The greenhouse effect of antibiotics: The influence pathways of antibiotics on methane release from freshwater sediment.

The impact of antibiotics on methane (CH) release from sediment involves both CH production and consumption processes. However, most relevant studies lack a discussion of the pathways by which antibiotics affect CH release and do not highlight the role played by the sediment chemical environment in this influence mechanism. Here, we collected field surface sediments and grouped them with various antibiotic combination concentration gradients (50, 100, 500, 1000 ng g) under a 35-day indoor anaerobic constant temperature incubation. We found that the positive effect of antibiotics on sediment CH release potential appeared later than the positive effect on sediment CH release flux. Still, the positive effect of high-concentration antibiotics (500, 1000 ng g) occurred with a lag in both processes. Also, the positive effect of high-concentration antibiotics was significantly higher than low-concentration antibiotics (50, 100 ng g) in the later incubation period (p < 0.05). We performed a multi-collinearity assessment of sediment biochemical indicators, followed by a generalized linear model with negative binomial regression (GLM-NB) to obtain essential variables. In particular, we conducted the interaction analysis on CH release potential and flux regression for the influence pathways construction. The partial least-squares path modeling (PLS-PM) demonstrated that the positive effect of antibiotics on CH release (Total effect = 0.2579) was primarily attributed to their effect on the sediment chemical environment (Direct effect = 0.5107). These findings greatly expand our understanding of the antibiotic greenhouse effect in freshwater sediment. Further studies should more carefully consider the effects of antibiotics on the sediment chemical environment, and continuously improve the mechanistic studies of antibiotics on sediment CH release.