Study On The Remediation Effect Of Different Passivators On Cd Contaminated Paddy Soil

Rice is the main food crop,feeding nearly 50% of the world’s population.However,the development of modern industry and agriculture causes different levels of cadmium pollution in some farmland,which seriously affects the quality and safety of rice.In view of the current situation of cadmium pollution in local paddy soil,it is of great significance to carry out the treatment and remediation of cultivated land to ensure the yield and quality of "grain bags".There are many methods for remediation of heavy metals in soil,and passivating agent remediation technology has been paid more attention by researchers because of its operability and practicability.This experiment through pot experiment,the soil cadmium pollution in paddy soil(more than agricultural risk control value)and rice "two optimal 8106" as the research object,to choose from all over the country,on the cadmium pollution in local repair 10 kinds of passivator as treatment with better effect,without passivation agent for comparison,each processing set 3 repetitions,repair different passivation effect research.By measuring soil Cd speciation characteristics and rice agronomic indexes,the distribution and accumulation of Cd in rice grains,husks and stalks were analyzed,in order to screen out effective passivators and provide reference and basis for remediation technology of Cd contaminated paddy fields in Anhui Province.The main results are as follows:(1)The soil pot experiment showed that the form of Cd in the soil was different at different stages of rice growth.The morphological contents of each treatment in the order of proportion to total amount at the tillering stage were as follows: exchangeable form >carbonate combined form > residue form > iron and manganese oxides combining form >organic combination form;In the booting stage,heading stage and maturity stage of rice growth,the order of the proportion of the total rice was as follows: carbonate combined form > residue form > organic combination form > iron and manganese oxides combining form.(2)All the passivators in this experiment changed the p H of the soil to some extent.Compared with the control soil at tillering stage and booting stage,the p H value of passivating agent treatment increased significantly.Among the soil p H values at the heading stage and maturity stage of rice planting,the soil p H values of 6 groups began to decrease in all treatments,but they were all higher than that of the control group.(3)The content of exchangeable Cd in the passivated soil decreased during the growth of rice.The range of decrease ranged from 0.79% to 7.02%.The content of carbonate-bound Cd in the soil of all treatments was higher than that of tillering stage,and the content of Fe and Mn oxidation state Cd in soil decreased.The content of organic Cd in soil tends to be stable after decreasing.From tillering stage to booting stage,soil residual Cd content showed an increasing trend with an increasing range of 1.31%-10.98%.From booting stage to heading stage,the content of residual Cd in soil treated by all passivating agents increased by 0.99%-106.78%,while the content of residual Cd in soil treated by CK decreased by 1.49%.(4)Rice grain biomass and rice husk biomass were increased by 5.75%-25.30% and10.58%-42.91% by each passivating agent.The plant height of T1 and T2 treatments was higher than that of the control,and the other passivating agents were 0.74%-10.35% lower than that of the control.T5 significantly increased the panicle length of rice,but T6 significantly increased the panicle length of rice.Compared with the control,the panicle length of each treatment changed from-2.21%-1.98%.The 100-grain weight of rice treated with passivating agents increased by 3.94%-64.23%.Seed setting rate was increased by0.31%-12.68%.Based on agronomic traits,the most significant effects of passivating agents were T1,T2 and T8.(5)The effects of passivating agents on the contents of Cd in rice grains,husks and straw were different.Compared with CK,the absorption and accumulation of grain,shell and straw of rice growing in Cd contaminated soil showed the pattern of straw>Shell>grain.The contents of Cd in rice grains and shells were decreased in all treatments except the brown rice under T3 treatment.Compared with the control,the application of T9 reduced the Cd content in brown rice by 71.50%,and the Cd content in straw by 22.31%,indicating the best application effect(p<0.05).(6)The extractable content of Cd in soil was negatively correlated with soil p H value.The passivators reduced the activity of Cd by increasing soil p H value.The extractable state content was positively correlated with the accumulation amount of brown rice,indicating that extractable state was conducive to the transfer of Cd to brown rice.