Numerical Modeling of Nitrate Removal in Anoxic Groundwater during River Flooding of Riparian Zones |
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Authors: | Jannick Kolbjørn Jensen Bertel Nilsson Peter Engesgaard |
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Affiliation: | 1. Department of Geosciences and Natural Resource Management, Section of Geology, University of Copenhagen, Øster Voldgade 10, 1350 Copenhagen K, Denmark The Capital Region of Denmark, Centre for Regional Development, Kongens Vænge 2, 3400 Hillerød, Denmark;2. Geological Survey of Denmark and Greenland (GEUS), Øster Voldgade 10, 1350 Copenhagen K, Denmark |
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Abstract: | A numerical study demonstrates the effects of flooding on subsurface hydrological flowpaths and nitrate removal in anoxic groundwater in riparian zones with a top peat layer. A series of two-dimensional numerical simulations with changing conditions for flow (steady state or transient with flooding), hydrogeology, denitrification, and duration of flooding demonstrate how flowpaths, residence times, and nitrate removal are affected. In periods with no flooding groundwater flows horizontally and discharges to the river through the riverbed. During periods with flooding, shallow groundwater is forced upwards as discharge through peat layers that often have more optimal conditions for denitrification caused by the presence of highly reactive organic matter. The contrast in hydraulic conductivity between the sand aquifer and the overlying peat layer, as well as the flooding duration, have a significant role in determining the degree of nitrate removal. |
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