Temporal And Spatial Variation Of Geochemical Characteristics Of Heavy Metals In Road Dust In Beijing

Because of its own characteristics,road dust is easy to accumulate heavy metals,which has an impact on human health.In this study,the content characteristics,spatial distribution characteristics,pollution characteristics,sources and human health risk assessment of heavy metals in road dust in Beijing in 2013,2017 and 2019 were studied and compared:1.Except As and Ni,the contents of other elements were higher than the soil background values,and the contents of Zn were the highest.The values of Cv,kurtosis and skewness of Hg are the highest in 2013 and 2019,and those of As are the highest in 2017.The change trend of Cr,Pb,Cd,As,Cu and Zn in the past three years was first increased and then decreased,Hg first decreased and then increased,and Ni successively increased.2.In the past three years,except that the average content of As and Ni in some functional areas was lower than the background value,the other elements were higher than the background value.The highest content of Cr,Pb,Cd and Cu was in the commercial aera in 2017,As and Zn were in the industrial area in 2017,and Hg and Ni were in the educational area in 2019.3.I_geo showed that in the past three years,except As and Ni were not polluted in some functional areas,other elements were polluted.Zn is the most serious in 2013 and 2017,and Hg is the most serious in 2019.E_rⁱ showed that in 2013,2017 and 2019,except for Cd and Hg,the other elements were all slight ecological hazards.Among them,the ecological hazards of Hg were the strongest in 2013 and 2019,and the ecological hazards of Cd were the strongest in 2017.In 2013,except As and Hg,the maximum values of I_geo and E_rⁱ of other elements were in the commercial area.In 2017,except As and Zn,the maximum values of Cd,Cu and Zn were in the commercial area.In 2019,the maximum values of As,Hg and Ni were in the educational area.Cr was in the industrial area.Pb was in the residential area.The change trend of I_geo and E_rⁱ are completely consistent.The maximum values of I_geo and E_rⁱ of Cr,Pb,Cd and Cu are in the commercial area in 2017,As and Zn are in the industrial area in 2017,and Hg and Ni are in the educational area in 2019.The maximum RI appears in the educational area in 2019.4.The results of sources indicate that the sources of Cr in recent years are automobile metal parts wear,exhaust emissions and industrial activities;the sources of Pb are automobile tire wear and oil leakage and leaded gasoline and yellow and white lines on roads;the sources of Cd are fertilizer,industrial activities,automobile tire wear and the use of lubricating oil;the sources of As are natural source and coal combustion;the source of Hg element is coal combustion;the sources of Ni element are natural source and coal combustion;the sources of Cu are automobile tire parts wear,oil leakage,exhaust emission and industrial activities;the sources of Zn are automobile tire wear and oil leakage,lubricating oil use and industrial activities.5.The results of human health risk assessment showed that the average daily exposure of children and adults in three years was direct ingestion>dermal absorption>inhalation.In 2013,2017 and 2019,there was no significant carcinogenic and non-carcinogenic risk of children and adults.In 2013,2017 and 2019,the∑ADD of non-carcinogenic heavy metals in road dust was children>adults,LADD_inh of carcinogenic heavy metals in road dust was adults>children,HI of heavy metals in road dust was children>adults,and Risk of heavy metals in road dust was adults>children.The three-year comparison shows that the∑ADD and HI of both children and adults of Cr,Pb,Cd,As,Cu and Zn are highest in 2017,and Hg and Ni are highest in 2019.The LADD_inh and Risk of both children and adults of Cr,Cd and As are highest in 2017,and Ni is highest in 2019.