Microorganisms and their metabolites affect the content of polycyclic aromatic hydrocarbons and their derivatives in pyrolyzed material

Abstract

Toxic polycyclic aromatic hydrocarbons (PAHs) and more toxic N- and O-containing derivatives can be determined in biochar. However, their fate in the environment and bioavailability depends on many parameters and was not studied yet. In the presented studies a set of biochars obtained from various feedstock at the same pyrolysis temperature (600 °C) subjected to environmental pressure e.g. soil microorganisms and enzymes was described. Presented study aimed to determine the effect of biological agents on the physicochemical characteristic and the content of PAHs and their derivatives in biochars after long-term treatment (6 months). The results indicated that enzymatic aging usually lowered (up to 94 %) the content of PAHs and their derivatives in biochar. Simultaneously, biological aging reduced the bioavailability of tested compounds. Considering the total fraction of PAHs and their derivatives, biochars treated with nutrients and microbial inoculum were characterized by the lowest content of analytes (even in comparison to biochars treated with nutrients alone). To complement the obtained results, the content of C, H, N, O, and ash as well as specific surface area, aromaticity, polarity, and hydrophilicity in biochar before and after modifications were determined. In general, enzymatic aging increased, and biological aging decreased the content of C% and H% in biochar. Both aging processes lowered the H/C ratio which indicated the decrease of the aromatization degree for artificially altered biochar.