2018—2020年西宁市城区PM_(2.5)中金属污染特征及健康风险评价

Pollution characteristics of metals in PM_(2.5) and their health risk assessment in Xining, China, 2018—2020

目的了解2018—2020年西宁市大气PM_(2.5)中的金属的污染特征,并对经呼吸暴露途径的人群健康风险进行评价。方法于2018—2020年每月的10—16日和出现霾污染情况时连续在西宁市城北区和城东区进行PM_(2.5)的采样,分析PM_(2.5)及其中铬,砷,镉,镍,铅,锰,汞的污染特征,通过富集因子法判别金属的来源,采用健康风险评估模型对人群呼吸暴露的健康风险进行评价。结果2018年西宁市城北区和城东区的PM_(2.5)年均质量浓度均高于《环境空气质量标准》(GB 3095-2012)中二级标准限定值(35μg/m^(3)),2019和2020年两城区PM_(2.5)年均质量浓度均低于35μg/m^(3)。2018—2020年两城区PM_(2.5)中金属质量浓度均为铅>锰>镍>砷>铬>镉>汞。富集因子法分析结果显示7种金属的富集因子均小于1。经呼吸暴露途径的人群年均超额非致癌风险从高到低依序为铅>锰>汞,经呼吸暴露途径的人群年均超额致癌风险从高到低依序为铬>砷>镉>镍,砷、镉、镍的人均超额致癌风险尚处于人群可接受的风险水平。城北区成年男性、城东区和城北区儿童铬暴露的人群年均超额致癌风险略高于10^(-6)。结论西宁市城区的大气PM_(2.5)中的金属污染主要来自于自然因素(岩石风化或土壤扬尘),应对铬重点关注。

Objective To understand the pollution characteristics of metal elements in ambient PM_(2.5) in Xining,China,from 2018 to 2020,and to evaluate the health risk of people exposed through respiratory routes.Methods From 2018 to 2020,PM_(2.5) samples were continuously collected from the north and east districts of Xining on the 10th to 16th of each month and when haze pollution occurred.The pollution characteristics of PM_(2.5) and its chromium,arsenic,cadmium,nickel,lead,manganese and mercury were analyzed.The source of metal elements was identified by the enrichment factor(EF)method,and a health risk assessment model was used to evaluate the health risk of population with respiratory exposure.Results In 2018,the average annual mass concentration of PM_(2.5) in the north and east districts of Xining was higher than the second-level standard limit(35μg/m^(3))according to the Ambient Air Quality Standard(GB 3095-2012),and was lower than 35μg/m^(3) in both urban areas in 2019 and 2020.The mass concentrations of metals in PM_(2.5) in the two urban areas were in the order of lead>manganese>nickel>arsenic>chromium>cadmium>mercury from 2018 to 2020.The EF analysis showed that the EF of the seven metals was all less than 1.The average annual excess non-carcinogenic risk of the population exposed through respiratory route from high to low was lead>manganese>mercury,and was chromium>arsenic>cadmium>nickel with non-carcinogenic risk.The per capita excess carcinogenic risk of arsenic,cadmium,and nickel was still at an acceptable risk level for the population,whereas the average annual excess carcinogenic risk of adult males and children exposed to chromium in the northern part of the city was slightly higher than 10^(-6).Conclusion The metal pollution in PM_(2.5) in Xining is mainly derived from natural factors(rock weathering or soil dust),and chromium pollution should be focused on.