Source Analysis And Health Risk Assessment Of Metallc Element Pollution In PM_2.5 And PM₁ In Foggy Days In Qingdao City

China’s industrialization process is accelerating,and smog weather is frequent.Fog and haze are two different weather phenomena.In the process of foggy days,the air humidity increases,atmospheric particulate matter is easy to change in the high humidity environment,and the atmospheric environment problems are complex and the situation is grim.Studies have shown that the biological and chemical characteristics,physicochemical characteristics and influencing factors of foggy days are few,but there is less analysis of metal elements in foggy particles,and the heavy metals in particulate matter have a greater impact on human health,so it is urgent to carry out the analysis of heavy metal pollution characteristics in foggy days.In this study,a modified six-channel particulate matter sampler was used to collect PM₁ at the time of fog onset.Through the pollution characteristics of PM₁and its metal elements in autumn,winter and summer foggy days in Qingdao,the enrichment factor method,the positive definite matrix factor model method,the backward trajectory of air flow and the potential source contribution factor method were used to understand the air pollution in foggy days in Qingdao.The main conclusions are as follows:（1）The mass concentration of PM₁ in autumn and winter foggy days is 1.18～1.65times that of clean days in the same year,and 0.42～0.70 times that of haze days.With the increase of particle size,its number and concentration decrease.The mass concentration of total metal elements in foggy days from 2018 to 2021 was（2.04±0.66）%,（2.72±2.36）%,（1.66±0.85）%and（3.05±4.21）%of PM₁ mass concentrations.The concentrations of Zn,Fe,Na,K,Ca and Al were relatively high in PM₁metal elements in autumn and winter foggy days,and the six metal elements accounted for（91.87±13.22）%,（93.52±10.34）%,（91.22±10.26）%and（91.05±7.57）%of the total mass concentrations of metal elements in autumn and winter foggy days from 2018 to 2021.（2）In PM₁ in foggy days in autumn and winter from 2018 to 2021,the enrichment factors of Ti,Ag,Mg and Al were less than 10,which were greatly affected by natural sources.The enrichment factors of Cr,Ni,Cu,Zn,As,Mo,Cd and Pb are greater than10,which are mainly affected by anthropogenic sources.The enrichment factors of metal elements As,Pb,Zn,Mo,Cu,Ni,Cr and V in summer PM_2.5 were greater than10.The enrichment factors of Ba,Na,Mg and Ti in PM_2.5 were greater than those in PM₁,which were 1.45,1.22,1.57 and 1.22 times of PM₁,respectively.（3）Six sources of metal elements in autumn and winter fog were analyzed,namely,vehicle emission source,dust source,industrial source,biomass or coal combustion source,crust source and ship source.The contributions of different sources are as follows:biomass/coal combustion source>industrial source>vehicle exhaust emission source>crust source>dust source>ship source,and their contributions are33.70%,30.60%,13.10%,12.70%,8.2%and 1.7%,respectively.Five types of sources of metal elements in summer fog were obtained by analysis,which were ship source,industrial source,Marine source,dust source and combustion source.From 2018 to2021,the backward trajectory of foggy weather flow in autumn and winter 2021,the contribution of short-range air mass was in the range of 14.58%～77.08%,and the contribution of long-range air mass was in the range of 8.33%～27.08%.In summer,the air mass transport was mainly from the southeast of the ocean,with a contribution rate of 70.97%.The contribution rate of long-distance air mass transmission in the ocean reached 32.26%.The contribution rate of short-range marine air masses originating off the coast of Qingdao reached 38.71%.（4）In foggy days,the ADD of the non-carcinogenic metal element Zn was the largest,and the ADD value of Zn in children was greater than that of adult males and females.Cr has the largest ADD among carcinogenic metal elements,especially in adult males with greater ADD values than in adult females and children.Mn is greater in children than in adults,and Cr is greater in adult males than in the other two populations.（5）The ILCR of foggy days is 0.74 times that of hazy days and 24.8 times that of clean days.In three different weather conditions,ILCR is from largest to smallest:Cr>As>Cd>Ni>Co.The ILCR range of Cd,Ni and Co in the clean world is between1×10^-9～1×10^-7,and there is no low carcinogenic risk;ILCR values for foggy and hazy days>1×10^-7,some of which have a low risk of carcinogenesis,but are within the acceptable range.The results of this study provide a reference for further analysis of the characteristics and sources of metal elements in foggy days,and have practical significance for the traceability and control of the causes of air pollution in Qingdao.