Equations describing particle transport to surfaces by diffusion, interception, impaction, and sedimentation have been used to preduct dry deposition onto five wild grass canopies. Detailed measurements of plant height and spacing, width of stems, leaves, and inflorescences, and wind data collected within and above each canopy have been applied as model input data. The resulting curves of deposition velocity versus particle diameter have then been used with size distribution data from the literature for Pb and sulfate to predict overall dry deposition. Results of these calculations suggest a wide range of dry deposition velocities of 0.05 to 1 cm/s for these species, the variation resulting from differences in surface structure and size distribution characteristics. At least 40% of the mass deposition of lead and sulfate results from the largest 10% of the airborne material.

This study presents data concerning long-term trends after neutralization of four acidified lakes in two regions on the Swedish west coast. Neutralization was achieved by a di-Ca-silicate with 52% CaO and about 11.5% MgO. Between 61 and 74% of the spread lime product dissolved during a 5 to 7 yr period. The liming increased pH, from a range of 4.5 to 5.2 to near neutral and restored alkalinity in the range of 0.2 to 0.3 meq/l and the Ca-content became 3 to 4 times higher than before liming. In two lakes transparency decreased significantly presumably due to changed phytoplankton composition. These changes successively declined due to dilution and continuous acid loading. The changes in water chemistry and development of stocked brown trout (Salmo trutta) populations initiated biotic changes. Phyto- and zooplankton communities reacted both instantly and later with successions in species composition. Changes of benthic macroinvertebrate species occurred over several years, but some pelagic species, e.g. corixids were rapidly reduced due to predation of fish. Observed changes were predominantly due to expanding populations of species present at very low abundances even during acid state of the lakes. Some organisms found during preacid state of the lakes did not establish new populations and this process may need a prolonged time with favourable conditions. Reacidification towards the end of the study period significantly stressed the brown trout population and also favoured expansion of the filamentous alga Mougeotia sp. and Sphagnum sp. that almost vanished during the first year after liming. Decreasing concentration of total P was not influenced by neutralization and may be mostly dependent on negative changes in the soils surrounding the lakes. If generally valid, this process may be an important factor for the oligotrophication of lakes in areas where acid deposition is high.

This paper presents the findings of initial investigation of the role of Spartina alterniflora Loisel. in the movement of chlorinated hydrocarbons. ('14)C-polychlorinated biphenyls and technical Aroclor(R) 1254 were used for the determinations. The findings demonstrate that Spartina accumulates ('14)C-radioactivity from sand and organic mud soil systems treated with ('14)C-PCB's. These findings also demonstrate that this plant has the capacity to accumulate ('14)C-radioactivity to levels elevated above that in the treated soil. Other experiments with Aroclor(R) 1254 demonstrate that cogeners of Aroclor(R) 1254 are present in Spartina stem and root extracts. These experiments also suggest that the chlorinated hydrocarbon uptake process is modulated by the plant and that this results in selective cogener uptake. The selectivity appears to be for the lesser chlorinated components of the commercial mixture. Overall, this study suggests that Spartina may act as an initial vector for mobilization of sediment bound chlorinated hydrocarbons to the estuarine food chain.

The combined effect of Ca and pH on fish and fisheries is considered for both laboratory and field studies. It can be seen that at concentrations less than 100 mu-eq/l, Ca can exert a significant influence on survival times of fish, and similarly in the field, the number of fishless lakes and the number of fish species found in lakes are less dependent on H('+) concentration at low concentrations of Ca than at high Ca levels. The limited historical field data available suggest that alongside any increase there may have been in surface water acidity, Ca concentrations have also increased, and the latter may have offset to some extent the deleterious biological effects of this increased acidity. Nevertheless, details of seasonal and spatial variations in these important water quality factors will need to be considered before a full understanding of the response to acidity of a fishery can be reached.

A detailed soil column leaching experiment was set up to investigate the changes in properties to a soil as a result of irrigation with an alkaline sanitary landfill leachate (pH 10.3). Chemistry of the soil was drastically altered as a consequence of the interaction. The soil was titrated from pH 5 to pH 10 and was changed from an exchangeable Mg dominated soil to an exchangeable Ca dominated soil. Magnesium was displaced by ion exchange reaction at acid pH, but at pH 10, 14.2 meq 100/g of Mg, i.e. up to three times the cation exchange capacity of Mg, was adsorbed in non-exchangeable forms at the immediate surface of the soil column by specific adsorption reactions. The leachate-treated soil was not stable on distilled water leaching. Structural breakdown led to clay dispersion and reduction in pore space, resulting in a 64 times reduction in hydraulic conductivity, 1.6 x 10('-4) to 2.5 x 10('-6) cm/s. The structural breakdown could be explained in term of the increase in Na adsorption ratio of the treated soil and the subsequent reduction in electrolyte concentration following the distilled water treatment.

Total airborne Hg as well as black particles (soot) were monitored in a number of clean air areas in Sweden. For some of the sampling sites, back trajectories for air movements at 850 mb were provided by the Norwegian Meteorological Institute. It is shown that the total Hg in air may be divided into two fractions. The most important one may be considered to be a background and is probably the result of re-emission of Hg by the ground and by natural water. The other fraction is highly dependent on wind direction in the same way as black particles. This fraction seems to be of anthropogenic origin.

Occurrence and distribution of organochlorine pesticides in the water of Lake Mariut, a brackish coastal Egyptian lake suffering from pollution, and their accumulation in the common fish Tilapia were studied. The major pesticides detected in the lake water were lindane, p, p'-DDE, o, p'-DDT, and p, p'-DDT. These compounds, except o, p'-DDT, were detected in the fish samples in exceedingly higher concentrations compared with those found in the lake water.

Numerous field and laboratory studies have shown measurable effects of soil acidification on soil processes and yet there is no indication to date that forest production is being affected even in heavily impacted areas. A discussion of possible reasons for this apparent contradiction is presented along with results of two computer simulations of possible responses to acid rain induced changes in (a) N availability and (b) soil organic matter decomposition rate. The first simulation shows a direct relationship between N availability and forest production. The second indicates the possibility for a more complex response with changes in total soil organic matter more than compensating for changes in decomposition rate and producing an inverse relationship between decomposition rate and N availability.

Effects of soil acidity on microbial decomposition of organic matter and transformation of N in an acid forest soil were investigated. In the oak-leaf-amended pH-adjusted acid soils, CO(,2) production in 14- and 150-day preincubated samples decreased by about 6 and 37%, respectively. In the control (unamended) acidified soils, reductions in CO(,2) production of 14% in 14-day preincubated samples and of 52% in 150-day samples were observed. Ammonia formation in the pH-adjusted acid soil was about 50% less than in the naturally acid soil. Increased rates of ammonification and nitrification were observed in the pH-adjusted neutral soil. Little autotrophic and heterotrophic nitrifying activity was detected in naturally acid and acidified forest soils. The rate of denitrification was rather slow in acid soils, and at greater acidities N(,2)O was the predominant end product. The abundance of N-fixing free-living bacteria was very low in acidic and acidified forest soils, and N gains by asymbiotic bacterial fixation in an acid forest ecosystem may be insignificant. These results suggest that further acidification of acid forest soils by addition of H(,2)SO(,4) or by acid precipitation may lead to significant reductions in the leaf litter decomposition, ammonification, nitrification, and denitrification and thus reduce nutrient recycling in the forest ecosystem.