Leytem April B, Walker John T, Wu Zhiyong, Nouwakpo Kossi, Baublitz Colleen, Bash Jesse, Beachley Gregory
Northwest Irrigation and Soils Research Laboratory, United States Department of Agriculture-Agricultural Research Service, Kimberly, ID 83341, USA.
Office of Research and Development, United States Environmental Protection Agency, Durham, NC 27711, USA.
Atmosphere (Basel). 2023 Dec 22;15(1):1-23. doi: 10.3390/atmos15010015.
Agriculture generates ~83% of total US ammonia (NH) emissions, potentially adversely impacting sensitive ecosystems through wet and dry deposition. Regions with intense livestock production, such as the dairy region of south-central Idaho, generate hotspots of NH emissions. Our objective was to measure the spatial and temporal variability of NH across this region and estimate its dry deposition. Ambient NH was measured using diffusive passive samplers at 8 sites in two transects across the region from 2018-2020. NH fluxes were estimated using the Surface Tiled Aerosol and Gaseous Exchange (STAGE) model. Peak NH concentrations were 4-5 times greater at a high-density dairy site compared to mixed agriculture/dairy or agricultural sites, and 26 times greater than non-agricultural sites with prominent seasonal trends driven by temperature. Annual estimated dry deposition rates in areas of intensive dairy production can approach 45 kg N ha y, compared to <1 kg N ha y in natural landscapes. Our results suggest that the natural sagebrush steppe landscapes interspersed within and surrounding agricultural areas in southern Idaho receive NH dry deposition rates within and above the range of nitrogen critical loads for North American deserts. Finally, our results highlight a need for improved understanding of the role of soil processes in NH dry deposition to arid and sparsely vegetated natural ecosystems across the western US.
农业产生了美国氨（NH₃）排放总量的约83%，可能通过干湿沉降对敏感生态系统产生不利影响。畜牧生产密集的地区，如爱达荷州中南部的奶牛养殖区，是氨排放的热点地区。我们的目标是测量该地区氨的时空变异性，并估算其干沉降量。2018年至2020年期间，使用扩散被动采样器在该地区两条样带的8个地点测量了环境氨含量。利用地表平铺气溶胶和气体交换（STAGE）模型估算了氨通量。与混合农业/奶牛场或农业场地相比，高密度奶牛场的氨峰值浓度高4至5倍，比非农业场地高26倍，且呈现出由温度驱动的显著季节性趋势。集约化奶牛生产地区的年干沉降率估计可达45千克氮/公顷·年，而自然景观地区则小于1千克氮/公顷·年。我们的研究结果表明，散布在爱达荷州南部农业区域内及周边的天然鼠尾草草原景观所接受的氨干沉降率，处于并高于北美沙漠氮临界负荷范围。最后，我们的研究结果凸显了需要更好地理解土壤过程在美国西部干旱和植被稀少的自然生态系统氨干沉降中的作用。
