摘要
针对现有研究多基于单一站点的挥发性有机物(VOCs)监测,难以捕捉到其传输及老化特征的问题,选取长三角东部典型城市站点(苏州城区)及其主导风下风向区域背景站点(太湖西山传输通道),采用在线气相色谱-质谱联用技术(GC-MS),于夏季同步开展了45d的VOCS在线观测,并结合正交矩阵因子分解(PMF)模型,研究VOCs的来源及传输老化过程.结果表明:苏州城区φ(TVOCs)平均值为28.6×10^(-9),高于传输通道站点的17.5×10^(-9),城市VOCs烷烃占比更高,经传输后含氧挥发性有机物(OVOCs)和卤代烃占比升高.PMF来源解析表明下风向站点的VOCs主要受城市污染传输影响,其机动车尾气、汽油挥发、溶剂使用和工业因子的成分谱及时间变化特征与城区吻合,但均呈现显著的老化特征(OVOCs占比系统性增加).因受到生物源的额外贡献,该站点异戊二烯较城区升高143.8%.副热带高压控制下的高温、小风及少云条件促进O_(3)生成与累积,而台风外围环流则通过增强扩散和湿沉降显著降低O_(3)污染浓度.区域性的污染过程由城市交通排放(尤其是早晚高峰一次污染物浓度抬升)驱动,本地臭氧(O_(3))污染加剧,一次排放的VOCs向下风向区域传输的过程中持续老化,主要表现为烷烃向OVOCs的转化,氧化产物的生成导致了传输通道站点的O_(3)污染.O_(3)与细颗粒物(PM_(2.5))呈现协同污染特征,二者污染峰值时间一致,PM_(2.5)中的SOA(二次有机气溶胶)占比显著升高.以上结果揭示了交通污染排放的VOCs不仅作为前体物直接导致本地O_(3)污染,在下风向传输过程中伴随着老化过程,引起区域性的O_(3)污染,并抬升PM_(2.5)的浓度.
Most existing studies of VOCs based on single monitoring sites cannot fully characterize VOC transport and aging.Here,we conducted 45-day synchronous online VOC measurements in summer using GC–MS at an urban site in Suzhou(eastern Yangtze River Delta)and a downwind site on Xishan Island,Taihu Lake.Combined with positive matrix factorization(PMF),we investigated the sources and transport-aging processes of VOCs.The averageφ(TVOCs)in urban Suzhou was 28.6×10^(-9),higher than 17.5×10^(-9)downwind.Urban VOCs were dominated by alkanes,whereas OVOCs and halocarbons showed larger fractions at the transport site.PMF revealed four factors(vehicle exhaust,gasoline evaporation,solvent use,and industrial emissions)with source profiles and temporal patterns consistent between sites,but all exhibited pronounced aging downwind,reflected by systematic increases in OVOC contributions.Biogenic emissions were also important downwind,where isoprene levels were 143.8%higher than urban values.Subtropical high-pressure systems with elevated temperatures and weak winds promoted O_(3) formation,whereas typhoon circulation mitigated O_(3) pollution via enhanced dispersion and wet deposition.Regional pollution episodes were driven by urban traffic emissions,especially during rush hours when primary pollutants peaked.During transport,primary VOCs underwent continuous aging with alkanes converting to OVOCs,further enhancing downwind O_(3) pollution.O_(3) and PM_(2.5) exhibited synchronized peaks,and SOA contributions in PM_(2.5) increased markedly.These findings demonstrate that traffic-related NOx and VOC emissions contribute to local O_(3) formation and,through aging during transport,drive regional O_(3) pollution,providing critical insights into compound air pollution mechanisms in the Yangtze River Delta.
作者
孙鹏
顾晓明
钟声
郁建桥
徐政
SUN Peng;GU Xiao-ming;ZHONG Sheng;YU Jian-qiao;XU Zheng(Jiangsu Provincial Environmental Monitoring Center,Nanjing 210019,China;Jiangsu Provincial Suzhou Environmental Monitoring Center,Suzhou 215000,China)
出处
《中国环境科学》
北大核心
2026年第2期636-645,共10页
China Environmental Science
基金
国家自然科学基金资助项目(42105096)
2025年度江苏省生态环境监测科研基金(25B04)
江苏省生态环境科研项目(2025016)。
