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.

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.

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.

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.

Crambe Crambe abyssinica and kenaf Hibiscus cannabinus were grown for 3 years on stripmine land in three replications of the four treatments: control (no soil amendment); added commercial fertiliser; and two levels of digested sewage sludge (42% solids at the rate of 112 and 224 metric tons ha-1). Favourable growth responses to sludge and commercial fertiliser were observed with both crops, although performance of crambe on the sludge-treated plots were adversely affected by weed competition. The yield of kenaf increased with sludge amendment of the soil. Concentrations of eight metals (Fe, An, Mn, Cu, Pb, Cr, Cd, and Hg) in crambe seed were unaffected by plot treatment, but kenaf stems appeared to accumulate higher metal concentrations with soil amendment by sewage sludge. Neither crambe seed nor kenaf stalks accumulated unusual quantities of these metals, and thus neither crop would be expected to remove significant quantities of metals from soils. Metal concentrations of both soil and sludge samples were determined to evaluate translocation of metals to both crops.