Passivation And Remediation Effects Of Biochar On Cadmium Contaminated Soil

Biochar is the decomposition which produced by animal and plant biomass or related materials of heat under hypoxia,high temperature,and is often used as a chemical passivation agent.In order to investigate the effect of biochar on the passivation and improvement of soil cadmium pollution,and the effect of helping plants to resist cadmium stress was discussed.In this paper,"Yue Sang 11" mulberry was used as the material,and CK(without applying cadmium),C1(1 mg/kg),C2(5 mg/kg),C3(10 mg/kg),and C4(50 mg/kg)were set through pot experiments.Five cadmium treatments and three biochar rates of 0%,1%,and 2% were used to study the effects of biochar on cadmium-contaminated soil fertility and cadmium stress.The main results are as follows:(1)The application of biochar significantly increased soil organic matter content,increased content of soil available P and available K,and reduced soil P content.The effects on available N,CEC,total N,total K,exchangeable Ca and Mg were not significantly.The average pH values of biochar at 0%,1%,and 2% were 8.068,8.253,and 8.103,respectively,indicating that biochar increased soil pH and increased available nutrient content,as a whole.(2)The activity of catalase and alkaline phosphatase in soil were significantly increased when the biochar rates was 2%.Although the effect of biochar rates on the invertase activity was not significant,but the addition of biochar treatment often increased the sucrase activity.Biochar has a significant effect on soil catalase activity at biochar rates of 2%.There was a significant difference between 2% biochar rates and 0% and1% rates,which were 173.350% and 391.7786% higher than the other.(3)When the added rates of biochar was 1% or 2%,the available cadmium content in soil was significantly lower than the 0% control group.In the treatment of C1,the application of biochar had no significant effect on the available cadmium content in soil.When treated with C2,C3 and C4,the content of available cadmium in biochar treated soil was significantly lower than that of the control.At the same time,the content of available cadmium in soil was the lowest at 2% biochar treatment.(4)The total cadmium content of each part of mulberry was as follows: root> whole plant> stem> leaf.At the CK concentration of cadmium,the effect of biochar treatment on cadmium content in mulberry is not significant.At the treatment of C2,C4,and the effective cadmium content was significantly reduced under the treatment of 1% and 2% biochar.The application of biochar at a higher concentration of cadmium(≥5mg/kg)effectively reduced the cadmium content of mulberry roots,stems and leaves,and the cadmium adsorption capacity of mulberry whole plants.(5)As a whole,biochar has no significant effect on the transport of cadmium among various organs in mulberry seedlings.The transfer coefficient is expressed as leaf-root> stem-root.(6)1%,2% biochar treatment increased the ratio of aboveground biomass and belowground biomass.After the biochar was added,there was no significant difference in above-ground and below-ground biomass at the treatment of CK,C1,C2,and C3.At the treatment of C4,the amount of each biochar increased.Above ground and below ground biomass,2% biochar treatment increased biomass above 1%.(7)There was little difference in the dynamics of plant height before and after the winter deciduous period,which showed that low concentration of cadmium promoted plant growth,and the plant height decreased with the increase of cadmium concentration.There was no significant difference in plant height and diameter between different treatments of biochar.As a whole,the treatment of biochar treated at C1,C2,and C4 was better,and the plant height was improved.Biochar got better repair effect at C2,C3,and C4 concentrations on the diameter.(8)Biochar treatment increased content of leaf chlorophyll a,chlorophyll b,and carotenoid.High-concentration cadmium treatment increased MDA content in roots and leaves.After the application of biochar,the content of MDA in roots decreased,and the content of MDA in leaves increased but not significantly.At the 2% rates of biochar,MDA content of the root was the lowest.Biochar has a positive effect on the prevention and control of soil cadmium pollution in agriculture and forestry.It can passivate and improve cadmium-contaminated soil to a certain extent,and at the same time can help mulberry trees alleviate the harm caused by cadmium stress.