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Effects of magnetite on microbially driven nitrate reduction processes in groundwater
1College of New Energy and Environment, Jilin University, Changchun, Jilin 130021, China; Institute of Water Resources and Environment, Jilin University, Changchun, Jilin 130021, China.
The Science of the Total Environment
|September 23, 2022
Summary
Magnetite enhances nitrate-nitrogen bioreduction rates by 1.48% and influences microbial communities. This iron mineral impacts denitrification and dissimilatory nitrate reduction to ammonium (DNRA) processes in aquatic sediments.
Area of Science:
- Environmental Microbiology
- Geochemistry
- Biogeochemical Cycles
Background:
- Nitrate is a pervasive aquatic pollutant, with denitrification and dissimilatory nitrate reduction to ammonium (DNRA) being key nitrogen cycling processes.
- The competition between denitrification and DNRA in sediments dictates ecosystem nitrogen fate.
- Magnetite, a common sediment mineral, may influence these nitrate reduction pathways, but its specific role is unclear.
Purpose of the Study:
- To investigate the effect of magnetite on nitrate-nitrogen (NO3--N) bioreduction rates and pathways.
- To understand how magnetite influences microbial community structure and activity during nitrate reduction.
- To elucidate the interaction mechanisms between magnetite and nitrate-reducing bacteria in aquatic environments.
Main Methods:
- Batch experiments were conducted to assess the impact of magnetite on NO3--N bioreduction.
- Microbial community structure and the activity of the electron transport system (ETS) were analyzed.
- Changes in Fe(II) concentration and the role of microbial metabolism in magnetite dissolution were examined.
Main Results:
- Magnetite increased the overall NO3--N reduction rate by 1.48% and initially inhibited, then promoted DNRA.
- Magnetite altered microbial community composition, favoring Sphingomonas under high carbon conditions and Flavobacterium (Fe-oxidizing, NO3--N reducing) under low carbon conditions.
- Magnetite significantly enhanced microbial ETS activity (nearly doubled) and promoted Fe(II) release through microbial acid production, benefiting autotrophic denitrifiers.
Conclusions:
- Magnetite plays a significant role in modulating nitrate reduction processes in aquatic sediments.
- The mineral influences microbial community dynamics and enhances overall nitrate bioreduction efficiency.
- Findings reveal a complex interaction mechanism involving magnetite, nitrate reducers, and Fe cycling, crucial for understanding nitrogen dynamics in natural systems.
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