Terrestrial Microcosm Evaluation of Two Army Smoke-Producing Compounds

An intact soil-core microcosm and static exposure system were used to evaluate the potential ecological effects of two obscurant smokes--red phosphorus/butyl rubber (RP/BR) and white phosphorus/felt (WP/F), used by the U.S. Army in training exercises. Three plant species (white sweetclover, perennial rye-grass, and wheat) where chosen for preliminary and microcosm tests, because they have wide geographic distributions, can be used to reclaim disturbed ground, are different physiologically and morphologically, and were shown to be capable of field representative growth in the small surface area of the microcosms. The preliminary stress-ethylene tests indicated that extremely high doses of either smoke would be required to elicit a response in the microcosm test. Minor ecosystem effects were detected only at the highest smoke concentration, including increased nutrient (Ca) loss in leachate, increased (wheat) or decreased (sweetclover) biomass yield, and increased element (A1, As, Pb, and P) uptake in plant tissue. Even the highest smoke concentrations did not affect soil microorganism respiration. No negative ecological effects of either smoke were detected at smoke concentrations equal to or below 600 mg/cubic meter, even for semiweekly exposures over an 8-week period. It was concluded that deployment of these two smokes at or below the above concentration and frequency was possible without significant problems to most terrestrial systems.