薄雾
能见度
空气质量指数
北京
质量浓度(化学)
微粒
环境科学
污染
气溶胶
空气污染
分数(化学)
大气科学
质量分数
环境化学
硝酸盐
线性回归
气象学
化学
中国
统计
地理
数学
生态学
有机化学
考古
物理化学
地质学
生物
作者
Shuya Hu,Gang Zhao,Tianyi Tan,C. Li,Taomou Zong,Nan Xu,Wenfei Zhu,Min Hu
标识
DOI:10.1016/j.envpol.2021.118032
摘要
The annual mean PM2.5 mass concentration has decreased because of the stringent emission controls implemented in Beijing, China in recent years, whereas the nitrate NO3- mass fraction in PM2.5 increases gradually. Low-visibility events occur frequently even though PM2.5 pollution has been mitigated significantly, with the daily mean PM2.5 mass concentration mostly less than 75 μg/m3. In this study, the non-linear relationship was analyzed between atmospheric visibility and PM2.5 based on chemical composition from a two-year field observation. Our results showed that NO3- became the main constituent of PM2.5, especially during the haze pollution episodes. A localized parameterization scheme was proposed between the atmospheric extinction coefficient (σext) and major chemical constituents of PM2.5 by multiple linear regression (MLR). The contribution of NO3- to σext increased with increasing air pollution, and NO3- became the most important contributor for PM2.5 above 75 μg/m3. The visibility decreased with increasing NO3- mass fraction for the same PM2.5 mass concentration when PM2.5 was above 20 μg/m3. The hygroscopicity of PM2.5 increased with increasing mass fraction of hygroscopic NO3-. These results stressed the importance of reducing particulate NO3- and its precursors (for instance, NH3) through effective emission control measures as well as the tightening of PM2.5 standards to further improve air quality and visibility in Beijing.
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