Study On The Stability Of Perishable Waste Biochar And Its Migration In Soil Environment

Perishable waste has the characteristics of high yield,high moisture content,and high organic perishability,which brings serious environmental pressure and resource waste.As an organic biomass raw material,it can be prepared into biochar through carbonization for soil fertility improvement.Therefore,carbonization of perishable waste as soil fertilizer is an effective way to achieve efficient reduction and treatment of perishable waste,resource utilization and carbon sequestration,which has great research and practical application value.Clarifying the physicochemical properties of perishable waste biochar and the suitability of soil application is an urgent issue to be resolved in promoting the carbonization and resource utilization of perishable waste.In this study,the difference in physicochemical properties between perishable waste biochar and plant-based biochar(walnut shell biochar and maize straw biocahr)prepared at different carbonization temperatures were compared.Through simulated culture experiments and field experiments,the effects of aging on the physicochemical properties of perishable waste biochar were studied.A soil column experiment was conducted to study the migration of soil substances applied to perishable waste biochar under acid leaching conditons.The stability characteristics of perishable waste biochar and plant-based biochar were analyzed and compared,and their key influencing factors were discussed.The contents of heavy metals,salts and other harmful substances of perishable waste biochars were analyzed to preliminarily explore its impact on the soil environment and plant growth.The main conclusions are summarized as follows:(1)As the carbonization temperature increases,the C content of plant-based biochar increases,while the C content of perishable waste biochar has a weak response to increased the carbonization temperature.At a carbonization temperature of 350～650 ℃,the C content of perishable waste biochar fluctuates from 34.13% to35.17%.Compared with plant-based biochar,perishable waste biochar has the characteristics of high ash content,N content,and pH,rich in mineral elements such as Ca,Si.The results of principal component analysis showed that ash content is a key factor that affects the physicochemical properties of biocharand its response to carbonization temperature.High ash content would increased pH and EC values,and decreased C content in biochar.(2)During the aging process,raw materials are the main factor affecting the stability of biochar prepared at low carbonization temperatures.Biochar with higher ash content is more stable.Under the preparation conditions of high carbonization temperature,the stability of biochar is further improved.The thermal stability(thermal temperature below 600 ℃)and chemical stability of perishable waste biochar are better than those of plant-based biomass biochar.Aging in the field significant affect on the surface structure and physicochemical properties of perishable waste biochar,with a significant decrease in C and N content,a significant increase in specific surface area and pore volume.(3)Biochar increased the pH value,C content and the dissolution of dissolved organic carbon(DOC),and while reduced the loss of dissolve organic nitrogen(DON)in the acid-rain leaching experiment.Among them,perishable waste biochar has the best remediation effect for acidic soil.Perishable waste biochar increased soil bulk density and decreased water hold capacity(WHC).The application of walnut shell biochar and maize straw biochar had a small impact on soil bulk density and increased water hold capacity.(4)The heavy metal content of perishable waste biochar meets the national standard limit requirements for fertilizers.When applying perishable waste biochar to soil,it did not cause excessive heavy metals in the soil,and could promote plant growth.