2017—2022年台州市某城区空气PM_(2.5)中重金属和多环芳烃分布特征及来源分析

Distribution characteristics and sources of heavy metals and polycyclic aromatic hydrocarbons in PM_(2.5)in an urban area of Taizhou City from 2017 to 2022

[背景]环境空气中的细颗粒物(PM_(2.5))是重金属和多环芳烃(PAHs)的重要载体,长期吸入重金属和PAHs对人类健康存在潜在威胁。[目的]分析台州市某城区空气PM_(2.5)质量浓度(后称“浓度”)及其成分中重金属、PAHs的分布特征及来源,以期为台州市大气污染防治以及人群健康防控等工作提供基础资料和科学依据。[方法]2017—2022年每月10日至16日9点至次日8点(23 h·d^(−1)),在台州市主城区某单位顶楼设置的监测点采集PM_(2.5)样品(采样流量为2.3 m^(3)·h−1),测量其浓度。分析PM_(2.5)成分中12种重金属和16种优先控制PAHs污染分布特征。采用富集因子法和异构体特征比值法分别判断重金属和PAHs的污染来源。[结果]2017—2022年该城区PM_(2.5)日均浓度范围为(4~141)μg·m^(−3),6年年均中位浓度均低于国家二级标准限值,其浓度存在季节性差异,表现为:冬季>春季>夏、秋季,差异具有统计学意义(H=134.077,P<0.01);且2017.1—2020.1>2020.2—2022.12,差异具有统计学意义(Z=−3.989,P<0.01)。该城区主要重金属污染为锰(Mn)、铅(Pb)、砷(As)、镍(Ni)和铬(Cr);除了铍(Be)和汞(Hg),其余重金属浓度均具有季节性差异(P<0.01),表现为冬、春季>夏、秋季;除锰(Mn)和砷(As)外,其他重金属浓度均表现为:2017.1—2020.1>2020.2—2022.12,差异具有统计学意义(P<0.05)。富集因子法分析提示锑(Sb)、镉(Cd)、硒(Se),存在人为污染源。PAHs日均浓度范围为(0.88~24.56)ng·m^(−3),表现为冬季>春季>秋季>夏季,差异具有统计学意义(H=231.387,P<0.01)。16种PAHs污染物中居前列的依次为苯并[b]荧蒽(BbF)(25.36%)、茚并[1,2,3-c,d]芘(IcdP)(11.22%)和苯并[g,h,i]苝(BghiP)(9.02%);特征比值法结果显示该城区16种PAHs污染物是汽油燃烧、燃煤以及生物质燃烧共同作用产生。[结论]台州市该城区PM_(2.5)、重金属和PAHs浓度均呈逐年下降趋势,污染水平相对较低,PM_(2.5)、重金属、PAHs浓度季节性分布明显,表现为冬、春季污染水平较高。人为污染是重金属的主要来源,汽车尾气排放、工业燃煤以及垃圾焚烧可能是PAHs的主要来源。

[Background]Fine particulate matter(PM_(2.5))in ambient air is an important carrier of heavy metals and polycyclic aromatic hydrocarbons(PAHs),and long-term inhalation of heavy metals and PAHs poses a potential threat to human health.[Objective]To analyze the ambient PM_(2.5)concentrations and the distribution characteristics and sources of heavy metals and PAHs in PM_(2.5)in an urban area of Taizhou City,aiming to provide basic data and a scientific basis for local air pollution management and population health prevention.[Methods]From 9am to 8pm on the 10th to 16th of each month from 2017 to 2022(23 h·d^(−1)),a monitoring point was set up on the top floor of a building in the main urban area of Taizhou to collect PM_(2.5)samples(sampling flow rate:2.3 m^(3)·h−1)and measure its concentration.The characteristics of 12 heavy metals and 16 priority PAHs in PM_(2.5)were analyzed.The pollution sources of heavy metals and PAHs were determined by enrichment factor method and isomer characteristic ratio method,respectively.[Results]From 2017 to 2022,the average daily concentration of PM_(2.5)in this urban area ranged from 4 to 141μg·m^(−3),and the median annual concentrations were lower than the national secondary standard limit.The seasonal concentration of PM_(2.5)was as follows:winter>spring>summer and autumn,and the difference was statistically significant(H=134.077,P<0.01).The concentration of PM_(2.5)in 2017.1 to 2020.1 was higher than that in 2020.2 to 2022.12(Z=−3.989,P<0.01).The main heavy metal pollutants in this area were manganese(Mn),lead(Pb),arsenic(As),nickel(Ni),and chromium(Cr).Except for beryllium(Be)and mercury(Hg),the concentrations of other heavy metals had seasonal differences(P<0.01),higher in winter and spring than in summer and autumn.Except for manganese(Mn)and arsenic(As),the concentrations of other heavy metals were higher from 2017.1 to 2020.1 than from 2020.2 to 2022.12,and the difference was statistically significant(P<0.05).The results of enrichment factor indicated anthropogenic pollution sources of antimony(Sb),cadmium(Cd),and selenium(Se).The average daily concentration of PAHs ranged from 0.88 to 24.56 ng·m^(−3),with a seasonal trend of winter>spring>autumn>summer,and the difference was statistically significant(H=231.387,P<0.01).Among the 16 PAHs,the top pollutants were benzo[b]fluoranthene(BbF)(25.36%),indene[1,2,3-c,d]pyrene(IcdP)(11.22%),and benzo[g,h,i]perylene(BghiP)(9.02%).The results of characteristic ratio method showed that the 16 PAHs pollutants were produced by a combined action of gasoline buring,coal burning,and biomass burning.[Conclusion]In selected urban area of Taizhou City,the concentrations of PM_(2.5),heavy metals,and PAHs all show a downward trend year by year at a relatively low level,and obvious seasonal distributions which are higher in winter and spring.Man-made pollution is the main source of heavy metals,and automobile exhaust emissions,industrial coal burning,and waste incineration may be the main sources of PAHs.