A review on dissolved organic matter derived from biochar in soil: Characterizations, interaction with pollutants, and transformation

Biochar-derived dissolved organic matter (BCDOM), an essential component of biochar, plays a vital role in regulating the physicochemical and biological properties of soils during biochar application. However, the influence of BCDOM on soil organisms has not been clearly explained. Hence, this review aims to discuss the factors affecting BCDOM and its interaction with soil substances including organic pollutants, heavy metals, and microorganisms. Results displayed that the quantity of BCDOM ranges from 0.17 to 37.03 mg/g, which was influenced by feedstock, preparation methods of biochar, and extraction methods. With the decrease in lignin content of feedstocks, carbonization temperature, and acidity of extraction solution, the content of BCDOM increased. Through complexation and adsorption, protein-like components in BCDOM interact with heavy metals, promoting the adsorption and immobilization of heavy metals onto biochar. Furthermore, BCDOM enhances the adsorption of organic pollutants by biochar through pi-pi interactions, hydrogen bonding, and redox processes. More importantly, BCDOM promotes plant growth by enhancing microbial activities, providing nutrients, and improving soil properties. However, the transport and fate of BCDOM in soil have not been well studied, and more researches are needed to explore the interaction mechanisms between BCDOM and soil organisms.