| With the cadmium pollution in farmland caused by heavy metals,the problems of soil environment and food security are becoming more and more serious.The remediation of heavy metals in farmland mostly exists in the acidic soil of south China.In recent years,with the increasing content of heavy metals in the salinized soil of north China,the safety of agricultural products has been gradually paid attention to.Chemical in situ passivation has been widely used in soil remediation because of its advantages of low cost,fast speed and simple operation.Therefore,this study carried out field experiments for two consecutive years in north China polluted by cadmium salinization.Research on seven different passivation agent(biological carbon(BC),sepiolite(Sep),bentonite(Be),humic acid(HA),palygorskite(Pa),sodium silicate(SS),acid manganese(Mn))and not use treatment(CK)on oat growth and cadmium content in different organs,soil cadmium availability and the influence of physical and chemical and biological properties,To clarify the inhibition effect of different passivators on the absorption of soil cadmium by crops and the absorption,transport and enrichment process of cadmium in oat plants,and then screen suitable for local heavy metal pollution remediation and promotion of blocking control materials,in order to provide theoretical and technical basis for the safe utilization of contaminated cultivated land.The results show that:1.Different passivator treatments had significant effects on yield and yield components of oat(P<0.05).Passivator increased oat yield by 1.5%～34.1%,plant height,panicle length,spikelet number,grain weight per panicle,grain weight per panicle by0.3%～2.0%,0.6%～8.5%,13.8%～26.7%,5.5%～37.3%,3.7%～47.1%,Therefore,passivator treatment can promote the yield and yield composition of oat,and palygorskite treatment is the best.2.Under the treatment of different passivators,the cadmium content of oat was in the order of root > leaf > glume > stem > grain,and decreased by 1.1%～27.0%,12.0%-36.0%,2.9%～17.6%,7.5%～14.9%,22.2%～50.0%,respectively,compared with the control.The application of passivator can effectively inhibit the absorption of cadmium in different parts of oats and reduce the content of cadmium in grains,and sepiolite treatment has the best effect.3.The cadmium enrichment coefficient of different passivators in different parts of Oats showed that the enrichment coefficient of root was >1,the enrichment coefficient of stem,leaf and glume was <1,and the enrichment coefficient of grain was <0.5,and the enrichment coefficient of sepiolite and sodium silicate in grains was lower than that of the control.Except for the translocation coefficient from stem to leaf,the translocation coefficient from root to stem was <1,and the translocation coefficient from root to stem was <0.5.The transport of cadmium to aboveground was effectively inhibited.4.The passivator can effectively reduce the total and available cadmium contents in soil and change the occurrence form of cadmium.Compared with the control,the total and available cadmium contents in soil treated by different passivators decreased by6.3%～32.9% and 4.8%～48.0%,which promoted the transition from high active state to low active state,the exchangeable content decreased by 12.3%～74.3%,and the residual content increased by 0.4%～95.8%,thus reducing the bioavailability of cadmium.Humic acid and sepiolite were the best treatments.5.Soil physical properties were changed by different passivators,and soil bulk density decreased by 0.5%～9.0%,and biochar decreased the most in two years.Passivator increased soil porosity by 0.4%～15.0%,enhanced soil water holding capacity,promoted the transformation from small grain size to large grain size,and improved soil aggregate structure.Sepiolite treatment had the best effect,and the proportion of large grain size in two years increased by 15.4% and 14.3%,respectively,compared with the control.6.Different passivators increased soil p H by 0.01～0.26 units,among which sepiolite increased the most.The effective cation content and organic matter content under each treatment were 0.2%～12.9% and 3.6%～26.2%,respectively,and humic acid and sepiolite had the best effect.Different treatments had different effects on nutrient contents,and the alkali-hydrolyzed nitrogen,available potassium and available phosphorus increased by6.2%～71.8%,5.0%～16.2% and 2.8%～14.8% compared with the control,while total nitrogen,total potassium and total phosphorus increased by 1.2%～66.4%,1.2%～15.0%and 1.7%～82.6% compared with the control.Therefore,the passivator treatment has a significant effect on improving soil environment,among which sepiolite is the best.7.The activities of catalase,urease and alkaline phosphatase increased by0.1%～14.1%,0.2%～14.3% and 0.1%～3.3% respectively.All treatments increased bacterial species richness and community α-diversity,and the Shannon and Simpson indices under palygorskite treatment were significantly different from those under control(P<0.05).Passivator treatment changed the β-diversity of soil microbial community,and the change of bacterial community structure was more obvious,especially Sep and Mn treatment. |
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