Modeling the Sources and Transport Processes During Extreme Ammonia Episodes in the US Corn Belt
Modeling the Sources and Transport Processes During Extreme Ammonia Episodes in the US Corn Belt
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DOI：
10.1029/2019jd031207
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发表时间：
2020-01-27
影响因子：
4.4
通讯作者：
Lee, Xuhui
中科院分区：
文献类型：
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作者：
Hu, Cheng;Griffis, Timothy J.;Lee, Xuhui
大气氨（NH3）是活性氮（N-r）的主要形式，也是铵（NH 4+）气溶胶的前体。氨与对人类健康的不利影响、生态系统生物多样性的丧失有关，并在气溶胶辐射强迫中起着关键作用。美国中西部是北美地区主要的NH3来源，因为密集的畜牧业和合成氮肥的大量使用。在这里，我们结合联合收割机高塔（100米）在明尼苏达州的观测和天气研究和预报模型，再加上化学（WRF-Chem）建模调查高和低NH3排放事件在美国玉米带，以提高我们的排放源和运输过程的分布的理解。我们检查了2017年2月至2018年11月的观察结果，并对案例进行了模型模拟。结果表明：（1）2017年11月的峰值排放量因高于正常气温而增加，这意味着Q（10）（即，温度升高10摄氏度时NH3排放量的变化）为2.5。(2)从北方爱荷华州，约400公里远的高塔，密集的牲畜排放占17.6%的丰富的高塔NH3混合比。(3)最内区域3中的氨混合比经常（即，336小时，2017年11月的48%）超过5.3 ppb，这是一个重要的空气质量健康标准。(4)2017年11月，模拟的NH3净生态系统交换（NH3排放与干沉降之间的差异）占农业地区NH3总排放量的60-65%，是森林地区排放量的2.8-3.1倍。(5)我们估计平均每年NH3净生态系统交换为1.60 +/- 0.06 nmol。m（-2）。s（-1）为农业用地，-0.07 +/-0.02nmol. m（-2）。s（-1）为林地。这些结果意味着，未来温暖的秋季温度将提高农业NH3排放，增加危险的NH3事件的频率，并提高干燥NH3沉积在邻近的林地。
Atmospheric ammonia (NH3)is the primary form of reactive nitrogen (N-r) and a precursor of ammonium (NH4+) aerosols. Ammonia has been linked to adverse impacts on human health, the loss of ecosystem biodiversity, and plays a key role in aerosol radiative forcing. The midwestern United States is the major NH3 source in North America because of dense livestock operations and the high use of synthetic nitrogen fertilizers. Here, we combine tall-tower (100 m) observations in Minnesota and Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) modeling to investigate high and low NH3 emission episodes within the U.S. Corn Belt to improve our understanding of the distribution of emission sources and transport processes. We examined observations and performed model simulations for cases in February through November of 2017 and 2018. The results showed the following: (1) Peak emissions in November 2017 were enhanced by above-normal air temperatures, implying a Q(10) (i.e., the change in NH3 emissions for a temperature increase of 10 degrees C) of 2.5 for emissions. (2) The intensive livestock emissions rom northern Iowa, approximately 400 km away from the tall tower, accounted for 17.6% of the abundance in tall-tower NH3 mixing ratios. (3) Ammonia mixing ratios in the innermost domain 3 frequently (i.e., 336 hr, 48% of November 2017) exceeded 5.3 ppb, an important air quality health standard. (4) In November 2017, simulated NH3 net ecosystem exchange (the difference between NH3 emissions and dry deposition) accounted for 60-65% of gross NH3 emissions for agricultural areas and was 2.8-3.1 times the emissions of forested areas. (5) We estimated a mean annual NH3 net ecosystem exchange of 1.60 +/- 0.06 nmol . m(-2) . s(-1) for agricultural lands and -0.07 +/- 0.02 nmol . m(-2) . s(-1) for forested lands. These results imply that future warmer fall temperatures will enhance agricultural NH3 emissions, increase the frequency of dangerous NH3 episodes, and enhance dry NH3 deposition in adjacent forested lands.