The environmentally relevant concentration of triclosan induces carbon dioxide emission in estuarine sediment associated with disrupted microbial metabolism.

Emerging contaminants in urban areas can accumulate in estuarine sediment through household and hospital wastewater discharge. During the pandemic, the use of disinfectants such as triclosan (TCS) increased, potentially leading to higher levels of these substances in the environment. This study aims to investigate the effects of environmentally relevant concentrations of TCS (0.01 and 1 mg kg-1 wt) on CO2 emissions, microbial community, and activities. We observed a significant increase in CO2 flux in sediment spiked with 0.01 and 1 mg kg-1 of TCS (3.78 and 4.02 mg h-1, respectively) compared to the control (2.09 mg h-1) after 14 days of incubation. Additionally, TCS at these concentrations substantially stimulated microbial metabolic respiration in estuarine sediments (>1.9-fold increase). Notably, the relative abundance of Methanolobus sp. and Methanococcoides sp. significantly increased from 0.8 % to 1.9 % following 1 mg kg-1 TCS exposure, with about 2-fold increase in Bacillus sp. Furthermore, the carbon metabolism-related genes associated with anaerobic CO oxidation, carbon fixation, and methanogenesis were highly stimulated in TCS-spiked sediments (>1.2-fold increase). Our findings suggest that the environmentally relevant concentration of TCS can enhance CO2 emission in the estuarine sediments, likely by promoting microbial respiration and carbon metabolism. This study provides valuable insights into the impact of disinfectants on estuarine sediment, highlighting their potential contribution to carbon footprint and underscoring the need for remediation efforts to achieve sustainable development goals (SDGs).