| In recent years,with the development of economy and industrial production,soil cadmium（Cd）pollution has become a serious environmental problem,the quality of ecological environment has been affected seriously.Cd is one of nonessential and deleterious heavy metals for plants,it can easily enter the food chain through the soil-plant system,and poses a threat to human’s health due to its high mobility.Therefore,it’s important and effective to explore the bioavailability in soil-rice system.This study is based on 18 Ultisols in China and selected rice（Oryza sativa L.）as the test plant.Pot experiment and field samples were used to explore the transportation and distribution characteristics of Cd in different biological tissues under different external cadmium treatment.What’s more,prediction models of Cd bioavailability in rice were constructed based on soil total Cd and EDTA-,HNO3-extractable Cd.The main research results are as follows:（1）The Cd absorption and transportation characteristics in rice were analyzed.The results showed that the exceeding rate of Cd concentration in rice to the food safety standard was 11.1%for the control,44.4%for low Cd treatment(p H<7.5,0.3 mg·kg-1;p H>7.5,0.6 mg·kg-1),and 88.9%for high Cd treatment(p H<7.5,0.6 mg·kg-1;p H>7.5,1.2 mg·kg-1),respectively.The Cd content in various tissues of rice from high to low was:root>stem>rice;and the order of bioconcentration factors（BCF）was root>stem>rice,while the transfer factors（TF）was stem>rice.Correlation analyses were applied to study the effects of soil physicochemical properties on Cd bioavailability,the soil p H value was the main controlling factor.（2）The multiple regression equations were constructed to estimate the bioavailability of Cd in brown rice.Based on soil total Cd,EDTA-,HNO3-extractable Cd content and soil physicochemical properties,three prediction models for Cd content in rice were constructed.The optimal factors in three prediction models were p H and labile manganese（Mn）,and R2 were greater than 0.70.In addition,by inferring the model from the measured values,the three models fitted scatter values were evenly distributed on both sides of the 1:1 line,and the prediction results were good.The prediction model based on total Cd can predict more effectively when total Cd content is below 1.0 mg·kg-1,and when total Cd content is greater than 1.0 mg·kg-1,the prediction model based on EDTA-extractable Cd is more suitable.The field samples were collected to verify the models,which showed high reliability.（3）The remediation effect of soil conditioner silicon calcium magnesium potassium fertilizer on the Cd contaminated soil was verified.This part of study is selected Ultisol and Alfisol as the test soils.When the soil Cd content is near the risk intervention values,the biomass of brown rice is not reduced significantly,while the application of silicon calcium magnesium potassium fertilizer can increase the yield significantly.The bioavailability of Cd in the soil decreased significantly,and the proportion of residual Cd increased significantly with the soil conditioner.Soil total Cd,EDTA-extractable Cd,acid-extractable Cd and residues can affect the content of cadmium in brown rice significantly according to correlation analyses.Silicon calcium magnesium potassium fertilizer is mainly used to improve the soil quality by increasing p H value,including reducing the bioavailability of Cd and the effect of soil acidification on nutrient availability.The high level soil conditioner treatment（2‰）is more effective. |
