Quantitative and qualitative characteristics of dissolved organic matter derived from biochar depending on the modification method and biochar type

With the increasing utilization of biochar (BC), various modification methods have been developed; the evaluation of the environmental impact of modified BC is insufficient. In this study, three types of BC (rice husk, wood chip, and mixture) were modified through five different methods (oxidation, acidification, alkalinization, and impregnation of MnOx and FeOx), and the quantitative and qualitative characteristics of modified BC derived from dissolved organic matter (DOM) were evaluated. Quantitative analysis revealed that the yield of dissolved organic carbon (DOC) derived from modified BC was significantly lower than from BC_raw, suggesting that DOM derived from BC was reduced following the modification of BC. In wood BC, the DOC yield was different from that of other types of BC, confirming that the quantitative characteristics of released DOC from modified BC depend on its type. DOM derived from BC_oxidic, BC_alkaline, and BC_MnOx was characterized by highly condensed aromatic humic-like substances, with high trihalomethane and haloacetic acid formation potential. In contrast, DOM from BC_acidic and BC_FeOx showed a low degree of humification and disinfection by-product formation potential, suggesting that the qualitative properties and environmental impact of BC-derived DOM differ depending on the modification method. Overall, our findings extend our understanding of environmental impact and differences in BC-derived DOM depending on the BC types and modification methods.