Synchronous regulation of MPs release and H₂S accumulation by SRB in landfill environments

The formation of microplastics (MPs) and the release of H₂S in landfill environments show a synchronous pattern, yet lack clear scientific explanation. In this study, simulated landfill systems were constructed under varying moisture and temperature conditions to explore the direct coupling mechanism between these two processes from the perspectives of key functional genes and enzymatic activities. The results revealed that the release of MPs exhibited distinct stage-specific characteristics and was highly coupled with the sulfate reduction process, which became particularly pronounced under high-moisture conditions. The sulfate reduction process not only drove the early rapid release of MPs but also determined the subsequent variations in release intensity. The dominant genus Thiobacillus contributed most to the key genes involved in sulfur metabolism, yet its dominance gradually declined with increasing temperature. SRB not only promote the aging of MPs through metabolic products, but specific groups (such as Desulfovibrio) may also directly participate in degradation, with plastic degradation genes being genus-specific and environmentally regulated. Fourteen SRB genera were found to harbor multiple plastic-degrading genes, the abundances of which were influenced by moisture and temperature. A degradation enzyme system centered on CAZymes and PDZymes gradually formed within the landfill environment, suggesting that SRB may regulate plastic degradation and release of MPs by modulating related enzyme activities. In conclusion, this study further unveils the coupling mechanism between MPs release and sulfate reduction in landfill systems at the genetic and enzymatic activity levels, clarifying the multiple ecological functions of SRB in the MPs release process, and providing new theoretical insights for landfill management and pollution control.