Characteristics And Risk Assessment Of Heavy Metals In Soils Of Shenbei New Area

Shenbei New Area is a typical area with rapid urbanization and intensive agricultural management.Agricultural planting and industrial production can cause heavy metal pollution in soil.In this paper,the physical and chemical properties of soil and the contents of Cadmium（Cd）,lead（Pb）,copper（Cu）,zinc（Zn）,arsenic（As）,mercury（Hg）,nickel（Ni）and chromium（Cr）in the topsoil（0-20 cm）of Shenbei New Area were measured.This study aims to understand the pollution situation of heavy metals and to provide support for the prevention and control of heavy metal pollution.Existence form,main pollution sources,the risk of ecological and human health of heavy metals were analysed.Results showed that the soil organic matter content of different utilization types in SNA is extremely high(≥25 g?kg^-1),among which the OM average of forest land（SL）,paddy field（ST）,green land（LD）and upland field（HT）The content were 48.20 g?kg^-1,28.70 g?kg^-1,28.46 g?kg^-11 and 25.30 g?kg^-1,respectively.The content of phosphorus in paddy field（ST）,forest land（SL）and green land（LD）is low,and available phosphorus content is 0.006 g·kg^-1,0.013 g·kg^-11 and 0.014 g·kg^-1,respectively.The content of available phosphorus in upland field is moderate(0.049 g·kg^-1).The order of the average content of 8 heavy metals from high to low is Zn>Cu>Ni>Pb>Cr>As>Hg>Cd.The proportion of Cu,Zn,As,Hg and Ni above the background value of the soil in Shenyang was 14.9%,49.5%,3.0%,68.3%and 1.0%respectively.Compared with the second grade standard of soil environmental quality standard（GB15618-2018）,the proportion of Hg exceeded the standard sample was the highest（17.8%）,and the other heavy metals were not exceeded the standard.The spatial distribution characteristics of different heavy metals are different.The spatial distribution characteristics of Cd,Zn,As,Cr is high in the east and north,and low in the west and south.The spots more polluted of Hg were concentrated in Magang Town in the east.The higher concentration spot of Pb located in the east and west of Shenbei New Area.The higher Ni concentration spot is in the north and south of Shenbei New Area,and the higher Cu concentration is mainly in the upland field soil in the west and east of Shenbei New Area and the industrialized planting area in the middle of the region.The main pollution sources of heavy metals were analyzed combining correlation analysis with principal component analysis and cluster analysis.Results showed that Cd,Zn,As and Cr come from soil parent material and industrial source.Pb and Ni originate from soil parent material layer.The sources of Cu are chemical fertilizer and pesticide.Hg comes from coal combustion pollution,and the content of As,Pb,Ni,Cris affected by many sources.The results of exposure model showed that the risk index of carcinogenic and non-carcinogenic pollutants did not reach the level of threat to human body.The highest risk of exposure to heavy metals in humans is oral intake,followed by skin contact and respiratory inhalation.Under the same exposure pathway,the risk of carcinogenesis in children is higher than that in adults.