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A national-scale review of air pollutant concentrations measured in the U.S. near-road monitoring network during 2014 and 2015

机译：2014年至2015年在美国近距离道路监控网络中对空气污染物浓度进行的国家级审查

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In 2010, the U.S. Environmental Protection Agency (EPA) revised the National Ambient Air Quality Standards (NAAQS) for NO2 to include a primary health-based standard for hourly NO2, and required air quality monitoring next to major roadways in urban areas in the U.S. Requirements for near-road measurements also include carbon monoxide (CO) and particulate matter smaller than 2.5 mu m in diameter (PM2.5). We performed a national-scale assessment of air pollutants measured at 81 sites in the near-road environment during the first two years (2014 and 2015) of the new measurement program. We evaluated how concentrations at these locations compared to the NAAQS, to concentrations measured at other sites within the same urban areas, and when considering their site characteristics (distance of monitor to road, traffic volume, and meteorology). We also estimated the contribution of emissions from adjacent roadways at each near-road site to the PM2.5 concentrations above the local urban background concentrations, i.e., the near-road "increment." Hourly values of CO reached a maximum of 4.8 ppm across 31 sites in 2014 and 9.6 ppm across 47 sites in 2015, and were well below the NAAQS levels for both the 1-hr (35 ppm) and 8-hr (9 ppm) standards. Hourly concentrations of near road NO2 reached 258 ppb across 40 sites in 2014; however, there were only two occurrences of a daily 1-hr maximum NO2 concentration above 100 ppb (the level of the hourly NO2 standard). In 2015, hourly concentrations of near-road NO2, monitored at 61 sites in 55 urban areas, reached 154 ppb. Only 0.0015% (n = 5) of hourly NO2 observations in 2015 exceeded 100 ppb. The highest annual NO2 average recorded in 2015 (29.9 ppb) occurred at the Ontario site located along I-10 in the Los Angeles, California, area and was below the level of the NO2 annual standard (53 ppb); in 2014, the highest annual mean NO2 was also observed in Los Angeles at the Anaheim site (27.1 ppb). In 2014, sites in Cincinnati, Indianapolis, and Louisville recorded annual average PM2.5 concentrations at or above 12 mu g/m(3) (the level of the annual standard). There were 15 occurrences in 2014 of 24-hr PM2.5 concentrations above the NAAQS level of 35 mu g/m(3). Annual average PM2.5 exceeded 12 mu g/m(3) at near-road sites in five urban areas in 2015, and there were 33 days across 12 near-road locations with 24-hr PM2.5 concentrations above 35 mu g/m(3). Across the near-road monitoring network, annual average PM2.5 concentrations did not have a significant relationship with traffic volume or distance between the monitor and the adjacent roadway; rather, variations in PM2.5 were mostly driven by urban-scale PM2.5, with a typically small "increment" above urban-scale concentrations due to a site's proximity to the roadway. We estimated this increment, i.e., the difference between near-road PM2.5 concentrations and the concentrations at sites in the urban area of each near-road monitor, to be on average 1.2 mu g/m(3) (sigma = 0.3 mu g/m(3)), with a range of -1.2 mu g/m(3) to 3.1 mu g/m(3) across the 26 sites (four of which had a negative increment). The near-road increment is on average 13% of the near-road PM2.5, and 15% of the near-road PM2.5 for sites within 20 m of the roadway.
机译：2010年，美国环境保护局（EPA）修订了《国家环境空气质量标准》（NO2），将基于健康的主要NO2每小时标准纳入其中，并要求在美国城市主要道路旁进行空气质量监测近路测量的要求还包括一氧化碳（CO）和直径小于2.5微米的颗粒物（PM2.5）。在新的测量计划的前两年（2014年和2015年）中，我们对在近道路环境中81个站点测量的空气污染物进行了国家级评估。我们评估了与NAAQS相比这些位置的浓度，以及同一城市区域内其他地点测量的浓度，并考虑了它们的地点特征（监控器与道路的距离，交通量和气象）。我们还估计了每个邻近道路站点的相邻道路的排放对高于当地城市本底浓度的PM2.5浓度（即邻近道路“增量”）的贡献。 2014年31个站点的每小时CO最大值达到4.8 ppm，2015年47个站点的每小时CO最大值达到9.6 ppm，并且远低于1小时（35 ppm）和8小时（9 ppm）标准的NAAQS水平。 2014年，在40个站点​​中，NO2道路附近的每小时浓度达到258 ppb；但是，每天只有两次出现1小时最大NO2浓度超过100 ppb（每小时NO2标准水平）的情况。 2015年，在55个城市地区的61个站点进行监测的每小时近路NO2浓度达到154 ppb。 2015年每小时仅观察到0.0015％（n = 5）的NO2超过100 ppb。 2015年记录的最高二氧化氮年度平均值（29.9 ppb）发生在位于加利福尼亚州洛杉矶地区I-10的安大略省站点，低于二氧化氮年度标准（53 ppb）的水平； 2014年，洛杉矶的阿纳海姆站（Anaheim site）也观测到最高的二氧化氮年度平均值（27.1 ppb）。 2014年，辛辛那提，印第安纳波利斯和路易斯维尔的站点记录的年平均PM2.5浓度等于或高于12μg / m（3）（年标准水平）。 2014年有15次24小时PM2.5浓度高于NAAQS水平35μg/ m（3）的情况。 2015年，五个城市地区的近道路站点的年平均PM2.5超过12μg / m（3），并且在12个近道路站点中有33天的时间，其中PM2.5浓度超过35μg / m的24小时m（3）。在整个近路监控网络中，年平均PM2.5浓度与监控器与相邻道路之间的交通量或距离没有显着关系；相反，PM2.5的变化主要是由城市规模的PM2.5驱动的，由于站点靠近道路，通常会比城市规模的浓度小“增量”。我们估计此增量（即，近路PM2.5浓度与每台近路监控器的市区内站点浓度之间的差）平均为1.2μg / m（3）（sigma = 0.3 mu g / m（3）），跨26个站点（其中四个负增量）在-1.2μg / m（3）至3.1μg / m（3）之间。对于道路20 m以内的站点，近路增量平均为近路PM2.5的13％，为近路PM2.5的15％。

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