Measurements of ozone and its precursors in Beijing during summertime: impact of urban plumes on ozone pollution in downwind rural areas
Measurements of ozone and its precursors in Beijing during summertime: impact of urban plumes on ozone pollution in downwind rural areas
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DOI：
10.5194/acp-11-12241-2011
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发表时间：
2011-12
影响因子：
6.3
通讯作者：
Jiwei Xu;Jianmin Ma;Xiaoling Zhang;Xiaobin Xu;Xiaofeng Xu;Weili Lin;Y. Wang;W. Meng;
中科院分区：
文献类型：
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作者：
Jiwei Xu;Jianmin Ma;Xiaoling Zhang;Xiaobin Xu;Xiaofeng Xu;Weili Lin;Y. Wang;W. Meng;
抽象。夏季影响北京地区的中尺度天气系统主要是海陆环流和山谷环流。在这两股环流的影响下，下午到半夜盛行西南风，然后到上午转为东北风。本研究对沿着盛行风路径的4个站点（包括2个上风城市站点）的地面臭氧（O3）、一氧化碳（CO）、一氧化氮（NO）、二氧化氮（NO2）、氮氧化物（NOx）和非甲烷碳氢化合物（NMHCs）进行了测定（丰台“FT”和宝莲“BL”）、上风向郊区站点（顺义“SY”）和下风向农村站点（上店子“SDZ”）。目的是提高我们对北京城市和农村地区臭氧光化学的认识，以及城市羽流对下风向农村地区臭氧污染的影响。结果表明，北京市城乡臭氧污染具有同步性，与区域尺度的天气过程相吻合。由于高交通密度和本地排放，在非农村站点的反应性气体NOx和NMHCs的平均水平远高于SDZ。在SDZ的长寿命气体CO的水平是可比的，虽然略低于，在城市网站。我们估计的光化学反应性（L OH和臭氧形成潜力（OFP）在城市（BL）和农村（SDZ）地区使用测量的CO和NMHCs。在BL和SDZ位点，OH损失速率系数（L OH/NMHC）分别为50.7s-1和15.8s-1。虽然烯烃对L OH做出了主要贡献，但芳烃在城市和农村地区的OFP中占主导地位。就单个物种而言，CO在农村地区具有最大的臭氧形成潜力，而在城市地区，芳香族物种是主要的贡献者。O3日变化在4个站点都是典型的污染区，但O3峰值沿盛行风由SW向NE的路径沿着在一个站点之后。微量气体的交叉分析表明，到达SDZ的污染空气质量更老，更高的O3和OX浓度比BL。结果表明，城市烟羽不仅能输送O3，而且还能输送O3的前体物质，后者与下风向农村背景大气混合时，导致更多的光化学O3产生。
Abstract. Sea-land and mount-valley circulations are the dominant mesoscale synoptic systems affecting the Beijing area during summertime. Under the influence of these two circulations, the prevailing wind is southwesterly from afternoon to midnight, and then changes to northeasterly till forenoon. In this study, surface ozone (O 3 ), carbon monoxide (CO), nitric oxide (NO), nitrogen dioxide (NO 2 ), nitrogen oxide (NO x ) and non-methane hydrocarbons (NMHCs) were measured at four sites located along the route of prevailing wind, including two upwind urban sites (Fengtai "FT" and Baolian "BL"), an upwind suburban site (Shunyi "SY") and a downwind rural site (Shangdianzi "SDZ") during 20 June–16 September 2007. The purpose is to improve our understanding of ozone photochemistry in urban and rural areas of Beijing and the influence of urban plumes on ozone pollution in downwind rural areas. It is found that ozone pollution was synchronism in the urban and rural areas of Beijing, coinciding with the regional-scale synoptic processes. Due to the high traffic density and local emissions, the average levels of reactive gases NO x and NMHCs at the non-rural sites were much higher than those at SDZ. The level of long-lived gas CO at SDZ was comparable to, though slightly lower than, at the urban sites. We estimate the photochemical reactivity ( L OH and the ozone formation potential (OFP) in the urban (BL) and rural (SDZ) areas using measured CO and NMHCs. The OH loss rate coefficient ( L OH by total NMHCs at the BL and SDZ sites are estimated to be 50.7 s -1 and 15.8 s -1 , respectively. While alkenes make a major contribution to the L OH , aromatics dominate OFP at both urban and rural sites. With respect to the individual species, CO has the largest ozone formation potential at the rural site, and at the urban site aromatic species are the leading contributors. While the O 3 diurnal variations at the four sites are typical for polluted areas, the ozone peak values are found to lag behind one site after another along the route of prevailing wind from SW to NE. Intersection analyses of trace gases reveal that polluted air masses arriving at SDZ were more aged with both higher O 3 and O x concentrations than those at BL. The results indicate that urban plume can transport not only O 3 but its precursors, the latter leading more photochemical O 3 production when being mixed with background atmosphere in the downwind rural area.