Seasonal variation and origins of dicarboxylic acids in the marine atmosphere over the western North Pacific

Abstract

Concentrations of homologous (C2–C11) dicarboxylic acids were measured in the atmosphere over Chichi‐jima Island (27°04′N, 142°13′E), western North Pacific, from April 1990 to November 1993. The monthly averaged concentrations of straight‐chain C2–C7 dicarboxylic acids, and some branched, keto‐, and unsaturated dicarboxylic acids showed a maximum in winter to spring and a minimum in the summer season. In contrast, straight‐chain C8–C11 dicarboxylic acids showed an opposite trend with a maximum in spring to summer. Principal component analysis revealed that there is a source characterized by a strong contribution of C2–C7 dicarboxylic acids, phthalic acid, some keto‐dicarboxylic acids, and unsaturated‐dicarboxylic acids, whereas there seems to be another source(s) for the C8–C11 dicarboxylic acids. A combined model of backward trajectories and emission inventories was used to better understand the sources and source regions of the dicarboxylic acids. The results show that concentrations of various C2–C7 dicarboxylic acids in the western North Pacific atmosphere are largely controlled by their emissions and/or their precursor emissions from anthropogenic sources in the Asian continent, followed by long‐range atmospheric transport. On the other hand, longer‐chain dicarboxylic acids cannot be explained by long‐range atmospheric transport from a continental region, which implies emissions and/or formation from natural sources, possibly from the ocean.