沈阳市大气PM_(2.5)中水溶性离子的季节变化特征

Seasonal variation of water soluble ions in PM_(2.5) in Shenyang

为研究沈阳市大气中PM_(2.5)及其水溶性离子的污染特征、季节差异和来源情况,使用URG-9000D在线监测系统对沈阳市2019年大气颗粒物进行连续的采样分析,并利用正交矩阵因子分析法(PMF)进行污染物的来源解析.结果表明,2019年沈阳市秋冬季节PM_(2.5)质量浓度变化受相对湿度影响较大,冬季PM_(2.5)平均质量浓度达到85.76μg·m^(-3),细粒子污染较为严重.沈阳市大气PM_(2.5)中SNA(SO_(4)^(2-)、NO_(3)^(-)和NH_(4)^(+))所占比重表现为春季最高秋季最低;夏季SO_(4)^(2-)和NH_(4)^(+)浓度较高,而NO_(3)^(-)浓度较低.SO_(4)^(2-)在夏季呈单峰型日变化,与NO_(3)^(-)变化趋势相反.春夏秋三季NH_(4)^(+)与SO_(4)^(2-)、NO_(3)^(-)主要结合为(NH_(4))_(2)SO_(4)和NH_(4)HSO_(4),冬季NH_(4)^(+)主要以(NH_(4))_(2)SO_(4)和NH4HSO4的形式存在.沈阳市存在较强的SO_(2)和NO_(x)二次转化现象,且各季节中SO_(2)的转化率均高于NO_(2).PMF源解析结果表明,二次源对沈阳市大气污染贡献最大,夏秋季生物质燃烧和冬季燃煤源贡献同样不可忽视.

In order to study the pollution characteristics,seasonal differences and sources of water-soluble ions in PM_(2.5) in Shenyang,the samples of atmospheric particulate matter were analyzed by the URG-9000D online monitoring system.The source of pollutants was analyzed using the orthogonal matrix factor analysis(PMF).The results showed that relative humidity had a great influence on the mass concentration of PM_(2.5) during autumn and winter of 2019 in Shenyang.The average PM_(2.5) mass concentration in winter reached 85.76μg·m^(-3),and fine particle pollution was serious.The proportion of SNA(SO_(4)^(2-),NO_(3)^(-) and NH_(4)^(+))in PM_(2.5) was the highest in spring and the lowest in autumn.In summer,the concentration of SO_(4)^(2-) and NH_(4)^(+) was higher,while the concentration of NO_(3)^(-)was lower.In summer,the diurnal variation of SO_(4)^(2-) showed uni-modal trend,which was contrary to that of NO_(3)^(-).The formation of(NH_(4))_(2)SO_(4)and NH_(4)HSO_(4) existed in spring,summer and autumn,while those of(NH_(4))_(2)SO_(4)and NH_(4)HSO_(4)in winter.There were strong secondary conversion of SO_(2)and NO_(x)in Shenyang,and the conversion rate of SO_(2)was higher than that of NO_(2)in the four seasons.PMF showed that secondary sources were the largest contributor to air pollution in Shenyang,and biomass combustion in summer and autumn and coal combustion in winter could not be ignored.