四川盆地大气氨与氮氧化物排放对细颗粒物污染的影响及减排潜力

基于IASI、OMI与TROPOMI卫星数据识别了2008~2019年四川盆地氨与氮氧化物柱浓度的变化趋势，并进一步采用空气质量模型CMAQ对2019年冬季四川盆地氨排放的大气环境影响进行了研究，评估了氨与氮氧化物单独减排及氨与氮氧化物协同减排情景下对四川盆地颗粒物污染的影响.结果表明：2008~2012年四川盆地氮氧化物排放逐年升高随后在2013~2019年迅速下降，而氨柱浓度在2008~2013年期间较为稳定，自2014年起迅速增长.四川盆地氨排放的高值区主要集中在人为活动强烈的成都及周边地区和川南城市群以及农业源氨排放主导的川西北地区.铵根离子在川南城市群的PM_2.5当中占比高达11.4%，而对川西地区城市的PM_2.5贡献较低.敏感性实验结果表明，氨与氮氧化物协同减排50%能有效降低大气中硝酸铵与硫酸铵的浓度，从而减少细颗粒物污染，改善四川盆地区域环境空气质量.

Impacts of ammonia and nitrogen oxides emissions on fine particle matter pollution and mitigation potential over the Sichuan Basin

In this study, satellite data derived from IASI, OMI and TROPOMI were adopted to infer the trend of ammonia and NO_x emissions over 2008~2019 and the weather research forecast model (WRF) and the Community Multiscale Air Quality (CMAQ) were used to assess the environmental consequence of ammonia emissions over the Sichuan Basin in the winter of 2019. Furthermore, sensitivity experiments were performed to evaluate impacts of ammonia or NO_x emission reduction and ammonia and nitrogen oxides coordinated emission reduction scenarios on fine particles. The results show that nitrogen oxides emissions increased interannually from 2008 to 2012 and then decreased rapidly from 2013 to 2019, while ammonia columns were relatively stable over 2008~2013 and increased significantly from 2014 onwards. The hotspots of ammonia emissions in the Sichuan Basin were mainly concentrated in southern Sichuan city cluster and Chengdu and surrounding areas where anthropogenic activities were intense. The elevated ammonia emissions were also observed in the northwestern Sichuan city cluster dominated by agricultural sources. Ammonia ions accounted for a relatively high fraction of PM_2.5 in southern Sichuan city cluster, up to 11.4%, while its contribution to PM_2.5 in the cities of western Sichuan were relatively low. Sensitivity experiments indicate that the coordinated emission regulation in simultaneously reducing 50% NO_x and ammonia could effectively diminish the concentrations of ammonium nitrate and ammonium sulfate in PM_2.5, therefore reduce fine particulate pollution and improve the regional ambient air quality across the Sichuan Basin.