云南低纬度高原城市大气PM_(2.5)中水溶性离子特征及来源分析

Characteristics and source analysis of water soluble ions in atmospheric PM_(2.5) in low latitude plateau cities of Yunnan Province

为研究低纬度高原城市大气PM_(2.5)中水溶性离子特征及来源,于2016年春、秋季节在云南省文山市和保山市主城区分别设立3个采样点采集了大气PM_(2.5)样品.利用离子色谱分析9种水溶性离子(F^(-)、CI^(-)、NO^(-)_(3)、SO^(2-)_(4)、K^(+)、Na^(+)、Mg^(2+)、Ca^(2+)、NH_(+)_(4))的质量浓度.结果表明,9种水溶性离子总浓度均值在文山为(13.31±4.61)μg·m^(-3),保山为(7.75±2.12)μg·m^(-3),分别占PM_(2.5)质量浓度的29.68%和23.55%.SO^(2-)_(4)、NO^(-)_(3)和NH^(+)_(4)等3种离子是大气PM_(2.5)中最主要的二次污染成分,分别占文山和保山总水溶性离子浓度的72.54%和67.42%.观测期间,通过E-AIM-Ⅱ模型表明文山和保山的气溶胶均呈弱酸性,NH^(+)4、SO^(2-)_(4)、NO^(-)_(3)在文山主要以(NH_(4))_(2)SO_(4)和NH_(4)NO_(3)的形式存在.文山和保山NO^(-)_(3)/SO^(2-)_(4)比值分别为0.19、0.51,表明两个城市均以固定源为主,但是移动源在保山秋季的贡献较为明显.来源分析表明,文山和保山大气PM_(2.5)中水溶性离子主要来源于二次反应转化,其次是扬尘、海盐及生物质燃烧.

The PM_(2.5)samples were collected in Wenshan and Baoshan city during spring and autumn in 2016 to investigate the characteristics and source of water-soluble ions in atmospheric PM_(2.5)in low-latitude plateau cities.Nine water-soluble ions,including F^(-),CI^(-),NO^(-)_(3),SO^(2-)_(4),K^(+),Na^(+),Mg^(2+),Ca^(2+),NH^(+)_(4),were determined by ion chromatography.The results showed that the average concentration of the water-soluble ions were(13.31±4.61)μg·m^(-3)in Wenshan and(7.75±2.12)μg·m^(-3)in Baoshan,accounted for 29.68%and 23.55%of the PM_(2.5)mass concentration,respectively.SO^(2-)_(4),NO^(-)_(3)and NH^(+)_(4)were the most important secondary pollutants in atmospheric PM_(2.5),accounted for 72.54%and 67.42%of the total water-soluble ion concentrations in Wenshan and Baoshan,respectively.The E-AIM-II model showed that the aerosols of Wenshan and Baoshan were weakly acidic.NH^(+)_(4),SO^(2-)_(4)and NO^(-)_(3)were probably existed in the form of(NH_(4))_(2)SO_(4)and NH_(4)NO_(3)in Wenshan.Furthermore,the ratio of NO^(-)_(3)/SO^(2-)_(4)in Wenshan and Baoshan were 0.19 and 0.51,respectively,indicating that the both cities were dominated by fixed sources,but in autumn the mobile source contribution was more significant in Baoshan.Source analysis showed that secondary reaction conversion was the major source of the water-soluble ions in PM_(2.5)of Wenshan and Baoshan followed by dust,sea salt and biomass burning.