天津市环境空气中细粒子的污染特征与来源

于2006年8─12月,在天津市中心城区采集细粒子(PM2.5)并测定其中水溶性无机离子和元素的质量浓度,应用因子分析与多元线性回归技术解析PM2.5的来源.结果表明:ρ(PM2.5)月均值为103.9~217.4μg/m3,呈冬季最高、夏季最低的特征.水溶性无机离子质量浓度占ρ(PM2.5)的比例为24.90%~49.76%,其中ρ(SO42-),ρ(NO3-),ρ(NH4+)与ρ(Cl-)之和约占离子总质量浓度的90%.在夏季,二次粒子质量浓度占ρ(PM2.5)比例最大,这与SO2向SO42-,NO2向NO3-的转化率升高有关.PM2.5中Cl富集主要与燃煤等人为排放有关,海盐源对Cl-的贡献不足20%.天津PM2.5中含量最高的元素为Si,约占元素总质量浓度的28.4%.微量元素中以Zn和Pb的含量最高,二者主要来自燃煤和机动车排放.源解析结果表明,二次污染、化石燃料燃烧、土壤尘和建筑粉尘是天津市环境空气中PM2.5的主要来源,贡献率分别为53.4%,25.8%,12.3%和8.6%.

Pollution Characteristics and Sources of Fine Particulate Matter in Ambient Air in Tianjin City

Ambient PM_(2.5) samples were collected using 48 pieces of quartz and organic filter membranes at an urban site of Tianjin City from August to December, 2006. Concentrations of water-soluble inorganic ions and elements were determined separately. Major contributing sources to inorganic fine particulates were identified by factor analysis and multiple linear regression (FA-MLR) techniques. The results showed that monthly mean PM_(2.5) mass concentrations ranged from 103.9 to 217.4 μg/m~3, with the highest concentration in winter and the lowest in summer. Water-soluble inorganic ions mass concentrations accounted for 24.90%- 49.76% of PM_(2.5) mass concentration, and SO_4~(2-), NO_3~-, NH_4~+ and Cl~- were the major ions constituting about 90% of the total ion mass concentrations. The proportion of secondary species in PM_(2.5) was the largest in summer, due to the increased transformation rates of SO_2 to SO_4~(2-), and NO_2 to NO~(3-). The chloride enrichment in PM_(2.5) in the Tianjin atmosphere mostly resulted from anthropogenic emissions such as coal combustion; the contribution of sea salt was less than 20%. Si was the dominant inorganic element, accounting for about 28.4% of elemental mass concentration. Zn and Pb, from coal burning and vehicle exhaust, were the most abundant trace elements. Results of source apportionment indicated that secondary particles, fossil fuel burning, soil dust and construction dust were the major sources of inorganic fine particulates in Tianjin City, with contributions of 53.4%, 25.8%, 12.3% and 8.6% respectively.