近年来，由于严格的排放控制，我国的大气颗粒物污染问题得到了实质性缓解，但低能见度雾霾事件的改善并不明显。在此现象的基础上，结合6年冬季观测、卫星反演、热力学模型和理论计算，本研究分析了气溶胶化学成分和吸湿行为对能见度的复杂影响。我们发现，从2013年到2018年，由于不平衡的减排措施，气溶胶质量浓度中硝酸盐的比例增加了约10%。这种气溶胶化学成分的转变与近年来环境湿度的增加共同提高了气溶胶的消光效率，并且在2017年之后，硝酸盐占比增加占据重要作用。气溶胶消光效率的提高是近年来中国东部地区气溶胶质量浓度显著降低，但能见度无明显改善的原因。
Though China has witnessed substantial particular matter pollution mitigation owing to the strict emission control in recent years, the frequency of haze events with low visibility is not improved as much as expected, especially in cold seasons. Here, 6‐year wintertime observations, satellite retrievals, a thermodynamic model, and theoretical calculation were integrated to better understand the complex influence of aerosol chemical composition and hygroscopic behaviors on visibility impairment. We found that the proportion of nitrate in aerosol mass concentration increased by approximately 10% from 2013 to 2018. Such a transition in aerosol chemical compositions together with increasing ambient humidity in past years jointly enhanced aerosol extinction efficiency, and the elevated proportion of nitrate played an increasingly critical role after 2017. The increased aerosol extinction efficiency is responsible for the less improved visibility despite large decrease in aerosol mass concentrations in eastern China.
 

硝酸盐；能见度；吸湿性，相对湿度