山西省五台山夏季降水化学特征及来源解析

Chemical Characteristics and Source Apportionment of Summer Precipitation at the Mount Wutai, Shanxi Province

  • 摘要: 基于2022年6—8月山西省五台山20次降水过程观测数据,利用富集因子法、正定矩阵因子分解模型、后向轨迹模型等方法分析降水pH值、电导率、离子组分及来源。结果表明:五台山夏季降水pH降水量加权平均值为6.16,电导率降水量加权平均值为15.51 μS·c-1,酸雨污染不严重,降水较为洁净,SO2-4、NO-3、NH+4和Ca2+离子质量浓度较大,不同离子在上游气团影响下随降水量呈现不同特征;在0.01显著性水平下,由于NO-3和SO2-4化学性质相似及前体物排放特征相关,二者相关系数最高,且与Na+的相关系数均超过0.94;K+和Mg2+相对于海洋均发生富集,Cl-相对于海洋和地壳均被稀释,Mg2+既有海洋源又有陆地源,Cl-源自海洋和化石燃料燃烧;交通活动和扬尘、施肥等农业活动、生物质燃烧、化石燃料燃烧及汽车尾气排放是五台山降水离子的主要来源;不同方向轨迹的气团对五台山降水离子影响各异,总体上五台山夏季降水受偏南气团的影响较为明显。

     

    Abstract: In order to reveal chemical characteristics of precipitation at the Mount Wutai, based on continuous precipitation observation data from 20 events at the Mount Wutai in Shanxi Province from June to August in 2022. pH value, conductivity, composition and sources of major water-soluble ions in precipitation are analyzed using methods such as the enrichment factor method, positive matrix factorization model (PMF) and Hybrid Single Particle Lagrangian Integrated Trajectory Model (HYSPLIT). Results indicate that the weighted average pH and conductivity values of rainfall during the summer at Mount Wutai are 6.16 and 15.51 μS·cm-1, respectively. It suggests that the acid rain pollution is not severe, and the precipitation composition is relatively clean. The ranking of the mass concentrations of major ions in precipitation, from highest to lowest, is as follows: SO2-4, NO-3, NH+4, Ca2+, K+, Na+, Cl-, Mg2+ and F-. Percentages of NH+4 and Ca2+ in the total ion mass concentration are 20% and 7%, while percentages of SO2-4 and NO-3 in the total ion mass concentration are 33% and 27%. Different ions exhibit different characteristics with rainfall under the influence of upstream air masses. Overall, compared with other high-altitude stations, it presents typical precipitation chemical characteristics of inland high-altitude stations. In the case of 0.01 significant level, the highest correlation coefficient is observed between SO2-4 and NO-3 due to their similar chemical properties and related precursor emission characteristics, the correlation coefficient between K+ and Na+ is 0.899, the correlation coefficient between Mg2+and Ca2+ is 0.827, and the correlation coefficient between Mg2+ and Na+ is 0.778. K+ and Mg2+ are enriched relative to the ocean, and Cl- is diluted relative to the ocean and crust. Traffic activities and dust contribute significantly to levels of Cl- and Ca2+. Agricultural practices, such as fertilization, result in elevated concentrations of F- and NH+4. Additionally, biomass combustion is associated with higher levels of K+. SO2-4 and nitrate (NO-3) primarily originate from fossil fuel combustion and automobile exhaust emissions. Additionally, summer precipitation at the Mount Wutai is significantly influenced by the southerly air mass. The precipitation from the southern air mass (excluding NH+4) is greater than that from the northern air mass. The total ion concentration in the southern air mass is 1.3 times greater than that in the northern air mass.

     

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