Investigation of the atmospheric reactions of chloropicrin

An experimental and modeling study was conducted to assess the atmospheric impacts of chloropicrin emissions. Chloropicrin absorption cross sections were measured in the 270–390 nm wavelength region, and its overall photodecomposition quantum yield under simulated sunlight conditions was found to be 0.87 ± 0.26. In environmental chamber experiments, chloropicrin significantly enhanced rates of NO oxidation, O3 formation, and consumptions of alkanes and other organic reactants. This is attributed to the formation of Cl atoms and NOx in its photodecomposition. A previously developed atmospheric chemical mechanism was expanded to include chloropicrin and Cl atom reactions. It gave reasonably good simulations of the chamber experiments. This mechanism predicted that when emitted into polluted urban atmospheres, chloropicrin would have between 0.4 and 1.5 times the ozone impact of the average of emitted VOCs on a mass emitted basis. This value varied depending on environmental conditions and assumptions made concerning the photodecomposition mechanism. The data obtained in this study were inconsistent with a previous study of chloropicrinʹs photodecomposition in air, probably due to differences in the light sources employed.