北京市核心区冬春季大气离子沉降量特征及来源解析

Characteristics and Source Apportionment of Atmospheric Ion Deposition During Winter and Spring in the Core Area of Beijing

近年来生态环境部和北京市不断加严降尘量控制指标,为了掌握降尘量中离子沉降量特征及其来源,采用过滤法和离子色谱法分别测定北京市核心区冬春季降尘量及离子沉降量,采用PMF模型开展离子沉降量来源解析.结果表明:(1)离子沉降量及其在降尘量中占比平均值分别为0.87 t·(km^(2)·30 d)^(-1)和14.2%,工作日降尘量和离子沉降量分别是休息日的1.3倍和0.7倍.(2)离子沉降量与降水量、相对湿度、温度和平均风速的线性方程可决系数分别为0.54、 0.16、 0.15和0.02,离子沉降量与PM_(2.5)浓度和降尘量的线性方程可决系数分别为0.26和0.17,控制PM_(2.5)浓度对控制离子沉降量非常重要.(3)离子沉降量中阴、阳离子分别占61.6%和38.4%,SO_(4)^(2-)、 NO_(3)^(-)和NH_(4)^(+)合计占60.6%;阴阳离子电荷沉降量比值为0.70,降尘呈碱性;离子沉降量中ρ(NO_(3)^(-))/ρ(SO_(4)^(2-))为0.66,与15年前相比有所提高.(4)二次源、扬尘源、燃烧源、融雪剂源和其他源对离子沉降量的贡献率分别为51.7%、 17.7%、 13.5%、 13.5%和3.6%.

In recent years,the Ministry of Ecology and Environment and the Beijing Municipal Government have continuously strengthened the control indicators of dustfall.In order to grasp the characteristics and sources of ion deposition in dustfall,the filtration method and ion chromatography were used to determine the dustfall and ion deposition during winter and spring in the core area of Beijing,and the PMF model was carried out to analyze the sources of ion deposition.The results indicated:①the average values of ion deposition and its proportion in dustfall were 0.87 t·(km^(2)·30 d)^(-1) and 14.2%,respectively.The dustfall and ion deposition on working days were 1.3 times and 0.7 times that on rest days,respectively.②The coefficient of determination in the linear equations between ion deposition and precipitation,relative humidity,temperature,and average wind speed were 0.54,0.16,0.15,and 0.02,respectively.In addition,the coefficient of determination in the linear equations between ion deposition and PM_(2.5) concentration and dustfall were 0.26 and 0.17,respectively.Therefore,controlling the concentration of PM_(2.5) was crucial to treating ion deposition.③Anions and cations accounted for 61.6%and 38.4%,respectively,in the ion deposition,and SO_(4)^(2-),NO_(3)^(-),and NH_(4)^(+)accounted for 60.6%in total.The ratio of anion and cation charge deposition was 0.70,and the dustfall was alkaline.Theρ(NO_(3)^(-))/ρ(SO_(4)^(2-))in the ion deposition was 0.66,which was higher than that of 15 years ago.④The contribution rates of secondary sources,fugitive dust sources,combustion sources,snow-melting agent sources,and other sources were 51.7%,17.7%,13.5%,13.5%,and 3.6%,respectively.