期刊
APPLIED GEOCHEMISTRY
卷 140, 期 -, 页码 -出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.apgeochem.2022.105272
关键词
Riverbank filtration; Nitrogen; Hydrogeochemistry; Isotopic tracing; Dissimilatory nitrate reduction to ammonium; Denitrification
资金
- National Natural Science Foundation of China [41877178, 41977160, 41372238]
River eutrophication and nitrogen pollution pose a potential threat to groundwater quality in riverbank filtration systems. This study used hydrogeochemical and stable isotope tracing techniques to investigate the geochemical reactions controlling nitrogen migration and transformation during riverbank filtration in a typical site in NE China. The results revealed that mixing, adsorption, organic nitrogen mineralization, denitrification, and dissimilatory nitrate reduction to ammonium (DNRA) are the main geochemical reactions. Denitrification primarily occurs close to the riverbed surface and accounts for NO3- attenuation, while DNRA is more active at a certain depth and plays a significant role in NH4+ enrichment.
River eutrophication and nitrogen pollution poses a potential threat to the groundwater quality in riverbank filtration systems. The river filtration process is often accompanied by complex redox reactions. Therefore, identification of nitrogen biogeochemical processes is essential to scientifically characterize the cause of NO3- attenuation and NH4+ accumulation in groundwater, optimize the design of groundwater pumping wells, and design protection strategies in sudden environmental pollution accidents. Hydrogeochemical and stable isotope tracing techniques were employed in this study at a typical riverbank filtration site located in Songyuan, NE China, to explore the main geochemical reactions controlling the migration and transformation of nitrogen along the groundwater flow path during riverbank filtration. The results indicate that mixing, adsorption, organic nitrogen mineralization, denitrification, and dissimilatory nitrate reduction to ammonium (DNRA) represent the major geochemical reactions. Denitrification primarily occurs within 10-20 m from the riverbed surface along the filtration path and is the primary reaction accounting for NO3- attenuation, whereas DNRA typically occurs between 1.5 and 6 m from the riverbed surface along the filtration path and is more active in the wet season, characterized by high temperatures (>15-17 degrees C), low dissolved oxygen (DO, < 2-4 mg/L), and high carbon load i.e., organic carbon (OC):NO3- > 10-15. This work confirms that DNRA is an important nitrogen geochemical reaction during riverbank filtration, and emphasizes its role in NH4+ enrichment.
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