The Effects of Biochar Properties on Fomesafen Adsorption-Desorption Capacity of Biochar-Amended Soil

摘要

Carbon-rich biomass products from thermal pyrolysis have been considered as an appropriate alternative for the remediation of contaminated lands. However, the impacts of the physico-chemical properties of biochar on adsorption, desorption, and leaching processes are not fully understood. In this study, adsorption, desorption, and leaching of fomesafen in a soil amended with six biochars were investigated. The highest fomesafen adsorption coefficient (k(f)(ads) = 20.67) was observed when 2% of hardwood biochar (B4) was added onto the soil due to its highest specific surface area (SSA) (331.70 m(2)/g) and lowest dissolved organic carbon (DOC) content (0.43%) relative to the other tested biochars. By contrast, the lowest adsorption coefficient (k(f)(ads) = 16.64) was observed in the soil amended with 2% rice straw biochar (B1) with the lowest SSA (63.10 m2/g) and highest DOC content (3.67%). Nevertheless, during desorption process, the lowest coefficients were observed in the soil amended with softwood (B2) and walnut (B5) biochars, which possessed higher SSA and lower pH than B1, most likely due to their lower micro-pore volume/total pore volume ratios (MPV/TPV). Moreover, fomesafen adsorption in the soils amended with B2 and B5 was highly reversible. The outcomes of the leaching experiment also showed that fomesafen leaching from the soil column followed the same trend as desorption. These results suggested that although the adsorption capacity of biochar is most likely controlled by SSA and DOC, desorption and leaching processes are mainly affected by MPV/TPV.