| Title | Current challenges of improving visibility due to increasing nitrate fraction in PM2.5 during the haze days in Beijing, China |
| Authors | Hu, Shuya Zhao, Gang Tan, Tianyi Li, Chengcai Zong, Taomou Xu, Nan Zhu, Wenfei Hu, Min |
| Affiliation | Peking Univ, Coll Environm Sci & Engn, Int Joint Res Ctr Atmospher Res IJRC, State Key Joint Lab Environm Simulat & Pollut Con, Beijing 100871, Peoples R China Peking Univ, Dept Atmospher & Ocean Sci, Beijing 100871, Peoples R China |
| Keywords | PARTICULATE MATTER POLLUTION AEROSOL OPTICAL-PROPERTIES CHEMICAL-COMPOSITION LIGHT EXTINCTION AIR-POLLUTION ANTHROPOGENIC EMISSIONS HYGROSCOPIC GROWTH RELATIVE-HUMIDITY FINE PARTICLES BOUNDARY-LAYER |
| Issue Date | 1-Dec-2021 |
| Publisher | ENVIRONMENTAL POLLUTION |
| Abstract | The annual mean PM2.5 mass concentration has decreased because of the stringent emission controls imple-mented 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 mu g/m(3). 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 co-efficient (sigma(ext)) and major chemical constituents of PM2.5 by multiple linear regression (MLR). The contribution of NO3- to sigma(ext) increased with increasing air pollution, and NO-3 became the most important contributor for PM2.5 above 75 mu g/m(3). The visibility decreased with increasing NO3- mass fraction for the same PM2.5 mass concen-tration when PM2.5 was above 20 mu g/m(3). 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. |
| URI | http://hdl.handle.net/20.500.11897/625887 |
| ISSN | 0269-7491 |
| DOI | 10.1016/j.envpol.2021.118032 |
| Indexed | EI SCI(E) |
| Appears in Collections: | 环境科学与工程学院 环境模拟与污染控制国家重点联合实验室 物理学院 |
