxides, resuspended wood-chip sediments were especially efficient scavengers of CH3Hg+. The results indicate that in any pollution abatement plan aimed at lowering the Hg levels in the biota of lakes fed by the Wabigoon River, immobilization, removal, or detoxification of dissolved as well as particulate forms of Hg in the river would probably have to be considered. Possibly, Hg species could be ‘scrubbed’ from the river water by increasing the suspended load and by sedimentation and treatment with Hg-binding agents in special receiving basins.

Notes: Abstract In Brazil mercury is used indiscriminately at prospecting sites for gold extraction, with a consequent enormous discharge of this metal into the aquatic ecosystem. Mercury concentration was investigated in 1995, 1996 and 1997 in the sediments of ten sites along the Carmo stream, MG, Brazil, almost all of them located in prospecting areas. Analysis of mercury in the sediments of all sampling sites showed that the levels were above the tolerable limit (0.1μg g−1), except for sites P4 (1997), P6 (1995) and P9 (1995 and 1997). The results showed wide mercury contamination in an environment not limited to the active or inactive prospecting areas, but also including sites outside these areas but downstream from them. There was a high incidence of bacteria resistant to mercury in the aquatic communities of the sites under study, ranging from 27.3 to 77.1%, except for P1 (an ecological station upstream from the sites under study) in which all bacteria isolated from water were sensitive. Furthermore, the fall in mercury concentration in the sediment at site P5 was not as marked as at other sites, with a frequency of resistant bacteria of only 27.3%, possibly indicating a slower detoxification. The statistical analysis (Pearson’s correlation = − 0,527) showed that the hypothesis about negative correlation between the incidence of bacterial resistance and the total mercury concentration in this environment is supported. Hence, all these data denote a moderate association between the distribution of resistant bacteria and the presence of mercury compounds.

Notes: Abstract Seasonal and regional variations in the speciation, sediment-water partitioning, and dynamics of mercury (Hg) were studied at selected sites along the Hg-polluted Wabigoon River, and at unpolluted headwater and tributary sites, during April–September, 1979. ‘Dissolved’ and ‘particulate’ forms of Hg in the water were separated by continuous-flow centrifugation in the field. The Hg and other pollutants such as wood chips and salt had been discharged from a chlor-alkali plant and paper mill at Dryden, Ontario. Concentrations and loadings of particulate methyl mercury (CH3Hg+) and total particulate Hg (and loadings of total ‘dissolved’ Hg) were greatest during the spring flood (April-May) owing to accelerated resuspension and transport of sediments. Concentrations of ‘dissolved’ CH3Hg+, however, were highest in the summer (July–September), probably reflecting stimulation of microbial methylating activity by elevated temperatures, together with factors such as reduced levels of metal-scavenging particulates and minimal dilution by runoff. Total dissolved Hg concentrations were relatively high in September at polluted sites only, possibly because of desorption from sediments due to elevated concentrations of Cl− ions. Loadings of dissolved CH3Hg+ tended to be high in the summer but were generally depressed (suggesting sorption by suspended particles) during the major spring-flood episode in May. During July–August dissolved CH3Hg+ was a function of total dissolved Hg, suggesting rapid biomethylation of desorbed inorganic Hg; but in general dissolved and suspended CH3Hg+ levels depended on environmental variables and were unrelated to total Hg concentrations. In the summer only, total dissolved Hg was a function of dissolved Cl−. Hg species in particulates were associated with sulfides, hydrated Fe and Mn oxides, organic matter (notably high molecular weight humic and humic-Fe components), and selenium (Se); but CH3Hg+ and total Hg differed in their specific preferences for binding agents, implying that binding sites discriminate between CH3Hg+ and Hg2+ ions. CH3Hg+ was associated with sulfide and (in the spring only) with Fe oxides, whereas total Hg was associated with organic matter and Se and with DTPA- and NaOH-extractable Fe in the spring but with Mn oxide and NaOH-extractable organics in the summer. Sulfides were most abundant in May, indicating that they were eroded from bottom sediments, but Fe and Mn oxides were most abundant in the summer, probably owing to activities of filamentous iron bacteria and other micro-organisms. Particulate Hg was 98–100% nonextractable by mild solvents such as Ca acetate, CaCl2, dilute acetic acid, and (at polluted sites only) DTPA solutions, suggesting that the particulate Hg mobilized in the spring may not be readily available to organisms; association with Se and high molecular weight humic matter also supports this hypothesis. Hg probably becomes more bio-available in the summer, as suggested by the upsurge in dissolved CH3Hg+ and total dissolved Hg levels, and by increases in the solubility of particulate Hg in acetic acid, DTPA, H2O2, and NaOH solutions, as well as an increase in the relative importance of lower molecular weight fractions of NaOH-extractable Hg (in September). Regional variations in Hg speciation and partitioning reflected a gradient in sediment composition from wood chips near Dryden to silt-clay mud further downstream. Hg in silt-clay mud relatively far (〉 35 km) downstream from the source of pollution or in unpolluted areas appeared to be more readily solubilized by Cl− ions or chelators such as DTPA, more readily methylated (as indicated by downstream increases in dissolved CH3Hg+ levels and CH3Hg+/total Hg ratios), and was to a greater degree organically bound (H2O2-extractable), and thus was probably more bio-available, than Hg in wood-chip deposits. Possible explanations include weaker binding of Hg by the mud, the more finely divided state of the mud, and improved microbial growth at lower concentrations of toxic pollutants. Owing to enrichment in sulfides and Fe oxides, resuspended wood-chip sediments were especially efficient scavengers of CH3Hg+. The results indicate that in any pollution abatement plan aimed at lowering the Hg levels in the biota of lakes fed by the Wabigoon River, immobilization, removal, or detoxification of dissolved as well as particulate forms of Hg in the river would probably have to be considered. Possibly, Hg species could be ‘scrubbed’ from the river water by increasing the suspended load and by sedimentation and treatment with Hg-binding agents in special receiving basins.

Notes: Summary Owing to the international importance of the Wadden Sea for waders and waterfowl a long-term program to monitor chemical contamination of birds breeding in the Wadden Sea has been established in the early 1980s with Oystercatcher (Haematopus ostralegus) and Common Tern (Sterna hirundo) as monitor species. However, numbers of birds breeding in the area are only 10% compared to numbers of birds using it as a wintering, moulting or staging area, and little is known about contamination of those non-breeding birds. In 1993 we compared contamination levels in eggs from eight species (ShelduckTadorna tadorna; EiderSomateria mollissima; Oystercatcher; AvocetRecurvirostra avosetta; RedshankTringa totanus; Black-headed GullLarus ridibundus; Herring GullLarus argentatus; Common Tern) breeding at the island of Spiekeroog (German Wadden Sea) with those from Dunlins (Calidris alpina alpina) breeding in Northern Norway (Gamvik). It is known that many Dunlin from this area use the German Wadden Sea for staging. We analyzed contaminant levels of 21 industrial chemicals (PCBs, HCB, Moschusxylol, Octachlorstyrol, Mercury) and biocides (DDT and metabolites, HCH-Isomers, Bromocyclen). Common Tern and Herring Gull eggs reached highest Σ-PCB levels whereas mercury had the highest concentrations in eggs of Eider, Oystercatcher and Common Tern as well as Σ-DDT in eggs of Black-headed Gull. Bromocyclen could not be detected in eggs of the breeding species, whereas Moschusxylol was found in 29% of the eggs and Octachlorostyrol in 57%. Contaminant levels were in most cases above the levels given by German law for eggs used for human food but are probably not high enough to show an effect on the breeding success of the different species. In comparison to these results contaminant levels in eggs of Dunlins from Northern Norway were low and showed a similar chemical pattern as for migrating waders breeding in the Wadden Sea detected. For the first time Bromocyclen residues could be detected in bird eggs.

Notes: Abstract Bacteria were isolated from soil samples, containing high exchangeable lead concentrations, obtained from a busy freeway in the México City metropolitan area. Forty-five selected strains (86.7% Gram-positive) had a single MIC distribution pattern for lead (800–1600 µg/ml lead nitrate) and were considered lead-resistant. The isolates showed variable levels of resistance to arsenate (86.7%), chromate (66.7%), cadmium (57.6%), and mercury (31.1%) ions. Multiple inorganic-ion resistance was shown by all strains.

Notes: Abstract The recent canalisation (in the nineteen sixties) of the upper Rhine has modified the exchange processes between the river and its groundwater in the floodplain of Alsace. The Rhine seeps through its gravelly bed and in this way feeds the nearby groundwater table by means of the so-called ‘Rhine filtrates’. Using a few groundwater stream examples, this paper presents the characterization and localisation of these infiltrations. The Rhine filtrates are characterized by a high level of chloride and a low level of nitrate, these compounds being hydrological tracers, specific for the Alsatian floodplain (chloride resulting from contamination by the potash mines in the south of Alsace). They are also defined by high levels of phosphate and mercury (very localized injection). Phosphate is responsible for eutrophication which is observable in the appearance of specific aquatic macrophyte communities. Groundwater contamination by mercury is reflected by its accumulation in the bryophyte Fontinalis antipyretica sampled in ground-water streams. Thus aquatic vegetation, and more particularly the distribution of macrophyte communities, is used as an ecological descriptor of the exchange between the Rhine and its groundwater. The maximum injection of Rhine filtrates occurs between two areas of stillwater (hydroelectric dams), where the Rhine dominates its plain and where the substrate is constituted of coarse gravels.

Notes: Abstract Piscivorous birds and mammals in areas remote from point sources of Hg contamination may be exposed to dietary methylmercury concentrations that are sufficiently high to cause reproductive impairment. Common loons (Gavia immer) were observed to show aberrant nesting behavior and low overall reproductive success when Hg concentrations in prey (small fish and crayfish) averaged 〉 0.3 µg g−1 wet weight (Barr, 1986), levels known to occur in fish from many lakes in central Ontario. We used data on Hg in Ontario fish to estimate the proportion of lakes where fish small enough for loons to eat (〈 250 g) had Hg concentrations that exceeded estimated thresholds for reproductive impairment. Up to 30 % of lakes exceeded thresholds for reproductive impairment, depending on the species of fish and the threshold Hg concentrations chosen. There was a significant negative correlation between fish-Hg concentration and lake pH in most fish species examined. For these species, reductions in sulfate deposition rates are predicted to result in a corresponding reduction of lakes in Ontario having fish with potentially toxic concentrations of Hg.

Notes: Summary 1. The effects of heavy metals (Pb2+, Hg2+, and Zn2+) on synaptic transmission in the identified neural network ofHelix pomatia L. andLymnaea stagnalis L. (Gastropoda, Mollusca) were studied, with investigation of effects on inputs and outputs as wells as on interneuronal connections. 2. The sensory input running from the cardiorenal system to the central nervous system and the synaptic connections between central neurons were affected by heavy metals. 3. Lead and mercury (10−5−10−3 M) eliminated first the inhibitory, then the excitatory inputs running from the heart to central neurons. At the onset of action lead increased the amplitude of the excitatory postsynaptic potentials, but blockade of sensory information transfer occurred after 10–20 min of treatment. 4. The monosynaptic connections between identified interneurons were inhibited by lead and mercury but not by zinc. Motoneurons were found to be less sensitive to heavy metal treatment than interneurons or sensory pathways. 5. The treatment with Pb2+ and Hg2+ often elicited pacemaker and bursting-type firing in central neurons, accompanied by disconnection of synaptic pathways, manifested by insensitivity to sensory synaptic influences. 6. Zn2+ treatment also sometimes induced pacemaker activity and burst firing but did not cause disconnection of the synaptic transmission between interneurons. 7. A network analysis of heavy metal effects can be a useful tool in understanding the connection between their cellular and their behavioral modulatory influences.

Notes: Abstract 1. The effects of inorganic Hg2+ and methylmercuric chloride on the ionic currents of cultured hippocampal neurons were studied and compared. We examined the effects of acute exposure to the two forms of mercury on the properties of voltage-activated Ca2+ and Na+ currents and N-methyl-D-aspartate (NMDA)-induced currents. 2. High-voltage activated Ca2+ currents (L type) were inhibited by both compounds at low micromolar concentrations in an irreversible manner. Mercuric chloride was five times as potent as methylmercury in blocking L-channels. 3. Both compounds caused a transient increase in the low-voltage activated (T-type) currents at low concentrations (1 μM) but blocked at higher concentrations and with longer periods of time. 4. Inorganic mercury blockade was partially use dependent, but that by methylmercury was not. There was no effect of exposure of either form of mercury on the I–V characteristics of Ca2+ currents. 5. Na+- and NMDA-induced currents were essentially unaffected by either mercury compound, showing only a delayed nonspecific effect at a time of overall damage of the membrane. 6. We conclude that both mercury compounds show a relatively selective blockade of Ca2+ currents, but inorganic mercury is more potent than methylmercury.

Notes: Abstract Seasonal and regional variations in the speciation, sediment-water partitioning, and dynamics of mercury (Hg) were studied at selected sites along the Hg-polluted Wabigoon River, and at unpolluted headwater and tributary sites, during April–September, 1979. ‘Dissolved’ and ‘particulate’ forms of Hg in the water were separated by continuous-flow centrifugation in the field. The Hg and other pollutants such as wood chips and salt had been discharged from a chlor-alkali plant and paper mill at Dryden, Ontario. Concentrations and loadings of particulate methyl mercury (CH3Hg+) and total particulate Hg (and loadings of total ‘dissolved’ Hg) were greatest during the spring flood (April-May) owing to accelerated resuspension and transport of sediments. Concentrations of ‘dissolved’ CH3Hg+, however, were highest in the summer (July–September), probably reflecting stimulation of microbial methylating activity by elevated temperatures, together with factors such as reduced levels of metal-scavenging particulates and minimal dilution by runoff. Total dissolved Hg concentrations were relatively high in September at polluted sites only, possibly because of desorption from sediments due to elevated concentrations of Cl− ions. Loadings of dissolved CH3Hg+ tended to be high in the summer but were generally depressed (suggesting sorption by suspended particles) during the major spring-flood episode in May. During July–August dissolved CH3Hg+ was a function of total dissolved Hg, suggesting rapid biomethylation of desorbed inorganic Hg; but in general dissolved and suspended CH3Hg+ levels depended on environmental variables and were unrelated to total Hg concentrations. In the summer only, total dissolved Hg was a function of dissolved Cl−. Hg species in particulates were associated with sulfides, hydrated Fe and Mn oxides, organic matter (notably high molecular weight humic and humic-Fe components), and selenium (Se); but CH3Hg+ and total Hg differed in their specific preferences for binding agents, implying that binding sites discriminate between CH3Hg+ and Hg2+ ions. CH3Hg+ was associated with sulfide and (in the spring only) with Fe oxides, whereas total Hg was associated with organic matter and Se and with DTPA- and NaOH-extractable Fe in the spring but with Mn oxide and NaOH-extractable organics in the summer. Sulfides were most abundant in May, indicating that they were eroded from bottom sediments, but Fe and Mn oxides were most abundant in the summer, probably owing to activities of filamentous iron bacteria and other micro-organisms. Particulate Hg was 98–100% nonextractable by mild solvents such as Ca acetate, CaCl2, dilute acetic acid, and (at polluted sites only) DTPA solutions, suggesting that the particulate Hg mobilized in the spring may not be readily available to organisms; association with Se and high molecular weight humic matter also supports this hypothesis. Hg probably becomes more bio-available in the summer, as suggested by the upsurge in dissolved CH3Hg+ and total dissolved Hg levels, and by increases in the solubility of particulate Hg in acetic acid, DTPA, H2O2, and NaOH solutions, as well as an increase in the relative importance of lower molecular weight fractions of NaOH-extractable Hg (in September). Regional variations in Hg speciation and partitioning reflected a gradient in sediment composition from wood chips near Dryden to silt-clay mud further downstream. Hg in silt-clay mud relatively far (〉 35 km) downstream from the source of pollution or in unpolluted areas appeared to be more readily solubilized by Cl− ions or chelators such as DTPA, more readily methylated (as indicated by downstream increases in dissolved CH3Hg+ levels and CH3Hg+/total Hg ratios), and was to a greater degree organically bound (H2O2-extractable), and thus was probably more bio-available, than Hg in wood-chip deposits. Possible explanations include weaker binding of Hg by the mud, the more finely divided state of the mud, and improved microbial growth at lower concentrations of toxic pollutants. Owing to enrichment in sulfides and Fe oxides, resuspended wood-chip sediments were especially efficient scavengers of CH3Hg+. The results indicate that in any pollution abatement plan aimed at lowering the Hg levels in the biota of lakes fed by the Wabigoon River, immobilization, removal, or detoxification of dissolved as well as particulate forms of Hg in the river would probably have to be considered. Possibly, Hg species could be ‘scrubbed’ from the river water by increasing the suspended load and by sedimentation and treatment with Hg-binding agents in special receiving basins.

Notes: Summary 1. The GABAA receptor-chloride channel complex has been shown to be modulated by a variety of chemicals. Scores of chemicals with diverse and unrelated structures augment the GABA-induced chloride current, while some other chemicals suppress the current. Certain heavy metals and a variety of polyvalent cations increase or decrease the current in a potent and efficacious manner. 2. We have studied the mechanisms whereby mercury, copper, zinc, and lanthanides modulate the GABA system by whole-cell and single-channel patch clamp techniques as applied to the rat dorsal root ganglion neurons in primary culture. 3. Mercuric chloride augmented the GABA-induced current to 115% of control at 0.1 µM and to 270% of control at 100 µM. It also generated a slowly developing inward current carried by a variety of ions. In contrast, methylmercury suppressed the GABA-induced current. The potent stimulation of the GABA system by mercuric chloride is deemed important in mercury intoxication. 4. Copper and zinc suppressed the GABA-induced current with an EC50 of 16 and 19 µM, respectively. They bound to a common site on the external surface of the GABA receptor-channel complex. 5. Lanthanum augmented the GABA-induced current with an EC50 of 230 µM by increasing the affinity of the receptor for GABA. It bound to a site on or near the external surface of the GABA receptor-channel complex which is different from the sites for GABA, barbiturates, benzodiazepines, picrotoxin, and copper/zinc. 6. Six other lanthanides with larger atomic numbers also exerted the same stimulatory effect with their efficacies increasing with the atomic number. 7. Single-channel analyses have revealed that the augmentation of whole-cell current by terbium, a lanthanide, is due to three actions: an increase in the overall mean open time, a decrease in the overall mean closed time, and an increase in the overall mean burst time.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Notes: Abstract Lake Superior is called the greatest of the Great Lakes for good reason. It is the largest of the Great Lakes and also the cleanest. Although Lake Superior fish contain enough PCBs, mercury, and toxaphene to warrant fish consumption advisories, levels of toxic chemicals in Lake Superior are low compared to other Great Lakes. Because of the relatively clean waters of the lake and the basin's small industrial base, Lake Superior governments have agreed to set aside the basin as a special demonstration area with a goal of zero discharge and zero emission for nine toxic chemicals. Some of these chemicals have been associated with electric utilities. The governments recognize that electric utilities, industry and residents of the basin will all have a role in the march towards zero. The Lake Superior governments urge the electric utilities to consider 1) the proposed load reduction schedules for Lake Superior, 2) a US inventory of PCB equipment and 3) innovative solutions that bring facilities closer to zero discharge and zero emission.

Notes: Abstract Total mercury (Hg) concentrations in benthic insects from a 14 years old hydroelectric reservoir (La Grande 2) were 2 to 3 times higher than those from a reference lake and, in some groups, up to 7 times. The difference was even more pronounced for methylmercury (MeHg) concentrations, with a mean of 4 fold and a maximum of 12 fold between systems. The enrichment factors (dw) of insects, relative to the substrate in which they reside was around 3 for total Hg and 6 to 22 for MeHg. On the basis of their diet, we have classified the insects into four different trophic levels: detritivores, grazers, grazers-predators and predators. In insects collected in the reservoirs, the McHg:Hg ratio was 20–25% in dipterans-ephemeropterans (detritivores) and 30–40% in trichopterans (grazers), but 60–85% in heteropterans-coleopterans (grazers-predators) and 95% in odonates (predators). The pattern was similar in the lake with slightly lower values. In both systems, the proportion of MeHg increases in direct relation to our defined trophic levels. Given that insects are an important food source for many fish, our results suggest that they are a strong vector of McHg to these fish in hydroelectric reservoirs. The bioavailability of MeHg to insect larvae appears to depend on the nature and composition of the substrate in which they reside.

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.

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.

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.

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.

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.

Notes: This paper describes differences in the excretion of methyl mercury between male and female Quail Coturnix coturnix after a single dose. Since feathers are often used to monitor mercury pollution it is important to take into account biases in feather mercury levels that may arise as a result of mercury loss through egg-laying. Evidence is presented to support the use of bird eggs to sample for environmental mercury contamination. Birds were monitored up to twelve weeks after administration. Mercury concentrations in the kidney exceeded those in the liver which exceeded those in the pectoral muscle. Significant differences in mercury levels between male and female birds were found up to eight weeks after administration. Mercury was initially distributed through most of the internal tissues and was lost relatively slowly in a negative exponential manner. Mercury loss through excretion differed between the sexes for the first eight weeks after mercury administration. Initial mercury concentration in eggs was 3.5 μg g-1 but no mercury was detected in eggs five weeks after the dose was administered. At this point over 40% of the females' intake had been lost into the eggs.

Notes: Abstract Mercury concentrations were determined in surface soil and biota at a contaminated terrestrial field site and were used to calculate transfer coefficients of mercury through various compartments of the ecosystem based on trophic relationships. Mercury concentrations in all compartments (soil, vegetation, invertebrates, and small mammals) were higher than mercury concentrations in corresponding samples at local reference sites. Nonetheless, mercury concentrations in biota did not exceed concentrations in the contaminated surface soil, which averaged 269 μg g-1. Plant tissue concentrations of mercury were low (0.01 to 2.0 μg g-1) and yielded soil to plant transfer coefficients ranging from 3.7×10-5 for seeds to 7.0×10-3 for grass blades. Mercury concentrations in invertebrates ranged from 0.79 for harvestmen (Phalangida) to 15.5 μg g-1 for undepurated earthworms (Oligochaeta). Mean food chain transfer coefficients for invertebrates were 0.88 for herbivores/omnivores and 2.35 for carnivores. Mean mercury concentrations in target tissue (kidney) were 1.16±1.16 μg g-1 for the white-footed mouse (Peromyscus leucopus), a granivore, and 38.8±24.6 μg g-1 for the shorttail shrew (Blarina brevicauda), an insectivore. Transfer coefficients for diet to kidney were 0.75 and 4.40 for P. leucopus and B. brevicauda, respectively. A comparison of kidney mercury residues measured in this study with values from controlled laboratory feeding studies from the literature indicate that B. brevicauda but not P. leucopus may be ingesting mercury at levels that are nephrotoxic.

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.

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.

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.

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.