珠江三角洲海岸背景区大气VOCs污染特征与来源

挥发性有机物（volatile organic compounds，VOCs）是臭氧（O₃）污染防控备受关注的重要前体物.本研究基于2019年8月~2020年7月在杨梅坑生态环境监测站开展的VOCs连续在线观测数据，对珠江三角洲海岸背景区大气VOCs的时间变化规律、物种组成进行了分析，并利用受体模型和后向轨迹模型分析了VOCs的来源特征.结果表明，珠江三角洲海岸背景区人为源VOCs年平均浓度（体积分数）为9.30×10^-9，呈秋、冬季高，夏季低的特点.与一般城市和背景点的日变化规律不同，珠江三角洲海岸背景区人为源VOCs峰值主要出现在10：00~11：00；凌晨和15：00之后浓度会维持在较低水平.乙烯、丙烯、甲苯、异戊烷、异戊二烯、间/对-二甲苯、正丁烷和乙炔是影响珠江三角洲海岸背景区VOCs化学组成的关键物种.影响珠江三角洲海岸背景区的气团主要来源：省内短距离气团（25%）、海洋气团（27%）、沿海气团（31%）和省外内陆气团（17%），其中海洋气团影响下VOCs平均浓度水平最低，主要受到船舶排放与老化VOCs混合源、汽油挥发与汽车排放源影响；其他气团影响下平均较海洋气团影响下VOCs浓度升高了70.1%~148.8%，以工业源、LNG与LPG挥发源、石化源这三类源的传输影响较为突出.

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

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.