Four- and Five-Carbon Dicarboxylic Acids Present in Secondary Organic Aerosol Produced from Anthropogenic and Biogenic Volatile Organic Compounds

To better understand precursors of dicarboxylic acids in ambient secondary organic aerosol (SOA), we studied C4-C9 dicarboxylic acids present in SOA formed from the oxidation of toluene, naphthalene, alpha-pinene, and isoprene. C4-C9 dicarboxylic acids present in SOA were analyzed by offline derivatization gas chromatography-mass spectrometry. We revealed that C4 dicarboxylic acids including succinic acid, maleic acid, fumaric acid, malic acid, DL-tartaric acid, and meso-tartaric acid are produced by the photooxidation of toluene. Since meso-tartaric acid barely occurs in nature, it is a potential aerosol tracer of photochemical reaction products. In SOA particles from toluene, we also detected a compound and its isomer with similar mass spectra to methyltartaric acid standard; the compound and the isomer are tentatively identified as 2,3-dihydroxypentanedioic acid isomers. The ratio of detected C4-C5 dicarboxylic acids to total toluene SOA mass had no significant dependence on the initial VOC/NOx condition. Trace levels of maleic acid and fumaric acid were detected during the photooxidation of naphthalene. Malic acid was produced from the oxidation of alpha-pinene and isoprene. A trace amount of succinic acid was detected in the SOA produced from the oxidation of isoprene.

Automated summary

The study focused on the presence of C4-C9 dicarboxylic acids in ambient secondary organic aerosol formed from the oxidation of toluene, naphthalene, alpha-pinene, and isoprene. Various dicarboxylic acids were identified, with toluene oxidation producing a range of C4 dicarboxylic acids.