| Autor: |
Andrew Binley, Katrina Lansdown, Xiaomin Mao, Haizhu Hu, Catherine M. Heppell |
| Rok vydání: |
2014 |
| Předmět: |
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| Zdroj: |
Advances in Water Resources. 73:185-197 |
| ISSN: |
0309-1708 |
| Popis: |
Small streambed structures (or microforms, 0.01–1 m in length) exist ubiquitously in riverbed systems. Small-scale topography is potentially important in controlling hyporheic exchange flow and transport of conservative and reactive solutes at the groundwater–surface water interface. The role of microforms on NO 3 - transfer in a riffle-scale (macroforms of >1 m length) hyporheic zone within a gaining river setting is investigated using a 2-D flow and transport model which accounts for both nitrification and denitrification. Results show that t he short pathlines caused by microforms lead to more NO 3 - discharge to the river compared with a macroform-only condition due to shortened residence times of both surface water and groundwater in mixing zones. Short hyporheic exchange flow pathways caused by microforms could remain oxic along their entire length or switch from nitrate producing to nitrate consuming as oxygen concentrations decline. Microforms affect net NO 3 - flux by the combined effect of introducing more stream mass flux and reducing their residence time in mixing zones under different hydrological and biogeochemical conditions. Our findings underscore that ignoring microforms in river beds may underestimate NO 3 - load to the river and have practical implications for pore water sampling strategies in groundwater–surface water studies. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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Full Text from ScienceDirect