2010—2019年台州市市区降水化学组成特征及变化趋势

为了解台州市市区大气降水化学成分组成特征及变化规律,对2010—2019年台州市市区降水监测数据进行了统计分析。结果表明:2010—2019年降水样品pH为4.20～4.84夏高冬低,强酸性降水频率下降显著,电导率平均值为3.16 mS/cm。SO_4~(2-)和NO_3~-是降水中最主要的阴离子,NH_4~+和Ca~(2+)是降水中最主要的阳离子。Ca~(2+)浓度在2018年开始有所抬升,SO_4~(2-)和NO_3~-浓度整体呈波动下降趋势。SO_4~(2-)与NO_3~-浓度比均值为1.50,呈下降趋势,同大气中SO_2与NO_2的质量浓度比变化趋势基本一致。SO_4~(2-)和NO_3~-相关性显著,Cl~-、Na~+及Mg~(2+)三者之间具有较好相关性。降水与气态污染物相关性不大,对颗粒物有明显冲刷去除作用。SO_2和NO_x的排放量显著下降,酸雨污染呈现改善过程。

Chemical Characteristics and Trends of Precipitation in Urban Taizhou from 2010 to 2019

The observational data of precipitation in urban area of Taizhou from 2010 to 2019 was statistically analyzed to investigate its chemical characteristics and trends of the chemical composition of atmospheric precipitation.The results showed that the pH varied from 4.20 to 4.84, which was higher in summer and lower in winter.The frequency of heavy acid precipitation was decreased significantly.The mean electrical conductivity was 3.16 mS/cm.SO₄^2- and NO₃^- were the dominant anions, while NH₄⁺ and Ca²⁺ were the dominant cations.The concentration of Ca²⁺ began to rise in 2018, and the concentration of SO₄^2- and NO₃^- showed a decreased trend with fluctuation.The mean of the concentration ratio of SO₄^2- and NO₃^- was 1.50, showing a decreasing trend over the past decades, which was basically consistent with the trends of the mass concentration ratio of SO₂ and NO₂.Significant correlations were observed between SO₄^2- and NO₃^-.Other relatively good correlations were observed among Cl^-, Na⁺ and Mg²⁺.There was little correlation between precipitation and gaseous pollutants, and the scavenging effects of precipitation on the removal of particulates were obvious.The emissions of SO₂ and NO_x were reduced significantly, and the acid rain pollution has improved.