Effect Of The Combination Of Foliar Inhibitors And Soil Possivators On The Accumulation Of Heavy Metals In Rice

Based on the pollution condition of farmland in Taihe County,Jiangxi Province,a field remediation study was carried out in a contaminated paddy soil with its area of 0.67 ha.The soil was red paddy soil where the level of cadmium(Cd)in its surface soil was the most serious problem.Exceeding the standard points accounted for 41.7%.To solve the problem of excessive Cd in red paddy fields,the combined passivators were selected and used in field experiments to explore the effects of the combined passivators on the available heavy metals(Cd,Pb and Cu)in soil and their uptake by rice in red paddy soil.Sepiolite(S),quicklime(Q)and polyacrylamide(A)were used as the components of combined passivators in field experiment,because laboratory screening results showed that they decreased available Cd,Pb and Cu by 32.4% ～ 89.2%,19.5% ～ 99.1% and49.4% ～ 92.4%,respectively.In field experiments,the combined passivators(a mixture of Q,A and S)and Si-/Se-containing foliar inhibitors(Si or Se)at low(1)and high(2)application rates were added into the red paddy soil.After rice harvest,the soil samples were collected to examine the soil properties,bacterial community,and the availability of heavy metals(Cd,Pb,and Cu)in soil.The rice samples were obtained to investigate the accumulation of heavy metals by rice.All of the treatments increased the soil’s p H,but the treatments excluding QSe2 decreased the total P and soil organic matter(SOM),which was favourable for the immobilisation of heavy metals in red paddy soil by decreasing 14.29% ～42.86% of available Cd,10.18% ～ 63.17% of available Pb,and 6.95% ～36.81% of available Cu.With the increasing application rates,QAS significantly decreased the available heavy metals because of the enhanced immobilisation of these heavy metals,while QSi and QSe significantly increased the available heavy metals because of the inhibited rice uptake.Q1,QA1,QSi2,and QSe2 most effectively decreased the uptake Cd by rice in the present red paddy soil to solve the problem of Cd exceeding the threshold value according to the National Food Safety Standard of China(GB2762-2017).Additionally,the treatments,with the exception of Q1,QA1,QSi1,and QSi2,did not dramatically change the community structure of bacteria at the genus level in soil.Considering the safety and stability of soil,QSe2 was the primary recommendation for remediating Cd-contaminated red paddy soil.