Effects of pH, initial Pb concentration, and polyculture on lead remediation by three duckweed species.

Various geographical duckweed isolates have been developed for phytoremediation of lead. The Pb removal efficiency of Lemna aequinoctialis, Landoltia punctata, and Spirodela polyrhiza was investigated in monoculture and polyculture at different levels of pH and initial Pb concentrations. L. aequinoctialis was not sensitive to the tested pH but significantly affected by initial Pb concentration, whereas synergistic effect of pH and initial Pb concentration on removal efficiency of L. punctata and S. polyrhiza was found. Although the majority of polycultures showed median removal efficiency as compared to respective monocultures, some of the polycultures achieved higher Pb removal efficiencies and can promote population to remove Pb. Besides, the three duckweed strains could be potential candidates for Pb remediation as compared to previous reports. Conclusively, this study provides useful references for future large-scale duckweed phytoremediation.