| Mercury?Hg? and methylmercury?MeHg? can be accumulated in rice,and this is an important Hg exposure pathway to human beings.Therefore,the reduction of mercury content in rice is one of major public health issues.So far the studies related to effect of biochar on MeHg formation and bioaccumulation in different paddy soils is insufficient.In the present study,five different kinds of biochar were selected to study their physico-chemical characteristics and adsorption mechanism toward mercury.The complexion of Hg with biochar was identified by FTIR.The effect of biochar application on the change of available-Hg were conducted by simulation experiment in laboratory.In addition,one kind of biochar was selected and applied into two mercury contaminated soils with an attempt to reveal the the effects of biochar on mercury accumulation by rice through pot experiments.The main findings of this study are as follows:?1?The adsorption process of biochar for Hg2+ follow Pseudo-second order reaction kinetics with a linear coefficient R2 of 0.985-0.999.The results indicate that the adsorption of Hg2+ by biochar was mainly through chemical adsorption.FTIR showed that the major adsorption sites were hydroxyl,carboxyl and other oxygen-containing functional groups.?2?Biochar can reduce 77.5-87.1% of available mercury in paddy soil.Among five different biochars,the adsorption capacities of bamboo biochar was better than others while cow dung biochar was weakest due to the lackage of oxygen functional groups and low sulfur content,?3?Biochar may promote Hg methylation in neutral soil and MeHg content increased gradually during rice growth.However,biochar application can inhibit both Hg and MeHg accumulation in different rice tissues,and the contents of Hg and MeHg in the rice grains decreased by up to 73.4 and 81.9%,respectively.This demonstrates that biochar can effectively reduce the mercury enrichment ability of rice.However,the inhibitory effect was less pronounced in calcareous paddy soil. |
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