Compositional DOM of biochar from different raw materials

DOM content and composition of biochar are varied with from different raw materials. In this study， seven feedstocks including rice straw （RS）， wheat straw（WS）， soybean straw（SS）， rape straw（YS）， peanut husk（PH）， pine wood（PW） and bamboo powder（BS） were selected to prepare biochar at 450 ℃ by calcination. The spectral characteristics and fluorescence components of DOM in biochar were characterized by ultravioletvisible spectrum（UV-vis） and EEM fluorescence spectroscopy combined with PARAFAC. Results showed that the DOM content of woody biochar was lower than that of straw biochar， and the molecular weight of woody biochar was higher than that of straw biochar. Four components were identified and separated from the DOM derived from biochar， which were visible region fulvic acid component（C1）， shorter wavelength humic acid component （C2）， longer wavelength humic acid component（C3） and protein component（C4）. The maximum fluorescence intensity（Fmax） values of various components of biochar DOM derived from different raw materials were C1 > C2 > C3， C4， and the Fmax values of various components of straw DOM were significantly higher than those of woody DOM. C1 component accounted for 48.87%~79.97% of the DOM derived from biochar， which was the dominant component. C2 and C3 components accounted for the highest proportion in YSB and SSB-DOM， reaching up to 32.71% and 23.25%， respectively. Only a small amount of C4 component were found in YSB and PHB-DOM. The organic and inorganic mineral contents of woody raw materials were much lower than those of straw. The cellulose content in raw materials was significantly positively correlated with the total DOM content of biochar and C3 component， and the Ca content was significantly positively correlated with DOM content of biochar and its Fmax value and C3 component. The results indicated that the composition of different biomass raw materials had significant impacts on the composition characteristics of DOM derived from biochar. The results provide an important scientific theoretical basis for comprehensive evaluation of DOM effect of the biomass derived from biochar.