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  • 1
    Electronic Resource
    Electronic Resource
    Leaf surface properties of Norway spruce needles exposed to sulphur dioxide and ozone in an open-air fumigation system at Liphook (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 18 (1995), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Samples of current-year and 1-year-old foliage were taken from Norway spruce (Picea abies (L.) Karst.) trees in April 1991, 4 months after a 3–4 year controlled fumigation with O3 and SO2 in the open at Liphook, south-east England. Trees were grown in seven plots, and treated in a factorial design with three levels of SO2 and two levels of O3 (ambient and c. 1.3 × ambient), with an extra ambient air plot. All statistical analyses were made on plot means.Leaf wettability, as measured by the contact angle of water droplets, was significantly affected by needle age and by SO2 treatment (P≤0–05. in older needles, decreasing with increasing SO2 concentration. There was no effect of O3 on wettability, and no effect of any treatment on amounts of surface wax extracted by immersion of needles in chloroform. Electrolyte leakage rates from detached current-year needles were not affected by prior exposure to O3, but decreased significantly (P= 0.034) with increasing exposure to SO2. There was no detectable effect of fumigation on the rate of water loss from detached needles. Similarly, there was no effect of fumigation on the dry weight/fresh weight ratio of needles. The total sulphur content of needles increased significantly (P≤0.0001) with exposure to SO2 and with needle age. Amounts of water-extractable sulphate, however, varied greatly among plots, but with no pattern with respect to fumigation treatment.It is concluded that leaf wettability and electrolyte leakage rates may be good indicators of the persistent effects of SO2 on Norway spruce growing in the open air, and that the observed changes in leaf surface properties in response to SO2 fumigation have implications for the processes, both biotic and abiotic, that occur on leaf surfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1995.tb00363.x
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  • 2
    Electronic Resource
    Electronic Resource
    The interpretation of leaf-drying curves (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 19 (1996), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A theoretical expression for the rate of water loss through the surface of excised leaves has been derived so that curves fitted to experimental data can be used to infer physical properties of the leaves such as the solute concentration and the conductance for water vapour loss. The use of the equations is illustrated by reference to data from an experiment in which red spruce (Picea rubens Sarg.) and Norway spruce (P. abies(L.) Karst.) seedlings were grown under five different regimes: outdoors (±50% shade), in a greenhouse (±50% shade) and in controlled-environment chambers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1996.tb00258.x
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  • 3
    Electronic Resource
    Electronic Resource
    Rainfall acidity in northern Britain (1982)
    [s.l.] : Nature Publishing Group
    Nature 297 (1982), S. 383-385 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The term 'acid rain' refers to rain more acid than water in equilibrium with atmospheric concentrations of carbon dioxide (pH 5.6, 2.5 jxEquiv. H+1"1). Although several factors are involved, the areas in Scandinavia with significantly altered fish populations are subject to rainfall acidities of ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/297383a0
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  • 4
    Electronic Resource
    Electronic Resource
    Measurement of the NO + O3 Reaction Rate at Atmospheric Pressure Using Realistic Mixing Ratios (1998)
    Springer
    Journal of atmospheric chemistry 29 (1998), S. 299-314 
    Details
    ISSN: 1573-0662
    Keywords: rate constant ; temperaturedependence ; troposphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Accurate values for the rate and temperature dependence of the reaction NO + O3 → NO2 + O2 are important in the chemical modelling of photochemical processes in the atmosphere. Previous measurements have been made at low total pressures and/or with very large mixing ratios relative to those observed in the atmosphere. In this study the reaction rate has been measured using a novel approach under tropospheric conditions of temperature and pressure, and at tens of ppb (mixing ratios of 1 in 108) between 263 and 328 K. The resultant Arrhenius expression (k=Ae-Ea/RT) gives a larger activation energy (Ea/R=1670 ± 100) than the recommended literature value (Ea/R=1400 ± 200), and a larger pre-exponential factor (A=5.1 ± 1.6 × 10-12 cf. recommended A=2.0 × 10-12), but the second-order rate constant at 298 K (1.90 × 10-14 molecules cm-3 s-1 ± 10%) is similar to the recommended value. The results confirm a lack of pressure dependence of the reaction, but were made over too small a range in temperature to address the issue of curvature of the simple Arrhenius expression.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005936016311
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  • 5
    Electronic Resource
    Electronic Resource
    Systematic Biases in Measurement of Urban Nitrogen Dioxide using Passive Diffusion Samplers (2000)
    Springer
    Environmental monitoring and assessment 62 (2000), S. 39-54 
    Details
    ISSN: 1573-2959
    Keywords: air monitoring ; chemical model ; nitrogen oxides ; passive sampler
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Measurement of nitrogen dioxide using passivediffusion tube over 22 months in Cambridge, U.K. areanalysed as a function of sampler exposure time, andcompared with NO2 concentrations obtained from aco-located chemiluminescence analyser. The averageratios of passive sampler to analyser NO2 at acity centre site (mean NO2 concentration 22 ppb)are 1.27 (n = 22), 1.16 (n = 34) and 1.11 (n = 7) forexposures of 1, 2 and 4-weeks, respectively. Modellingthe generation of extra NO2 arising from chemicalreaction between co-diffusing NO and O3 in thetube gave a ratio (modelled/measured) of 1.31 for1-week exposures. Such overestimation is greatest whenNO2 constitutes, on average, about half of totalNOx (= NO + NO2) at the monitoring locality.Although 4-week exposures gave concentrations whichwere not significantly different from analyserNO2, there was no correlation between thedatasets. At both the city-centre site and anothersemi-rural site (mean NO2 concentration 11 ppb)the average of the aggregate of four consecutive1-week sampler exposures or of two consecutive 2-weeksampler exposures was systematically greater than fora single 4-week exposure.The results indicate two independent and opposingsystematic biases in measurement of NO2 bypassive diffusion sampler: an exposure-timeindependent chemical overestimation with magnitudedetermined by local relative concentrations of NO andO3 to NO2, and an exposure-time dependentreduction in sampling efficiency. The impact of theseand other potential sources of systematic bias on theapplication of passive diffusion tubes for assessingambient concentrations of NO2 in short (1-week)or long (4-week) exposures are discussed in detail.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006249016103
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  • 6
    Electronic Resource
    Electronic Resource
    Effects of air pollution on the chemistry of surface waxes of scots pine (1986)
    Springer
    Water, air & soil pollution 31 (1986), S. 393-399 
    Details
    ISSN: 1573-2932
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Surface waxes from Scots pine (Pinus sylvestris) trees from the same provenance, but growing at a polluted and an unpolluted site, were sampled for each year class of needles at least twice during the year.There was no change in the amount of wax per unit area over the lifetime of the needles, but less wax was obtained from trees at the polluted site.Quantitative thin-layer chromatography of the wax gave several components which decreased in amount with time. They were identified as long-chain alcohols and ketones, and comprised only a small proportion of the total wax. The rate of change was greater in polluted air than in clean air, and there was a strong correlation with measured contact angles for water droplets. The degradation in structure observed by scanning electron microscopy may be associated with particular chemical components of the surface wax.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00630856
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  • 7
    Electronic Resource
    Electronic Resource
    Throughfall deposition of ammonium and sulphate during ammonia fumigation of a scots pine forest (1995)
    Springer
    Water, air & soil pollution 85 (1995), S. 2247-2252 
    Details
    ISSN: 1573-2932
    Keywords: throughfall ; dry deposition ; sulphur dioxide ; ammonia ; co-deposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The estimation of the dry deposition of sulphur dioxide to forests is confounded by the possibility of co-deposition of SO2 with NH3 on leaf surfaces. A sector of Scots pine forest was selectively fumigated with NH3 to give average concentrations up to 15 ppbV (nL L−1) above ambient, in order to test the hypothesis that increased air concentrations of NH3 would enhance the dry deposition of SO2, and the consequent amounts of SO4 2− measured in throughfall below the forest canopy. Ammonia gas, generated by evaporation of concentrated aqueous solution, was released above the canopy in proportion to wind speed when the wind direction was between south and west. Concentrations of NH3 at canopy height were measured using passive diffusion tubes; throughfall was preserved with thymol and measured weekly. Meteorological data and SO2 concentrations were recorded continuously, to permit the estimation of dry deposition input. Deposition of NH4 + in throughfall over 8 months was increased by up to 40 meq m−2 relative to ‘control’ sites upwind of the NH3 release point, with largest values closest to the release point. Deposition of SO4 2− in throughfall was also enhanced in the fumigated area, by up to 20 meq m−2, even though average ambient SO2 concentrations were 2.3 ppbV. The results are discussed in terms of the factors controlling SO2 deposition on forest surfaces, the development of appropriate deposition models, and their relevance to using throughfall as an estimate of total S deposition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01186168
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  • 8
    Electronic Resource
    Electronic Resource
    Studies of Oxidant Production at the Weybourne Atmospheric Observatory in Summer and Winter Conditions (1999)
    Springer
    Journal of atmospheric chemistry 33 (1999), S. 111-128 
    Details
    ISSN: 1573-0662
    Keywords: Weybourne Atmospheric Observatory ; ozone production ; peroxy radicls ; nitrogen oxides ; peroxy acetyl nitrate ; oxidant (O3+NO2)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Detailed studies have been made of the behaviour of gases and radicals involved in the production of oxidants at the Weybourne Atmospheric Observatory in both summertime and wintertime conditions. In June 1995 the range of meteorological conditions experienced varied such that ozone destruction was observed in clean northerly air flows reaching Weybourne down the North Sea from the Arctic, and ozone production was observed in varying degrees in air with different loadings of nitrogen oxides and other precursors. The transition point for ozone destruction to ozone production occurred at a nitric oxide concentration of the order of 50 pptv. Plumes of polluted air from various urban areas in the U.K. were experienced in the June campaign at Weybourne. Quantitative studies of ozone production in a plume from the Birmingham conurbation on 18 June 1995 showed that the measurement of ozone production agreed well with calculated production rates from the product of the nitric oxide and peroxy radical concentrations (r2=0.9). In wintertime conditions (October–November 1994) evidence was also found for oxidant production, defined as the sum of O3+NO2. At this time of year the peroxy radical concentrations (RO2) were much lower than observed in the summertime and the nitric oxide (NO) was much higher. There was still sufficient RO2 during the day, however, for a slow accumulation of oxidant. Confirmatory evidence for this comes from the diurnal co-variance of (O3+NO2) with PAN, an excellent tracer of tropospheric photochemistry. The same type of covariance occurs in summer between PAN and ozone. The results obtained in these series of measurements are pertinent to understanding the measures necessary to control production of regional photochemical air pollution, and to the production of ozone throughout the northern hemisphere in winter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005969204215
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  • 9
    Electronic Resource
    Electronic Resource
    Processing of oxidised nitrogen compounds by passage through winter-time orographic cloud (1996)
    Springer
    Journal of atmospheric chemistry 24 (1996), S. 211-239 
    Details
    ISSN: 1573-0662
    Keywords: air pollution ; field study ; modelling ; atmospheric chemistry ; troposphere ; clouds ; nitrogen compounds ; NO x ; NO3 ; N2O5 ; NO3 - ; NO2 - ; HNO3 ; HNO2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Four case studies are described, from a three-site field experiment in October/November 1991 using the Great Dun Fell flow-through reactor hill cap cloud in rural Northern England. Measurements of total odd-nitrogen nitrogen oxides (NO y ) made on either side of the hill, before and after the air flowed through the cloud, showed that 10 to 50% of the NO y , called NO z , was neither NO nor NO2. This NO z failed to exhibit a diurnal variation and was often higher after passage through cloud than before. No evidence of conversion of NO z to NO3 - in cloud was found. A simple box model of gas-phase chemistry in air before it reached the cloud, including scavenging of NO3 and N2O5 by aerosol of surface area proportional to the NO2 mixing ratio, shows that NO3 and N2O5 may build up in the boundary layer by night only if stable stratification insulates the air from emissions of NO. This may explain the lack of evidence for N2O5 forming NO3 - in cloud under well-mixed conditions in 1991, in contrast with observations under stably stratified conditions during previous experiments when evidence of N2O5 was found. Inside the cloud, some variations in the calculated total atmospheric loading of HNO2 and the cloud liquid water content were related to each other. Also, indications of conversion of NO x to NO z were found. To explain these observations, scavenging of NO x and HNO2 by cloud droplets and/or aqueous-phase oxidation of NO2 - by nitrate radicals are considered. When cloud acidity was being produced by aqueous-phase oxidation of NO x or SO2, NO3 - which had entered the cloud as aerosol particles was liberated as HNO3 vapour. When no aqueous-phase production of acidity was occurring, the reverse, conversion of scavenged HNO3 to particulate NO3 -, was observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00210284
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  • 10
    Electronic Resource
    Electronic Resource
    Rainfall acidity in northern Britain — Exploring the data (1986)
    Springer
    Water, air & soil pollution 30 (1986), S. 239-244 
    Details
    ISSN: 1573-2932
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Daily rainfall pH measurements from a site in south Scotland were found to have a bimodal distribution. Similarly, monthly data from a network of bulk rain collectors in northern Britain gave bimodal distributions. Sites with an annual average pH of 4.7 had occasional monthly pH values of pH 4 or less. The annual average pH was a poor indicator of the frequency of such acidic periods, and may not be a good indicator of potential effects. Data from a daily and monthly collector at the same site are compared and the discrepancies discussed. Daily pH measurements gave significantly greater acidities than monthly pH measurements, but these differences were small for months with rain-weighted pH 〈 5.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00305194
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