【摘要】 目的 了解北京市某区大气细颗粒物(fine particulate matter,PM_2.5)浓度及其成分特征。方法 2019—2023 年在北京某区某建筑物楼顶进行大气 PM_2.5采样，用称重法测定 PM_2.5日均质量浓度，分别用电感耦合等离子质谱仪及离子色谱仪法测定 12 种金属和类金属元素及 5 种水溶性离子浓度，并用 Kruskal-Wallis H 检验比较分析不同年份及季度的浓度差异，用Mann-Whitney U 检验比较分析供暖对 PM_2.5浓度及其成分的影响。结果 2019—2023 年共采集空气样品 423 份，PM_2.5年均质量浓度分别为 39.00、40.50、46.00、41.50 和 34.00 μg/m³，各年份之间差异无统计学意义（H=3.879,P>0.05）;PM_2.5日均浓度超标率呈现春冬季较高，夏秋季较低，各季度之间差异有统计学意义（H=11.198,P<0.05）;PM_2.5浓度在供暖季与非供暖季差异无统计学意义（U=0.133,P>0.05）。 PM_2.5中 12 种金属和类金属元素的浓度排名前 5 的元素为铝（Al）>锰（Mn）>铅（Pb）>砷（As）>硒（Se），除元素铝、砷、锰外，其他金属元素在 2019—2023 年各年份之间质量浓度差异有统计学意义；除砷元素在2023 年浓度升高外，铝、铅、硒元素质量浓度逐年降低；除锑元素外，其他金属元素质量浓度均存在季节差异，硒、砷元素秋季浓度较高，铝、铅元素春季浓度较高，锰元素冬季浓度较高；除元素锑、砷、铍、镍和铊外，其余金属元素在供暖季与非供暖季质量浓度不同，金属元素铝、镉、铬、铅和锰的质量浓度供暖季高于非供暖季。 PM_2.5中 5 种水溶性离子，硫酸盐(SO₄^2-)、硝酸盐（NO₃^-）、氯离子（Cl^-）、氟化物（F^-）和铵盐（NH₄⁺）的质量浓度 M(P₂₅,P₇₅)分别为 3.74（1.95,7.11）、6.33（2.005,14）、0.32（0.16,0.81）、0.05（0.02,0.07）和 2.68（0.86,5.75）μg/m³，质量浓度为硝酸盐>硫酸盐>铵盐>氯离子>氟化物，差异有统计学意义（H=1 392.100,P<0.05）。氯离子、氟化物在不同年份之间差异有统计学意义（H=18.193、77.386，均 P<0.05）,5 种水溶性离子在不同季度之间浓度不同，除硫酸盐在秋季浓度最高外，其余 4 种水溶性离子春季浓度最高；硝酸盐、氯离子、氟化物在供暖季与非供暖季之间质量浓度存在差异（H=2.248、12.985、7.421，均 P<0.05），除硝酸盐和铵盐外，其余 3 种水溶性离子浓度均为供暖季高于非供暖季。结论 北京市空气污染在一系列措施实施之后空气质量有了显著改善，但依旧存在污染现象，应进一步控制污染。更多还原

【Abstract】 Objective To understand the concentration of atmospheric fine particulate matter(PM_2.5) and its component characteristics in a district of Beijing.Methods The atmospheric PM_2.5samples were collected from the roof of a building in a district of Beijing from 2019 to 2023.The average daily mass concentration of PM_2.5was determined by weighing method.The concentrations of 12metals and metal-like and 5 water-soluble ions were determined by inductively coupled plasma mass spectrometer and ion chromatography,respectively.Kruskal-Wallis H test was used to analyze the differences in concentrations among different years and seasons,and Mann-Whitney U test was used to compare and analyze the impact of heating on PM_2.5concentration and its components.Results A total of 423 air samples were collected from 2019 to 2023,and the average annual mass concentrations of PM_2.5were 39.00,40.50,46.00,41.50 and 34.00μg/m³,respectively,with no statistically significant differences among years （H=3.879,P>0.05）.The exceedance rate of average daily PM_2.5concentration was significantly higher during spring and winter,while it was comparatively lower in summer and autumn,and the difference was statistically significant among different seasons（H=11.198,P<0.05）.There was no statistically significant difference in PM_2.5concentration between the heating season and non-heating season（U=0.133,P>0.05）.The top five elements of the concentration of 12 metals and metal-like elements in PM_2.5were aluminum（Al）>manganese （Mn）>lead （Pb）>arsenic （As）>selenium （Se）.Except for Al,As and Mn,there were statistically significant differences in the mass concentration of other metallic elements among years of 2019-2023.Except the increase of As in 2023,there was a gradual decrease in the mass concentrations of Al,Pb and Se over the years.With the exception of Sb,the seasonal variations were observed in the mass concentration of other metallic elements,Se and As exhibited higher concentrations during autumn,Al and Pb showed higher concentrations during spring,while Mn displayed higher concentrations during winter.Apart from Sb,As,Be,Ni and Ti,the differences observed between heating season and non-heating season regarding the mass concentrations of other metals.Al,Cd,Cr,Pb and Mn exhibited higher mass concentrations during heating season compared to non-heating season.The mass concentrations[M (P₂₅,P₇₅)]of sulfate (SO₄^2-),nitrate （NO₃^-）,chloride ion （Cl^-）,fluoride （F^-） and ammonium salt（NH4+） in PM_2.5were 3.74（1.95,7.11）,6.33（2.005,14）,0.32（0.16,0.81）,0.05（0.02,0.07） and 2.68（0.86,5.75）μg/m³,respectively.The mass concentrations of five water-soluble ions were:nitrate>sulfate>ammonium salt>chloride ion>fluoride,and the difference was statistically significant （H=1 392.1,P<0.05）.There were statistically significant differences in the concentration of chloride ion and fluoride among years （H=18.193,77.386,both P<0.05）.The concentration of five water-soluble ions was different in different seasons.Except for sulfate,which had the highest concentration in autumn,the other four watersoluble ions had the highest concentration in spring.There were statistically significant differences in the mass concentrations of nitrate,chloride ion and fluoride between heating season and non-heating season （H=2.248,12.985,7.421,all P<0.05）.Except nitrate and ammonium salt,the concentrations of the other three water-soluble ions were higher in heating season than in nonheating season.Conclusion The air pollution in Beijing has improved significantly after the implementation of a series of measures,but air pollution still exists,and further pollution control should be implemented.更多还原