Air pollutant concentrations near three Texas roadways, part II: Chemical characterization and transformation of pollutants
Air pollutant concentrations near three Texas roadways, part II: Chemical characterization and transformation of pollutants
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DOI：
10.1016/j.atmosenv.2009.06.044
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发表时间：
2009-09-01
影响因子：
5
通讯作者：
Zhu, Yifang
中科院分区：
文献类型：
--
作者：
Clements, Andrea L.;Jia, Yuling;Zhu, Yifang
在德克萨斯州奥斯汀地区的三条公路附近测量了车辆排放的空气污染物的空间梯度：(1)71号州际公路（SH-71），这是一条以客运车辆为主的交通干线公路；(2) 35号州际公路（I-35），一条位于乔治城奥斯汀以北的有限通道公路；(3) Farm to Market Road 973 (FM-973)，这是一条交通繁忙的地面道路，卡车流量很大。利用移动监测平台表征CO和NOx浓度随距离每条道路距离的增加而变化的梯度，同时在固定的上风站点和一个（I-35和FM-973）或两个（SH-71）顺风站点测量气相羰基浓度和细颗粒物质量和组成。无论道路类型或风向如何，在距离道路几百米的范围内，一氧化碳（CO）、一氧化氮（NO）和氮氧化物（NOx）的浓度都会恢复到背景水平。垂直风条件下，CO、NO和NOx浓度随垂直距离的增加呈指数型下降。NO的衰减率比CO的衰减率高出两倍以上，并且在靠近道路的位置比顺风位置的位置包含更大的NOx比例，这表明靠近道路的化学处理和大气稀释的潜在意义。大多数羰基物种的浓度随着SH-71顺风距离的增加而降低。然而，在SH-71顺风处，乙醛和丙烯醛的浓度增加了，这表明主要的车辆排放的氧化产生了化学物质。颗粒结合的有机物种的行为是复杂的，进一步研究颗粒物质（PM）的大小分离的化学成分在增加顺风距离的道路是必要的。细颗粒物（PM2.5）质量浓度、多环芳烃（PAHs）、藿烷和单质碳（EC）浓度随SH-71顺风距离的增加而降低。有机碳（OC）浓度从SH-71顺风处的逆风浓度开始增加，并在顺风处继续增加。这种行为可能主要是由于车辆排放的半挥发性有机物质在道路顺风处运输时凝结造成的。2009爱思唯尔有限公司版权所有。
Spatial gradients of vehicular emitted air pollutants were measured in the vicinity of three roadways in the Austin, Texas area: (1) State Highway 71 (SH-71), a heavily traveled arterial highway dominated by passenger vehicles; (2) Interstate 35 (I-35), a limited access highway north of Austin in Georgetown; and (3) Farm to Market Road 973 (FM-973), a heavily traveled surface roadway with significant truck traffic. A mobile monitoring platform was used to characterize the gradients of CO and NOx concentrations with increased distance from each roadway, while concentrations of carbonyls in the gas-phase and fine particulate matter mass and composition were measured at stationary sites upwind and at one (I-35 and FM-973) or two (SH-71) downwind sites. Regardless of roadway type or wind direction, concentrations of carbon monoxide (CO), nitric oxide (NO), and oxides of nitrogen (NOx) returned to background levels within a few hundred meters of the roadway. Under perpendicular wind conditions, CO, NO and NOx concentrations decreased exponentially with increasing distance perpendicular to the roadways. The decay rate for NO was more than a factor of two greater than for CO, and it comprised a larger fraction of NOx closer to the roadways than further downwind suggesting the potential significance of near roadway chemical processing as well as atmospheric dilution. Concentrations of most carbonyl species decreased with distance downwind of SH-71. However, concentrations of acetaldehyde and acrolein increased farther downwind of SH-71, suggesting chemical generation from the oxidation of primary vehicular emissions. The behavior of particle-bound organic species was complex and further investigation of the size-segregated chemical composition of particulate matter (PM) at increasing downwind distances from roadways is warranted. Fine particulate matter (PM2.5) mass concentrations, polycyclic aromatic hydrocarbons (PAHs), hopanes, and elemental carbon (EC) concentrations generally exhibited concentrations that decreased with distance downwind of SH-71. Concentrations of organic carbon (OC) increased from upwind concentrations immediately downwind of SH-71 and continued to increase further downwind from the roadway. This behavior may have primarily resulted from condensation of semi-volatile organic species emitted from vehicle sources with transport downwind of the roadway. (C) 2009 Elsevier Ltd. All rights reserved.