成都市城区大气细颗粒物水溶性离子污染特征

为了解成都市城区大气细颗粒物水溶性离子污染特征,在成都市城区四季采集PM_2.5有效样品共计102 个,测得颗粒物质量浓度以及水溶性离子质量浓度(NH₄⁺、Ca²⁺、Na⁺、Mg²⁺、K⁺、F^-、NO₃^-、SO₄^2-、Cl^-),并分析其浓度变化特征,重点关注二次无机离子的污染特征及形成影响.结果表明,成都市城区水溶性离子与大气细颗粒物的污染浓度变化基本一致,其中二次无机离子(NH₄⁺、NO₃^-、SO₄^2-)是离子中最主要的组成部分,占总水溶性离子浓度的84.8%.大气细颗粒物春秋冬三季为酸性,其原位PH值分别为1.9、2.6和2.0.城区硫酸盐和硝酸盐化学特性存在差异,硫酸盐主要表现为非均相反应过程中形成的NH₄HSO₄,并主要受区域传输过程的影响;硝酸盐主要表现为均相反应过程形成的NH₄NO₃,并主要受局地排放的影响.

Characterization of water-soluble ions pollution of atmospheric fine particles in Chengdu City

In order to understand the characteristics of water-soluble ion pollution of atmospheric fine particles in the urban area of Chengdu, a total of 102 PM_2.5 samples were collected in the urban areas of Chengdu in four seasons. Mass concentrations of particles matter (PM) and its water-soluble ions (NH₄⁺、Ca²⁺、Na⁺、Mg²⁺、K⁺、F^-、NO₃^-、SO₄^2-、Cl^-) were measured and analyzed to characterize its seasonal, with special attentions to characteristics and formation of secondary ions. The results showed that concentration changes of water-soluble ions and atmospheric fine particles in Chengdu’s urban area generally followed the same pattern. Secondary inorganic ions (NH₄⁺、NO₃^-、SO₄^2-) were the main components of water-soluble ions in PM, accounting for 84.8%. Atmospheric fine particles appeared to be acidic in Spring, Autumn, and Winter, and their in-situ PH values were 1.9, 2.6 and 2.0, respectively. Sulfate and nitrate in the atmospheric PM exhibited differences in its chemical characteristics. For example, the dominating form of sulfate was NH₄HSO₄, which mainly resulted from heterogeneous reaction processes and was heavily affected by the regional atmospheric transportation; while the dominating form of nitrate was NH₄NO₃, which mainly resulted from homogeneous reaction processed and was heavily affected by local emissions.