State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China; State Environmental Protection Key Laboratory of Sources and Control of Air Pollution Complex, Beijing 100084, China.
Pacific Northwest National Laboratory, Richland, WA 99352, USA.
Sci Total Environ. 2020 Jun 15;721:137700. doi: 10.1016/j.scitotenv.2020.137700. Epub 2020 Mar 5.
SO concentration decreased rapidly in recent years in China due to the implementation of strict control policies by the government. Particulate sulfate (pSO) and gaseous HSO (SA) are two major products of SO and they play important roles in the haze formation and new particle formation (NPF), respectively. We examined the change in pSO and SA concentrations in response to reduced SO concentration using long-term measurement data in Beijing. Simulations from the Community Multiscale Air Quality model with a 2-D Volatility Basis Set (CMAQ/2D-VBS) were used for comparison. From 2013 to 2018, SO concentration in Beijing decreased by ~81% (from 9.1 ppb to 1.7 ppb). pSO concentration in submicrometer particles decreased by ~60% from 2012-2013 (monthly average of ~10 μg·m) to 2018-2019 (monthly average of ~4 μg·m). Accordingly, the fraction of pSO in these particles decreased from 20-30% to <10%. Increased sulfur oxidation ratio was observed both in the measurements and the CMAQ/2D-VBS simulations. Despite the reduction in SO concentration, there was no obvious decrease in SA concentration based on data from several measuring periods from 2008 to 2019. This was supported by the increased SA:SO ratio with reduced SO concentration and condensation sink. NPF frequency in Beijing between 2004 and 2019 remains relatively constant. This constant NPF frequency is consistent with the relatively stable SA concentration in Beijing, while different from some other cities where NPF frequency was reported to decrease with decreased SO concentrations.
近年来，由于政府实施了严格的控制政策，中国的 SO 浓度迅速下降。硫酸盐颗粒（pSO）和气态 HSO（SA）是 SO 的两种主要产物，它们分别在雾霾形成和新粒子形成（NPF）中发挥重要作用。我们利用北京长期测量数据研究了 SO 浓度降低对 pSO 和 SA 浓度的影响。模拟结果与使用二维挥发基组（CMAQ/2D-VBS）的多尺度空气质量模型（CMAQ）进行了比较。2013 年至 2018 年，北京市 SO 浓度下降了约 81%（从 9.1 ppb 降至 1.7 ppb）。亚微米颗粒中 pSO 的浓度下降了约 60%，从 2012-2013 年（每月平均约 10 μg·m）降至 2018-2019 年（每月平均约 4 μg·m）。因此，这些颗粒中 pSO 的比例从 20-30%下降到<10%。测量和 CMAQ/2D-VBS 模拟均观察到硫氧化比增加。尽管 SO 浓度降低，但根据 2008 年至 2019 年几个测量期间的数据，SA 浓度并没有明显下降。这与 SO 浓度降低时 SA:SO 比值增加和凝结汇相吻合。2004 年至 2019 年期间，北京的 NPF 频率保持相对稳定。这种相对稳定的 NPF 频率与北京相对稳定的 SA 浓度一致，而与其他一些报道称随着 SO 浓度降低 NPF 频率降低的城市不同。
