Pollution Characteristics And Health Risk Assessment Of Heavy Metals In Topsoil Of Hefei City Proper

Background:With the continuous development of urbanization and industrialization,a large number of pollutants are brought into the soil environment by human production and life,among which the heavy metal pollution in urban soil is the most serious.The quality of urban soil environment is closely related to the health of residents,and heavy metal pollution in urban soil will harm human health.Objective:To evaluate the pollution characteristics of heavy metals in surface soils and the potential health risks of heavy metals in the soil in Hefei,and to provide a theoretical basis for future urban construction,prevention and control of heavy metal pollution and protection of human health.Methods:（1）Inductively Coupled Plasma Emission Spectrometer（ICP-OES）and Graphite Furnace Atomic Absorption Spectrometer（GF-AAS）were used to detect the contents of As,Cr,Cu,Pb,Ni,Zn,Al,Fe,Mn and Cd in 111 samples of Hefei surface soil,then to describe the content characteristics of heavy metal elements in urban surface soil in Hefei.（2）Taking the soil environmental background value of Hefei as the evaluation benchmark,10 heavy metals as evaluation factors,the geological accumulation index(I_geo),single factor pollution index（P_i）,Nemerow comprehensive pollution index（IPI_N）and potential ecological risk index（RI）were used to evaluate the urban soil environmental quality and ecological risk in Hefei.（3）The Kriging interpolation was then used to describe the spatial distribution of heavy metal concentrations.（4）Spatial correlation analysis of heavy metals in soils,combined with multivariate statistical methods（correlation analysis,principal component analysis）,the sources of 10 heavy metals in urban soil of Hefei were analyzed.（5）The human health risk assessment model recommended by the United States Environmental Protection Agency（US.EPA）,was used to carryout human health risk assessment of heavy metals in urban surface soil in Hefei.（6）Monte Carlo simulation was used to analyze uncertainty about health risk assessment.Results:（1）The contents of As,Cd,Cu,Ni,Zn and Mn in urban soils of Hefei City exceed the soil background values,but the measured heavy metals content did not exceed screening values under the Risk control standard for soil contamination of development land.（2）The spatial distribution of metal concentrations was generally point-banded,mainly concentrated in the east and west urban areas.（3）Spatial correlation indicated that heavy metal pollution in urban soil in Hefei was affected by internal and external factors.Principal component analysis and correlation analysis show that Cr,Ni,Al,Fe and Mn make up the first principal component,and Cd,Cu,Pb and Zn form the second principal component,while the third principal component includes only As.（4）IPI_Nand RI show that metal elements in soil in Hefei was moderately polluted but low ecological risk.（5）The Hazard index（HI）for adults calculated according to the deterministic health risk assessment model was below 1 and is within a relative safety level,and for children the HI value was 1.16>1,exceeding the risk threshold.The carcinogenic risk（CR）for both children and adults were in the acceptable threshold range(10^-6～10^-4).（6）The results of Monte Carlo simulation for human health risk assessment were lower than the risk values of the deterministic model,and below the safety limit.In the uncertain parameters considered in the health risk model,Ingestion rate and weight were most sensitive to adults and children,respectively,As concentration in soil was also an important factor.Conclusion:（1）The contents of As,Cd,Cu,Ni,Zn and Mn in urban soils of Hefei City exceed the soil background values,but the measured heavy metals content did not exceed screening values under the Risk control standard for’soil contamination of development land.（2）The spatial distribution of heavy metals concentration in urban soils of Hefei was mainly in the east-west urban area.（3）The heavy metals pollution in Hefei urban soils was affected by internal and external factors,in which the sources of Cr、Ni、Al、Fe and Mn are similar,the sources of Cr,Ni,Al,Fe and Mn in soils of Hefei were similar,the pollution sources of Cd,Cu,Pb and Zn might be the same,and As had a unique source.（4）As and Zn should be listed as a local priority for heavy metals,but overall,the urban soil environment in Hefei was relatively good.（5）The results of the deterministic and uncertain model of health risk assessment showed that the potential health effects of heavy metals on local residents in urban soils of Hefei were within acceptable range.