Examination of a Proposed Test for Effects of Toxicants on Soil Microbial Processes.

摘要

We examined a soil toxicity test to measure CO sub 2 -effux and concentration of NH sub 4 and NO sub 2 in soil amended with a realistic substrate. Sieved silt-loam with ground alfalfa was challenged with CuCl sub 2 , CdCl sub 2 , streptomycin, phenol, or hexachlorobenzene. Efflux of CO sub 2 and inorganic N concentrations were ambiguous indicators of toxicant effects on decomposition because test substances can act as (1) pure toxicants reducing respiration and N mineralization, (2) selective toxicants releasing C and N from susceptible microbes, (3) C sources, or (4) mineral nutrient sources. Copper and Cd suppressed respiration, increased NH sub 3 , and decreased NO sub 3 . Streptomycin at all concentrations and phenol at 10 to 100 mu g/g raised CO sub 2 -efflux and NH sub 3 without affecting NO sub 3 . Phenol and Cu were used to test the effects of carbon source on soil responses; soil amended with nutrient broth showed respiration responses similar to alfalfa-amended soil but recovered faster. Broth-amended soils showed different patterns of NH sub 3 and NO sub 3 concentrations from alfalfa-amended and unamended soils. This system displays realistic responses but low sensitivity. (ERA citation 08:037358)