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Quantification of Hyporheic Nitrate Removal at the Reach Scale : Exposure Times vs. Residence Times

Title data

Frei, Sven ; Durejka, Stefan ; Le Lay, Hugo ; Thomas, Zahra ; Gilfedder, Ben:
Quantification of Hyporheic Nitrate Removal at the Reach Scale : Exposure Times vs. Residence Times.
In: Water Resources Research. Vol. 55 (November 2019) Issue 11 . - pp. 9808-9825.
ISSN 1944-7973
DOI: https://doi.org/10.1029/2019WR025540

Abstract in another language

The rate of biogeochemical processing associated with natural degradation and transformation processes in the hyporheic zone (HZ) is one of the largest uncertainties in predicting nutrient fluxes. We present a lumped parameter model that can be used to quantify the mass loss for nitrate in the HZ operating at the scale of river reaches to the entire catchments. The model is based on using exposure times (ET) to account for the effective timescales of reactive transport in the HZ. Reach scale ET distributions are derived by removing the portion of hyporheic residence times (RT) associated with flow through the oxic zone. The model was used to quantify nitrate removal for two scenarios: (1) a 100 m generic river reach and (2) a small agricultural catchment in Brittany (France). For the field site, hyporheic RT were derived from measured in‐stream 222Rn activities and mass balance modeling. Simulations were carried out using different types of RT distributions (exponential, power law, and gamma‐type) for which ET were derived. Mass loss of nitrate in the HZ for the field site ranged from 0 to 0.45 kg day−1 depending on the RT distribution and the availability of oxygen in the streambed sediments. Simulations with power law ET distribution models only show very little removal of nitrate due to the heavy weighting toward shorter flow paths that are confined to the oxic sediments. Based on the simulation results, we suggest that using ET will likely lead to more realistic estimates for nutrient removal in river and stream networks.

Further data

Item Type: Article in a journal
Refereed: Yes
Additional notes: BAYCEER154180
Institutions of the University: Research Institutions
Research Institutions > Research Centres
Research Institutions > Research Centres > Bayreuth Center of Ecology and Environmental Research- BayCEER
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Earth Sciences > Chair Hydrology
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Earth Sciences > Chair Hydrology > Chair Hydrology - Univ.-Prof. Dr. Stefan Peiffer
Result of work at the UBT: Yes
DDC Subjects: 500 Science
500 Science > 550 Earth sciences, geology
Date Deposited: 24 Jan 2020 09:12
Last Modified: 24 Jan 2020 09:12
URI: https://eref.uni-bayreuth.de/id/eprint/53819