Understanding ozone(O_(3))formation regime is a prerequisite in formulating an effective O_(3)pollution control strategy.Photochemical indicator is a simple and direct method in identifying O_(3)formation regimes.Most...Understanding ozone(O_(3))formation regime is a prerequisite in formulating an effective O_(3)pollution control strategy.Photochemical indicator is a simple and direct method in identifying O_(3)formation regimes.Most used indicators are derived from observations,whereas the role of atmospheric oxidation is not in consideration,which is the core driver of O_(3)formation.Thus,it may impact accuracy in signaling O_(3)formation regimes.In this study,an advanced three-dimensional numerical modeling system was used to investigate the relationship between atmospheric oxidation and O_(3)formation regimes during a long-lasting O_(3)exceedance event in September 2017 over the Pearl River Delta(PRD)of China.We discovered a clear relationship between atmospheric oxidative capacity and O_(3)formation regime.Over eastern PRD,O_(3)formation was mainly in a NO x-limited regime when HO_(2)/OH ratio was higher than 11,while in a VOC-limited regime when the ratio was lower than 9.5.Over central and western PRD,an HO_(2)/OH ratio higher than 5 and lower than 2 was indicative of NO x-limited and VOC-limited regime,respectively.Physical contribution,including horizontal transport and vertical transport,may pose uncertainties on the indication of O_(3)formation regime by HO_(2)/OH ratio.In comparison with other commonly used photochemical indicators,HO_(2)/OH ratio had the best performance in differentiating O_(3)formation regimes.This study highlighted the necessities in using an atmospheric oxidative capacity-based indicator to infer O_(3)formation regime,and underscored the importance of characterizing behaviors of radicals to gain insight in atmospheric processes leading to O_(3)pollution over a photochemically active region.展开更多
基金sponsored by the National Natural Science Foundation of China(Nos.91644221,41575009)。
文摘Understanding ozone(O_(3))formation regime is a prerequisite in formulating an effective O_(3)pollution control strategy.Photochemical indicator is a simple and direct method in identifying O_(3)formation regimes.Most used indicators are derived from observations,whereas the role of atmospheric oxidation is not in consideration,which is the core driver of O_(3)formation.Thus,it may impact accuracy in signaling O_(3)formation regimes.In this study,an advanced three-dimensional numerical modeling system was used to investigate the relationship between atmospheric oxidation and O_(3)formation regimes during a long-lasting O_(3)exceedance event in September 2017 over the Pearl River Delta(PRD)of China.We discovered a clear relationship between atmospheric oxidative capacity and O_(3)formation regime.Over eastern PRD,O_(3)formation was mainly in a NO x-limited regime when HO_(2)/OH ratio was higher than 11,while in a VOC-limited regime when the ratio was lower than 9.5.Over central and western PRD,an HO_(2)/OH ratio higher than 5 and lower than 2 was indicative of NO x-limited and VOC-limited regime,respectively.Physical contribution,including horizontal transport and vertical transport,may pose uncertainties on the indication of O_(3)formation regime by HO_(2)/OH ratio.In comparison with other commonly used photochemical indicators,HO_(2)/OH ratio had the best performance in differentiating O_(3)formation regimes.This study highlighted the necessities in using an atmospheric oxidative capacity-based indicator to infer O_(3)formation regime,and underscored the importance of characterizing behaviors of radicals to gain insight in atmospheric processes leading to O_(3)pollution over a photochemically active region.
文摘为了解受焦化影响的下风向城区臭氧(O_(3))的污染特征及来源,基于2019年临汾市6个国控点的O_(3)浓度、气象参数(气温等)以及北大街站点VOCs监测数据开展研究。结果表明:2019年临汾市O_(3)日最大8 h滑动平均值(MDA8)的90百分位数(MDA8-90th)为204μg/m^(3),在山西省11个地市中排名第一;全年共有103 d O_(3)浓度超标,且超标天主要集中在5—9月;MDA8从2月开始升高,6月达到最大值,之后逐月下降;O_(3)小时浓度总体呈14:00—16:00出现峰值的单峰日变化。MDA8与日最高气温(T_(max))呈正相关、与日最低相对湿度(RH_(min))呈负相关,当T_(max)>22℃或RH_(min)<55%时,可能发生O_(3)浓度超标现象。VOCs的O_(3)生成潜势(OFP)分析结果表明,乙烯的OFP最高,占总OFP的44.5%,乙烯是导致O_(3)污染的关键VOCs活性物种;液化石油气(LPG)的使用、机动车尾气和炼焦活动等的排放对临汾市O_(3)污染有重要贡献。6个国控点中,城南和唐尧大酒店对临汾市区所有级别的O_(3)污染贡献均较大,2个站点均有77%的O_(3)超标出现在刮南风和西南风时,其中城南有16.6%的O_(3)超标出现在风速大于3 m/s时,作为焦化典型示踪物的萘在南风向其浓度高于均值的占比为30.4%,表明不合理的工业布局使临汾市区大气受到了焦化区的影响,O_(3)浓度更易在刮南风时超标。临汾市区O_(3)污染除受到本地生成影响外,还受到襄汾县、洪洞县、翼城县和浮山县的焦化企业和钢铁企业排放的含高浓度NO_(x)、VOCs污染气团传输的影响。因此,临汾市在对本地LPG使用和机动车尾气排放进行管控的同时,还要加强与上风向焦化地区的联防联控。
