| Heavy metal pollution not only makes the degradation of soil fertility, and also reduce the yield and quality of agricultural products, and ultimately endanger human health through the food chain. Because of its special properties, biochar has relatively high agricultural values and the potential to remediate environmental pollution. Study on the heavy metal contaminated soil renovation by biochar also become a new hot spot.The effects of biochar input on the environmental behavior and environmental effects of heavy metals in contaminated soil would have been confirmed, it makes sence to protect the soil environment, improve soil quality and has positive and long-term application prospect. In this study, rice straw and bamboo sawdust used as raw material were prepared for biochars. Through characterization of biochars and its simple adsorption experiments, biochars with better performance were screened for soybean pot experiment and soil column leaching test. The effects of biochar input on migration of soil heavy metal absorption and heavy metal accumulation of soybean were investigated. The main results are presented as follows:(1)SBC and BBC have higher pH values and C content, and also have high adsorption capacity for copper and lead. By the use of synchrotron radiation XANES analysis method, it was investigated that the main molecular form of copper in SBC samples was analogous humic acid copper (Cu-Humid acid) form, and the main molecular form of copper in BBC samples was analogous copper phosphate ((Cu3(PO4)2)) form.(2)Under the different treatment, SBC played a certain role in promoting the growth of soybean. At the5percent of SBC treatment, biomass of soybean was up to the most, meanwhile, accumulation of macronutrients essential for soybean also reached its maximum. And only at the0.1percent of BBC treatment, biomass of soybean was higher than the blank treatment. With the increase of BBC percent, BBC had an evident effect on inhibiting soybean growth. Reduction of chlorophyll content also corroborated this assertion. (3)The impact of SBC and BBC on accumulation of heavy metals for soybean were not the same. SBC and BBC both increased the stability of copper, zinc and lead in the soybean non-rhizo sphere soil to a certain extent, and promoted the mobility of chromium and cadmium in the soybean non-rhizosphere and its bioavailability. The main parts of soybean for assimilation of heavy metals copper, zinc, lead, chromium and cadmium were roots, accompanied by a small amount of heavy matals migration to the upper tissue.(4)The main existing forms of copper, zinc, lead and cadmium in soil from0to20cm at upper soil column were exchangeable and weak acid soluble fraction, and reducible fraction. While the main form of existence of chromium were residual fraction and oxidizable fraction. But from20to50cm at lower layer of soil column copper, zinc, lead, chromium and cadmium in soil were mainly present in the residual fraction with excellent stability.(5)There was a positive correlation between total concentration of heavy metals at corresponding depths of soil and corresponding soil pH. Both SBC and BBC were to a certain extent on the promotion of vertical migration of heavy metals copper, lead and cadmium in soil of column, and strengthened the stability of zinc. SBC had promoted its migration for chromium, while BBC had a positive effect on its stability to some extent. Overall, BBC had good adsorption and fixation for heavy metals, and SBC to some extent promoted the migration of heavy metals. |
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