广州市冬季一次典型臭氧污染过程分析

Analysis of a Typical Ozone Pollution Process in Guangzhou in Winter

为探究广州市2020年冬季(1月)一次臭氧污染过程,分析了气象条件对臭氧污染产生的影响;运用臭氧生成潜势(OFP)和正交矩阵因子分解法(PMF)分析了影响臭氧的主要挥发性有机物(VOCs)物种和来源;通过经验动力学建模方法(EKMA)识别了臭氧生成控制区,并提出了相应的前体物减排策略.结果表明,本次臭氧污染过程中同时出现了NO_(2)超标,并且PM_(10)和PM_(2.5)浓度也处于高位,体现出和夏、秋季不同的大气复合污染特征;夜间边界层高度低(<75 m)和大气稳定度高加剧了臭氧前体物和颗粒物的累积,日间温度升高约5℃、太阳辐射增强约10%和水平风速小(<1 m·s^(-1))等气象条件加剧了光化学反应,促进了臭氧和颗粒物的生成.冬季VOCs组分以烷烃为主(占比为68.2%),且烷烃和炔烃占比较其他季节更高,但芳香烃(二甲苯和甲苯)和丙烯是臭氧生成的关键VOCs物种;源解析结果显示,VOCs的主要来源为汽车尾气(22.4%)、溶剂使用(20.5%)和工业排放(17.9%),其中溶剂使用的OFP最高;臭氧本地生成主要受VOCs控制,前体物VOCs和NO_(x)按比例3∶1进行削减较为合理.研究探索了冬季臭氧污染的成因,为开展重污染季节O_(3)和PM_(2.5)协同控制提供科学支撑.

This study focused on an ozone pollution event occurring in winter(January) in Guangzhou. Various influencing factors were analyzed, including various atmospheric trace gases, meteorological conditions during the whole pollution process, as well as the characteristics of the main Oprecursor volatile organic compounds(VOCs). The main sources of VOCs and the Oformation regime were analyzed using an array of tools: the ozone potential formation(OFP), positive matrix factorization(PMF) model, and empirical kinetic modeling approach(EKMA) curve. Feasible strategies for Ocontrol were suggested. The results showed that Oand NOexceeded the corresponding standards in this winter pollution event, when the concentrations of PMand PMwere also high, differing from the air pollution characteristics in summer and autumn. Low boundary layer height(<75 m) and high atmospheric stability at night exacerbated the accumulation of ozone precursors and fine particles. Meteorological conditions such as the increased daytime temperature(5℃), stronger solar radiation(10%), and low horizontal wind speed(<1 m·s^(-1)) favored photochemical reactions and promoted the formation of ozone and fine particles. VOCs were mainly composed of alkanes, and the proportions of alkanes and alkynes in winter were higher than those in the other seasons. Aromatics(xylenes and toluene) and propylene were the key VOCs species leading to Oformation. The main VOCs sources were vehicle exhaust(22.4%), solvent usage(20.5%), and industrial emissions(17.9%);however, the source with highest OFP was identified as solvent usage. Oformation in this event was in the VOCs-limited regime, and reducing Oprecursors in the VOCs/NOratio of 3∶1 was effective and feasible for Ocontrol. This study explored the causes of an Opollution event in winter, which will serve as reference for the synergistic control of O_(3)and PM_(2.5)in heavy pollution seasons.