Source region identification and source apportionment of volatile organic compounds in the Tokyo Bay coastal area, Japan

Abstract

Alkenes and aromatics significantly contribute to the photochemical reactions in the Kanto Region, where the level of ozone frequently exceeds the level for photochemical smog warnings in summer. The major aromatic sources have been cataloged in the Pollutant Release and Transfer Register (PRTR) database in Japan; however, the major alkene sources are not included. We investigated the hourly variations in the volatile organic compound (VOC) concentrations at four sampling sites in the Tokyo Bay coastal area, which has a variety of VOC sources, including the petrochemical industry, chemical facilities, iron–steel plants, and refineries. The 116-component VOC data were used to conduct a positive matrix factorization (PMF) analysis to apportion the VOC sources; then, the source regions were estimated by combining the concentration ratios of the factors with the wind direction data. We used the hourly VOC data for the PMF analysis because alkenes are short-lived. Six factors were estimated using the PMF method and identified as liquefied petroleum gas + industry, aged air mass, fuel evaporation, petrochemical industry, aromatics, and solvent usage. The mean contribution ratios of these six factors were 8.9%, 19.9%, 9.3%, 10.4%, 9.9%, and 14.0%, respectively, whereas the mean contribution ratio of the residual was 27.7%. By combining the alkene concentration and factor contribution ratios with the wind direction, the petrochemical industry in the Kawasaki coastal area was demonstrated to be the main alkene source. In addition, the petrochemical industry makes the largest contribution to ozone production according to the OH radical loss rates of the six factors.

Keywords

• Volatile organic compounds
• Alkene
• Diagnostic ratios
• Positive matrix factorization
• Petrochemical industry
• OH radical loss rate