Pollution And Risk Analysis Of Heavy Metals And Polycyclic Aromatic Hydrocarbons In Urban Soils Of Kaifeng City

As an important part of urban ecosystem,urban soil is affected by people’s activities in the process of urbanization.Soil environmental quality plays an important role in urban ecological environment and human health.Based on the famous historical and cultural city of Kaifeng City,the soil profile samples of different land use types in Kaifeng City were collected,and the physical and chemical properties of the main pollutants were analyzed.The contents of heavy metals and polycyclic aromatic hydrocarbons(PAHs)Type of urban soil heavy metals and polycyclic aromatic hydrocarbons pollution status assessment.The conclusions are as follows:(1)The average contents of heavy metals Cu,Pb,Zn,Cr,Co and Ni in the surface soil of Kaifeng City were 35.94 mg / kg,29.79 mg / kg,108.88 mg / kg,49.30 mg / kg,14.76 mg / kg,36.09 mg /kg.In addition to the Cr element,the average of the other five heavy metal contents exceeded the soil background value of Henan Province,and the coefficient of variation of Cu was the largest,which indicated that the content of human activities was the most affected.The content of heavy metals in soils with different land use types showed that the contents of Cu,Pb and Zn were higher in different land use types,and the excess of Cu was the highest,and the pollution was the most serious.There is no definite law in the vertical direction of urban soil heavy metals,and the manifestations are varied.(2)The factors of Cu,Pb,Zn,Cr,Co and Ni in the soil were evaluated by single factor index method,and the pollution of Cu,Pb and Zn in industrial and mining land was the most serious and reached the level of heavy pollution.In different land use types of Cr pollution levels the lowest,in addition to forest for cleaning,the other is still in the clean level,indicating that the Cr element by the environmental impact of the smallest.The Nemerite index was used to evaluate the land use types.The pollution rate of the Nemero pollen was the highest,the level of heavy pollution was the same,and the other was mild pollution level,which was consistent with the single factor index method.Different heavy metals in different land use types are subject to a certain degree of pollution.(3)The PAHs content in the urban soil of Kaifeng City ranged from 13.72 to 4805.35μg·kg-1,with an average value of 433.14 μg·kg-1,compared with other cities,the pollution of PAHs in Kaifeng City was at a low level.The total content of soil PAHs in different land use types is Industrial and mining land(1249.6 6 μg·kg-1)> Residential land(453.96 μg·kg-1)> Public management land(313.08μg·kg-1)> Traffic land(194.08 μg·kg-1)> Commercial land(193.67 μg·kg-1)> Forest land(181.37 μg·kg-1).(4)For adults and children,three different exposure routes in the skin contact are the most important soil PAHs exposure pathways,followed by eating soil PAHs exposure pathways,respiratory contact soil PAHs are negligible.The health risks of children with different land use types are higher than those of adults.Different types of land use PAHs have different levels of contamination,Industrial and mining land(5.08 μg·kg-1)and Public management land(4.69 μg·kg-1)were heavily polluted,Traffic land(2.10 μg·kg-1)was moderately contaminated,Residential land(1.56 μg·kg-1)was mildly contaminated,Commercial land(0.87 μg·kg-1)belongs to the cordon range,Forest land(0.55 μg·kg-1)was safe.The carcinogenic risk of soil PAHs in industrial and mining land and public management land is more than 10-6,Residential soils PAHs have a carcinogenic risk to children more than 10-6.The existence of the human body can tolerate the potential risk of cancer,need to attract people’s attention.(5)The sources of PAHs in urban soils of Kaifeng City are both source of combustion and oil pollution,mainly oil,biomass and coal combustion,which are mixed sources.The urban soil is closely related to the urban ecological environment and the life of the urban residents.It is necessary to increase the importance of heavy metals and polycyclic aromatic hydrocarbons(PAHs)in the urban soils to the ecological environment,and take appropriate measures as soon as possible to prevent the ecological environment and human health from being greatly damaged.