Particle Size Effect And Health Risk Assessment Of Heavy Metals In Street Dust In Wuhan City

In this paper,road dust（<100μm）in Wuhan was selected as the research object,and road dust samples were collected from five functional areas:industrial,residential,educational,commercial and traffic areas.The p H value and particle size of road dust were measured,the basic physicochemical properties of road dust were analyzed,and the road dust was divided into four particle sizes:<20μm,20～53μm,53～75μm and75～100μm.The spatial distribution pattern of road dust heavy metals in different particle sizes was investigated by the ordinary kriging interpolation method,and the single factor pollution index method and pollution load index method were used to evaluate the single heavy metal pollution and comprehensive pollution level of road dust in different particle sizes in the study area;The health risk evaluation model was applied to assess the health risk of road dust heavy metals in different particle sizes and explore the regional distribution differences.The results of the study showed that:（1）Road dust in Wuhan is alkaline;the results of road dust particle size study show that road dust is enriched in 63～86μm and 10～17μm particle size bands.（2）The mean values of heavy metals Mn,Cd,Cu,As,Pb and Zn in the<20μm particle size range were higher than the background values of Hubei soil;the mean values of heavy metals Cd,Cu,As,Pb and Zn in the 20～53μm and 53～75μm particle size ranges were higher than the background values,and Mn was close to the background value;the mean values of heavy metals Cd,Cu,As,Pb and Zn in the75～100μm particle size range were higher than the background values.（3）The results of the spatial distribution of heavy metals in different particle size roads show that there are differences in the spatial distribution of each heavy metal in different particle size sections.The spatial distribution patterns of heavy metals Mn,Cr,and Ni are similar,showing a low distribution pattern from north to south and high distribution pattern in the middle;the distribution trends of heavy metals Cd,Pb,and Zn are similar,showing a gradual increase from north to south;the distribution patterns of Co and Cu are low in the north and northwest and high in the south,and the distribution trends of As are high in the north and south and low in the middle.（4）The results of the single-factor pollution index method show that the heavy metals Cd and Zn are heavily polluted,As and Pb are moderately polluted,Cu and Mn are lightly polluted,Co is slightly polluted,and Cr and Ni are not polluted in the<20μm particle size section of road dust in Wuhan;The heavy metal Cd is heavily polluted,Zn,As and Pb are moderately polluted,Cu and Mn are lightly polluted,Co is slightly polluted,and Cr and Ni are not polluted in the 20～53μm and 53～75μm particle size bands.The heavy metal Cd is heavily polluted,Zn,As and Pb are moderately polluted,Cu is lightly polluted,Mn and Co are slightly polluted,and Cr and Ni are not polluted in the 75～100μm particle size band.（5）The results of the pollution load index method and its spatial distribution show that the road dust heavy metals in Wuhan are lightly polluted,and the increasing pollution degree of different particle sizes are:75～100μm（1.39）,53～75μm（1.44）,20～53μm（1.53）,<20μm（1.70）;with smaller particle sizes,the pollution range of road dust heavy metals is expanding and the pollution degree is increasing.The high value areas of pollution are mainly located in the southeast,central south and central west of the study area.（6）On the whole,there is an obvious particle size effect of heavy metals in road dust in Wuhan,and the content of heavy metals tends to increase as the particle size of road dust decreases.Specifically,the particle size effects of nine heavy metal elements in road dust in different functional areas vary,among which the distribution patterns of Pb and Zn are similar,the pollution of each element is more serious in industrial and traffic areas,and<20μm is the main particle size segment of heavy metal pollution in the study area.（7）The results of the health risk assessment of road dust heavy metals showed that the THI values for adults and children were 0.25 and 1.72 for different exposure routes in different particle size bands,respectively,and the THI value for children was greater than 1,indicating that there was no non-carcinogenic risk for adults but possible non-carcinogenic health risk for children from road dust heavy metals in Wuhan.As,Cr and Pb were the three most important contributors to the non-carcinogenic risk for adults and children.The TCRI values for both adults and children were in the range of10^-4～10^-6 for different exposure routes in different particle sizes,which demonstrated that the carcinogenic risk of road dust in Wuhan was within the acceptable range for both adults and children.For both adults and children.As and Cr were the most significant contributing elements to the carcinogenic risk.Oral intake was the main route of non-carcinogenic and carcinogenic risks of road dust heavy metals in the study area,and the highest non-carcinogenic and carcinogenic risks were in the<20μm particle size segment.8 heavy metals had no non-carcinogenic risks in each functional area,5 heavy metals in 5 functional areas had carcinogenic risks after superposition,and the non-carcinogenic and carcinogenic risks were the highest in the industrial area,Zn and Cr were the non-carcinogenic risks in each functional area.Zn and Cr are the main influencing elements of non-carcinogenic risk in each functional area,and Cr and Ni are the main influencing elements of carcinogenic risk in each functional area,especially Cr should be focused on.