Trace organic compounds in rain—II. Gas scavenging of neutral organic compounds

Abstract

Concurrent rain and air sampling was conducted for seven rain events in Portland, Oregon during February through to April of 1984. Concentration data are presented for a number of neutral organic compounds for both the rain-dissolved phase and the atmospheric gas phase. The ambient temperature averaged 8°C. Measured gas scavenging ratios ranged from 3 for tetrachloroethene to 105 for dibutylphthalate, and were generally 3–6 times higher than those calculated from Henry's Law constant (H) values at 25°C taken from the literature. This discrepancy was due to the inappropriateness of applying 25°C H data at 5–10°C. Indeed, excellent agreement between the measured and predicted gas scavenging ratios was found for several polycyclic aromatic hydrocarbons for which temperature-dependent H data were available. These results demonstrate that equilibrium between rain and the atmospheric gas phase is attained for non-reactive neutral organic compounds.