Abstract: The typical wetland at the estuaries of the Le’an River and Raohe River to the Poyang Lake was selected as a subject for the study on methods for risk assessment of heavy metals (Cu, Pb and Cd) pollution of surface soil of the wetland. Four different methods, i.e. the single factor index method, the geo-accumulation index method, the Nemero comprehensive pollution index method and the potential ecological hazard index method, were used and compared for merits and shortcomings. Correlations between diversity of aquatic plants communities and heavy metals pollution of the surface soil were also analyzed by taking into account results of the investigations of aquatic plant communities in various sampling sites. It was found that the surface soil of the wetland was polluted mainly by copper and much less by lead and cadmium. The pollutant of Cu came mainly with the acid heavy metals-containing wastewater discharged through the Dawu River from the copper minings. The four methods were used to evaluate the 6 sampling sites exposed seriously to pollution of the acid heavy metals waste water from the copper minings in the upstreams of the Le’an River and yielded similar conclusions, i.e. extremely polluted. But they differed slightly in conclusion when used to evaluate sampling sites not so severely polluted. Generally speaking, the sampling sites along the Le’an River decreased in ecological risk of the heavy metals pollution with their locations from the mid-streams to the down-streams. Results of the four methods were quite objective. Significant negative relationships were observed of the diversity of aquatic plant communities with the integrated potential ecological risk index of heavy metals pollution in the surface soil and the single-factor potential ecological risk index of copper in various sampling sites.

Key words: Poyang Lake, Le’an River, surface soil, heavy metals pollution, plant species diversity, evaluation methods