Acidity of Aerosols during Winter Heavy Haze Events in Beijing and Gucheng, China
Acidity of Aerosols during Winter Heavy Haze Events in Beijing and Gucheng, China
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中国北京和故城冬季重霾天气气溶胶酸度
DOI：
10.1007/s13351-018-7063-4
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发表时间：
2018-02-01
影响因子：
3.2
通讯作者：
Xie, Zhouqing
中科院分区：
文献类型：
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作者：
Chi, Xiyuan;He, Pengzhen;Xie, Zhouqing
研究人员于2016年11月至2017年1月在北京市区和河北古城农村采集的pm2.5气溶胶样品中酸性和水溶性离子浓度，以了解次生无机物质的形成情况。城市SO42 -、NO3 -和NH4+的平均浓度分别为8.3、12.5和14.1 μg m-3，农村SO42 -、NO3 -和NH4+的平均浓度分别为14.0、14.2和24.2 μg m-3。北京市区氮、硫氧化比与相对湿度（相关系数分别为0.79和0.67）和气溶胶负荷相关。基于参数化模型，我们发现污染日so2的非均相反应速率常数比晴日高约10倍，表明气溶胶水中的非均相反应在雾霾事件中发挥了重要作用。利用ISORROPIA II模式预测城市和农村的气溶胶pH值，其平均值（范围）分别为5.0（4.9 ~ 5.2）和5.3（4.6 ~ 6.3）。在此预测的pH值条件下，溶解no2的氧化和n2o5的水解可能是霾中形成so42和no3的主要非均相反应。我们还分析了霾条件下气溶胶pH值对SO42 -、NO3 -和NH4+浓度变化的敏感性。气溶胶pH值对so42和NH4+浓度的敏感性高于no3浓度。pH值的敏感性总体上相对较弱，这与nh3分配的缓冲作用有关。
We investigated the acidity and concentrations of water-soluble ions in PM2.5aerosol samples collected from an urban site in Beijing and a rural site in Gucheng, Hebei Province from November 2016 to January 2017 to gain an insight into the formation of secondary inorganic species. The average SO42–, NO3–, and NH4+concentrations were 8.3, 12.5, and 14.1 μg m–3, respectively, at the urban site and 14.0, 14.2, and 24.2 μg m–3, respectively, at the rural site. The nitrogen and sulfur oxidation ratios in urban Beijing were correlated with relative humidity (with correlation coefficientr= 0.79 and 0.67, respectively) and the aerosol loadings. Based on a parameterization model, we found that the rate constant of the heterogeneous reactions for SO2on polluted days was about 10 times higher than that on clear days, suggesting that the heterogeneous reactions in the aerosol water played an essential role in haze events. The ISORROPIA II model was used to predict the aerosol pH, which had a mean (range) of 5.0 (4.9–5.2) and 5.3 (4.6–6.3) at the urban and rural site, respectively. Under the conditions with this predicted pH value, oxidation by dissolved NO2and the hydrolysis of N2O5may be the major heterogeneous reactions forming SO42–and NO3–in haze. We also analyzed the sensitivity of the aerosol pH to changes in the concentrations of SO42–, NO3–, and NH4+under haze conditions. The aerosol pH was more sensitive to the SO42–and NH4+concentrations with opposing trends, than to the NO3–concentrations. The sensitivity of the pH was relatively weak overall, which was attributed to the buffering effect of NH3partitioning.