Ismaeel Ali, Tai Amos P K, Wu Jin
Department of Earth and Environmental Sciences, Faculty of Science, The Chinese University of Hong Kong, Hong Kong, China.
Department of Earth and Environmental Sciences, Faculty of Science, The Chinese University of Hong Kong, Hong Kong, China; State Key Laboratory of Agrobiotechnology, and Institute of Environment, Energy and Sustainability, The Chinese University of Hong Kong, Hong Kong, China.
Sci Total Environ. 2024 Dec 1;954:176188. doi: 10.1016/j.scitotenv.2024.176188. Epub 2024 Sep 13.
Ammonia (NH) is the most abundant alkaline gas in the atmosphere, mainly emitted by agricultural activities. NH readily reacts with other atmospheric acidic pollutants, such as the oxidation products of sulfur dioxide (SO) and nitrogen oxides (NOₓ), to create fine particulate matter, which has far-reaching effects on human health and ecosystems. Here, we investigated long-term atmospheric NH trends in South Asia (SA) using satellite observations from the Infrared Atmospheric Sounding Interferometer (IASI). We analyzed 15 years (2008-2022) of IASI-NH retrievals against climate, biophysical, and chemical variables using an ensemble of multivariate statistical methods to identify the major factors driving the observed patterns in the region. Trend analysis of IASI-NH data reveals a significant rise in atmospheric NH over 51 % of SA plains, but a downward trend over 31 % of the region. Spatial correlation analysis reveals that biophysical factors, representing cropland expansion and agriculture intensification, have the highest positive correlation over 56 % of SA plains experiencing positive NH trends. However, our results reveal that the chemical conversion of NH to ammonium compounds, driven by the positive trends in NOₓ and SO pollution, is driving the apparently declining trend of NH in the other regions. Our results provide important insights into the NH trends detected by satellite data and can better inform the policy design aimed at reducing NH emissions and improving air quality for developing regions of the world.
氨（NH₃）是大气中含量最丰富的碱性气体，主要由农业活动排放。NH₃很容易与其他大气酸性污染物发生反应，比如二氧化硫（SO₂）和氮氧化物（NOₓ）的氧化产物，从而形成细颗粒物，这对人类健康和生态系统有着深远影响。在此，我们利用红外大气探测干涉仪（IASI）的卫星观测数据，研究了南亚地区大气NH₃的长期变化趋势。我们运用多种多元统计方法，分析了15年（2008 - 2022年）IASI - NH₃反演数据与气候、生物物理和化学变量之间的关系，以确定驱动该地区观测模式的主要因素。IASI - NH₃数据的趋势分析表明，南亚超过51%的平原地区大气NH₃显著上升，但该地区31%的区域呈下降趋势。空间相关性分析表明，在经历NH₃上升趋势的南亚56%的平原地区，代表农田扩张和农业集约化的生物物理因素具有最高的正相关性。然而，我们的研究结果表明，在NOₓ和SO₂污染呈上升趋势的推动下，NH₃向铵化合物的化学转化，正导致其他地区NH₃出现明显下降趋势。我们的研究结果为卫星数据检测到的NH₃趋势提供了重要见解，并能更好地为旨在减少NH₃排放和改善全球发展中地区空气质量的政策设计提供参考。
