| At present,heavy metal pollution of agricultural soil in China situation is severe.After heavy metal pollutants contaminate the soil,they can enter the food chain,which not only affect food safety,but also pose a threat to soil microorganisms,animals and plants,as well as the ecosystem function of farmland soil.In-situ passivation remediation technology has been widely used in soil heavy metal pollution remediation due to its low cost and quick results.It has achieved good passivation effects in practical applications,but there are few studies on the passivation remediation effect of Cd contaminated soil.Therefore,based on the pot experiment,this article discussed the combination of passivation materials(Tebei calcium + sepiolite(TH),biochar +biological amendment(SX)and organic fertilizer + biological amendment(XA)),and different planting methods The passivation remediation effect of passivation materials on Cd contaminated soil under different tillage treatment conditions,and the in-depth study of the passivation remediation mechanism of sepiolite on Cd contaminated soil,aiming to apply passivation materials to Cd contaminated soil.The main findings are as follows:(1)The three passivation materials increased the p H value of Cd contaminated soil in Guangxi and Hunan under the treatment of rice rhizosphere.Correspondingly,the available Cd content of the Cd contaminated soil in Guangxi and Hunan all decreased under the treatment of TH,SX and XA,but only available Cd content of Guangxi Cd contaminated show a significant decrease(P<0.05).At the tillering stage,roots of rice planted in Guangxi Cd contaminated soil decreased significantly under TH and XA treatments,and the Cd content of rice stems decreased significantly under TH,SX and XA treatments(P<0.05).Roots of rice planted in Hunan Cd contaminated soil decreased significantly only under TH treatment,and Cd content in rice stems and leaves decreased significantly under TH,SX and XA treatments(P<0.05).At the booting stage,the Cd content of roots,stems and leaves of rice planted in Guangxi Cd contaminated soil decreased significantly under the treatment of the three combinations of passivation materials(P<0.05),and the Cd content of rice brown decreased significantly under SX and XA treatments(P<0.05).Roots of rice planted in Hunan Cd contaminated soil decreased significantly under TH and XA treatments,while leaves and brown rice decreased significantly under TH,SX and XA treatments(P<0.05).During the maturity stage,roots,leaves and brown rice of rice planted in Guangxi Cd contaminated soil significantly reduced under TH,SX and XA treatments(P<0.05).Cd content of roots and stems of rice planted in Hunan Cd contaminated soil were significantly reduced under TH,SX and XA treatments.Cd content of leaves and brown rice only decreased significantly under SX and TH treatments(P<0.05).The plant height and yield of rice grown in Guangxi and Hunan Cd contaminated soil were improved under the treatment of the three combinations of passivation materials,and ice yields only increased significantly under SX and TH treatments(p<0.05).(2)The pH of Cd contaminated soil in different regions of Guangxi and Hunan was the highest under the direct seeding treatment.Correspondingly,the available Cd content of the soil in the two places was the lowest under the direct seeding method,and the available Cd content of the Cd contaminated soil in Hunan under the direct seeding method was significantly lower than that seedling throwing method(P<0.05).At the tillering stage and booting stage,the rice planted in the Cd contaminated soil of Guangxi had the lowest Cd content in roots,stems,leaves and brown rice under the direct seeding planting mode,while the rice planted in the Cd contaminated soil of Hunan had the lowest root,stem and leaf content under the transplanting planting mode,and the Cd content under the transplanting mode was significantly different from that under the direct seeding and throwing mode(P<0.05).To the maturity stage,the Cd content(except roots)of rice stems,leaves and brown rice in Cd contaminated soil of Guangxi was the lowest under direct seeding planting,while the Cd content in roots,stems,leaves and brown rice planted in Cd contaminated soil of Hunan was relatively the lowest under the transplanting planting method.Planted in Cd-contaminated soil of Guangxi,plant height of the rice was the largest under the direct seeding method,and there was a significant difference in the rice plant height between the direct seeding and transplanting planting methods(P<0.05).While planted in Cd contaminated soil of Hunan,the rice plant height was the largest under the transplanting mode,but the difference was not significant(P>0.05).There were both the highest yield of rice planted in Cd contaminated soil Guangxi and Hunan under the seedling throwing method,and they were significantly different from the other two planting methods(P<0.05).(3)Rhizosphere test showed that the soil p H value between the rhizosphere and the non-rhizosphere soil increased by 1.0-1.16 and 0.59-1.21 units,the effective concentration of Cd in the rhizosphere and non-rhizosphere soils decreased by 0.02-3.1%,and 1.0-7.8% under different depth treatments,respectively.Interestingly,the remediation effect was best under T2 treatment(a depth of 5 cm).Moreover,the Cd concentration in each part of rice decreased under different depth treatments and there was biggest drop under T4,especially the Cd concentration in the root had a significant decrease(p<0.05).At the same time,the plant height and yield of rice increased under different depth treatments and there was the biggest rise under treatments of T2 and T4 respectively with significant differences(p<0.05).Overall,sepiolite under treatments of T2 and T4 with a depth of 5 cm possessed the best remediation effect on the bioavailability of Cd in soil;rice root exudates and sepiolite could synergistically reduce the absorption of Cd in different parts of rice. |
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