Chemical extraction methods are being widely used to assess bioavailability of mercury in contaminated soils and predict mercury bioaccumulation in corps.However,validation of these methods,e.g.,correlating mercury extraction from different soils and its bioaccumulation in corps,has rarely been reported,which hindered application of these methods in risk assessment of mercury in contaminated soils.In the present study,three common chemical extraction methods(CaCl2,DTPA and(NH4)2S2O3 extractions)were applied to assess phytoavailability of methylmercury(MeHg)in soils of different properties,which were collected from different parts of China.And MeHg extractions were correlated with determined MeHg concentrations in rice grains.Our results indicated that single soil parameter(e.g.,soil composition,pH)could not provide a good estimate of MeHg bioavailability to rice plants and could not be used to predict MeHg concentrations in rice for different soil types.This may be because that absorption and bioaccumulation of MeHg in rice were controlled by multiple factors simultaneously.Among the three extraction methods,MeHg extraction by(NH4)2S2O3 could best predict bioaccumulation of MeHg in rice grains for different soils(r2=0.661,p<0.01),suggesting that migration of MeHg from binding sites within soils(e.g.,reduced organic sulfur groups)to those on root surface could be the limiting step of MeHg bioaccumulation in rice.Therefore,MeHg extraction by(NH4)2S2O3,which is simple and fast,could possibly be used to assess bioavailability of MeHg in different soil types and predict MeHg bioaccumulation in rice grains.According to our knowledge,this is the first study validating MeHg extraction by different chemical extractants with MeHg bioaccumulation in rice grains.