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(09-05) Fraction Transformation and Plant Accumulation Kinetics of Copper in Maize Rhizosphere Soil. Tao, Shu*,1, Chen, Youjian1, Huang, Yi1, Xu, Fuliu1, 1 Dept. of Urban and Environ. Sci., Peking University, Beijing, China ABSTRACT- Chemical forms of copper in the maize rhizosphere soil and the bulk soil were investigated using rhizobox cultivation and sequential extraction technique to study copper fraction transformation kinetics in the rhizosphere of developing maize plant. The accumulation of copper in the maize plant was determined as well. It was demonstrated that there were continuous changes in copper fractionation in the maize rhizosphere. The exchangeable copper increased at the beginning and dropped below the initial level after 40 days or so. The carbonate associated copper followed a similar trend of change but with a slower pace than the exchangeable copper and the increase only became evidential after 30 days and a net loss occurred after 60 days. There were also initial increase in the oxide bound copper and decrease in the organic matter associated copper, both followed by a turnover after 40-50 days. The accumulation of copper in the maize plant was biomass dependent. The accumulated amount of copper absorbed in the plant exceeded the initial quantity of the exchangeable copper in the soil, revealing the occurrence of transformation from less bioavailable to more bioavailable fractions. During the cultivation, decrease in redox potential and increase in pH, DOC, and microbial activity in the maize rhizosphere were observed. The transformation in copper fractions was eventually the results of root-induced changes in DOC, redox potential, and microbial activity in the rhizosphere. Key words: copper, soil, rhizosphere, fractionation |
