M.W. Ligotke

Influence of smoke exposure on soil enzyme activities and nitrification

SummarySoil was exposed to red phosphorous/butyl rubber (RP/BR) aerosols at various relative humidities in a recirculating environmental wind tunnel. Soil microbial and enzymatic activities were measured immediately after exposure and periodically thereafter for 56 days. The nitrification potential was significantly reduced in soil amended with ammonium sulfate and exposed to RP/BR smoke, and could be related to a decline in soil pH. The rate of nitrate formation in unamended soil with time was also reduced, but by 57 days postexposure, concentrations were similat to those of unexposed controls in all but the thinnest soil lense. Soil dehydrogenase and phosphatase enzyme activities were sensitive to RP/BR smoke and in some treatments no activity was detected. The measured activities did not recover within the 56-day postexposure period and in some cases declined. Soil lense thickness was the greatest factor controlling the degree of RP/BR effects, indicating that injury to soil microbial and enzymatic activities may be surficial. Deposition of smoke particles increased with increasing relative humidity, which had a significant impact on the activities measured.

Evaluate and characterize mechanisms controlling transport, fate and effects of Army smokes in the aerosol wind tunnel: Transport, transformations, fate, and terrestrial ecological effects of red phosphorus-butyl rubber and white phosphorus obscurant smokes: Final report

Abstract : The terrestrial transport, chemical fate, and ecological effects of hexachloroethane (HC) smoke were evaluated under controlled wind tunnel conditions. Primary objectives of this research are to characterize and assess the impacts of smoke and obscurants on: 1) natural vegetation characteristic of U.S. Army training sites in the U.S.; 2) physical and chemical properties of soils representative of these training sites; and 3) soil microbiological and invertebrate communities. Impacts and dose/responses were evaluated based on exposure scenarios, including exposure duration, exposure rate, and sequential cumulative dosing. Key to understanding the environmental impacts of HC smoke/ obscurants is establishing the importance of environmental parameters such as relative humidity and wind speed on airborne aerosol characteristics and deposition to receptor surfaces. Direct and indirect biotic effects were evaluated using 5 plant species and 2 soil types. Based on a deposited foliar dose (mass loading) of 12 to 40 microgram HC/cc, equivalent to 1- to 4-h exposure to smokes at 450 mg/cu.m. air, plant toxicity responses are judged low to moderate. Relative humidity has no dramatic effect on the quality or intensity of damage. Repetitive dosing at 2- to 3-day intervals resulted in substantially more damage than indicated by the total delivered dose. The observed effects likely result from the accumulation of Zn from foliar surfaces and subsequent toxicity. Residual effects are apparent, although not severe in several of the test series. (EDC)

Evaluate and Characterize Mechanisms Controlling Transport, Fate and Effects of Army Smokes in an Aerosol Wind Tunnel. Transport, Transformations, Fate and Terrestrial Ecological Effects of Fog Oil Obscurant Smokes

Abstract : The terrestrial transport, chemical fate, and ecological effects of fog oil (FO) smoke obscurants were evaluated under controlled wind tunnel conditions. The primary objectives of this research program are to characterize and assess the impacts of smoke and obscurants on: 1) natural vegetation characteristic of U.S. Army training sites in the United States; 2) physical and chemical properties of soils representative of these training sites; and 3) soil microbiological and invertebrate communities. Impacts and dose/responses were evaluated based on an exposure scenario, including exposure duration, exposure rate, and sequential cumulative dosing. Key to understanding the environmental parameters such as relative humidity and wind speed on airborne aerosol characteristics and deposition to receptor surfaces. Direct and indirect biotic effects were evaluated using five plant species and three soil types. Fog oil enhanced the microbial activities in most of the metabolic parameters evaluated. A cumulative dose of fog oil exposure stimulated soil respiration slightly and increased nitro-bacter population in Palouse soil, and greatly increased soil enzyme activity in both Palouse and Burbank soil. Earthworm bioassays indicated no adverse effect of fog oil with exposures up to 800 micrograms/sq. cm soil. In vitro studies, where fog oil was uniformly amended to soil, showed earth- worm survival to be 100% until an exposure of approx. 3600 micrograms/sq. cm (a soil concentration of 285 micrograms FO/g) was reached.

Evaluation and characterization of mechanisms controlling fate and effects of Army smokes

The primary objective of this study was to characterize the fate and response of soil and biotic components of the terrestrial environment to aerosols, deposited brass, and brass in combination with fog oil. Important physical, chemical, and biotic aspects were investigated using an environmental wind tunnel. Air/surface deposition rates were determined for foliar and soil surfaces, both in the absence and presence of fog oil. Deposition velocities for foliage ranged from 0.1 to 1.0 cm/s at wind speeds of 2 to 10 mph, respectively. Foliar contact toxicity was assessed using five different types of terrestrial vegetation representative of Army training sites and surrounding environments. No significant foliar contact toxicity was observed for brass. The weathering and chemistry of brass aerosols deposited and amended to soils was assessed, along with the impacts of acid precipitation and moisture regimes on weathering rates. Rates of brass weathering and the fate of solubilized Cu and Zn are discussed. The influence of soil weathering processes and brass solubilization on seed germination indicated no detectable effects of brass. However, moderate toxicity effects were noted after seed germination indicated no detectable effects of brass. However, moderate toxicity effects were noted after 160 days of soil incubation. The effects were proportional to soil-loading levels. Influence of soil weathering processes and contaminant solubilization on soil microbiological activities indicated that soil dehydrogenase activity was more susceptible to impacts than was phosphatase activity or microbial biomass. Nitrifying bacteria and heterotrophic bacteria were not significantly affected by brass. Invertebrates (earthworms) associated with soil contaminated with brass were only slightly impacted, and only at loading rates >445 {mu}g/cm{sup 2}.

Evaluation of terrestrial microcosms for assessing the fate and effects of genetically engineered microorganisms on ecological processes

This project evaluates and modifies the existing US Environmental Protection Agencys Office of Pesticides and Toxic Substances (EPA/OPTS) terrestrial microcosm test system and test protocols such that they can be used to determine the environmental fate and ecological hazards of genetically engineered microorganisms (GEMs). The intact soil-core microcosm represents terrestrial ecosystems, and when coupled with appropriate test protocols, such microcosms may be appropriate to define and limit risks associated with the intentional release of GEMs. The terrestrial microcosm test system was used to investigate the survival and transport of two model GEMs (Azospirillum lipoferum and Pseudomonas sp. Tn5 mutants) to various trophic levels and niches and through intact soil cores. Subsequent effects on nutrient cycling and displacement of indigenous microorganisms were evaluated. The model organisms were a diazotrophic root-colonizing bacterium (A. lipoferum) and a wheat root growth-inhibiting rhizobacterium (Pseudomonas sp.). The transposable element Tn5 was used as a genetic marker for both microorganisms in two separate experiments. The organisms were subjected to transposon mutagenesis using a broad host-range-mobilizable suicide plasmid. The transposon Tn5 conferred levels of kanamycin resistance up to 500 ..mu..g/ml (Pseudomonas sp.), which allowed for selection of the bacteria from environmental samples. The presence of Tn5 DNA in the genome of the model GEMs also allowed the use of Tn5 gene probes to confirm and enumerate the microorganisms in different samples from the microcosms. Two types of root growth-inhibiting Pseudomonas sp. Tn5 mutants were obtained and used in microcosm studies: those that lacked the ability to inhibit either wheat root growth or the growth of other microorganisms in vitro (tox/sup /minus//) and those which retained these properties (tox/sup +/). 53 refs., 7 figs., 6 tabs.