Abstract This study investigates air pollutant concentrations across the international airshed spanning Detroit, Michigan, USA and Windsor, Ontario, Canada. The Geospatial Determinants of Health Outcomes Consortium (GeoDHOC) measured air quality concurrently in Detroit and Windsor using consistent sampling methods and locations during separate, two-week periods in September 2008 and May/June 2009. This paper presents 2009 results and compares them to previously reported 2008 campaign results to assess spatial and temporal variability. A high-density array of 100 passive and 50 active samplers was used to measure nitrogen dioxide (NO2), 26 volatile organic compounds (VOCs), 23 polycyclic aromatic hydrocarbons (PAHs), and three size fractions of particulate matter (PM) in both campaigns. Geospatial and non-spatial tools were used to investigate changes in concentration distributions and site classification into low/medium/high tertiles between the campaigns. During the two-week 2009 campaign, general pollution patterns remained consistent with those observed during 2008. Higher concentrations in Detroit, strong correlations amongst the BTEX group, and consistency of sites falling into the low and high tertiles were observed. Similar spatial patterns for NO2, VOCs, BTEX, and PAHs were also found during both campaigns. Conversely, PM1-2.5 and PM2.5-10 distributions showed greater variability, as did toluene/benzene ratios. Observed differences are attributable to changes in point source emissions associated with changes in localized activities, possibly related to decreased economic and industrial activity in response to the downturn that began in late 2008. Repeated sampling at multiple locations is important to determine spatial and temporal variability in absolute concentrations. However, if the definition of relatively high and low concentrations regions within a well-established urban area is adequate to estimate future air pollutant exposures, a single multi-location campaign may suffice.

中文翻译：

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底特律（美国）和温莎（加拿大）国际空气流域空气质量的年际变化：两个城市两次采样活动的比较

摘要 本研究调查了跨越美国密歇根州底特律和加拿大安大略省温莎的国际气域的空气污染物浓度。健康结果的地理空间决定因素联盟 (GeoDHOC) 在 2008 年 9 月和 2009 年 5 月/2009 年 6 月的两周期间使用一致的采样方法和地点同时测量了底特律和温莎的空气质量。本文介绍了 2009 年的结果并将它们与以前报告了 2008 年活动结果，以评估时空变异性。100 个被动采样器和 50 个主动采样器的高密度阵列用于测量二氧化氮 (NO2)、26 种挥发性有机化合物 (VOC)、23 种多环芳烃 (PAH) 和颗粒物质 (PM) 的三种粒度分数活动。地理空间和非空间工具用于调查活动之间浓度分布和站点分类为低/中/高三分位数的变化。在 2009 年为期两周的活动中，总体污染模式与 2008 年观察到的情况保持一致。观察到底特律的浓度较高，BTEX 组之间的相关性强，以及落入低三分位数和高三分位数的地点的一致性。在这两个活动中也发现了 NO2、VOC、BTEX 和 PAH 的类似空间模式。相反，PM1-2.5 和 PM2.5-10 分布表现出更大的可变性，甲苯/苯比率也是如此。观察到的差异归因于与本地活动变化相关的点源排放的变化，可能与 2008 年末开始的经济衰退导致经济和工业活动减少有关。在多个地点重复采样对于确定绝对浓度的空间和时间变化非常重要。然而，如果在一个完善的城市区域内定义相对高浓度和低浓度区域足以估计未来的空气污染物暴露，单一的多地点运动可能就足够了。