Characteristics and Source Apportionment of Ambient VOCs in Spring in Liuzhou

Abstract

The objective was to investigate the characteristics and sources of ambient volatile organic compounds (VOCs) in the karst region in southwestern China. We monitored atmospheric VOCs in Liuzhou by the GC955 VOCs Online Monitoring System and analyzed the pollution characteristics, ozone formation potential (OFP), aerosol formation potential (AFP), and the positive matrix factorization (PMF) model in March 2019. The results show that ① 50 kinds of VOC components were detected during the supervised period, with an average daily concentration of 25.52×10-9 mol·mol-1, which was composed of alkanes (56.08%), alkenes (19.63%), alkynes (14.25%), and aromatics (10.04%), respectively. ② The concentration of VOCs was lower during the day and higher at night, with the highest value at 23:00. The VOC concentration was low in daytime and high at night. The peak value of VOCs with regard to diurnal variation was correlated with the time of morning and the evening traffic peak and may be influenced by various factors. ③ The contribution of alkenes, aromatics, and alkanes to OFP was 44.30%, 33.03%, and 19.96%, respectively. This indicates that the control of aromatic and olefin should prioritize alkanes. In addition, Liuzhou city is in the VOC sensitive area of O3 generation, and the reduction of VOCs had a controlling effect on O3 generation. ④ The contribution of aromatic hydrocarbons to AFP was up to 95.27%. Therefore, the improvement and control of the processes in motor vehicle exhaust emissions, solvent use, and the automobile industry and the chemical industry could effectively suppress ozone and haze pollution. ⑤ The emission sources of VOCs in spring were mainly industrial emission sources (28.34%), motor vehicle sources (25.47%), combustion sources (24.37%), solvent sources (13.28%), and plant emission sources (8.54%), respectively. This indicates that the control of industrial emission sources, motor vehicle sources, and combustion sources is the main way to control VOC pollution in Liuzhou City. Meanwhile, the olefin and aromatic hydrocarbons emitted by these emission sources should be mainly considered.