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Biochar has emerged as an effective solution to mitigate the environmental impact of ciprofloxacin (CIP) residues in soil. Recent research has shed light on how biochar-derived dissolved organic matter (DOM) influences the transformation and mobility of CIP in soils. This study explored biochar made from rice straw, pig manure, and cockroach shells, produced at two different pyrolysis temperatures (300°C and 600°C), to assess their effectiveness in transforming residual CIP.

The results showed that biochar amendments significantly increased the water-soluble CIP content in soil, indicating enhanced desorption from soil particles. The increase ranged from 55.2% with rice straw biochar at 600°C to an astonishing 1160.6% with cockroach shell biochar at 300°C. This variation underscores the importance of biochar feedstock in controlling soil CIP release.

Further analysis revealed that the presence of DOM, especially protein-like components, played a crucial role in forming stable complexes with CIP, making them less bioavailable and less harmful. In contrast, humus-like components were less effective in stabilizing CIP. Moreover, biochar produced at lower pyrolysis temperatures (300°C) generally formed more stable DOM-CIP complexes compared to higher temperatures (600°C), particularly with pig manure biochar.

These findings are pivotal for environmental management, suggesting that selecting appropriate biochar feedstocks and optimizing pyrolysis conditions can enhance the removal of CIP from soils. This approach not only aids in controlling CIP contamination but also helps in understanding the broader implications of antibiotic mobility in the environment.