Levels, sources and risk assessment of trace elements in wetland soils of a typical shallow freshwater lake, China

摘要

The deteriorating environmental conditions of Baiyangdian Lake have caused a wide public concern. Surface soils (0-20 cm) were collected at 10 sites of reed wetlands in raised fields of the Baiyangdian Lake. They were analyzed for total contents of trace elements to investigate their distribution and pollution levels in wetland soils of this region. Results showed that the mean contents of As, Cd, Cr, Cu, Ni, Pb and Zn all exceeded their environmental background values of Hebei Province and had various degree of spatial variations. As, Cr and Ni contents exceeded considerably the probable effect levels. Multivariate analysis indicated that Cr, Cd, Ni, Cu, Pb and Zn had common sources and As had different sources for these trace elements. The average toxic units (TU) of trace elements in the Baiyangdian Lake followed the order As > Ni > Cr > Zn > Pb > Cu > Cd. As, Ni and Cr made the higher contributions to ∑TUs(i.e.,41.3 ± 7.2,21.8 ± 4.1 and 16.2 ± 2.8 %, respectively). The potential ecological risk index of Cd (E~i_r) was 213.44, which was the highest value in the Baiyangdian Lake. The other trace elements had lower potential ecological risk indices (<40), following the order Cd > As > Cu > Pb = Ni > Cr > Zn. Potential toxicity response indices (RI) of trace elements for the whole lake region was 269.81, with a moderate potential toxicity response.