Closing the Regional Ammonia and Nitrous Oxide Budgets of an Intensive Agricultural Region

农业集约化正在增加氨和一氧化二氮的排放，它们分别改变着区域大气化学和全球气候。美国玉米带是卫星观测到的五大氨热点之一，主要来自那里高密度的大型牛和猪养殖场。排放的氨可以沉积在下风的土壤上，这可以促进一氧化二氮的产生。该提案将整合测量和建模，以量化氨通量如何放大美国大陆的一氧化二氮排放。科学将有助于制定未来可持续发展的最佳做法。研究重点是对自然和农业系统中氨通量和氧化亚氮交换的分析，提高了对这些过程的机理理解和模型表示。该方案的重点工作如下：(1)在明尼苏达大学高塔微量气体观测站对氨进行高精度、近连续测量，并利用测量结果对氨源输运和沉积进行模型验证；(2)开展密集的野外活动，在双向NH3交换的背景下描绘景观特征。(3)利用区域和全球模式模拟高分辨率大气Nr沉降，以限制土壤氮循环和氮排放。在将这些模型用于高分辨率区域尺度沉积和氧化亚氮排放模型之前，将对高密度数据集进行评估。该研究将测试氨沉积影响区域一氧化二氮排放的假设，并在区域（美国大陆）模型中确定这种挥发的约束排放因子。

Agricultural intensification is increasing the emissions of ammonia and nitrous oxide that are altering regional atmospheric chemistry and global climate, respectively. The US Corn Belt is one of the five major ammonia hotspot observed by satellites largely from the high density of large cattle and swine operations there. The emitted ammonia can deposit on soils downwind and this can promote nitrous oxide production. The proposal will integrate measurements and modeling to quantify how ammonia fluxes amplify nitrous oxide emissions in the continental US. The science will help develop best practices that are sustainable in the future.The research focus on analysis of ammonia fluxes and nitrous oxide exchange at natural and agricultural systems improve the mechanistic understanding model representations of these processes. The proposal focuses on the following tasks: (1) High precision and near-continuous measurement of ammonia at the University of Minnesota Tall Tower Trace Gas Observatory and using the results for model validation of its source transport and deposition; (2) Perform intensive field campaigns to characterize the landscape in the context of bi-directional NH3 exchange. (3) Simulate high-resolution atmospheric Nr deposition using regional and global models for constraining the soil nitrogen cycling and nitrous emissions. The models will be evaluated against the high-density data sets prior to their use for high-resolution regional scale deposition and nitrous oxide emission modeling. The research will test hypotheses that ammonia deposition impacts regional nitrous oxide emissions and determine constrained emission factors for this volatization in regional (continental US) models.