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Optimizing bioretention nitrogen control: woodchip mulching as vadose zone-focused amendment for pyrite systems
Xinyue Wang1, Haiyuan Ma1, Yunsong Yuan1
1Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), College of Environment and Ecology, Chongqing University, Chongqing 400045, China.
Bioresource Technology
|November 16, 2025
Summary
Woodchip mulching (WM) enhances nitrogen removal in pyrite bioretention systems by boosting vadose nitrification and plant uptake. However, long-term mulching may limit submerged denitrification due to carbon limitations.
Area of Science:
- Environmental Engineering
- Environmental Microbiology
- Soil Science
Background:
- Pyrite-based bioretention systems struggle with pollutant removal during heavy rainfall due to limited electron donation.
- Woodchip mulching (WM) is recognized for supplying organic matter, but its precise role in pyrite systems is not fully understood.
Purpose of the Study:
- To investigate the mechanisms by which woodchip mulching influences nitrogen transformation in pyrite-based bioretention systems over a 13-month period.
Main Methods:
- Monitoring of nitrogen removal efficiency, potential nitrification rates, cation exchange capacity, root activity, and microbial community composition (Nitrospira abundance).
- Analysis of nitrogen transformation processes in both vadose and submerged zones under the influence of WM.
Main Results:
- WM significantly enhanced vadose nitrogen transformation, increasing ammonium-nitrogen (NH4+-N) removal by 24.19% and potential nitrification rates by 9.50 ng N·g-1·h-1.
- Improved cation exchange capacity and root activity under WM facilitated NH4+-N adsorption and plant uptake, with a 1.97% increase in Nitrospira abundance.
- WM alleviated submerged NH4+-N accumulation by promoting nitrification, but long-term application favored heterotrophic denitrifiers, leading to carbon-limited submerged denitrification.
Conclusions:
- Woodchip mulching effectively improves vadose zone nitrogen conversion in pyrite bioretention systems.
- Optimizing electron donation in the submerged zone is recommended for enhanced overall nitrogen removal.
- Synergistic plant-microbe interactions play a crucial role in nitrogen removal enhancement mediated by WM.
Keywords:
BiofilterGreen infrastructureLow-impact developmentMixotrophic denitrificationNitrogen transformationMore Related Videos
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