Understanding primary and secondary sources of ambient oxygenated volatile organic compounds in Shenzhen utilizing photochemical age-based parameterization method.
Oxygenated volatile organic compounds (OVOCs) are key intermediates in the atmospheric photooxidation process. To further study the primary and secondary sources of OVOCs, their ambient levels were monitored using a proton-transfer reaction mass spectrometer (PTR-MS) at an urban site in the Pearl River Delta of China. Continuous monitoring campaigns were conducted in the spring, summer, fall, and winter of 2016. Among the six types of OVOC species, the mean concentrations of methanol were the highest in each season (up to 13-20ppbv), followed by those of acetone, acetaldehyde and acetic acid (approximately 2-4ppbv), while those of formic acid and methyl ethyl ketone (MEK) were the lowest (approximately 1-2ppbv). As observed from a diurnal variation chart, the OVOCs observed in Shenzhen may have been affected by numerous factors such as their primary and secondary sources and photochemical consumption. The photochemical age-based parameterization method was used to apportion the sources of ambient OVOCs. Methanol had significant anthropogenic primary sources but negligible anthropogenic secondary sources during all of the seasons. Acetone, MEK and acetic acid were mostly attributed to anthropogenic primary sources during each season with smaller contributions from anthropogenic secondary sources. Acetaldehyde had similar contributions from both anthropogenic secondary and anthropogenic primary sources throughout the year. Meanwhile, anthropogenic primary sources contributed the most to formic acid.