USDA Forest Service, Pacific Southwest Research Station, 4955 Canyon Crest Drive, Riverside, CA 92507, USA.
USDA Forest Service, Pacific Southwest Research Station, 4955 Canyon Crest Drive, Riverside, CA 92507, USA.
Sci Total Environ. 2018 Jun 1;625:909-919. doi: 10.1016/j.scitotenv.2017.12.313. Epub 2018 Jan 5.
We provide updated spatial distribution and inventory data for on-road NH emissions for the continental United States (U.S.) On-road NH emissions were determined from on-road CO emissions data and empirical NH:CO vehicle emissions ratios. Emissions of NH from on-road sources in urbanized regions are typically 0.1-1.3tkmyr while NH emissions in agricultural regions generally range from 0.4-5.5tkmyr, with a few hotspots as high as 5.5-11.2tkmyr. Counties with higher vehicle NH emissions than from agriculture include 40% of the U.S.
The amount of wet inorganic N deposition as NH from the National Atmospheric Deposition Program (NADP) network ranged from 37 to 83% with a mean of 58.7%. Only 4% of the NADP sites across the U.S. had <45% of the N deposition as NH based on data from 2014 to 2016, illustrating the near-universal elevated proportions of NH in deposition across the U.S. Case studies of on-road NH emissions in relation to N deposition include four urban sites in Oregon and Washington where the average NH-N:NO-N ratio in bulk deposition was 2.3. At urban sites in the greater Los Angeles Basin, bulk deposition of NH-N and NO-N were equivalent, while NH-N:NO-N in throughfall under shrubs ranged from 0.6 to 1.7. The NH-N:NO-N ratio at 7-10 sites in the Lake Tahoe Basin averaged 1.4 and 1.6 in bulk deposition and throughfall, and deposition of NH-N was strongly correlated with summertime NH concentrations. On-road emissions of NH should not be ignored as an important source of atmospheric NH, as a major contributor to particulate air pollution, and as a driver of N deposition in urban and urban-affected regions.
我们提供了美国大陆道路 NH 排放的更新的空间分布和清单数据。道路 NH 排放是根据道路 CO 排放数据和经验 NH:CO 车辆排放比确定的。城市地区的道路源 NH 排放量通常为 0.1-1.3tkmyr，而农业地区的 NH 排放量一般在 0.4-5.5tkmyr 之间，少数热点地区高达 5.5-11.2tkmyr。车辆 NH 排放量高于农业的县包括美国 40%的人口。
国家大气沉降计划（NADP）网络中 NH 导致的湿无机 N 沉降量范围为 37-83%，平均值为 58.7%。仅在美国 NADP 站点的 4%，基于 2014-2016 年的数据，N 沉降中 NH 的比例<45%，这表明 NH 在全美的沉降中普遍占比偏高。与 N 沉降有关的道路 NH 排放的案例研究包括俄勒冈州和华盛顿州的四个城市地点，其中在总沉降中 NH-N:NO-N 的平均比值为 2.3。在大洛杉矶盆地的城市地点，NH-N 和 NO-N 的总沉降量相当，而灌木下的穿透雨 NH-N 和 NO-N 的 NH-N:NO-N 比值在 0.6-1.7 之间。在太浩湖盆地的 7-10 个地点，NH-N:NO-N 的比值在总沉降和穿透雨中平均为 1.4 和 1.6，NH-N 的沉降与夏季 NH 浓度密切相关。道路 NH 排放不应被忽视，它是大气 NH 的重要来源，也是颗粒物空气污染的主要贡献者，也是城市和受城市影响地区 N 沉降的驱动因素。
