Influence of Dissolved Organic Matter on Cd Speciation in Rhizosphere Soil Solution and Phytoextraction by Sedum alfredii and Sedum sarmentosum

摘要

Cd contamination in soil is a global environmental issue and the remediation of contaminated soil is necessary. Phytoextraction, as a promising friendly technique, has a main drawback: low mobility and bioavailability of Cd. In this study, the influences of dissolved organic matter derived from chicken manure (DOMc), humus soil (DOMs), and rice hull (DOMr) on Cd speciation in soil solution, and the uptake of Cd by a hyper-accumulating ecotype (HE) and a non-hyperaccumulating ecotype (NHE) of Crassulaceae were investigated. After the addition of exogenous DOM and subsequent plant growth, the dissolved organic carbon (DOC) concentration increase resulted in a higher proportion of Cd-DOM complexation. Moreover, DOM derived from the chicken manure had the highest degree of Cd complex formation in rhizosphere soil, followed by DOMs and DOMr. Furthermore, because of the increasing fraction of Cd-DOM, the solvation of Cd in the soil matrix was remarkably favored. However, growth of HE decreased the dissolved Cd in rhizosphere soil solution compared to bulk soil, and may be attributed to the phytoaccumulation of Cd by HE plants. In addition, the amount of Cd phytoextracted by plants significantly increased with DOM concentration. The Cd concentrations in the HE shoots were in the range of 754.3 similar to 4234.2 mg.kg(-1) (DOMc), 714.9 similar to 4015.8 mg.kg(-1) (DOMs), and 656.7 similar to 900.4 mg.kg(-1) (DOMr), and were 15.4 similar to 47.0, 17.4 similar to 23.9, and 16.9 similar to 22.6 times higher than the NHE samples, respectively.