Abstract: Through the studies on Pb and Cd contents in various compositions of artificial wetland and their speciation distribution in upper clayey layer, the mechanism of artificial wetland treatment of heavy metal-containing wastewater is approached. The results show that various compositions of artificial wetland all have the capability of removing Pb and Cd from wastewater, and upper clayey layer makes the largest contribution. The contents of Pb and Cd in substrates are decreased in order of upper clay soil>soil>sand>crushed stone. Taxodium ascenders has a stronger capability of enriching Pb and Cd, which is decreased in order of root>stem>cortex>stem xylem>leaf. Pb is mainly bound with Fe/Mn oxide(47.0％) and carbonate(39.3％), and Cd is mainly in exchangeable form(39.5％) and bound with carbonate(37.10％).

Key words: Artificial wetland, Wastewater treatment, Lead, Cadmium, phytolith, subtropical forest, tropical forest, PhytOC