State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry (LAPC), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, 100029, China; University of Chinese Academy of Sciences, Beijing, 100049, China.
State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry (LAPC), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, 100029, China.
Environ Pollut. 2021 Jan 1;268(Pt B):115855. doi: 10.1016/j.envpol.2020.115855. Epub 2020 Oct 15.
A seven-year long-term comprehensive measurement of non-refractory submicron particles (NR-PM) in autumn and winter in Beijing from 2012 to 2018 was conducted to evaluate the effectiveness of the clean air actions implemented by the Chinese government in September 2013 on aerosols from different sources and chemical processes. Results showed that the NR-PM concentrations decreased by 44.1% in autumn and 73.2% in winter from 2012 to 2018. Sulfate showed a much larger reduction than nitrate and ammonium in both autumn (55%) and winter (86%) and that nitrate even slightly increased by 15.8% in autumn. As a result, aerosol pollution in winter gradually changed from sulfate-rich to nitrate-rich with a sudden change after 2016 and the dominant role of nitrate in autumn was also strengthened after 2016. Among primary organic aerosol (OA) types, biomass burning OA and coal combustion OA exhibited the largest decline in autumn and winter, with reductions of 87.5% and 77.3%, respectively, while hydrocarbon-like OA (HOA) exhibited the smallest decline in both autumn (24.4%) and winter (37.1%). These significant changes in aerosol compositions were highly consistent with the much faster reduction of SO (75-85%) than NOx (36-59%) and were mainly due to the clean air actions rather than the impact of meteorological conditions. What's more, the enhanced atmospheric oxidizing capacity, which was indicated by increased O, altered the chemical processes of oxygenated OA (OOA), especially in autumn. Both of less-oxidized OOA (LO-OOA) and more-oxidized OOA showed elevated contributions in OA by 4% in autumn. The increased oxygen-to-carbon ratios of LO-OOA in autumn (from 0.42 to 0.58) and winter (from 0.44 to 0.52) indicated the enhanced atmospheric oxidizing capacity strengthened photochemical reactions and resulted in the increased oxidation degree of LO-OOA. This study demonstrates the effectiveness of the clean air actions for air quality improvement in Beijing.
对 2012 年至 2018 年北京秋季和冬季为期 7 年的非难溶性亚微米颗粒物（NR-PM）进行了综合长期测量，以评估中国政府 2013 年 9 月实施的清洁空气行动对不同来源和化学过程气溶胶的有效性。结果表明，与 2012 年相比，2018 年秋季和冬季 NR-PM 浓度分别下降了 44.1%和 73.2%。硫酸盐在秋季（55%）和冬季（86%）的降幅均大于硝酸盐和铵盐，而硝酸盐在秋季甚至略有增加 15.8%。结果，冬季气溶胶污染逐渐由硫酸盐为主变为硝酸盐为主，2016 年后发生突然变化，秋季硝酸盐的主导作用也在 2016 年后增强。在一次有机气溶胶（OA）类型中，生物质燃烧 OA 和煤燃烧 OA 在秋季和冬季的降幅最大，分别为 87.5%和 77.3%，而烃类 OA（HOA）在秋季（24.4%）和冬季（37.1%）的降幅最小。气溶胶成分的这些显著变化与 SO（75-85%）比 NOx（36-59%）更快的减少高度一致，这主要是由于清洁空气行动，而不是气象条件的影响。更重要的是，大气氧化能力的增强，由 O 增加来表示，改变了含氧 OA（OOA）的化学过程，特别是在秋季。秋季 OA 中，较少氧化的 OOA（LO-OOA）和更多氧化的 OOA 的贡献均增加了 4%。秋季 LO-OOA 的氧碳比（从 0.42 增加到 0.58）和冬季（从 0.44 增加到 0.52）的增加表明大气氧化能力的增强加强了光化学反应，导致 LO-OOA 的氧化程度增加。本研究证明了清洁空气行动对改善北京空气质量的有效性。
