Many sensitive ecosystems in areas protected for biodiversity conservation in the United States suffer from exposure to excess reactive nitrogen (Nr) released by fossil fuel combustion and agricultural practices and deposited onto the land surface and water bodies. The Community Multiscale Air Quality (CMAQ) model was applied over the contiguous United States to link emissions and climate change to reactive nitrogen deposition by simulating both present‐day and future speciated Nr deposition to protected areas. Future conditions included examining the Representative Concentration Pathway 8.5 climate and the Shared Socio‐Economic Pathway 5 emission scenarios. We further identify protected areas that would benefit most from better Nr management strategies by comparing the simulated deposition with multiple critical loads (CLs) for both biodiversity and acidification in terrestrial and aquatic ecosystems. Achieved by further NO_x emission reductions from the mobile and power generation sectors, future Nr deposition is expected to decrease. However, in regions with intensive fertilizer application or hosting concentrated animal feeding operations, the reduction may be offset by rising agricultural NH₃ emissions. The protected areas having CL exceedances in 2050 are expected to increase by 5.5% for empirical lichen‐based CL, and by 11% and 22% for surface water and forest soil acidity, respectively, because of the agricultural NH₃ emission increase. By linking the deposition simulations with a water quality model, we identified that atmospheric deposition is the dominant source of nitrogen for several remote watersheds, including several lakes in National Parks and National Wilderness areas in Colorado, Montana, and Minnesota.

中文翻译：

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从农业来源到美国未来反应性氮沉积的更大贡献

在美国受保护的生物多样性保护区中，许多敏感的生态系统都暴露于化石燃料燃烧和农业实践所释放并沉积在陆地表面和水体上的过量活性氮（Nr）中。社区多尺度空气质量（CMAQ）模型已应用到美国各地，通过模拟当今和将来指定保护区的Nr沉积，将排放和气候变化与活性氮沉积联系起来。未来的条件包括检查“代表性浓度途径8.5”气候和“共享社会经济途径5”排放情景。通过将模拟沉积物与陆地和水生生态系统中生物多样性和酸化的多重临界负荷（CL）进行比较，我们进一步确定了将从更好的Nr管理策略中受益最大的保护区。进一步实现_x由于移动和发电部门的排放量减少，未来的Nr沉积有望减少。但是，在施肥密集或集中饲养动物的地区，农业NH ₃排放量的增加可能抵消了减排量。由于农业NH _3的存在，基于经验的基于地衣的CL的保护区预计将在2050年增加5.5％，对于地表水和森林土壤酸度的保护区将分别增加5.5％和11％和22％。排放增加。通过将沉积物模拟与水质模型联系起来，我们确定了大气沉积物是几个偏远流域（包括国家公园和科罗拉多州，蒙大拿州和明尼苏达州的国家荒野地区的几个湖泊）中氮的主要来源。