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- Title
Water Exchange and Solute Transport in the Hyporheic Zone on the West Side of Erhai Lake.
- Authors
QIN Ronggao; CHEN Xiangsen; CAO Guangzhu; LI Jinrong; QIANG Yi; LU Yanfeng
- Abstract
With the rapid development of tourism and agriculture in the alluvial fan and lacustrine sedimentary plain on the western side of Erhai Lake in Dali, Yunnan Province, large amounts of NH4 +-N, NO3 --N, and NO2 --N pollutants have been generated by agricultural cultivation at the margins of the alluvial fan and by human activities within the alluvial fan. The infiltration of the 18 streams in the Cangshan Mountains drives the nitrogen-contaminated groundwater to continuously discharge into Erhai Lake, which further increases the risk of eutrophication of the water bodies of the alpine lake. The hyporheic zone has a purifying effect on the infiltrated surface water. To investigate the migration and removal patterns of nitrogen in the hyporheic zone in the alluvial fan, a simulated infiltration system of the hyporheic zone was designed, including three hydrological processes affecting the migration of the aforementioned nitrogen pollutants, namely, the infiltration of urban domestic sewage in the alluvial fan, the vertical infiltration of fertilizer applied at the margins of the alluvial fan, and the alternate recharge of the hyporheic zone by surface water and groundwater at the apex of the alluvial fan. The experimental results revealed that the hyporheic zone has good NH4 +-N and NO3 --N removal efficiencies. Their removal in the alluvial fan mainly relies on denitrification during their vertical infiltration, which generally involves two processes with opposite effects: (1) a positive-effect process involving the alternate adsorption of anions and cations in the hyporheic zone, accompa nied by nitrification and denitrification, where denitrification is the primary nitrogen removal step and nitrification plays a supplementary role, leading to pollutant concentration reduction and water purification, and (2) a negative-effect process involving nitrification and anion/cation adsorption followed by the release of Ca2+ and Mg2+ into the aqueous phase, leading to increased total hardness of the water. During the alternate recharge of the hyporheic zone by surface water and groundwater at the apex of the alluvial fan, NO3 --N removal and water purification are mainly achieved through denitrification and partial ly through dissimilatory nitrate reduction to ammonium.
- Subjects
ALLUVIAL fans; WATER purification; WATER hardness; SEWAGE; BODIES of water; ARTIFICIAL groundwater recharge; NITROGEN removal (Water purification)
- Publication
Environmental Science & Technology (10036504), 2023, Vol 46, Issue 6, p16
- ISSN
1003-6504
- Publication type
Article