Evaluate and Characterize Mechanisms Controlling Transport, Fate, and Effects of Army Smokes in the Aerosol Wind tunnel

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)