Photochemical processing of organic aerosol at nearby continental sites: contrast between urban plumes and regional aerosol
Photochemical processing of organic aerosol at nearby continental sites: contrast between urban plumes and regional aerosol
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DOI：
10.5194/acp-11-2991-2011
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发表时间：
2011-01-01
影响因子：
6.3
通讯作者：
Abbatt, J. P. D.
中科院分区：
文献类型：
--
作者：
Slowik, J. G.;Brook, J.;Abbatt, J. P. D.
作为BAQS-Met 2007年实地活动的一部分，2007年6月17日至7月11日，在安大略西南部的两个地点部署了Aerodyne飞行时间气溶胶质谱仪（ToF-AMS）。一台仪器位于安大略省哈罗市，这是一个以农业为主的农村地区，位于底特律/温莎/温莎市区东南约40公里处，伊利湖以北5公里处。第二台仪器位于安大略省Bear Creek，这是一个位于Harrow站点东北约70 km和底特律/温莎以东50 km的农村站点。正矩阵分解分析相结合的有机质谱数据集产生的因素，二次有机气溶胶（SOA），直接排放，和一个因素暂时归因于异戊二烯的反应性吸收和/或冷凝的早期生成的反应产物。这是PMF在不同站点同步AMS测量的第一个应用，这种方法允许对数据集进行自洽的直接比较。案例研究被用来调查SOA的处理从（1）新鲜的排放从底特律/温莎和（2）区域气溶胶在站点间的流动期间。SOA/过量的CO和光化学年龄之间的相关性很强，底特律/温莎流出的NOx/NOy比为代表。虽然这种相关性是不明显的，更老的空气，测量在两个网站在站点间的运输过程中，但仍显示出持续的大气处理SOA生产的证据。然而，SOA的产生率随着气团年龄的增长而降低，从最初的10小时的烟羽处理的初始值10.1 μ g m（-3）ppmv（CO）（-1）h（-1）到老化气团（即几天后）的接近零。最初的SOA生产率与墨西哥城在类似时间尺度上观察到的速率相当。
As part of the BAQS-Met 2007 field campaign, Aerodyne time-of-flight aerosol mass spectrometers (ToF-AMS) were deployed at two sites in southwestern Ontario from 17 June to 11 July 2007. One instrument was located at Harrow, ON, a rural, agriculture-dominated area approximately 40 km southeast of the Detroit/Windsor/Windsor urban area and 5 km north of Lake Erie. The second instrument was located at Bear Creek, ON, a rural site approximately 70 km northeast of the Harrow site and 50 km east of Detroit/Windsor. Positive matrix factorization analysis of the combined organic mass spectral dataset yields factors related to secondary organic aerosol (SOA), direct emissions, and a factor tentatively attributed to the reactive uptake of isoprene and/or condensation of its early generation reaction products. This is the first application of PMF to simultaneous AMS measurements at different sites, an approach which allows for self-consistent, direct comparison of the datasets. Case studies are utilized to investigate processing of SOA from (1) fresh emissions from Detroit/Windsor and (2) regional aerosol during periods of inter-site flow. A strong correlation is observed between SOA/excess CO and photochemical age as represented by the NOx/NOy ratio for Detroit/Windsor outflow. Although this correlation is not evident for more aged air, measurements at the two sites during inter-site transport nevertheless show evidence of continued atmospheric processing by SOA production. However, the rate of SOA production decreases with airmass age from an initial value of similar to 10.1 mu g m(-3) ppmv(CO)(-1) h(-1) for the first similar to 10 h of plume processing to near-zero in an aged airmass (i.e. after several days). The initial SOA production rate is comparable to the observed rate in Mexico City over similar timescales.