Assessment of Heavy Metal Pollution in Soil and Plants from Dunhua Sewage Irrigation Area

To evaluate the heavy metal contamination of soil and plants in Dunhua sewage irrigation area (DIA), the area used wastewater for irrigation at least 20 years. 270 samples in different depth (0-120 cm) and 23 plant samples were collected at five different sites. Physical and chemical properties of the long-term sewage irrigation soil were analyzed, including soil texture, bulk density, pH, cation exchange capacity (CEC), organic matter; the heavy metal total concentrations were measured using AAS and AES. The average value of soil pH was 8.01, the soil was alkaline; the soil CEC changes from 59.35 mmol to 118.95 mmol, average value was 80.96 mmol; content of organic matter in surface soil maintained 1.27 % to 2.18%; the bulk density of soil ranges from 0.94 to 1.57 g/cm 3; average concentrations of heavy metals in surface samples were: Cr, 28.249 mg/kg; Cd, 1.247 mg /kg; Pb, 37.468 mg/kg; heavy metal concentration in the three different crops of different portions was: root>stem>leaf>grain; the vertical distribution and migration the concentration of 0-20 cm soil was significantly higher than other soil layers, showing the characteristic of enrichment at surface, relatively stable in deep. Heavy metals pollution degree was Cd(2.069)>Cr(0.113)>Pb(0.107), pollution risk degree of different sample point’s range was EC>MF>Xg>WD>XG. Irrigation by wastewater has increased the heavy metal concentrations in soil and plants of receiving area