Effects Of Biochar From Different Feedstock Types On Hydraulic Properties Of Unsaturated Granite Residual Soil

In recent years,biochar,as an environment-friendly renewable material,has attracted the attention of researchers in fields such as agriculture,environment,chemistry and civil engineering.Soil amended by biochar has favorable water retention,which is beneficial to plant growth.Thus,the application of biochar amended soil(BAS)to urban green infrastructure to improve vegetation growth and urban water management capacity has potential significance.However,the effects of biochar on soil erosion and soil water retention under complex urban environmental conditions are unknown.Therefore,it is necessary to systematically study the hydraulics properties of BAS.The main objective of this thesis is to gain a basic understanding of the hydraulic properties of soil amended by different type biochar.In this thesis,the granite residual soil,which widely distributes in the southeast coastal area of China,is taken as the research object.Meanwhile,different feedstock(i.e.,plant-based,wood-based and animal-based)are used to produce biochar by slow pyrolysis.Characterization experiment,temperature and humidity chamber experiment,soil column experiment and soil erosion experiment are planned to test biochar and biochar amended granite residual soil.The effects of biochar types and pyrolysis temperature on the properties of biochar are analyzed.The effects of different biochar on water absorption,water retention,gas permeability and soil erosion of granite residual soil are studied.The results show that both pyrolysis process and feedstock have a significant impact on the properties of biochar.Microstructure,chemical composition and surface functional groups of biochar from different feedstock types(plant-based,wood-based,and animal-based)are different.In addition,biochar produced by pyrolysis of the same feedstock at different temperature has different properties.Biochar significantly improves the water absorption of granite residual soil.Among all the biochar,the water hyacinth biochar(WHB)produced at 300? pyrolysis temperature has the best promotion.10% WHB addition increases the soil water absorption by 341%.Furthermore,both degree of compaction(DOC)and biochar content affect soil gas permeability.High DOC leads a weak gas permeability.The addition of biochar reduces the soil gas permeability with a certain suction range.Moreover,the runoff and soil erosion of kitchen waste biochar(KWB)sample are reduced by 4.1% and 9.8%,respectively.However,wood biochar(WB)and pig manure biochar(PMB)enhance the soil erosion.In addition,biochar particles are found in runoff and seepage in erosion experiment.Thus,it is important to note that measures should be taken to prevent biochar loss when using biochar as a soil amendment.Also,the biochar effects on soil hydraulic and hydrophobicity properties should be took into account before processing biochar application.This study find that plant-based biochar(WHB,KWB)have better performance in improving soil hydraulics.