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Creative Commons Lizenz creative commons licence
Titel (primär) Seasonal and short‐term controls of riparian oxygen dynamics and the implications for redox processes
Autor Nogueira, G.E.H.; Schmidt, C.; Trauth, N.; Fleckenstein, J.H.;
Journal / Serie Hydrological Processes
Erscheinungsjahr 2021
Department ASAM; HDG;
Band/Volume 35
Heft 2
Sprache englisch;
Keywords Dissolved oxygen; reactive potential; Damköhler number; discharge events; tracer‐tests; transit‐times; losing stream; Selke River
Abstract Riparian zones are highly‐dynamic transition zones between surface water (SW) and groundwater (GW) and function as key biogeochemical‐reactors for solutes transitioning between both compartments. Infiltration of SW rich in dissolved oxygen (DO) into the riparian aquifer can supress removal processes of redox sensitive compounds like NO3, a nutrient harmful for the aquatic ecosystem at high concentrations. Seasonal and short‐term variations of temperature and hydrologic conditions can influence biogeochemical reaction rates and thus the prevailing redox conditions in the riparian zone. We combined GW tracer‐tests and a one‐year high‐frequency dataset of DO with data‐driven simulations of DO consumption to assess the effects of seasonal and event‐scale variations in temperature and transit‐times on the reactive transport of DO. Damköhler numbers for DO consumption (DADO) were used to characterize the system in terms of DO turnover potential. Our results suggest that seasonal and short‐term variations in temperature are major controls for DO turnover and the resulting concentrations at our field site, while transit‐times are of minor importance. Seasonal variations of temperature in GW lead to shifts from transport‐limited (DADO>1) to reaction‐limited conditions (DADO<1), while short‐term events were found to have minor impacts on the state of the system, only resulting in slightly less transport‐limited conditions due to decreasing temperature and transit‐times. The data‐driven analyses show that assuming constant water temperature along a flowpath can lead to an over‐ or underestimation of reaction rates by a factor of 2‐3 due to different infiltrating water temperature at the SW‐GW interface, whereas the assumption of constant transit‐times results in incorrect estimates of NO3 removal potential based on DADO approach (40%‐50% difference).
ID 24160
dauerhafte UFZ-Verlinkung
Nogueira, G.E.H., Schmidt, C., Trauth, N., Fleckenstein, J.H. (2021):
Seasonal and short‐term controls of riparian oxygen dynamics and the implications for redox processes
Hydrol. Process. 35 (2), e14055