Physiological And Biochemical Effects Of Soil Remediation Nanomaterials On Earthworm And Its Mechanism

Nanomaterials are widely used due to their unique properties,but some properties of nanomaterials have made them widely used and their safety has also attracted attention.In recent years,the good performance of new-type nanomaterial deactivators in adsorbing heavy metals has been widely concerned and studied,but few studies have involved the soil animal effect of nanomaterials.The impact of nanomaterials on soil animal pollution on soil animals requires the selection of typical soil organisms for toxic effects and mechanisms.In this paper,nano-hydroxyapatite（n-HAP）,nano-zeolite（n-zeolite）,and nano-iron iron oxide（n-Fe3O4）,which are commonly used in soil heavy metal repair,are taken as research objects.Through specific surface area and pore size analysis,scanning Electron microscopy（SEM）analysis,transmission electron microscopy（TEM）analysis,Zeta potential analysis,X-ray diffractometer（XRD）and other characterizations were used to study the differences in surface properties of the three nanomaterials.The adsorption isotherm test and adsorption thermodynamic test were used to study the differences in the adsorption performance of three nanomaterials on Cd.Using Eisenia foetida as the test organism,the effects of three nanomaterials on the survival rate and biomarkers of earthworms were studied through filter paper culture experiments.The effects of three nanomaterials on the avoidance behavior of earthworms were studied by soil culture experiments,and the effects of nanomaterials on the ultrastructure of earthworm skin were studied by transmission electron microscopy.Using heavy metal Cd as the target pollutant for soil remediation,the effects of different nanomaterials on the individual physiological changes of earthworms,the response of biomarkers,and DNA damage were studied through soil culture tests,oxidative damage tests,and comet tests,and the application of different nanomaterials was clarified.Toxic effects of Cd contaminated soil on earthworms after remediation.The comprehensive biomarker response index（IBR）analysis was used to compare the toxicity of different nanomaterials to earthworms.By comparing the differences in properties between different nanomaterials,the toxic effect on earthworms,and the different mechanisms of binding with Cd;analyzing the correlation between the effective content of Cd in soil and the content of Cd in earthworms,and the effective content of Cd in soils and toxicity Correlation of physical impact indicators,the correlation between the affected indicators and the Cd content in earthworms;clarification of the toxicological mechanism of earthworms with different nanomaterials.The main findings of this article are as follows:（1）Among the three nanomaterials,n-Fe₃O₄ has the largest specific surface area and the smallest average pore size,followed by n-HAP,n-zeolite has the smallest specific surface area,the largest average pore size,and the largest charge density on the n-Fe₃O₄ surface with positive charge most.The adsorption capacity of nanomaterials for Cd²⁺is n-HAP>n-Fe₃O₄>n-zeolite.（2）The nanomaterial itself has a certain effect on earthworms,but its toxicity is weak without LC₅₀.As the concentration of nanomaterials rises,so does the impact on biomarkers.All three can significantly affect the CAT,POD,SOD activity and MDA content of earthworms,and produce oxidative stress response.At the same time,when the nanomaterial is applied at a concentration of 1.5%,the earthworms have obvious avoidance behavior.Exposure to nanomaterials can alter the nucleus of the skin cells of the earthworm and the ultrastructure of the epidermal stratum corneum.Causes epithelial microvilli disorder,atrophy,fracture,sparseness,separation from epithelial cells,nucleoli enlargement,chromatin aggregates into large electron density clumps,visible nuclear rupture.（3）n-HAP,n-Fe₃O₄,and n-zeolite enter the soil and have certain biological toxicity to soil biological earthworms,which will have a certain degree of impact on the survival rate of earthworms.Nanomaterials,Cd,nanomaterials-Cd all cause oxidative damage and genetic damage to earthworms.According to the IBR index study,the biotoxicity of the three nanomaterials in soil is n-HAP<n-zeolite<n-Fe₃O₄;in Cd-contaminated soil,the biotoxicity after compounding with Cd is n-HAP-Cd<n-zeolite-Cd<n-Fe₃O₄-Cd;Cd contaminated soil has the highest biological toxicity to earthworms.（4）The differences in the properties of n-HAP,n-zeolite,and n-Fe₃O₄ cause different toxic effects on the earthworms.n-Fe₃O₄ has the smallest particle size,the largest specific surface area,and the most positive charges on the surface,so it is the easiest to enter the earthworm body,and it is adsorbed on the cell surface and enters the cell by electrostatic adsorption,causing oxidative damage.All three materials can quickly absorb Cd and have strong stability.The effective Cd content in the soil is significantly related to the Cd content in the earthworm.The effective Cd content in the soil is related to the survival rate of the earthworm,the ROS content,the GSH content,the CAT activity,the LDH activity,and six toxicological indicators.The Cd content in the body is related to the above six toxicological indicators,so it can be concluded that the combination of nanomaterials and Cd has an antagonistic effect on earthworms.Nanomaterials reduce the effective Cd content in the soil and thus reduce the effective Cd content in the earthworm,thereby reducing The toxic effects on the oxidation damage of earthworms mainly come from the particle size,specific surface area,morphology and surface charge of nanomaterials,and the toxicity is much less than that of Cd.