Effect of aging in field soil on biochar's properties and its sorption capacity

Highlights: • The properties of biochar changed after being aged in a field soil. • The surface area of biochar first increased and then decreased with aging time. • The amendment of biochar enhanced soil sorption capacity for organic pollutants. • The high sorption capacity of biochar amended soil only maintained for up to 2.5 y. Due to its high sorption capacity for different kinds of contaminants, biochar is advocated as a novel remediation strategy for contaminated soils. However, it is not clear how long this extraordinary sorption capacity will be maintained after the biochar is applied to the soil. In this study, a commercial biochar was applied to an agricultural soil, and the sorption of atrazine and phenanthrene on biochar amended soils with different aging periods ranging from 0 to 2 y was investigated. The application of fresh biochar in soil led to an obvious enhancement of the sorption coefficients (K_d) of atrazine and phenanthrene (by 3.13 and 2.93 times at C_e = 0.01 S_w, respectively) compared with the untreated soil. The surface area of biochar first increased and then decreased with aging time. Correspondingly, the sorption of atrazine and phenanthrene on the biochar amended soils first increased and then decreased markedly. Based on the changing trend of the K_d values with aging time, it could be predicted that the sorption capacity of biochar amended soils will decrease to the level of the untreated soil after 2.5 y.