Pollution and Evaluation of Heavy Metals in the Wetland Soil of Shuangtaizi Estuary

Contents of five kinds of heavy metals (Cu, Pb, Zn, Cd, As) were determined from the surface and section of Shuangtaizi estuarine wetland, China, in October of 2008.The results indicated that, the average concentrations of Cu, Pb, Zn, Cd and As in surface soil were higher than background value, but the content of Cd exceeded the first environmental quality standard for soils, and became the main pollutant factor. The contents of Cu, Pb and As in the coastal marsh solonchak were relatively higher; while the content of Zn in the salt meadow soil was higher and Cd in the tidal shallow solonchak was high. Vertical distribution characteristics of the heavy metals in the basification meadow soil and the tidal shallow solonchak showed that, contents of the heavy metals except Cu in the tidal shallow solonchak were higher than those in the salt meadow soil; contents of Cu and Zn in the two sections and contents of Cd and As in the tidal shallow solonchak had no significant difference in the vertical distribution; the content of Pb showed a ups and downs trend as the depth increased; contents of Cd and As in the surface basification meadow soil were evidently higher than those in the other layers. Contents of heavy metals except Cd had positive correlations in different levels. The pollution level of the wetland soil was medium, with the pollution degree order of Cd>As>Cu>Zn>Pb.The heavy metals in the surface wetland soil had a low potential ecological risk for environment. The order of potential ecological risk coefficient was Cd>As>Cu>Pb>Zn.