Elliott E M, Kendall C, Wankel S D, Burns D A, Boyer E W, Harlin K, Bain D J, Butler T J
U.S. Geological Survey, Water Resources Division, 345 Middlefield Road, Menlo Park, California 94025, USA.
Environ Sci Technol. 2007 Nov 15;41(22):7661-7. doi: 10.1021/es070898t.
Global inputs of NO(x) are dominated by fossil fuel combustion from both stationary and vehicular sources and far exceed natural NO(x) sources. However, elucidating NO(x) sources to any given location remains a difficult challenge, despite the need for this information to develop sound regulatory and mitigation strategies. We present results from a regional-scale study of nitrogen isotopes (delta15N) in wet nitrate deposition across 33 sites in the midwestern and northeastern U.S. We demonstrate that spatial variations in delta15N are strongly correlated with NO(x) emissions from surrounding stationary sources and additionally that delta15N is more strongly correlated with surrounding stationary source NO(x) emissions than pH, SO4(2-), or NO3- concentrations. Although emission inventories indicate that vehicle emissions are the dominant NO(x) source in the eastern U.S., our results suggest that wet NO3- deposition at sites in this study is strongly associated with NO(x) emissions from stationary sources. This suggests that large areas of the landscape potentially receive atmospheric NO(y) deposition inputs in excess of what one would infer from existing monitoring data alone. Moreover, we determined that spatial patterns in delta15N values are a robust indicator of stationary NO(x) contributions to wet NO3- deposition and hence a valuable complement to existing tools for assessing relationships between NO3- deposition, regional emission inventories, and for evaluating progress toward NO(x) reduction goals.
全球氮氧化物（NO(x)）的输入主要来自固定源和移动源的化石燃料燃烧，远远超过天然NO(x)源。然而，尽管制定合理的监管和减排策略需要了解特定地点的NO(x)来源信息，但要确定任何给定地点的NO(x)来源仍然是一项艰巨的挑战。我们展示了美国中西部和东北部33个地点湿沉降硝酸盐中氮同位素（δ15N）的区域尺度研究结果。我们证明，δ15N的空间变化与周围固定源的NO(x)排放密切相关，此外，与pH值、硫酸根离子（SO4(2-)）或硝酸根离子（NO3-）浓度相比，δ15N与周围固定源的NO(x)排放相关性更强。尽管排放清单表明车辆排放是美国东部主要的NO(x)来源，但我们的结果表明，本研究中各地点的湿沉降硝酸根离子与固定源的NO(x)排放密切相关。这表明，该地区大片区域可能接收到的大气氮氧化物（NO(y)）沉降输入量超过仅从现有监测数据推断出的量。此外，我们确定，δ15N值的空间模式是固定源对湿沉降硝酸根离子贡献的有力指标，因此是评估硝酸根离子沉降、区域排放清单之间关系以及评估氮氧化物减排目标进展情况的现有工具的宝贵补充。
