Abstract:

Surface soil samples(185)and different depth of 20,40,60,80,100and 120cm samples(90) was collected in agricultural soils of Dunhua sewage irrigation area, the heavy metals (Cd，Cr，Hg) were determined by AAS and AES. Hakanson ecological risk method was used to assessment the potential ecological risk of heavy metals,and the vertical distribution and migration of heavy metals were discussed. The results showed that: Irrigated soil is alkaline (pH=8.01), The long-term sewage irrigation led to serious contamination of Cd with average content up to 1.265mg/kg, it was 2.11 times of the national standard value, pollution of Cd is the main factor causing the risk of soil. The comprehensive risk index RI distributed in 475.769 to 610.187, belong to a strong degree of pollution. The total risk index is contributed by heavy metal Cd, account for 68.4-74.6%, the other are lower. The organic matter tend to be concentrated in the cultivated horizon(>1%), and content tends to decrease with the depth;The relationship between heavy metals and the depth obey exponential distribution, consistent with the changes of organic matter.