贵阳市城区PM_(10)和PM_(2.5)水溶性离子特征分析

Characteristics of Water-Soluble Ions in PM_(10) and PM_(2.5) in Urban Areas of Guiyang City

分别于2013年10月和2014年2月、5月、7月在贵阳市城区3个环境空气质量监测国控点位(南明区市监测站、云岩区黔灵公园马鞍山和观山湖区贵阳一中)进行PM_(10)、PM_(2.5)样品采集,并对10种水溶性离子(SO_(4)^(2-)、NO_(2)^(-)、NO_(3)^(-)、NH_(4)^(+)、Cl^(-)、F^(-)、Na^(+)、K^(+)、Mg^(2+)、Ca^(2+))的含量进行了分析。结果表明,研究时段内,贵阳市3个点位PM_(10)、PM_(2.5)平均质量浓度分别为(64.8±25.5)、(46.6±21.2)μg/m~3。其中,云岩区黔灵公园马鞍山点位的颗粒物浓度最低,南明区市监测站点位最高。3个点位PM_(2.5)平均浓度与PM_(10)平均浓度的比值为0.719,表明贵阳市城区PM_(10)中,PM_(2.5)占主导地位。水溶性离子分析显示,SO_(4)^(2-)、NO_(2)^(-)、NO_(3)^(-)、NH_(4)^(+)、Cl^(-)、F^(-)、Na^(+)、K^(+)主要分布在PM_(2.5)中,Mg^(2+)、Ca^(2+)主要分布在PM_(10)中。3个点位PM_(10)和PM_(2.5)中的水溶性离子均表现为SO_(4)^(2-)、NH_(4)^(+)、Ca^(2+)浓度较大,F^(-)、NO_(2)^(-)较小,表明3个点位的污染源总体相同,且水溶性离子占PM_(10)、PM_(2.5)含量的比例达33.6%~48.1%。贵阳市城区大气中的SO_(2)转化率在5月、7月、10月较高,2月最低,主要是由于5月、7月、10月的高温、高湿、强辐射环境条件促进了SO_(2)向SO_(4)^(2-)的转化。阴阳离子平衡分析表明,贵阳市城区PM_(10)、PM_(2.5)呈现出偏碱性的特征。水溶性离子主成分分析表明,贵阳市城区PM_(10)中的水溶性离子主要来源于城市扬尘、生物质燃烧尘、煤烟尘、建筑尘以及二次粒子,PM_(2.5)中水溶性离子的来源与PM_(10)较为相似。

On October 2013 and February,May and July 2014,coarse(PM_(10))and fine(PM_(2.5))particles of ambient air at three national control atmospheric monitoring stations(Nanming,Maanshan,and Guanshanhu)in Guiyang City were sampled,and water^(-)soluble ions(SO_(4)^(2^(-)),NO_(2)^(-),NO_(3)^(-),NH_(4)^(+),Cl^(-),F^(-),Na^(+),K^(+),Mg2^(+)and Ca2^(+))in samples were analyzed.The results showed that the mass concentration of PM_(10)and PM_(2.5)were(64.8±25.5)μg/mPM_(2.5)(46.6±21.2)μg/m^(3)respectively,and the ratio of PM_(2.5)/PM_(10)was 0.719,indicating that the PM_(2.5)in Guiyang city were the main pollutants.The concentration of Maanshan station in Qianling mountain park was the lowest,and Nanming monitoring station was the highest.Ions analysis results showed that SO_(4)^(2^(-)),NO_(2)^(-),NO_(3)^(-),NH_(4)^(+),Cl^(-),F^(-),Na^(+),K^(+)were mainly distributed in fine particles,while Mg2^(+)and Ca2^(+)in coarse particles.In PM_(10)and PM_(2.5),concentrations of SO_(4)^(2^(-)),NH_(4)^(+)and Ca2^(+)were high,and F^(-)and NO^(-)2 were low,suggesting that three stations had similar sources,and water^(-)soluble ions accounted for 33.6%^(-)48.1%of the particles.The SO2 conversion rate(SOR)in the atmosphere of Guiyang was high in May,July and October,and the lowest in February.High temperature,high humidity and strong radiation in May,July and October promote the transformation of SO2 to SO_(4)^(2^(-)).The equilibrium analysis of anion and anion showed that particles in Guiyang were alkalescent.The principal component analysis of water^(-)soluble ions showed that the main sources of water^(-)soluble ions in PM_(10)were urban dust,biomass combustion,soot dust,construction dust,and secondary particles,which was consistent with water^(-)soluble ions in PM_(2.5).