Fractionation and solubility of cadmium in paddy soils amended with porous hydrated calcium silicate |
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Authors: | ZHAO Xiu-Lan and Saigusa Masaihiko |
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Institution: | 1. College of Natural Resources and Environmental Sciences,Southwest University,Chongqing 400716,China 2. Experimental Farm,Graduate School of Agricultural Sciences,Tohoku University,Naruko,Miyagi 989-6711,Japan |
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Abstract: | Previous studies have shown that porous hydrated calcium silicate (PS) is very effective in decreasing cadmium (Cd) content in brown rice. However, it is unclear whether the PS influences cadmium transformation in soil. The present study examined the effect of PS on pH, cadmium transformation and cadmium solubility in Andosol and Alluvial soil, and also compared its effects with CaCO3, acidic porous hydrated calcium silicate (APS) and silica gel. Soil cadmium was operationally fractionationed into exchangeable (Exch), bound to carbonates (Carb), bound to iron and manganese oxides (FeMnO(x)), bound to organic matters (OM) and residual (Res) fraction. Application of PS and CaCO3 at hig rates enhanced soil pH, while APS and silica gel did not obviously change soil pH. PS and CaCO3 also increased the FeMnO(x)-Cd in Andosol and Carb-Cd in Alluvial soil, thus reducing the Exch-Cd in the tested soils. However, PS was less effective than CaCO3 at the same application rate. Cadmium fractions in the two soils were not changed by the treatments of APS and silica gel. There were no obvious differences in the solubility of cadmium in soils treated with PS, APS, silica gel and CaCO3 except Andosol treated 2.0% CaCO3 at the same pH of soil-CaCl2 suspensions. These findings suggested that the decrease of cadmium availability in soil was mainly attributed to the increase of soil pH caused by PS. |
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Keywords: | porous hydrated calcium silicate solubility soil cadmium calcium silicate porous paddy soils cadmium solubility decrease availability increased suspensions differences fractions rates ApplicatiOn soil pH residual organic matters iron manganese oxides Carb bound |
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