Sources and Health Risk Assessment of Heavy Metals in PM2.5 in Lanzhou City
A total of 121 PM2.5 samples were collected in Chengguan District of Lanzhou during non-heating period(June 1,2022-August 31,2022)and heating period(November 1,2022-January 31,2023),and the pollution characteristics,sources and health risks of 14 elements were investigated.The results showed that the average PM2.5 concentration((44.1±12.2)μg/m3)in the heating period was about twice that in the non-heating period((20.8±3.05)μg/m3).The average concentration of 14 elements in PM2.5 in heating period((4 443±953)ng/m3)was much higher than that in non-heating period((2 854±426)ng/m3),among which Al,Ca,Fe,Cu and K were the main elements in PM2.5 in Lanzhou City.The results of enrichment factor analysis and positive matrix factorization showed that 14 heavy metal elements in PM2.5 were mainly from the mixed sources(soil dust,biomass combustion and industrial emissions)(39.1％),followed by industrial emissions(23.3％),traffic emissions(20.2％)and coal combustion emissions(17.4％).Health risk assessment results showed that Cr had the highest carcinogenic risk among all carcinogenic elements,and there were carcinogenic risks for adult males,adult females and children in non-heat-ing period and heating period.Mn had non-carcinogenic risks for adult males,adult females and children in heating period.Therefore,the emission of Cr and Mn in PM2.5 needs to arouse the high attention of relevant departments,and certain measures should be taken for emission reduction supervision of coal combustion and industrial production such as electro-plating,metallurgy,tanning and building construction that produce these two elements.The total carcinogenic risk and total non-carcinogenic risk were in the order of children＞adult males＞adult females.
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