2021年夏季新乡市城区臭氧超标日污染特征及敏感性

Ozone Pollution Characteristics and Sensitivity During the Ozone Pollution Days in Summer 2021 of Xinxiang City

基于2021年6~8月新乡市市委党校站点观测的挥发性有机物(VOCs)、常规空气污染物和气象参数,采用基于观测的模型(OBM)对臭氧(O_(3))超标日的O_(3)敏感性和前体物的管控策略进行了研究.结果发现,O_(3)超标日呈现高温、低湿和低压的气象特征.在臭氧超标日,O_(3)及其前体物的浓度均有上升.臭氧超标日的VOCs最高浓度组分为含氧挥发性有机物(OVOCs)和烷烃,臭氧生成潜势(OFP)和·OH反应性最大的VOCs组分为OVOCs.通过相对增量反应性(RIR)分析,新乡6月O_(3)超标日臭氧生成处于VOCs控制区,7月和8月处于VOCs和氮氧化物(NOx)协同控制区,臭氧生成对烯烃和OVOCs最为敏感.6月各前体物的RIR值在一天中会发生变化,但始终保持为VOCs控制区;7月和8月在上午为VOCs控制区,中午为协同控制区,下午分别为协同控制区和NOx控制区.通过模拟不同前体物削减情景,结果表明削减VOCs始终有利于管控臭氧,而削减NOx对管控O_(3)作用不大,还有导致O_(3)升高的风险.

This study was based on the observation of volatile organic compounds(VOCs),conventional gaseous air pollutants,and meteorological parameters observed at the Xinxiang Municipal Party School site from June to August 2021.The ozone(O_(3))characteristics and sensitivity of O_(3)pollution days and the control strategy of its precursors were studied using an observation-based model(OBM).It was found that the meteorological conditions were characterized by high temperature,low humidity,and low pressure in O_(3)-pollution days.The concentrations of O_(3)and its precursors all increased in the O_(3)pollution days.Oxygenated volatile organic compounds(OVOCs)and alkanes were the highest-concentration components of VOCs on O_(3)pollution days in Xinxiang,and OVOCs had the highest ozone formation potential(OFP)and hydroxyl(·OH)reactivity.According to the relative incremental reactivity(RIR)analysis,during the O_(3)pollution days in Xinxiang,O_(3)sensitivity was in the VOCs-limited regime in June and in the transitional regime in July and August.Ozone production was more sensitive to alkenes and OVOCs.The RIR values of the precursors in June changed throughout the day,but O_(3)sensitivity remained the VOCs-limited regime.In July and August,O_(3)sensitivity was the VOCs-limited regime in the morning,transitional regime at noon,transitional and NOx-limited regime,respectively in the afternoon.By simulating different precursor-reduction scenarios,the results showed that the reduction of VOCs was always beneficial to the control of O_(3),whereas the reduction of NOx had little effect on the control of O_(3)and a risk of increasing O_(3).