Biochar accelerates the removal of tetracyclines and their intermediates by altering soil properties

Highlights: • Biochar properties varied with the feedstocks. • Biochar amendment elevated soil pH, EC, TOC, TN, and C/N ratio. • Biochar amendment increased the removal of TTCs, OTCs, and CTCs. -- Abstract: Tetracyclines accumulation in soil environment potentially threatens agroecosystem safety. Interestingly, biochar could clean up organic pollutants, but to what extent biochar affects the removal of tetracyclines is unknown. To investigate it, five types of biochars derived from cow manure (CMB) and other four plant materials were respectively added into soils contaminated with a mixture of tetracycline, oxytetracycline, and chlortetracycline for 60-day incubation in the dark. Three parent tetracyclines and their corresponding intermediates (epitetracycline, anhydrotetracycline, epianhydrotetracycline, epioxytetracycline, epichlortetracycline, and demethylchlortetracycline) were respectively determined and named as TTCs, OTCs and CTCs. Obtained results showed biochar especially CMB could effectively remove the antibiotics (P < 0.05). Compared to control, the removal rate of TTCs, OTCs and CTCs respectively increased by up to 10.86%, 10.29% and 10.12% in CMB-added soil. The increased removal rate of the antibiotics after biochar addition was due to the increasing accessibilities for degrading microorganisms via the elevating electrical conductivity. Moreover, biochar addition might stimulate these microbial activities through the increase of C and N supplement. Our results indicate biochar accelerates the removal of tetracyclines and their intermediates by altering soil properties and thus increasing the antibiotics accessibilities, which provide insights into how biochar accelerates the removal for these antibiotics.