Beijing Key Laboratory of Farmland Soil Pollution Prevention and Remediation, College of Resources and Environmental Sciences, China Agricultural University, Beijing, 100193, China.
Beijing Key Laboratory of Farmland Soil Pollution Prevention and Remediation, College of Resources and Environmental Sciences, China Agricultural University, Beijing, 100193, China.
Environ Pollut. 2021 Jul 15;281:117027. doi: 10.1016/j.envpol.2021.117027. Epub 2021 Mar 30.
The Clean Air Action implemented by the Chinese government in 2013 has greatly improved air quality in the North China Plain (NCP). In this work, we report changes in the chemical components of atmospheric fine particulate matter (PM) at four NCP sampling sites from 2012/2013 to 2017 to investigate the impacts and drivers of the Clean Air Action on aerosol chemistry, especially for secondary inorganic aerosols (SIA). During the observation period, the concentrations of PM and its chemical components (especially SIA, organic carbon (OC), and elemental carbon (EC)) and the frequency of polluted days (daily PM concentration ≥ 75 μg m) in the NCP, declined significantly at all four sites. Asynchronized reduction in SIA components (large decreases in SO with stable or even increased NO and NH) was observed in urban Beijing, revealing a shift of the primary form of SIA, which suggested the fractions of NO increased more rapidly than SO during PM pollution episodes, especially in 2016 and 2017. In addition, unexpected increases in the sulfur oxidation ratio (SOR) and the nitrogen oxidation ratio (NOR) were observed among sites and across years in the substantially decreased PM levels. They were largely determined by secondary aerosol precursors (i.e. decreased SO and NO), photochemical oxidants (e.g. increased O), temperature, and relative humidity via gas-phase and heterogeneous reactions. Our results not only highlight the effectiveness of the Action Plan for improving air quality in the NCP, but also suggest an increasing importance of SIA in determining PM concentration and composition.
中国政府于 2013 年实施的《清洁空气行动计划》极大地改善了华北平原的空气质量。在这项工作中，我们报告了 2012/2013 年至 2017 年期间四个华北平原采样点大气细颗粒物（PM）化学组分的变化，以调查《清洁空气行动计划》对气溶胶化学的影响和驱动因素，特别是对二次无机气溶胶（SIA）的影响和驱动因素。在观测期间，所有四个站点的 PM 及其化学组分（特别是 SIA、有机碳（OC）和元素碳（EC））浓度和污染天数（每日 PM 浓度≥75μg·m）以及污染天数（每日 PM 浓度≥75μg·m）在华北平原均显著下降。在北京城区观察到 SIA 组分的非同步减少（SO 大幅减少，而 NO 和 NH 稳定或甚至增加），表明 SIA 的主要形式发生了转变，这表明在 PM 污染期间，NO 的增加速度比 SO 更快，尤其是在 2016 年和 2017 年。此外，在 PM 水平大幅降低的情况下，各站点和各年份的硫氧化比（SOR）和氮氧化比（NOR）均出现意外增加。它们主要由二次气溶胶前体（即 SO 和 NO 的减少）、光化学氧化剂（如增加的 O）、温度和相对湿度通过气相和非均相反应决定。我们的研究结果不仅突出了该行动计划在改善华北平原空气质量方面的有效性，还表明 SIA 在决定 PM 浓度和组成方面的重要性日益增加。
