Annual variations in characteristics and sources analysis of VOCs during the ozone season in the Taiyuan Basin, China, from 2020 to 2022

Abstract

As an important precursor of ozone (O₃), volatile organic compounds (VOCs) have garnered significant attention in recent years. In this study, VOCs were monitored by a real-time online instrument for three years (from April to September 2020–2022) in Jinzhong, Taiyuan Basin, and comprehensively reported the components characteristics, sources, and ozone formation potential (OFP). The interannual variation in VOCs concentration increased from 11.2 ± 8.2 ppbv in 2020 to 12.9 ± 9.2 ppbv in 2021 and 13.3 ± 8.9 ppbv in 2022. Alkanes were the major VOC groups, accounting for 55.8-64.6% of the total. However, alkenes were the primary contributors to OFP, accounting for 64.3-74.2%. After meteorological normalization, the concentrations of alkanes, alkynes, and aromatics were slightly higher than the observed concentrations, indicating that meteorological conditions favored the dispersion of pollutants. Based on positive matrix factorization (PMF) model, coking sources (28.4-30.7%), LPG/NG usage (17.9-30.5%), and vehicle exhaust (17.5-23.2%) were the major sources of VOCs during the three year observation period. The contributions of solvent usage, biogenic sources, and combustion sources increased with each year. Coking sources (47.5-52.7%) and vehicular emissions (23.2-32.3%), particularly ethylene, were major contributors to OFP. The analysis of potential source regions for VOCs concentration pointed to the southwest region (Qingxu, Wenshui, Xiaoyi, and Jiexiu) as a key emitter of VOCs. Therefore, the study recommends effective mitigation of ozone issues in Jinzhong and the downwind areas of the Taiyuan Basin by controlling coking sources and vehicular emissions, particularly targeting ethylene emissions.