The negligible effect of bed form migration on denitrification in hyporheic zones of permeable sediments

Kessler, Adam J.; Cardenas, M. Bayani; Cook, Perran

doi:10.1002/2014jg002852

Cited by 20 publications

(50 citation statements)

References 41 publications

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“…However, the increase of bed form migration rates time scale of solute exchange without moving bed forms can significantly affect solute exchange, as was shown for oxygen distribution by Precht et al (). Conversely, it was demonstrated by a modeling study that moving bed forms have a negligible effect on denitrification and on coupled nitrification‐denitrification (Kessler et al ).…”

Section: Discussionmentioning

confidence: 99%

Biodegradation of labile dissolved organic carbon under losing and gaining streamflow conditions simulated in a laboratory flume

2016

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Carbon in surface waters is widely recognized as a key element that influences nutrient cycling, metal availability, and water quality. Its degradation in streams occurs primarily by benthic microbial communities that colonize the underlying sediment, which is commonly termed the hyporheic zone (HZ). The biodegradation of a labile dissolved organic carbon (DOCL), exemplified by sodium benzoate, was studied in a novel laboratory flume system under a combination of different overlying water velocities, losing or gaining fluxes, and biofilm distribution (“surficial” or “homogeneous distribution”). The overall objective of this study was to evaluate the effect of different flow conditions on DOCL biodegradation in the HZ. The results showed that overlying velocity was the dominant factor affecting DOCL biodegradation, regardless of biofilm distribution. Gaining flow conditions also induced a slight increase in the biodegradation rates as compared to losing or neutral flow conditions, due to additional oxygen input from the upwelling water. The aerobic reactive zone under all flow conditions was limited to the upper section of the benthic biofilm (several millimeters), where the surficial biofilm showed the highest activity. Our results demonstrate the processes affecting DOCL biodegradation in the hyporheic zone and will help to implement future modeling of DOC transport in streams.

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Section: Discussionmentioning

confidence: 99%

Biodegradation of labile dissolved organic carbon under losing and gaining streamflow conditions simulated in a laboratory flume

2016

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“…Thus, hyporheic exchange plays an important role in the thermal pattern of the HZs (Norman & Cardenas, ) and the distribution and transformation of nutrients (Tonina et al, ; Zarnetske et al, , ). A number of prior studies have demonstrated that HZs are important sites for biogeochemical reactions (Bardini et al, ; Hill et al, ; Kessler et al, ; Wondzell & Swanson, ; Zarnetske et al, , ), regulating downstream nitrogen export in aquatic environments (Alexander et al, ; Alexander et al, ; Gomez et al, ; Kiel & Cardenas, ; Marzadri et al, , ; Peterson et al, ).…”

Section: Introductionmentioning

confidence: 99%

Diel Stream Temperature Effects on Nitrogen Cycling in Hyporheic Zones

Zheng

Cardenas

2018

JGR Biogeosciences

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Stream temperature often varies diurnally and seasonally, and these variations propagate into hyporheic zones (HZs), forming dynamic and heterogeneous thermal patterns. The complex thermal distribution creates potential biogeochemical hotspots and hot moments. Yet, how diel temperature variations affect HZ nitrogen cycling is unknown. We thus conducted a series of multiphysics numerical simulations of nonisothermal fluid flow and multicomponent reactive solute transport to investigate this problem. We imposed a sinusoidally varying stream temperature representing diel warming and cooling and studied the effects of different temperature means and amplitudes on HZ nitrate removal efficiency inside a streambed with a dune. The results showed that the time-variable nitrification, denitrification, and nitrate removal efficiency responded differently to the diel stream temperature signal. The temporal variation of spatially averaged nitrification rate tracks the stream temperature signal, whereas the spatially averaged denitrification variation pattern has a more complex connection to temperature. We observed a persistent hotspot where significant denitrification rates are present over the 24-hr period. We further evaluated and estimated the bulk nitrate removal efficiency calculated by time integration of spatially averaged reaction rates over a day. For denitrification-dominant systems, the bulk nitrate removal efficiency for cases with dynamic stream temperature was effectively the same as those with an equivalent constant mean temperature. Therefore, the bulk removal efficiency of a thermally dynamic diel system may be represented by an equivalent isothermal system given stable flow conditions. However, since large instantaneous variations in various rates were observed, the results imply that randomly timed field measurements are unlikely to be representative. This has to be considered for both past and future synoptic observational studies. Plain Language Summary Stream temperature naturally varies over daily and seasonal periods.This could cause temperature-dependent chemical and biological processes to vary simultaneously. Within the permeable streambed are areas called hyporheic zones where stream water circulates through in and out of the bed. The heat carried by this hyporheic flow that originates from the stream forms dynamic and complex temperature distributions in the hyporheic zone. The thermal patterns within the streambed could determine the presence of denitrification hotspots and hot moments since the hyporheic zone is an important site for many chemical reactions including nitrogen cycling. Through modeling the flow and reaction transport processes within the hyporheic zone, we found that denitrification hotspots persisted despite dynamic and complex hyporheic zone thermal patterns. Our simulation results can help explain previous observations of warmer stream temperature corresponding to lower in-stream nitrate concentrations. The results also imply that instantaneous snapshots through synoptic che...

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“…Given the strong influence of DO concentration on reactions and nitrogen cycling (Kessler, Cardenas, & Cook, ), the zones in which reactions occur are first identified based on DO concentration. According to previous studies (e.g., Hunt & Christensen, ; Michaud, ), the DO concentration in streams can vary between 0.2 and 0.4 mol/m 3 (approximately between 3.2 and 6.4 mg/L) in the natural state, whereas in groundwater, it varies depending on the source of groundwater recharge.…”

Section: Methodsmentioning

confidence: 99%

Numerical modelling to evaluate the nitrogen removal rate in hyporheic zone and its implications for stream management

Liu

Chui²

2019

Hydrological Processes

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The hyporheic zone (HZ) plays a vital role in the stream ecosystem. Reactions in the HZ such as denitrification and nitrification have been examined in previous studies.However, no numerical model has yet been developed that can accurately simulate nitrogen concentration changes in the HZ, because the zones for the two reactions can change throughout the reactions. This study proposes a method of evaluating the nitrogen removal rate in the HZ through numerical modelling. First, a basic twodimensional numerical model coupling flow conditions with biochemical reactions is proposed to consider both nitrification and denitrification. The zones for different reactions are determined under the assumption that related environmental variables (i.e., the dissolved oxygen) will not change throughout the reactions. Next, to exam-

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The negligible effect of bed form migration on denitrification in hyporheic zones of permeable sediments

Cited by 20 publications

References 41 publications

Biodegradation of labile dissolved organic carbon under losing and gaining streamflow conditions simulated in a laboratory flume

Biodegradation of labile dissolved organic carbon under losing and gaining streamflow conditions simulated in a laboratory flume

Diel Stream Temperature Effects on Nitrogen Cycling in Hyporheic Zones

Numerical modelling to evaluate the nitrogen removal rate in hyporheic zone and its implications for stream management

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