Chemical characterization of water-soluble organic acids in PM2.5 in Beijing, China

Water-soluble organic acids are important components in atmospheric aerosols and can act as cloud condensation nuclei to potentially affect the climate. In this study, a total of 25 PM2.5 samples were collected from summer to winter in 2002–2003 at an urban area in Beijing. C2–C5 dicarboxylic acids and malic, glyoxylic and pyruvic acids were determined using a capillary electrophoresis. Oxalic acid dominated in these acids with seasonal average concentrations of 107–412 ng m–3. Malonic and succinic acids were comparable in different seasons, with seasonal average concentrations ranging from 20 to 60 ng m–3. Glutaric acid was much less abundant with an average of 10 ng m–3. The sum of these seven detected acids accounted for 3–15% of organic carbon content in PM2.5. Seasonal differences of these acids were discussed in terms of their corresponding sources. Correlations of these acids with sulfate and MSA were also investigated to interpret their possible secondary formation pathways.