Effect of gasification biochar application on soil quality: Trace metal behavior, microbial community, and soil dissolved organic matter

[Display omitted] •Gasification biochars showed comparable performance in metal(loid) immobilization to that of pyrolysis biochar.•Biochar amendment affected soil microbial activity and the response of different microbials varied with different biochars.•Parameters from EEM-PARAFAC modeling of soil DOM showed close correlation with soil microbial activity. Compared to pyrolysis biochar (PBC), gasification biochar (GBC) differs in both composition and surface functionalities due to the use of an oxidizing purging gas. This work compares the effect of using PBC and GBC as soil amendments on the soil properties, trace metal bioavailability, soil microbial activity, and soil dissolved organic matter (DOM). Biochar-driven reduction of bioavailable metals does not necessarily result in a positive impact on the soil microbial growth. The DOM in the soil was strongly related to the soil microbial activity, as revealed by the strong correlation between the soil dehydrogenase activity (DHA) and soil dissolved organic carbon (r = 0.957, p