Distribution of chemical fractions of Pb in wastewater in mixed substrates of constructed wetlands

In this study, the wastewater containing 10mg/L lead was treated by five different kinds of mixed substrates of constructed wetlands. The results indicated: (1) For total Pb, substrates 1, 4 and 5 showed significantly higher capacity than other kinds; (2) In five fractions, bound to Fe-Mn oxides and residual Pb were treated with higher efficiency than other fractions; (3) There were significant changes between the content of total Pb and that of five fractions in substrate 5; (4) Bound to carbonates and residual Pb showed an upward trend, but exchangeable and bound to OM Pb showed upward trend firstly, and then showed downward trend. The bound to Fe-Mn oxdies fraction Pb showed downward trend.