南京市不同天气过程下颗粒物中水溶性离子分布特征及其来源解析

Distribution Characteristics and Source Analysis of Water-soluble Ions in Particulate Matter Under Different Weather Processes in Nanjing

于2018年11月16~28日使用在线气体组分及气溶胶监测系统MARGA ADI 2080观测了南京市颗粒物中的水溶性无机离子和一些痕量气体,结合气象要素和探空数据,分析了霾、雾、清洁和降水这4类过程中污染物及水溶性离子的分布特征及其昼夜差异.结果表明,在4类过程中PM_(2.5)平均浓度(μg·m^(-3))在26.9(降水)~96.4(霾),而总水溶性离子浓度(μg·m^(-3))在23.7(降水)~89.7(霾).在霾和雾过程中离子浓度大小排序为NO_(3)^(-)>NH_(4)^(+)>SO_(4)^(2-)>Cl^(-)>K^(+)>Ca^(2+)>Na^(+)>Mg(2+),而在清洁和降水过程中为NO_(3)^(-)>SO_(4)^(2-)>NH_(4)^(+)>Cl^(-)>Ca^(2+)>K^(+)>Na^(+)>Mg(2+).水溶性离子的昼夜分布特征在4类过程中差异较大,但昼夜间SO_(4)^(2-)、NO_(3)^(-)和NH_(4)^(+)(SNA)均呈现出在霾>雾>清洁>降水过程中的特征.由PMF源解析结果分析得到,二次源是影响霾的主导因素,二次源、海盐及燃烧源是雾过程的主要污染来源,降水过程对燃煤源和二次源的清除作用较清洁过程更明显.

From November 16 to 282018,water-soluble ions in particulate matter and some trace gases in Nanjing City were observed using the online gas composition and aerosol monitoring system MARGA ADI 2080.Combined with meteorological elements and sounding data,the distribution characteristics and day-night differences of pollutants and water-soluble ions during haze,fog,clear,and precipitation processes were analyzed.The results show that the average concentration of PM_(2.5)varied from 26.9μg·m^(-3)(precipitation)to 96.4μg·m^(-3)(haze)while total water-soluble ions varied between 23.7μg·m^(-3)(precipitation)and 89.7μg·m^(-3)(haze).The ranked order of ion concentrations was NO3->NH_(4)^(+)>SO42->Cl->K+>Ca2+>Na^(+)>Mg(2+)during haze and fog events,and NO3->SO42->NH+4>Cl->Ca2+>K+>Na^(+)>Mg(2+)during clear weather and precipitation period.The diurnal distributions of water-soluble ions were quite different under the four conditions,although SO42-,NO3-,and NH_(4)^(+)(SNA)were ranked haze>fog>clear>precipitation for both day and night periods.According to the PMF source analysis,secondary sources were the main factors affecting haze;secondary sources,sea salt,and combustion sources were the main pollution sources to foggy conditions;and the removal effect of precipitation on coal-fired sources and secondary sources was more notable than during clear conditions.