Baseflow and Coupled Nitrification-Denitrification Processes Jointly Dominate Nitrate Dynamics in a Watershed
Wang Shu1,2,3,4,5, Qiuying Zhang1, Joachim Audet6
1State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, 100012Beijing, China.
Environmental Science & Technology
|December 16, 2024
Summary
Nitrogen pollution from mining is significant. Groundwater and soil nitrogen are key sources, with baseflow and denitrification being major pathways and processes influencing nitrate levels in rivers.
Area of Science:
- Environmental Science
- Hydrology
- Geochemistry
Background:
- Mining activities significantly contribute to nitrogen pollution in watersheds.
- Understanding nitrate transport, transformation, and control in mining areas is limited.
Purpose of the Study:
- To investigate nitrate dynamics and drivers in a rare earth mining watershed.
- To reveal nitrogen sources, pathways, and transformation processes.
Main Methods:
- Utilized nearly 4-year groundwater and river observations.
- Employed stoichiometry-based load modeling, molecular biology, and multi-isotope analyses.
Main Results:
- Nitrate dynamics are controlled by precipitation, terrestrial inputs, sediment supply, hydrology, and biological processes.
- Groundwater (36%) and soil nitrogen (25%) are primary sources; baseflow contributes 66.8% of nitrate load.
- Denitrification (58%) is a key process, influenced by dissolved organic carbon and oxygen.
Conclusions:
- Effective nitrogen pollution control requires reducing inputs and managing hydrological pathways and transformation mechanisms.
- Highlights the role of groundwater, baseflow, and denitrification in mining watershed nitrogen pollution.
- Identifies *Burkholderia* as key microbes in nitrate transformation.
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