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TP7 Metallic and Organometallic Distribution and Effects
() Effect of earthworms (Eisenia fetida) on the fractionation and bioavailability of REEs in soils.
Wen, Bei 1, Hu, Xiao-yu 2, Liu, Ying 3, Shan, Xiao-quan 4, 1 Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, Beijing, China2 Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, Beijing, China3 Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, Beijing, China4 Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, Beijign, China
ABSTRACT- The effects of earthworm (Eisenia fetida) activity on soil pH, dissolved organic carbon (DOC), microbial populations, fraction distribution and bioavailability of rare earth elements (Y, La, Ce, Pr, Nd) in nine Chinese soils were investigated using pot experiments. A three-step extraction procedure recommended by European Community Bureau of Reference (BCR) (now Standards, Measurements and Testing Programme of European Community) was used to fractionate the metals in soils into water soluble, exchangeable and carbonate bound (B1), Fe- and Mn-oxides bound (B2) and organic matter and sulfide bound (B3). After the soils were treated with earthworms, the soil pH, water-soluble rare earth element fraction and DOC increased. A significant correlation was obtained between the increased DOC and the increased rare earth elements in the water-soluble fraction. The rare earth elements in fraction B1 increased after earthworm treatments, while those in fraction B3 decreased. No significant differences were observed for rare earth elements in fraction B2. The microbial populations in soil were enumerated with the dilution plate method using several media in the presence of earthworms. The microbial populations increased due to earthworm activity. The biomass of wheat shoots and roots and the rare earth element concentrations in wheat roots and shoots were also increased due to the earthworm activity. The present results demonstrated that earthworm activity increases the mobility and bioavailability of rare earth elements in soils.
Key words: Earthworm, Rare earth elements, Fractionation and Bioavailability, Dissolved organic carbon
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