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Frankignoulle, Michel; Borges, Alberto

doi:10.1023/a:1015251010481

Cited by 98 publications

(26 citation statements)

References 21 publications

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“…In the field, the partial pressure of CO 2 (pCO 2 ) in the groundwater, stream water and river water was measured directly using an equilibrator (Frankignoulle and Borges, 2001;Polsenaere et al, 2013). This equilibrator was connected to an infrared Gas analyser (LI-COR Ò , LI-820), which was calibrated one day before sampling on two linear segments because of its non-linear response in the range of observed pCO 2 values (0-90,000 ppmv).…”

Section: Field Workmentioning

confidence: 99%

Carbon dioxide degassing at the groundwater-stream-atmosphere interface: isotopic equilibration and hydrological mass balance in a sandy watershed

Deirmendjian

Abril

2018

Journal of Hydrology

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a b s t r a c tStreams and rivers emit significant amounts of CO 2 and constitute a preferential pathway of carbon transport from terrestrial ecosystems to the atmosphere. However, the estimation of CO 2 degassing based on the water-air CO 2 gradient, gas transfer velocity and stream surface area is subject to large uncertainties. Furthermore, the stable isotope signature of dissolved inorganic carbon (d 13 C-DIC) in streams is strongly impacted by gas exchange, which makes it a useful tracer of CO 2 degassing under specific conditions. For this study, we characterized the annual transfers of dissolved inorganic carbon (DIC) along the groundwater-stream-river continuum based on DIC concentrations, stable isotope composition and measurements of stream discharges. We selected a homogeneous, forested and sandy lowland watershed as a study site, where the hydrology occurs almost exclusively through drainage of shallow groundwater (no surface runoff). We observed the first general spatial pattern of decreases in pCO 2 and DIC and an increase in d 13 C-DIC from groundwater to stream orders 1 and 2, which was due to the experimentally verified faster degassing of groundwater 12 C-DIC compared to 13 C-DIC. This downstream enrichment in 13 C-DIC could be modelled by simply considering the isotopic equilibration of groundwater-derived DIC with the atmosphere during CO 2 degassing. A second spatial pattern occurred between stream orders 2 and 4, consisting of an increase in the proportion of carbonate alkalinity to the DIC accompanied by the enrichment of 13 C in the stream DIC, which was due to the occurrence of carbonate rock weathering downstream. We could separate the contribution of these two processes (gas exchange and carbonate weathering) in the stable isotope budget of the river network. Thereafter, we built a hydrological mass balance based on drainages and the relative contribution of groundwater in streams of increasing order. After combining with the dissolved CO 2 concentrations, we quantified CO 2 degassing for each stream order for the whole watershed. Approximately 75% of the total CO 2 degassing from the watershed occurred in first-and second-order streams. Furthermore, from stream order 2-4, our CO 2 degassing fluxes compared well with those based on stream hydraulic geometry, water pCO 2 , gas transfer velocity, and stream surface area. In first-order streams, however, our approach showed CO 2 fluxes that were twice as large, suggesting that a fraction of degassing occurred as hotspots in the vicinity of groundwater resurgence and was missed by conventional stream sampling.

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Section: Field Workmentioning

confidence: 99%

Carbon dioxide degassing at the groundwater-stream-atmosphere interface: isotopic equilibration and hydrological mass balance in a sandy watershed

Deirmendjian

Abril

2018

Journal of Hydrology

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“…Measurements of TA and pH were used to compute pCO 2 and DIC using the carbonic acid thermodynamic dissociation constants of Cai and Wang (1998), with an estimated accuracy of 5 % and 5 µmol kg -1 , respectively (Frankignoulle and Borges, 2001). 10…”

Section: Sample Collection and Analysismentioning

confidence: 99%

Carbon dynamics in the Mekong Delta

Borges

Abril

Bouillon

2017

Preprint

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We report a data-set obtained in the three branches (My Tho . The CO 2 emission to the atmosphere from the Mekong inner estuary was higher than reported in the Yangtze and Pearl River inner estuaries. This was probably due to the lower salinity in the Mekong delta branches, possibly due to different morphology; relatively linear channels in the Mekong delta versus funnel-15 shaped estuaries for the Yangtze and Pearl River inner estuaries.,Biogeosciences Discuss., https://doi

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“…For the river Seine, we used data described in Servais et al (2003). Land-based fluxes of DIC and TA were estimated based on a compilation of DIC and TA concentrations in the Seine and the Scheldt rivers (Frankignoulle et al, 1996Frankignoulle and Borges, 2001b;Abril, personal communication) and river discharges, making use of the "apparent zero end-member" method (Kaul and Froelich, 1984). Atmospheric pCO 2 was extracted from the Mace Head (53 • 33 N 9 • 00 W, Southern Ireland) and the National Oceanic and Atmospheric Administration/climate Monitoring and Diagnostics Laboratory/Carbon Cycle Greenhouse Gases Group (NOAA/CMDL/CCGG) air sampling network (available at http://www.cmdl.noaa.gov/).…”

Section: Model Runsmentioning

confidence: 99%

Carbon dynamics and CO<sub>2</sub> air-sea exchanges in the eutrophied coastal waters of the Southern Bight of the North Sea: a modelling study

Gypens

Lancelot

Borges³

2004

Biogeosciences

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Abstract.A description of the carbonate system has been incorporated in the MIRO biogeochemical model to investigate the contribution of diatom and Phaeocystis blooms to the seasonal dynamics of air-sea CO 2 exchanges in the Eastern Channel and Southern Bight of the North Sea, with focus on the eutrophied Belgian coastal waters. For this application, the model was implemented in a simplified three-box representation of the hydrodynamics with the open ocean boundary box 'Western English Channel' (WCH) and the 'French Coastal Zone' (FCZ) and 'Belgian Coastal Zone' (BCZ) boxes receiving carbon and nutrients from the rivers Seine and Scheldt, respectively. Results were obtained by running the model for the 1996-1999 period. The simulated partial pressures of CO 2 (pCO 2 ) were successfully compared with data recorded over the same period in the central BCZ at station 330 (51 • 26.05 N; 002 • 48.50 E). Budget calculations based on model simulations of carbon flow rates indicated for BCZ a low annual sink of atmospheric CO 2 (−0.17 mol C m −2 y −1 ). On the opposite, surface water pCO 2 in WCH was estimated to be at annual equilibrium with respect to atmospheric CO 2 . The relative contribution of biological, chemical and physical processes to the modelled seasonal variability of pCO 2 in BCZ was further explored by running model scenarios with separate closures of biological activities and/or river inputs of carbon. The suppression of biological processes reversed direction of the CO 2 flux in BCZ that became, on an annual scale, a significant source for atmospheric CO 2 (+0.53 mol C m −2 y −1 ). Overall biological activity had a stronger influence on the modelled seasonal cycle of pCO 2 than temperature. Especially Phaeocystis colonies which growth in spring were associated with an important sink of atmospheric CO 2 that counteracted the temperature-driven increase of pCO 2 at this period of the year. However, river inputs of organic and inorganic carbonCorrespondence to: N. Gypens (ngypens@ulb.ac.be) were shown to increase the surface water pCO 2 and hence the emission of CO 2 to the atmosphere. Same calculations conducted in WCH, showed that temperature was the main factor controlling the seasonal pCO 2 cycle in these open ocean waters. The effect of interannual variations of fresh water discharge (and related nutrient and carbon inputs), temperature and wind speed was further explored by running scenarios with forcing typical of two contrasted years (1996 and 1999). Based on these simulations, the model predicts significant variations in the intensity and direction of the annual air-sea CO 2 flux.

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Cited by 98 publications

References 21 publications

Carbon dioxide degassing at the groundwater-stream-atmosphere interface: isotopic equilibration and hydrological mass balance in a sandy watershed

Carbon dioxide degassing at the groundwater-stream-atmosphere interface: isotopic equilibration and hydrological mass balance in a sandy watershed

Carbon dynamics in the Mekong Delta

Carbon dynamics and CO<sub>2</sub> air-sea exchanges in the eutrophied coastal waters of the Southern Bight of the North Sea: a modelling study

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Untitled

Cited by 98 publications

References 21 publications

Carbon dioxide degassing at the groundwater-stream-atmosphere interface: isotopic equilibration and hydrological mass balance in a sandy watershed

Carbon dioxide degassing at the groundwater-stream-atmosphere interface: isotopic equilibration and hydrological mass balance in a sandy watershed

Carbon dynamics in the Mekong Delta

Carbon dynamics and CO&lt;sub&gt;2&lt;/sub&gt; air-sea exchanges in the eutrophied coastal waters of the Southern Bight of the North Sea: a modelling study

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Carbon dynamics and CO<sub>2</sub> air-sea exchanges in the eutrophied coastal waters of the Southern Bight of the North Sea: a modelling study