高温极端天气影响下的成都平原一次典型臭氧污染过程分析

Analysis of a Typical Ozone Pollution Process in the Chengdu Plain Under the Influence of High Temperature Extremes

基于气象再分析资料及成都市芳邻路站点大气综合观测数据,采用PMF、PSCF和CWT等方法对成都市2022年发生的一次持续性臭氧(O_(3))污染过程进行分析.结果表明,本次污染过程持续了18 d,O_(3)浓度最大8 h平均值第90百分位数达242.62μg·m^(-3).由于副热带高压强大且长时间控制四川,气温屡创新高,成都市日最高温度达到41.63℃,异常持久高温强辐射为O_(3)生成提供有利气象条件.面对持续高温干旱灾害性天气影响,四川电网面临极其严峻的保供形势,污染期间四川省多地出现不同程度的让电于民.分析对比让电前后空气质量科研数据发现:(1)让电后O_(3)前体物NO_(2)和VOCs浓度均有不同程度降低,O_(3)浓度削峰效果较好;(2)让电后大气反应活性OFP和L_(·OH)中烷烃和芳香烃贡献率均下降,但贡献前10物种贡献率较让电前提高,主要是因为高温所致植物排放异戊二烯增加;(3)从源解析结果来看,让电前后移动源、工业源和油气挥发源贡献率基本不变,天然源贡献率上升,溶剂源贡献率下降;(4)让电前成都近郊短距离传输叠加眉山一带传输对成都有影响,强潜在源位于主城区偏东区域,让电后潜在源区域缩小、强潜在源弱化、影响减弱,由此可见联防联控对成都市O_(3)污染防治作用较大.

Based on meteorological reanalysis data and comprehensive atmospheric observation data from the Fanglin Road site in Chengdu,the positive matrix factorization(PMF),potential source contribution function(PSCF),and concentration weighted trajectory(CWT)methods were used to analyze a continuous ozone pollution process in Chengdu in 2022.The results showed that the process lasted 18d,with a maximum 8h mean 90th percentile O_(3) concentration of 242.62µg·m-3.Owing to the strong and prolonged control of Sichuan by the subtropical high pressure,temperatures reached record highs,with a daily maximum temperature of 41.63℃in Chengdu.The unusually high and persistent temperatures and strong radiation provided favorable meteorological conditions for ozone production.In the face of the catastrophic effects of persistent high temperatures and drought,the Sichuan power grid faced an extremely challenging situation to maintain supply.During the pollution period,power restrictions of varying degrees occurred in many parts of Sichuan province.In this study,we found that:①concentrations of the ozone precursors NO_(2) and VOCs were reduced to varying degrees after the power restriction,and the O_(3) concentrations had a good peak-shaving effect.②The proportion of alkanes and aromatic hydrocarbons in the atmospheric reactivity ozone formation potential(OFP)and·OH radical loss rate(L_(·OH))decreased after the power restriction,but the proportion of the top ten contributing species increased compared with that before the power restriction,mainly due to the increase in isoprene emission from plants caused by high temperature.③From the source analysis results,the contribution of mobile sources,industrial sources,and oil and gas volatile sources remained the same before and after the power restriction,whereas the contribution of natural sources increased and that of solvent sources decreased.④Before the power restriction,the short-range transmission in the suburbs of Chengdu and the transmission around Meishan had an impact on Chengdu;however,after the power restriction,the potential source area was narrowed,the strong potential source weakened,and the impact weakened,which indicated that joint prevention and control had a greater effect on ozone pollution prevention and control in Chengdu.