Sulfate reduction behavior in response to changing of pressure coupling with temperature inside landfill

Microplastic release and sulfate reduction response in the early stage of a simulated landfill

Landfills are essential facilities for treating and disposing municipal solid waste. They emit sulfur-containing odors and serve as an important sink for a new type of pollutant called microplastics (MPs). This study focused on the initial stage of anaerobic degradation to establish the relationship between the release of MPs and odor generation. Our findings show the rapid release of MPs into the leachate in the early stage of landfill and their predominant accumulation in the leachate sediment. The circulating leachate contained 1.45 times higher concentrations of MPs than the noncirculating leachate, with a peak concentration of 39 items·L-1. In addition, fragmentation of MPs occurred. The percentage of MPs with particle sizes of 2.5-5 mm decreased from 66.70 % to 22.32 %, while those measuring 0.1-0.5 mm increased by 33.12 %. A positive correlation was observed between MP release and sulfate reduction. Although leachate circulation increased the release of MPs, it also reduced the overall release time and total amount of MPs exported from the landfill. Compared with the initial landfill waste, the leachate operation mode, regardless of circulation, resulted in a 6.15-8.93-fold increase in MP release. These findings provide a valuable foundation for the simultaneous regulation of traditional pollutant odor and new pollutants (MPs) in landfills.

Microplastic, a possible trigger of landfill sulfate reduction process

The environmental impact of microplastics (MPs) formed from landfill has not been gained enough attention. This research investigated the characteristics of the MPs occurrence in landfills through field sampling. It shows that the MPs abundance in the landfill surface soil and non-landfill areas can reach 3573 items·g-1 and 3041 items·g-1, respectively. The vertical abundance of MPs increases significantly with depth, ranging from 387 to 11,599 items·g-1 with small size (≤10 μm, 65.61 %) and flake or wedge shape (38.48 %). The leachate movement in a longitudinal direction enables MPs to accumulate more easily in the landfill bottom layer with high moisture abundance. The abundance of MPs are significantly correlated with SO42- and S2- content, the two typical metabolic substrate and product of sulfate reduction process. In such heterogeneous environment, this significant correlation is not a random phenomenon in terms of the MPs have known substantial impact on biogeochemical processes. Microplastic is a possible trigger of landfill odor emission related with sulfate reduction. This research could serve as a reference for MPs and odor pollution management in landfills.

Dynamics of the sedimentary bacterial communities in a plain river network: similar coalescence patterns with bacterioplankton communities driven by distinct assembly processes

IMPORTANCE

Microorganisms play important roles in driving the biogeochemical cycles within river ecosystems. It has been suggested that hydrologic conditions could influence microbial communities in rivers, but their specific effects on the behaviours of microbial coalescence have not been thoroughly investigated. In this study, the dynamics of sedimentary bacterial communities within a plain river network were analyzed by amplicon sequencing followed by several ecological models to uncover the underlying assembly processes. Additionally, a comparative analysis between bacterioplankton communities and sedimentary bacterial communities was performed to unveil their coalescence patterns. The results suggested that similar coalescence patterns between sedimentary bacterial and bacterioplankton communities were driven by distinct assembly processes under dynamic hydrological conditions. These findings enhanced our understanding of microbial diversity features within river ecosystems.