| With the rapid development of industry,excessive use of agricultural chemical fertilizers,and interference from various human activities,heavy metal pollution in arable land has become increasingly serious,seriously harming the quality and safety of agricultural products,and causing great harm to human health.The chemical passivation repair technology has the advantages of fast repair speed,simple operation,low economic cost,etc.It is one of the hotspots of research on heavy metal contaminated soil restoration.The passivation material screening is an important part of the soil passivation repair technology.At present,the screening of passivated materials mainly depends on field tests to evaluate the material properties.The interannual time is long,and it is influenced by the changes of field environmental factors,and the human and material resources High consumption and insufficient data reliability.This study proposes a technical scheme based on the combination of DGT indoor simulation and pot experiment verification,and establishes a set of convenient,high-efficiency,low-cost,reliable performance and batch screening methods for heavy metal passivation materials.The main findings are as follows:1.The performance test of the homemade LDH-DGT shows that the diffusion coefficient of LDH-DGT diffusion phase is DCd of 5.66E-06cm2/s,which is basically not affected by changes in p H and solution ionic strength.The combined phase has the characteristics of high adsorption capacity of heavy metals,fast adsorption rate,wide range of adaptability to p H change,full-scale dissociation at 1 mol/L nitric acid,and so on,which can satisfy the theoretical assumption of gradient diffusion membrane technology and adapt to the needs of this experiment.2 Gradient diffusion thin film technology can effectively indicate the variation and difference of available heavy metal Cd under different treatments.The comparison and evaluation results show that in two kinds of experimental soils,the passivation effect of sulfhydryl modified palygorskite and silkworm sand is the most excellent.The passivation effect of Zn-Fe-LDH and calcium carbonate on Cd was the second,the effect of pig manure and biochar was the weakest,and the passivation effects of the last four materials in the two soils were also different.Comprehensive comparison of assessment parameters,priority selection of three indicators as an indicator of good inactivation of the initial assessment,namely CDGT <5?g / L,passivation rate> 50%,passivation duration> 90 days.Calculate the kinetic parameters,the total amount of available state and the change of corresponding components in the passivation process of heavy metals based on gradient diffusion membrane technology.The combination shows that DGT technology can not only reflect the change of the effective state of the passivation process,but also the volatility of the available state components of the heavy metal passivation process,which is conducive to a more comprehensive understanding of the difference of passivation process after passivation materials are applied to soil.The experimental results show that the change trend of CDGT and the total amount of heavy metal effect are consistent.3.The rice verification test results showed that the change trend of Cd content in rice with different passivation agents was similar to that of indoor passivation test data.Passivation material containing Fe would change the micro ecological environment of rice,and CDGT-Fe was added to the detection parameters.The Fe index can effectively characterize the effect of Fe on rice Cd enrichment.To sum up: DGT technology as the core,the use of indoor simulation experiments complemented by pot validation experiments,can effectively screen the heavy metal passivation materials,thus avoiding the drawbacks of field experiments,improve the effectiveness of passivation material screening. |
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