辽宁西南典型城市冬季大气细颗粒物水溶性无机离子污染特征及来源解析

本研究于2018年12月3日—2019年1月1日在辽宁省西南典型城市葫芦岛市和朝阳市分别布设3个城区采样点,在区域传输点龙屯水库布设1个采样点,采集大气细颗粒物PM_2.5样品(n=201)。使用离子色谱检测样品中的Na⁺、Mg²⁺、Ca²⁺、K⁺、NH₄⁺、SO₄^2-、F^-、Cl^-和 NO₃^-的质量浓度。观测期间PM_2.5的平均浓度为葫芦岛市(54.25±26.14)μg·m^-3>朝阳市(45.38±20.64)μg·m^-3>区域背景点龙屯水库(33.73±21.64)μg·m^-3。水溶性无机离子是PM_2.5中的主要成分,朝阳市、葫芦岛市和龙屯水库中的水溶性离子分别占PM_2.5质量浓度的49%,52%和49%。其中NH₄⁺、NO₃^-、SO₄^2-是PM_2.5中最主要的水溶性离子.葫芦岛市和朝阳市的SOR(硫氧化率)、NOR(氮氧化率)值均大于0.1,说明两个城市存在明显的气溶胶二次转化过程。在不同污染状况下,朝阳市污染天中F^-、NH₄⁺、Cl^-和K⁺均为清洁天的2.5倍左右,葫芦岛市污染天中NH₄⁺、SO₄^2-和NO₃^-均为清洁天的3倍左右。朝阳市和葫芦岛市污染天SOR分别为0.13和0.18,分别为清洁天的0.76倍和1.5倍;NOR值分别为0.17和0.23,分别是清洁天的1.13倍和1.91倍,除朝阳市SOR外,污染天的SOR和NOR均大于清洁天,表明污染天中SO₂和NO₂向SO₄^2-和NO₃^-的二次转化增强。主成分分析结果表明,葫芦岛市和朝阳市PM_2.5的主要污染源来自于二次转化和燃煤、生物质燃烧;龙屯水库的主要污染源来自于二次转化。后向轨迹说明气团主要由内蒙古、俄罗斯及蒙古国传输至辽宁省。

Characteristics and source analysis of water-soluble inorganic ion pollution of fine atmospheric particles in winter in typical cities of southwest Liaoning Province

In this study,three urban sampling sites were set up in Huludao and Chaoyang of typical cities in southwestern Liaoning Province,of China.And one regional transportation site was at Longtun reservoir.A total of 201 samples of atmospheric fine particulate(PM_2.5)were collected at these sampling sites from December 3,2018 to January 1,2019.The mass concentrations of Na⁺,Mg²⁺,Ca²⁺,K⁺,NH₄⁺,SO₄^2-,F^-,Cl^-and NO₃^-in the samples were detected by ion chromatography.During the sampling period,the average mass concentration of PM_2.5showed as Huludao City(54.25±26.14)μg·m^-3>Chaoyang City(45.38±20.64)μg·m^-3>Longtun Reservoir(33.73±21.64)μg·m^-3.Water-soluble inorganic ions are the main components of PM_2.5accounting for 49%,52%and 49%of PM_2.5mass concentrations in Chaoyang City,Huludao City and Longtun reservoir,respectively.NH₄⁺,NO₃^-and SO₄^2-were the major components of the water-soluble ions in PM_2.5;The sulfur oxidation rate(SOR)and nitrogen oxidation rate(NOR)were both greater than 0.1 in Huludao City and Chaoyang City,indicating that there was an obvious secondary aerosol transformation process in the two cities.The concentrations of F^-,NH₄⁺,Cl^-and K⁺in PM_2.5during polluted periods in Chaoyang city are about 2.5 times higher than clean periods;NH₄⁺,SO₄^2-and NO₃^-in pollution periods in Huludao City are about three times than clean periods.The values of SOR were 0.13 and 0.18 during pollution periods in Chaoyang City and Huludao city,which were 0.76 and 1.13 times than those values during clean periods.NOR values during polluted periods were 0.17 and 0.23,respectively,which were 1.5 and 1.91 times than that of clean days.Except SOR in Chaoyang city,SOR and NOR in the polluted days were both larger than those in the clean days,indicating that the secondary transformation of SO₂and NO₂to SO₄^2-and NO₃^-in the polluted day was enhanced;The results of principal analysis showed that the main sources of PM_2.5 in Huludao City and Chaoyang City were secondary transformation,coal combustion and biomass burning,while the main pollution source in Longtun reservoir was secondary transformation.The backward trajectories showed that the air masses are mainly originated from Inner Mongolia and Russia to Liaoning Province.