Quantitative Method And Charter Reseaech For Easily Oxidized Part Of Biochar During Its Degradation

Biochar is formed via imcomplete combustion under completely or partially anoxic condition. It plays an important role in substance cycle in soil and atmosphere. Biochar has a certain degree of stability with slow degradation in the environment, and involved in organic carbon cycle. Compared to other forms of organic matter in soil, biochar degradation is not yet understood clearly. There are probably many factors affecting its reaction, and some unknown pathways resulting in significant loss of biochar. The surface property changes occurring in the process of biochar degradation has been of concern.Although Biochar has a relative stability, its extent of degradation can be indicated in the surface property changes, such as increase in oxygen concentration, specific surface area, CEC and positive surface charge, decrease in surface pH, zero net charge, and negative surface charge, occurrence of oxygen-containing functional groups, and so on. Biochar degradation can be quantified with the release of CO2during the process of mineralization. But this method maybe underestimates the impact of environmental factors. The degradation occurs at the surface of biochar and then extends to the internal. Thus, assuming that the easily oxidized portion is formed in the surface of Bochar, and the oxidation resistance of this part is different with the internal biochar.Husk char were employed, wash it, oxide it and culture it. Firstly, the quantitative method for the easily oxidized portion was researched. Then research the influence of pretreatment on easily oxidized portion. Finally, on this basis, carbon content (carbon content of easily oxidized part) and characters of the easily oxidized portion were analyzed, and the easily oxidized portion was further discussed. Providing both an insight into environmental effects of biochar, and a theoretical basis for stabilization mechanism and environment behaviors of soil biochar. The main results of this thesis are as follows:(1) With consideration of analysis theory of soil easily oxidized organic matter. K2Cr2O7were used as oxidants to explore bio-oxidation resistance of biochar surface. Further discussing some conditions for identifying the easily oxidized portion, like outside temperature, the ratio of oxidant to sulfate, reaction time. The optimum reaction conditions are a2:1ratio of H2SO4:K2Cr2O7. and40minutes of water bath at100℃.(2) Washing pretreatment method affects the bio-oxidation resistance of biochar. The better washing pretreatment method is water-ethanol. The washing pretreatment still remain something, for removaling the interference of biochar easily oxidized portion quantitative from residue, adding the oxidizing agent biochar easy link after the washing treatment is necessary.(3) Culture biochar after water-ethanol washing treatment and oxidizing use oxidant, then quantitativing easily oxidized part of biochar before and after incubation by established menthod. There are easily oxidized Material produced during biochar preparation, and Oxygen-containing functional groups、phenolic hydroxyl group and lipids increase.