The influence of water regime on cadmium uptake by Artemisia: A dominant vegetation in Poyang Lake wetland.

Abstract

An analysis of the influence of water regime on the metal accumulation processes of wetland plants can improve the efficiency of phytoremediation. However, few studies have clearly explored the mechanism of influence of water regime on the process of accumulation of metals by the dominant vegetation in Poyang Lake wetland, the largest freshwater lake in China. The aim of this study was to investigate the influence of water regime (Flooding condition [FC], Dry condition [DC] and alternate dry and flooding condition [DFC]) on the accumulation of cadmium (Cd) by Artemisia selengensis Turcz. ex Bess., a dominant plant in the Poyang Lake wetland. The results indicated that FC treatment significantly enhanced the accumulation of Cd by Artemisia roots compared with DFC and DC treatments. In addition, the DFC treatment significantly increased the translocation of Cd from roots to shoots compared with the FC treatment. A multivariate statistical analysis indicated that the rhizosphere Cd fraction, iron plaque on the root surface and rhizosphere pH directly or indirectly significantly influence the process of accumulation of Cd. The conversion of exchangeable fraction to Fe/Mn oxide bound and organic fraction under the DFC and FC treatments decreased the accumulation of Cd in Artemisia. The formation of increased amounts of iron plaque under the FC treatment may enhance the accumulation of Cd in roots, while it may reduce the translocation of Cd to aboveground tissues. In addition, a higher rhizosphere pH under the FC treatment may promote accumulation of Cd in the root by inducing formation of iron plaque. Similarly, compared with the FC treatment, a lower rhizosphere pH and iron plaque can induce the processes of Cd translocation under the DFC treatment. Based on the bioaccumulation factor, translocation factor and the ratio of root/aerial Cd content, treatment with DC benefited the phytoextraction of Cd, while treatment with DFC and FC enhanced the phytostabilization of Cd by Artemisia. This study provides valuable information for deeply understanding the resilience of wetland ecosystems and for enhancing the phytoremediation with wetland plants using water management.