Feasibility-based approach to sustainable remediation of tricyclazole-contaminated soil using sewage sludge derived biochar: physicochemical adsorption and soil microbial recovery

Abstract Agricultural soils are facing elevated levels of pesticide contamination, highlighting the necessity for remediation methods that simultaneously immobilize contaminants and restore soil health. Sewage sludge biochar (SB) was evaluated for its capacity to adsorb tricyclazole (TCZ), with particular attention to its effects on soil microbial communities. When pyrolyzed at 700 °C for 1 h, SB showed effective TCZ adsorption capacity (Langmuir Q m = 9.84 mg g −1 ; desorption = 11.51%), particularly under mildly acidic conditions (pH 4–6). Spectroscopic (FTIR, XPS) and textural (BET, BJH) characterization revealed that TCZ adsorption occurred mainly through physical mechanisms including π–π interactions, hydrophobic partitioning, and pore filling, while surface functional groups played a smaller role. In soil microcosm experiments, SB addition alongside TCZ helped mitigate TCZ-induced changes in microbial community structure, maintaining the relative abundance of several genera involved in nitrogen, carbon, and phosphorus cycling, although certain nitrifier-associated groups remained reduced. Temporary reductions in alkaline phosphatase and N-acetyl-β-D-glucosaminidase activities were observed when SB and TCZ were added to soil, likely due to matrix effects such as substrate sorption and metal interactions rather than direct TCZ toxicity. The findings indicate that SB can effectively immobilize TCZ while partially mitigating TCZ-related disruptions to microbial communities, suggesting that SB amendments are a viable strategy for managing pesticide contamination in agricultural settings, provided that heavy metal input is carefully monitored and minimized.