The Effects Of Different Carbon-based Materials Returning On Soil And Peanuts In Cd Contaminated Soil

With the rapid development of industry and agriculture,the problem of food pollution has gained widely attention,and it is urgent to solve the problem of soil cadmium pollution.The blind expansion of Chinese cities and the extensive development of industry and agriculture have led to the increasing prominence of soil pollution in many areas.Existing studies have shown that by returning carbon materials not only can reduce the harm of soil polluted by cadmium,improve soil properties,and improve the quality of agricultural products safety,also respond to the basic policy of the sustainable development of agriculture in our country.This study based on a large number of literature about the impact of heavy metals on peanut farmlands with the treatment of biochar,rice straw and peanut cane to reduce the soil polution of Cd and the growth of peanuts.We have set four groups of experiments,three kinds of carbon materials was studied for cadmium adsorption,returning three kinds of carbon materials on the influence of cadmium pollution in soil cadmium form transformation,returning three carbon-based materials of cadmium pollution soil biological effectiveness,and the influence of different carbon materials is returning to the event to take root soil physical and chemical properties.Adsorbtion test results showed that the adsorption of Cd²⁺on Langmuir could be well fitted by the isotherm equation.The adsorption kinetics could be well fitted by the quasi two stage kinetic equation and the absolute coefficient was closer to 0.999,the adsorption capacity of the adsorbent to Cd²⁺in twenty minutes was basically reached equilibrium.When the initial pH of the solution was equal to 6,the removal rate of the three adsorbents to Cd²⁺reached the maximum and the removal rate of Cd²⁺was the best in this experiment,which was 97.9%.The removal rate of Cd²⁺increased with the increase of the dosage of the three adsorbents.According to the result of soil culture experiment,under the condition of this experiment,returning biochar,rice straw and peanut cane to field respectively could increase the pH in cadmium contaminated soil,the amount of three kinds of microbe,urease activity,dehydrogenase activity,nitrate reductase activity and DOC.Moreover,the Eh was decreased in cadmium contaminated soil.Compared with the control group,biochar application,returning rice straw to field and returning peanut vine to field all improved water-soluble Cd,EDTA-bound Cd and residual Cd in Cd-polluted soil.Because the DOM is rich in carboxyl and phenol into the biochar,the DOM is also rich in carboxyl,aldehyde groups and ketone groups into the straw.After four months of soil culture experiment,aromaticity increased.Three kinds of organic materials in soil all reduced the content of soil exchangeable Cd.In this study,pH,Eh and DOC were significantly correlated with each form of Cd in Cd-contaminated soil.Pot experiments were designed to study the effects of three kinds of organic materials returning to field on bio-availability of Cd in Cd-contaminated soil.The results showed that biochar application,rice straw returning and peanut vine returning could alleviate the toxic effect of cadmium on peanuts and increased the biomass of peanuts.The treatment of biochar and two kinds of straw treatments did not reach significant difference in the photosynthesis of peanuts?P>0.05?and physiological characteristics?P>0.05?.In this study,three kinds of organic materials returning to field significantly reduced the concentration of cadmium in each part of peanut,followed by biochar,rice straw and peanut vine.But in the peanut shell and peanut kernels,two straw treatments did not reach significant level?P>0.05?.From the enrichment coefficient of each part of peanut,it could be concluded that the cadmium uptake by peanut roots was more transferred to the stem and leaf of peanut.In the field experiment,the data showed that the application of biochar and straw mulching can reduce volume-weight and increase porosity,moreover,that can improve the permeability and structure of soil,which is good for the growth of crops under the same planting mode.Meanwhile,the Ph,nitrate nitrogen,organic materials,available phosphorus,available potassium of peanut rhizosphere under the applying biochar increased by 7.06%,31.62%,94.52%,17.53%,25.08%?monoculture peanut?and 8.47%,37.10%,89.94%,17.93%,22.87%?cassava/peanut intercropping?compared with CK in the same planting patterns.In addition,the ammoniacal nitrogen,available nitrogen,organic materials,available phosphorus,available potassium of peanut rhizosphere under the straw mulching increased by 21.05%,89.80%,60.92%,5.95%,9.98%?monoculture peanut?and 16.56%,67.09%,52.34%,6.96%,11.94%?cassava/peanut intercropping?compared with CK in the same planting patterns.And not only that,in the same treatment conditions,volume-weight decreased and porosity and saturated permeability coefficient increased slightly,but there is no significant difference between the two.At the same time,cassava/peanut intercropping could increase soil nutrients in rhizosphere soil,the ammoniacal nitrogen,nitrate nitrogen,available nitrogen,organic materials,available phosphorus and available potassium content of intercropping rhizosphere soil increased compared with monoculture soil.Therefore,it is benefical to apply biochar and straw mulching,and the suitable intercropping row spacing is more beneficial to increase soil nutrient contents.To summary,treatments of carbon-based materials?biochar,rice straw,peanut cane?returning can improve soil physical and chemical properties,and effectively reduce the cadmium soil biological effectiveness and cadmium content of each part of the peanut,the treatment of biochar could significantly reduce the concentration of soil cadmium.