Leong Y J, Sanchez N P, Wallace H W, Karakurt Cevik B, Hernandez C S, Han Y, Flynn J H, Massoli P, Floerchinger C, Fortner E C, Herndon S, Bean J K, Hildebrandt Ruiz L, Jeon W, Choi Y, Lefer B, Griffin R J
a Department of Civil and Environmental Engineering , Rice University , Houston , TX , USA.
b Department of Earth and Atmospheric Sciences , University of Houston , Houston , TX , USA.
J Air Waste Manag Assoc. 2017 Aug;67(8):854-872. doi: 10.1080/10962247.2017.1296502. Epub 2017 Feb 28.
The sources of submicrometer particulate matter (PM) remain poorly characterized in the industrialized city of Houston, TX. A mobile sampling approach was used to characterize PM composition and concentration across Houston based on high-time-resolution measurements of nonrefractory PM and trace gases during the DISCOVER-AQ Texas 2013 campaign. Two pollution zones with marked differences in PM levels, character, and dynamics were established based on cluster analysis of organic aerosol mass loadings sampled at 16 sites. The highest PM mass concentrations (average 11.6 ± 5.7 µg/m) were observed to the northwest of Houston (zone 1), dominated by secondary organic aerosol (SOA) mass likely driven by nighttime biogenic organonitrate formation. Zone 2, an industrial/urban area south/east of Houston, exhibited lower concentrations of PM (average 4.4 ± 3.3 µg/m), significant organic aerosol (OA) aging, and evidence of primary sulfate emissions. Diurnal patterns and backward-trajectory analyses enable the classification of airmass clusters characterized by distinct PM sources: biogenic SOA, photochemical aged SOA, and primary sulfate emissions from the Houston Ship Channel. Principal component analysis (PCA) indicates that secondary biogenic organonitrates primarily related with monoterpenes are predominant in zone 1 (accounting for 34% of the variability in the data set). The relevance of photochemical processes and industrial and traffic emission sources in zone 2 also is highlighted by PCA, which identifies three factors related with these processes/sources (~50% of the aerosol/trace gas concentration variability). PCA reveals a relatively minor contribution of isoprene to SOA formation in zone 1 and the absence of isoprene-derived aerosol in zone 2. The relevance of industrial amine emissions and the likely contribution of chloride-displaced sea salt aerosol to the observed variability in pollution levels in zone 2 also are captured by PCA.
This article describes an urban-scale mobile study to characterize spatial variations in submicrometer particulate matter (PM) in greater Houston. The data set indicates substantial spatial variations in PM sources/chemistry and elucidates the importance of photochemistry and nighttime oxidant chemistry in producing secondary PM. These results emphasize the potential benefits of effective control strategies throughout the region, not only to reduce primary emissions of PM from automobiles and industry but also to reduce the emissions of important secondary PM precursors, including sulfur oxides, nitrogen oxides, ammonia, and volatile organic compounds. Such efforts also could aid in efforts to reduce mixing ratios of ozone.
在德克萨斯州休斯顿这个工业化城市中，亚微米颗粒物（PM）的来源仍未得到充分描述。在2013年德克萨斯州DISCOVER - AQ活动期间，采用移动采样方法，基于对非难熔性PM和痕量气体的高时间分辨率测量，来描述休斯顿地区PM的成分和浓度。基于在16个站点采集的有机气溶胶质量负荷的聚类分析，确定了两个PM水平、特征和动态存在显著差异的污染区域。在休斯顿西北部（区域1）观测到最高的PM质量浓度（平均11.6±5.7µg/m³），主要由夜间生物源有机硝酸盐形成驱动的二次有机气溶胶（SOA）质量主导。区域2位于休斯顿南部/东部的工业/城市地区，PM浓度较低（平均4.4±3.3µg/m³），有机气溶胶（OA）有显著老化现象，并有一次硫酸盐排放的证据。日变化模式和后向轨迹分析能够对以不同PM来源为特征的气团聚类进行分类：生物源SOA、光化学老化的SOA以及休斯顿航道的一次硫酸盐排放。主成分分析（PCA）表明，在区域1中，主要与单萜相关的二次生物源有机硝酸盐占主导（占数据集变异性的34%）。PCA还突出了区域2中光化学过程以及工业和交通排放源的相关性，该分析确定了与这些过程/源相关的三个因素（约占气溶胶/痕量气体浓度变异性的50%）。PCA显示异戊二烯对区域1中SOA形成的贡献相对较小，且区域2中不存在异戊二烯衍生的气溶胶。PCA还捕捉到了工业胺排放的相关性以及氯化物置换海盐气溶胶对区域2中观测到的污染水平变化的可能贡献。
本文描述了一项城市尺度的移动研究，以表征大休斯顿地区亚微米颗粒物（PM）的空间变化。数据集表明PM来源/化学组成存在显著的空间变化，并阐明了光化学和夜间氧化剂化学在产生二次PM中的重要性。这些结果强调了整个地区有效控制策略的潜在益处，不仅要减少汽车和工业的一次PM排放，还要减少重要的二次PM前体的排放，包括硫氧化物、氮氧化物、氨和挥发性有机化合物。这些努力也有助于降低臭氧的混合比。
