Effects Of Biochar On Character And Greenhouse Gas Emissions In Soil With Metal Pollution

Nowadays,the increase in greenhouse gases leads to global warming,which has a great impact on agricultural production and sustainable development.Greenhouse gas emission from farmland is one of the important reasons for Greenhouse Effect.At the same time,heavy metal pollution in farmland in China is becoming increasingly serious,resulting in a great threat to the quality and safety of agricultural products,which is harmful to human health.Therefore,it is urgent to study the regulation of soil properties,remediation of soil heavy metal pollution and mitigation of greenhouse gas emissions.In this study,pig manure biochar,corn straw biochar and pine block biochar were used as experimental materials.Indoor soil culture experiments were conducted to study the effects of biochar application rates of different raw materials(1%,2% mass ratio)on the chemical properties(p H,cation exchange capacity,organic matter,available phosphorus,available potassium,total nitrogen,ammonium nitrogen,nitrate nitrogen,urease and sucrase),greenhouse gas emissions and cadmium content of different types of cadmium-contaminated soils(paddy soil,yellow soil and purple soil).Furthermore,the effects of biochar on the remediation of cadmium-contaminated soil and carbon sequestration and emission reduction were discussed,in order to provide theoretical reference for the application of biochar in the improvement and remediation of contaminated soil.The main results are as follows:(1)On the whole,the three kinds of biochar can optimize soil properties to a certain extent.Compared with the soil without biochar,pig manure biochar,corn straw biochar and pine block biochar could increase the p H value of paddy soil and yellow soil without exogenous cadmium,and decrease the p H value of paddy soil polluted by exogenous cadmium.However,the p H value of purple soil without exogenous cadmium changed little,and the p H value of purple soil polluted by exogenous cadmium increased except that the p H value of 2% corn straw biochar treatment(ZY2Cd)decreased slightly.Each treatment had little effect on soil cation exchange capacity(CEC),but could increase the content of soil organic matter.The application of pig manure biochar can greatly increase the content of available phosphorus and potassium in soil.Moreover,the three kinds of biochar could increase the content of total nitrogen in paddy soil and yellow soil,but had little effect on the content of total nitrogen in purple soil.(2)Compared with the soil without biochar,the change of soil urease activity was not obvious.Among them,the urease activity of pig manure treated with biochar was the strongest in paddy soil.In the yellow soil without exogenous cadmium,1% corn straw biochar treatment(HY1)had the highest urease activity,while in the yellow soil polluted by exogenous cadmium,2% pine block biochar treatment(HS2Cd)had the strongest urease activity.In the purple soil without exogenous cadmium,the urease activity of 2%corn straw biochar treatment(ZY2)was the strongest,and in the purple soil polluted by exogenous cadmium,the urease activity of all biochar treatments decreased.However,in the soil polluted by exogenous cadmium,the three kinds of biochar could increase the sucrase activity in paddy soil,yellow soil and purple soil.In the soil without exogenous cadmium,biochar could reduce the sucrase activity in paddy soil and increase the sucrase activity in yellow soil.In purple soil,sucrase activity decreased in all treatments except 1%biochar treatment of pig manure(ZZ1).(3)Compared with the cumulative gas emissions without biochar treatment,the three kinds of biochar had the best effect on reducing greenhouse gas emissions from paddy soil.Compared with the global warming potential(GWP)without biochar treatment,all three kinds of biochar could reduce the GWP value of paddy soil without exogenous cadmium,and increase the GWP value of yellow soil polluted by exogenous cadmium,yellow soil without exogenous cadmium and purple soil without exogenous cadmium.Corn straw biochar and 1% pine block biochar can reduce the GWP value of paddy soil polluted by exogenous cadmium.And corn straw biochar and 2% pine block biochar can reduce the GWP value of purple soil polluted by exogenous cadmium.Pine block biochar decreased the global warming potential(GWP)of low concentration cadmium paddy soil most obviously.(4)All the three kinds of biochar could reduce the content of available cadmium in soil in varying degrees,but the content of total cadmium changed little.Pig manure biochar has better passivation effect on paddy soil and purple soil polluted by exogenous cadmium.Pine block biochar has a good passivation effect on yellow soil without exogenous cadmium pollution.Corn straw biochar has a good passivation effect on yellow soil polluted by exogenous cadmium and purple soil without exogenous cadmium.(5)Pine block biochar has a strong remediation effect on paddy soil with low cadmium content and slows down greenhouse effect,especially the comprehensive effect of pine block biochar with a mass ratio of 1% is the best.In addition,the global warming potential(GWP)of soils with high cadmium content was generally higher than that of soils with low cadmium content.