天津冬季PM_(2.5)中水溶性无机离子污染特征研究

Characteristics of water-soluble inorganic ions in PM_(2.5) during winter in Tianjin

2015年12月3—21日对天津冬季 PM2.5进行了采样分析,重点分析了 Na^+、Mg^(2+)、NH_4^+ 、Ca^(2+)、K^+、Cl^-、SO_4^(2-) 、NO_3^-8种水溶性无机离子,结合风速、相对湿度、温度等气象资料,并利用主成分分析对水溶性无机离子来源进行了解析。结果表明,风速小、气温高和相对湿度大的天气条件以及冬季燃煤的人为原因是引起霾天的重要原因。采样期间PM_(2.5)平均质量浓度为104.22μg/m^3。霾天中,轻微霾天、轻度霾天、中度霾天、重度霾天的PM_(2.5)中总离子平均质量浓度分别为27.63、26.89、105.03、143.92μg/m^3,远高于非霾天的15.43μg/m^3。SO_4^(2-)是水溶性无机离子中含量最高的离子,约占总离子的1/3,SO_4^(2-)、NO_3^-、Cl^-和NH_4^+浓度之和占总离子的90%以上。随着霾程度加重,NH_4NO_3占比增加,(NH_4)_2SO_4占比减少。水溶性无机离子主要来源于海盐粒子、生物质燃烧、机动车尾气排放和燃煤等。

On December 3-21(winter),2015,PM 2.5 was sampled and analyzed in Tianjin.Eight water-soluble inorganic ions(Na^+,Mg^2+,NH4^+,Ca^2+,K^+,Cl^-,SO4^2-and NO3^-)in PM 2.5 were focused.Combined with meteorological data(wind speed,relative humidity,temperature,etc.),the source of water-soluble inorganic ions was analyzed by principal component analysis.Results showed that low wind speed,high temperature and high relative humidity as well as human source like coal firing in winter,were the important causes of the formation of haze.During the sampling period,the average mass concentration of PM2.5 was 104.22 μg/m^3.In haze days,total ions mass concentrations of ultralight,light,mediate and heavy haze were 27.63,26.89,105.03 and 143.92 μg/m^3 ,respectively,higher than that in non-haze days(15.43 μg/m^3).SO4^2-was the most abundant water-soluble inorganic ion,accounting for about 1/3 and SO4^2-,NO3^-,Cl^-and NH4^+ accounted for more than 90% of total ions.The formation of NH4NO3 increased with haze aggravating,while(NH4)2SO4 decreased.Water-soluble inorganic ions were mainly derived from sea salt particles,biomass combustion,vehicle emission and coal firing.