黄石市大气PM2.5中水溶性离子浓度特征及来源分析

Characteristics and Source Analysis of Water-Soluble Inorganic Ions in PM2. 5 in Huangshi City

为研究黄石市大气PM2.5中水溶性离子组成、质量浓度变化特征及来源,于2012年3月—2013年2月在湖北省黄石市利用MiniVol颗粒物采样器采集PM2.5样品,用离子色谱分析了9种水溶性离子(NH4^+、Ca^2+、Mg^2+、Na+、K^+、Cl-、NO3^-、SO4^2-、F^-)的质量浓度,并采用PMF(正定矩阵因子分析法)模型讨论了不同离子的来源.结果表明:观测期间黄石市大气PM2.5中ρ(总水溶性离子)的年均值为(61.5±26.8)μgm^3,占ρ(PM2.5)的63.9%,各离子质量浓度的高低顺序依次为ρ(SO4^2-)>ρ(NO3^-)>ρ(NH4^+)>ρ(Na+)>ρ(Cl-)>ρ(Ca^2+)>ρ(K^+)>ρ(F^-)>ρ(Mg^2+).二次无机离子SNA(为SO4^2-、NO3^-和NH4^+的统称)是水溶性离子的主要成分,占全部所测水溶性离子的74.4%.ρ(NO3^-)ρ(SO4^2-)范围为0.12~1.29,平均值为0.53±0.30,说明全年观测点附近主要以固定源污染为主.4个季节的SOR(硫氧化率)和NOR(氮氧化率)均大于0.10,说明黄石市PM2.5中的SO4^2-和NO3^-主要是经二次转化形成的.阴、阳离子相关性研究发现,4个季节阴、阳离子总体相关性(R2为0.98)较好,并且全年PM2.5组分偏酸性.通过PMF模型源解析发现,黄石市大气PM2.5中水溶性离子主要来源于燃烧源、二次转化源和土壤矿物扬尘源.研究显示,黄石市大气PM2.5中主要水溶性离子成分是SNA,燃烧、二次转化和土壤矿物扬尘是其主要来源.

To investigate the composition,chemical characteristics and sources of water-soluble inorganic ions,PM 2.5 samples were collected with a MiniVol portable air sampler from March 2012 to February 2013 in Huangshi City,Hubei Province.Nine water-soluble inorganic ions(NH4^+,Ca^2+,Mg^2+,Na^+,K^+,Cl^-,NO3^-,SO4^2-and F^-)were analyzed by ion chromatography(IC),and the possible sources of these species were determined with the positive matrix factorization(PMF)method.The average mass concentrations of total water-soluble ions were(61.5±26.8)μg m^3,accounting for 63.9%of the PM 2.5 mass.The concentrations of these species were in the order ofρ(SO4^2-)>ρ(NO3^-)>ρ(NH4^+)>ρ(Na^+)>ρ(Cl^-)>ρ(Ca^2+)>ρ(K^+)>ρ(F^-)>ρ(Mg^2+).The water-soluble ions were mainly composed of secondary ions(NH4^+,NO3^-and SO4^2-),accounting for 74.4%of total water-soluble ions.The ratio ofρ(NO3^-)toρ(SO4^2-)was in the range of 0.12-1.29,with a mean value of 0.53±0.30,indicating that anthropogenic stationary sources had more contributions to the atmospheric pollution in Huangshi City.The sulfur oxidation rate(SOR)and nitrogen oxidation rate(NOR)were greater than 0.10 in the four seasons,suggesting that sulfate and nitrate in PM 2.5 were formed mainly through secondary transformation.The overall correlation between cations and anions in spring,summer,autumn and winter were strong(R^2=0.98),and the annual PM 2.5 components were partial acidic.PMF analysis indicated that the major sources of PM 2.5 were combustion,secondary transformation and soil mineral dust.In conclusion,results showed that SNA were the main water-soluble ions in PM 2.5 in Huangshi City,and combustion,secondary transformation and soil mineral dust were the main sources.