Terrestrial environment

Heavy metal (Pb, Zn) uptake and chemical changes in rhizosphere soils offour wetland plants with di erent radial oxygen loss

Junxing Yang , Zuoluo Ma , Zhihong Ye , Xueyan Guo , Rongliang Qiu


Received July 15, 2009,Revised October 16, 2009, Accepted , Available online

Volume 22,2010,Pages 696-702

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Lead and Zn uptake and chemical changes in rhizosphere soils of four emergent-rooted wetland plants; Aneilema bracteatum, Cyperus alternifolius, Ludwigia hyssopifolia and Veronica serpyllifolia were investigated by two experiments: (1) rhizobag filled with “clean” or metal-contaminated soil for analysis of Pb and Zn in plants and rhizosphere soils; and (2) applied deoxygenated solution for analyzing their rates of radial oxygen loss (ROL). The results showed that the wetland plants with di erent ROL rates had significant e ects on the mobility and chemical forms of Pb and Zn in rhizosphere under flooded conditions. These e ects were varied with di erent metal elements and metal concentrations in the soils. Lead mobility in rhizosphere of the four plants both in the “clean” and contaminated soils was decreased, while Zn mobility was increased in the rhizosphere of the “clean” soil, but decreased in the contaminated soil. Among the four plants, V. serpyllifolia, with the highest ROL, formed the highest degree of Fe plaque on the root surface, immobilized more Zn in Fe plaque, and has the highest e ects on the changes of Zn form (EXC-Zn) in rhizosphere under both “clean” and contaminated soil conditions. These results suggested that ROL of wetland plants could play an important role in Fe plaque formation and mobility and chemical changes of metals in rhizosphere soil under flood conditions.

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