聊城市冬季PM_(2.5)载带金属元素污染特征、风险评价及来源分析

Characteristics,Risk Assessment,and Sources of the Polluted Metallic Elements in PM_(2.5) During Winter in Liaocheng City

为研究聊城市冬季环境空气中PM_(2.5)载带金属元素的污染特征、风险评价及来源,分别于2018年和2019年的1月采集了环境空气PM_(2.5)样品并分析了其中19种金属元素的浓度.结果表明,采样期间聊城市冬季ρ(PM_(2.5))和金属元素浓度平均值分别为(87.7±39.9)μg·m^(-3)和(6.92±2.91)μg·m^(-3),金属元素中ρ(Ca)和ρ(Al)最高,分别为1.97μg·m^(-3)和1.35μg·m^(-3),其他元素浓度相对偏低,相较于清洁天,污染天时ρ(Ca)、ρ(Al)、ρ(Fe)及ρ(Ti)有所降低,而其他元素浓度均有所升高.地累积指数(Igeo)结果表明,聊城市冬季Cd、Zn、Pb、Sn和Cu的Igeo均高于2.5,受污染程度均在重度污染以上,其他元素Igeo均小于1,属于轻度污染或无污染程度.潜在生态风险评价结果显示金属元素的RI指数高达10 114.2,潜在危害较强,其中Cd的Er最高为9 802.2,其次为Pb、As和Cu,Cd贡献率达到96.9%,是聊城市冬季金属元素潜在生态风险的关键因子,且清洁天时潜在生态风险较高;对于人群健康风险评估,Mn、Cr、Pb、Ni、As、Co、Cd、V和Ba这9种元素的综合效应具有一定的非致癌风险及致癌风险,致癌风险最高的为As,R值为1.16×10^(-5),其次为Cr(Ⅵ),污染天相关元素的非致癌及致癌风险均明显高于清洁天.富集因子结果及主成分分析结果显示,Cd、Pb、Zn和Sn元素富集程度显著,除Ca元素外,其他元素污染天富集因子均明显升高,金属元素的主要来源包括交通源、燃烧源、扬尘源及煤炭燃烧源,贡献率分别为37.5%、22.5%、17.5%和7.2%,整体看聊城市冬季PM_(2.5)载带金属元素受人为源影响较大,其中交通源和燃烧源为重点管控源类.

In order to study the pollution characteristics,risk assessment,and sources of the metallic elements in ambient PM_(2.5) during winter in Liaocheng City,PM_(2.5) measurements was conducted daily for two consecutive years in January 2018 and 2019.The results showed that the average PM_(2.5) and metallic element concentrations were(87.7±39.9)µg·m-3 and(6.92±2.91)µg·m^(−3),respectively,during the sampling period in winter in Liaocheng City.The concentrations of Ca and Al,1.97µg·m^(−3) and 1.35µg·m^(−3),respectively,were highest,and the concentrations of other elements were relatively low.Additionally,the concentrations of Ca,Al,Fe,and Ti decreased on polluted days compared with those on clean days,whereas the concentrations of other elements increased.The results of the ground accumulation index(Igeo)showed that the Igeo of Cd,Zn,Pb,Sn,and Cu were all higher than 2.5,which was above the heavy pollution level,and the Igeo of other elements were less than 1,which belonged to the degree of light pollution or no pollution.The potential ecological risk assessment results showed that the RI index of metallic elements was 10114.2,and the potential harm was strong.The Er of Cd was 9802.2 with a contribution of 96.9%,followed by Pb,As,and Cu;thus,Cd was the key factor of the potential ecological risk of metallic elements,and it was higher on clean days.For population health risk assessment,the combined effects of nine elements,namely Mn,Cr,Pb,Ni,As,Co,Cd,V,and Ba,had certain non-carcinogenic risks and carcinogenic risks.The highest carcinogenic risk element was As,with an R value of 1.16×10^(−5),followed by Cr(Ⅵ).The potential ecological,non-carcinogenic,and carcinogenic risks on polluted days were higher than those on clean days of related elements.The results of enrichment factor and principal component analysis showed that the enrichment degree of the Cd,Pb,Zn,and Sn elements were significant,and the enrichment factors of other elements increased to some extent on polluted days,except for Ca.The main sources of metallic elements included traffic sources,combustion sources,dust sources,and coal combustion sources,with contributions of 37.5%,22.5%,17.5%,and 7.2%,respectively.As a whole,the metallic elements of PM_(2.5) were greatly affected by human sources in Liaocheng City in winter,among which traffic sources and combustion sources were the key control sources.