Deposition of Cl2 on soils during outdoor releases

Synthetic soil blends were exposed to dense chlorine (Cl2) plumes released at Dugway Proving Ground, UT, during Spring 2010 with the purpose of determining the magnitude of Cl2 deposition onto soil and assessing its potential for attenuating a high-concentration plume. Samples were exposed at varying distances from the release point to include exposure to the pooling liquid (2-3m) and dense vapor (10-17 m). Following exposure, soil samples were cored, fractionated vertically and analyzed for chloride (Cl(-)) to quantify the integrated amount of Cl2 deposited. Cl(-) was detected as deep as 4 cm in samples exposed to dense Cl2 vapor and in the deepest fractions (13 cm) of samples exposed to liquid Cl2. Chloride concentration, [Cl(-)], in the soil samples positively correlated with soil mass fractions of organic matter and water, and while their individual contributions to Cl2 deposition could not be quantitatively determined, the data suggest that organic matter was the primary contributor. [Cl(-)] results from the top vertical fractions (1.3 cm nearest the surface) were used in an analysis to determine the magnitude of deposition as a loss term under low-wind (≤ 1.6m/s) conditions. The analysis revealed up to 50% of a 1814-kg release could be deposited within 20 m from the release point for soil with high organic matter (43%) and/or water content (29%).