郑州市2018—2019年降水中无机离子的特性分析

Characteristic of Inorganic Ions in Precipitation in Zhengzhou from 2018 to 2019

郑州市位于河南省中北部,是中国重要的交通枢纽城市。近年来,郑州市秋冬季节污染问题日益严重。为了了解该地区的降水污染组成及来源,收集2018年5月—2019年4月期间郑州市降水样品,利用电导率仪和pH计测量雨水的电导率和pH值,用离子色谱仪分析降水样品中的9种主要无机离子(F^−、Cl^−、NO3^−、SO4^2−、Na^+、NH4^+、K^+、Ca^2+、Mg^2+),结合郑州市地面常规气象资料参数分析了降水中无机离子质量浓度变化趋势及气象参数与离子质量浓度之间的相关性系数等。pH计和电导率仪测量数值表明,采样期间郑州市降水pH值总体呈弱碱性,没有酸雨出现,电导率平均值为52.47μs·cm−1。离子质量浓度分析表明,降水总无机离子平均质量浓度为20.26μg·mL^−1,NO3^−和Ca^2+分别为最主要的阴离子和阳离子,占离子总质量浓度比例为28.75%和19.87%。连阴雨对阴离子的冲刷效果比对阳离子的冲刷效果好,NH4^+受大气中的NH3和降水强度的影响,质量浓度变化幅度最大。相关性分析表明,所有离子质量浓度之间均呈正相关,NO3^−和SO4^2−相关系数最大(r=0.938),其次是Ca^2+和Mg^2+(r=0.852)。降水中SO4^2−/NO3^−当量浓度比值为1.05,表明郑州市降水污染类型转变为硫酸、硝酸的混合型污染,这与之前的研究有所不同。

Zhengzhou,located in the north central of Henan Province,is an important transportation hub city in China.In recent years,the pollution issues in autumn and winter are becoming more and more serious in Zhengzhou.In order to investigate the composition and source of precipitation pollution in this area,precipitation samples were collected from May 2018 to April 2019 in Zhengzhou.Electrical conductivity and pH of precipitation were measured with the electrical conductivity meter and pH meter.9 kinds of main inorganic ions(F^−,Cl^−,NO3^−,SO4^2−,Na^+,NH4^+,K^+,Ca^2+,Mg^2+)in the samples of precipitation were analyzed by ion chromatograph.Based on the conventional meteorological data of Zhengzhou,the variation trend and the correlation coefficient of ionic mass concentration were discussed.The data of pH and electrical conductivity during the sampling period showed that pH of precipitation in Zhengzhou was generally weakly alkaline,without acid rain occurred,and the average of electrical conductivity was 52.47μs·cm−1.Analysis of ionic mass concentration indicated that the average mass concentration of total inorganic ions in precipitation was 20.26μg·mL^−1.NO3^−and Ca^2+,accounting for 28.75%and 19.87%of the total ionic mass concentration ratio,were the most important anions and cations respectively.The scour effect of continuous rain on anions was better than that of cations.NH4^+followed the largest change range of concentration was influenced by NH3 in the atmosphere and precipitation intensity.The correlation analysis suggested that there was a positive correlation between all ionic mass concentrations,with the largest correlation coefficients for NO3^−and SO4^2−(r=0.938),followed by Ca^2+and Mg^2+(r=0.852).The ratio of SO4^2−/NO3^−equivalent concentration in precipitation is 1.05.This result indicates that the type of precipitation pollution in Zhengzhou has changed to mixed pollution of sulfuric acid and nitric acid,which is different from previous research.