Elevated reactive nitrogen (N_r) deposition is a concern for alpine ecosystems, and dry NH₃ deposition is a key contributor. Understanding how emission hotspots impact downwind ecosystems through dry NH₃ deposition provides opportunities for effective mitigation. However, direct NH₃ flux measurements with sufficient temporal resolution to quantify such events are rare. Here, we measured NH₃ fluxes at Rocky Mountain National Park (RMNP) during two summers and analyzed transport events from upwind agricultural and urban sources in northeastern Colorado. We deployed open-path NH₃ sensors on a mobile laboratory and an eddy covariance tower to measure NH₃ concentrations and fluxes. Our spatial sampling illustrated an upslope event that transported NH₃ emissions from the hotspot to RMNP. Observed NH₃ deposition was significantly higher when backtrajectories passed through only the agricultural region (7.9 ng m^–2 s^–1) versus only the urban area (1.0 ng m^–2 s^–1) and both urban and agricultural areas (2.7 ng m^–2 s^–1). Cumulative NH₃ fluxes were calculated using observed, bidirectional modeled, and gap-filled fluxes. More than 40% of the total dry NH₃ deposition occurred when air masses were traced back to agricultural source regions. More generally, we identified that 10 (25) more national parks in the U.S. are within 100 (200) km of an NH₃ hotspot, and more observations are needed to quantify the impacts of these hotspots on dry NH₃ deposition in these regions.

中文翻译：

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可追溯到农业排放热点的高山生态系统中的氨干沉积

升高的活性氮 (N _r ) 沉积是高山生态系统关注的问题，而干燥的 NH ₃沉积是一个关键因素。了解排放热点如何通过干燥的 NH ₃沉积影响下风向生态系统为有效缓解提供了机会。然而，具有足够时间分辨率来量化此类事件的直接 NH ₃通量测量很少见。在这里，我们测量了落基山国家公园 (RMNP) 两个夏季的NH ₃通量，并分析了科罗拉多州东北部逆风农业和城市源的运输事件。我们在移动实验室和涡流协方差塔上部署了开放路径 NH ₃传感器来测量 NH ₃浓度和通量。我们的空间采样说明了将 NH ₃排放从热点传输到 RMNP的上坡事件。当反向轨迹仅通过农业区 (7.9 ng m ^–2 s ^–1 ) 与仅通过城市地区 (1.0 ng m ^–2 s ^–1 ) 以及城市和农业地区 (2.7 ng m ^–2 s ^–1 ) 相比，观察到的 NH ₃沉积显着更高^–2秒^–1 )。使用观察到的、双向建模的和间隙填充的通量计算累积的 NH ₃通量。超过总干 NH _{3 的}40%当气团追溯到农业源区时，就发生了沉积。更一般地说，我们发现美国还有 10 (25) 个国家公园位于 NH ₃热点的100 (200) 公里范围内，需要更多的观察来量化这些热点对这些地区干 NH ₃沉积的影响。