Pollution Characteristics and Source Analysis of Atmospheric VOCs in the Coastal Background of the Pearl River Delta

Abstract

As an important precursor of ozone, volatile organic compounds (VOCs) have attracted much attention. This study analyzed the temporal variation and composition of atmospheric VOCs in the coastal background of the Pearl River Delta, using real-time online monitoring data of VOCs obtained at the Yangmeikeng Ecological Environment Monitoring Station from August 2019 to July 2020. The major sources of VOCs were identified using a receptor model based on the PMF (positive matrix factorization) and HYSPLIT (hybrid single particle Lagrangian integrated trajectory) models. The results showed that the annual mean concentration of anthropogenic VOCs in the coastal background area of the Pearl River Delta was 9.30×10-9(volume fraction). There was obvious seasonal variation of VOCs in this area, with higher values in autumn and winter and lower values in summer. The coastal background area of the Pearl River Delta exhibited a different diurnal variation pattern to that of cities and other backgrounds. While the peak of VOCs concentration mainly occurred in the morning, from 10:00 to 11:00, concentration remained at a low level during the early morning and after 15:00. Ethylene, propylene, toluene, isopentane, isoprene, m/p-xylene, n-butane, and acetylene were the key species that affected the chemical composition of VOCs. The air masses affecting the coastal background area of the Pearl River Delta were mainly short-distance air masses from elsewhere in the province (25%), ocean air masses (27%), coastal air masses (31%), and inland air masses outside the province (17%). Among them, the average concentration of VOCs was lowest under the influence of ocean air masses, which is mainly affected by the mixed source of ship emissions and aging VOCs, gasoline volatilization, and vehicle emissions. In comparison, the concentration level of VOCs increased by 70.1% to 148.8% under the influence of other air masses. The transmission effects of industrial sources, LNG and LPG volatiles, and petrochemical sources were more prominent. Generally, the atmosphere of coastal background areas was severely affected by anthropogenic pollution, especially by air pollution masses transported from the land, while the impact of pollution by ships near shore and tourist traffic cannot be ignored.