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.

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.

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.

An important consequence of acidification is the mobilization of Al from the edaphic to the aquatic environment. Elevated Al levels in acidic waters may be toxic to fish. Eggs, larvae, and postlarvae of white suckers (Catostomus commersoni) and brook trout (Salvelinus fontinalis) were exposed in laboratory bioassays to pH levels 4.2 to 5.6 and inorganic Al concentrations of 0 to 0.5 mg/l. Aluminium toxicity varied with both pH and life history stage. At low pH levels (4.2 to 4.8), the presence of Al (up to 0.2 mg/l for white suckers; 0.5 mg/l for brook trout) was beneficial to egg survival through the eyed stage. In contrast, Al concentrations of 0.1 mg/l (for white suckers) or 0.2 mg/l (for brook trout) and greater resulted in measurable reductions in survival and growth of larvae and postlarvae at all pH levels (4.2 to 5.6). Aluminium was most toxic in over-saturated solutions at pH levels 5.2 to 5.4. The simultaneous increase in Al concentration with elevated acidity must be considered to accurately assess the potential effect of acidification of surface waters on survival of fish populations.

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.

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.