Insights into the chemistry of aerosol growth in Beijing: implication of fine particle episode formation during wintertime
Insights into the chemistry of aerosol growth in Beijing: implication of fine particle episode formation during wintertime
复制标题
深入了解北京气溶胶生长的化学性质：冬季细颗粒事件形成的影响
DOI：
10.1016/j.chemosphere.2021.129776
复制
发表时间：
2021
期刊：
影响因子：
8.8
通讯作者：
Yuesi Wang
中科院分区：
文献类型：
--
作者：
Shuanghong Yang;Zirui Liu;Jiayun Li;Shuman Zhao;Zhongjun Xu;Wenkang Gao;Bo Hu;Yuesi Wang
成核颗粒的生长在细颗粒物的产生中起着重要作用，但在大城市复杂的大气环境中，新颗粒物的形成机制尚不清楚，这阻碍了pm2.5污染缓解措施的制定。在2018年11月15日至2019年1月15日期间，利用两套扫描迁移率粒子谱仪（SMPS）和Aerodyne高分辨率飞行时间气溶胶质谱仪（hrtof - ams）研究了北京市区超细颗粒在成核事件生长阶段的化学性质。在这个激烈的运动中，观察到11个NPF事件，纳米颗粒的生长速率（GR）在12.5到24.5 nm h−1之间。确定了pm2.5发作的四个周期，包括气溶胶颗粒生长到颗粒物污染。基于qgr - qams理论框架，探索可冷凝蒸汽源速率与纳米粒子生长速率之间的平衡，我们清楚地展示了纳米粒子在生长过程中的物理和化学演化过程，以环境-大气尺寸（>100 nm）。总的来说，当硝酸盐浓度和低氧化的含氧有机气溶胶（LO-OOA）较高时，气溶胶颗粒的模态直径增长大于100 nm（11个NPF事件中有7个）；然而，当硫酸盐含量高时，另一类气溶胶颗粒的生长被限制在50-100 nm（11个NPF事件中的3个）。注意，由于在生长后期无法获得观测数据，因此无法确定剩余的一个NPF事件是否可以生长到100 nm。通过将气溶胶生长与化学成分联系起来，发现硫酸盐和有机物在气溶胶生长的初始阶段是主要的贡献者，而烹饪相关的OA （COA）增强了过渡阶段，硝酸盐和更氧化的OOA （MO-OOA）主导了气溶胶向环境-大气大小的后续增长。pm2.5中气溶胶生长的重要部分是由半挥发性有机蒸汽控制的，半挥发性有机蒸汽可以通过吸附的物理过程划分为积累模式和粗化模式的外部凝聚相。通过量化气溶胶颗粒生长的物理和化学性质，评价成核引发pm2.5污染事件的详细过程，为特大城市北京冬季雾霾污染的形成机制提供观测证据。
Nucleation particle growth plays a major role in the occurrence of fine particles, yet the mechanism of new particle formation (NPF) remains ambiguous in the complex atmosphere of megacities and hinders the development of measures to mitigate PM2.5pollution. In this study, the chemistry of ultrafine particles during the growth phase of nucleation events was investigated in urban Beijing from Nov. 15, 2018 to Jan. 15, 2019, using two scanning mobility particle spectrometers (SMPS) systems and an Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). During this intense campaign, 11 NPF events were observed and the growth rate (GR) of nanoparticles ranged from 12.5 to 24.5 nm h−1. Four periodic cycles of PM2.5episodes that included aerosol particle growth to particulate matter pollution were identified. Based on theQGR–QAMStheoretical frame that exploring the balance between the source rate of condensable vapors and the observed growth rate of nanoparticles, we clearly showed the physical and chemical evolution of nano-particle during the growth processes to ambient-atmosphere sizes (>100 nm). Generally, the modal diameter of aerosol particles grew by more than 100 nm (7 out of 11 NPF events) when the nitrate concentration and less-oxidized oxygenated organic aerosol (LO-OOA) were high; however, another class of aerosol particle growth was limited to 50–100 nm (3 out of 11 NPF events) when sulfate was high. Note that the remaining one NPF event could not be identified if it can grow up to 100 nm or not due to the unavailable of observation data during the late growth stage. By linking the aerosol growth with chemical compositions, sulfate and organics were found to be the main contributors during the initial stage of the aerosol growth, while cooking-related OA (COA) enhanced the transition stage, and nitrate and more-oxidized OOA (MO-OOA) dominated the subsequent growth of aerosol to ambient-atmosphere sizes. An important portion of aerosol growth in PM2.5was controlled by semi-volatile organic vapors, which can partition into the externally condensed phase of the accumulation mode and coarse mode via the physical process of adsorption. Through quantifying the physical and chemical properties of aerosol particle growth, the detail processes of nucleation initiated PM2.5pollution episodes were evaluated and provided observational evidence on the formation mechanism of winter haze pollution in the megacity of Beijing.