Division of Environmental Health and Risk Management, School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, United Kingdom; School of Earth Sciences and Resources, China University of Geosciences, Xueyuan Road 29, 100083, Beijing, China.
Ministry of Education Key Laboratory for Earth System Modeling, Department of Earth System Science, Tsinghua University, Beijing, 100084, China.
Environ Pollut. 2020 Nov;266(Pt 1):115078. doi: 10.1016/j.envpol.2020.115078. Epub 2020 Jun 26.
This study was designed to investigate the seasonal characteristics and apportion the sources of organic carbon during non-haze days (<75 μg m) and haze (≥75 μg m) events at Pinggu, a rural Beijing site. Time-resolved concentrations of carbonaceous aerosols and organic molecular tracers were measured during the winter of 2016 and summer 2017, and a Chemical Mass Balance (CMB) model was applied to estimate the average source contributions. The concentration of OC in winter is comparable with previous studies, but relatively low during the summer. The CMB model apportioned seven separate primary sources, which explained on average 73.8% on haze days and 81.2% on non-haze days of the organic carbon in winter, including vegetative detritus, biomass burning, gasoline vehicles, diesel vehicles, industrial coal combustion, residential coal combustion and cooking. A slightly lower percentage of OC was apportioned in the summer campaign with 64.5% and 78.7% accounted for. The other unapportioned OC is considered to consist of secondary organic carbon (SOC). During haze episodes in winter, coal combustion and SOC were the dominant sources of organic carbon with 23.3% and 26.2%, respectively, followed by biomass burning emissions (20%), whereas in summer, industrial coal combustion and SOC were important contributors. Diurnal contribution cycles for coal combustion and biomass burning OC showed a peak at 6-9 pm, suggesting domestic heating and cooking were the main sources of organic aerosols in this rural area. Backward trajectory analysis showed that high OC concentrations were measured when the air mass was from the south, suggesting that the organic aerosols in Pinggu were affected by both local emissions and regional transport from central Beijing and Hebei province during haze episodes. The source apportionment by CMB is compared with the results of a Positive Matrix Factorization (PMF) analysis of ACSM data for non-refractory PM, showing generally good agreement.
本研究旨在探究北京平谷农村地区非霾(<75μg/m)和霾天(≥75μg/m)条件下有机碳的季节特征及其来源。在 2016 年冬季和 2017 年夏季，我们对碳质气溶胶和有机分子示踪剂进行了时间分辨测量，并应用化学质量平衡(CMB)模型来估算平均源贡献。冬季 OC 的浓度与先前的研究相当，但夏季相对较低。CMB 模型分配了七个单独的原始源，它们在霾天平均解释了 73.8%，在非霾天平均解释了 81.2%的有机碳，包括植物碎屑、生物质燃烧、汽油车、柴油车、工业煤炭燃烧、民用煤炭燃烧和烹饪。在夏季，分配的 OC 百分比略低，占 64.5%和 78.7%。其他未分配的 OC 被认为是由二次有机碳(SOC)组成。在冬季霾事件中，煤炭燃烧和 SOC 是有机碳的主要来源，分别占 23.3%和 26.2%，其次是生物质燃烧排放(20%)，而在夏季，工业煤炭燃烧和 SOC 是重要的贡献者。煤炭燃烧和生物质燃烧 OC 的日贡献循环在 6-9 点达到峰值，表明家庭取暖和烹饪是该农村地区有机气溶胶的主要来源。后向轨迹分析表明，当空气团来自南方时，OC 浓度较高，这表明平谷的有机气溶胶受到当地排放和来自北京中部和河北省的区域传输的影响。CMB 的源分配与 ACSM 数据的正矩阵因子化(PMF)分析结果进行了比较，结果基本一致。
