Quantifying groundwater fluxes from an aapa mire to riverside esker formation

Abstract Water flows in peatland margins is an under-researched topic. This study examines recharge from a peatland to an esker aquifer in an aapa mire complex of northern Finland. Our objective was to study how the aapa mire margin is hydrogeologically connected to the riverside aquifer and spatial and temporal variations in the recharge of peatland water to groundwater (GW). Following geophysical studies and monitoring of the saturated zone, a GW model (MODFLOW) was used in combination with stable isotopes to quantify GW flow volumes and directions. Peatland water recharge to the sandy aquifer indicated a strong connection at the peatland–aquifer boundary. Recharge volumes from peatland to esker were high and rather constant (873 m3 d−1) and dominated esker recharge at the study site. The peat water recharging the esker boundary was rich in dissolved organic carbon (DOC). Stable isotope studies on water (δ18O, δ2H, and d-excess) from GW wells verified the recharge of DOC-rich water from peatlands to mineral soil esker. Biogeochemical analysis revealed changes from DOC to dissolved inorganic carbon in the flow pathway from peatland margin to the river Kitinen. This study highlights the importance of careful investigation of aapa mire margin areas and their potential role in regional GW recharge patterns.

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Groundwater data improve modelling of headwater stream CO<sub>2</sub> outgassing with a stable DIC isotope approach

10.5194/bg-2017-357 ◽

2017 ◽

Author(s):

Anne Marx ◽

Marcus Conrad ◽

Vadym Aizinger ◽

Alexander Prechtel ◽

Robert van Geldern ◽

...

Keyword(s):

Inorganic Carbon ◽

Dissolved Inorganic Carbon ◽

Stream Water ◽

Temporal Variations ◽

Headwater Stream ◽

Integral Approach ◽

Gas Transfer ◽

Transfer Velocity ◽

Outgassing Rate ◽

Carbon Dioxide Co2

Abstract. A large portion of terrestrially-derived carbon outgasses as carbon dioxide (CO2) from streams and rivers to the atmosphere. Particularly, the amount of CO2 outgassing from small headwater streams was indicated as highly uncertain. Conservative estimates suggest that they contribute 36 % (i.e., 0.93 petagrams C yr−1) of total CO2 outgassing from all rivers and streams worldwide. In this study, stream pCO2, dissolved inorganic carbon (DIC) and δ13CDIC data were used to determine CO2 outgassing from an acidic headwater stream in the Uhlirska catchment (Czech Republic). This stream drains a catchment with silicate bedrock. The applied stable isotope model is based on the principle, that the 13C / 12C ratio of its sources and the intensity of CO2 outgassing control the isotope ratio of DIC in stream water. It avoids the use of the gas transfer velocity parameter (k) that is highly variable and mostly difficult to constrain. Model results indicate that CO2 outgassing contributed 80 % to the annual stream inorganic carbon loss in the Uhlirska catchment. This translated to a CO2 outgassing rate from the stream of 5.2 t C yr−1 and to 2.9 g C m−2 yr−1, when normalised to the catchment area. Large temporal variations with maximum values during spring snowmelt and summer emphasise the need for investigations at higher temporal resolution. We improved the model uncertainty by incorporating groundwater data to better constrain the isotope compositions of initial DIC. Due to the large global abundance of acidic, humic-rich headwaters, we underline the importance of this integral approach for global applications.

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Methodologies for extraction of dissolved inorganic carbon for stable carbon isotope studies: Evaluation and alternatives

10.3133/wri826 ◽

1982 ◽

Keyword(s):

Carbon Isotope ◽

Inorganic Carbon ◽

Dissolved Inorganic Carbon ◽

Stable Carbon Isotope ◽

Stable Carbon ◽

Isotope Studies

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Hydrological and biogeochemical controls on temporal variations of dissolved carbon and solutes in a karst river, South China

Environmental Sciences Europe ◽

10.1186/s12302-021-00495-x ◽

2021 ◽

Vol 33 (1) ◽

Author(s):

Jing Liu ◽

Jun Zhong ◽

Shuai Chen ◽

Sen Xu ◽

Si-Liang Li

Keyword(s):

Climate Change ◽

Chemical Weathering ◽

Inorganic Carbon ◽

Dissolved Inorganic Carbon ◽

Global Climate ◽

Carbon Dynamics ◽

Temporal Variations ◽

High Flow ◽

Dissolved Carbon ◽

Weathering Processes

Abstract Background Understanding the responses of riverine dissolved carbon dynamics and chemical weathering processes to short-term climatic variabilities is important to understand the Surface-Earth processes under ongoing climate change. Temporal variations of solutes and stable carbon isotope of dissolved inorganic carbon (δ13CDIC) were analysed during a hydrological year in the Guijiang River, South China. We aimed to unravel the chemical weathering processes and carbon dynamics in karst areas under ongoing climate changes. Results Significant positive relationships were found between weathering rates and climatic factors (i.e. temperature and discharge) over the hydrological year. The total flux of CO2 consumption (760.4 × 103 mol/km2/year) in the Guijiang River was much higher than the global mean flux, with a higher CO2 consumption capacity in the Guijiang River relative to most other global rivers. Chemical weathering fluxes in this karst area showed high sensitivity to global climate change. CO2 evasion during the warm–wet seasons was much lower than those during cold–dry seasons. Light δ13CDIC values occurred under high-flow conditions, corresponding with the high temperatures in high-flow seasons. IsoSource modelling revealed that biological carbon could account for 53% of all dissolved inorganic carbon (DIC), controlling the temporal carbon variabilities. Conclusion This study quantitatively evaluated the temporal variations in CO2 fluxes and carbon cycling of karstic river systems and demonstrated that riverine carbon cycling will have a higher sensibility to ongoing global climate change. High discharges accelerate solutes transport, with relatively large quantities of 13C-depleted carbon being flushed into rivers. Meanwhile, high temperatures also accelerate organic carbon mineralisation, producing high content of soil CO2, whose influx can shift the 13C-depleted values in the high-flow seasons. Taken together, biological carbon influx should be responsible for the temporal carbon dynamics.

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Temporal variations of surface oceanic and atmospheric CO2 fugacity and total dissolved inorganic carbon in the northwestern North Pacific

Journal of Oceanography ◽

10.1007/bf02742616 ◽

1998 ◽

Vol 54 (4) ◽

pp. 323-336 ◽

Cited By ~ 5

Author(s):

Tomonori Watai ◽

Masaaki Kikuchi ◽

Takakiyo Nakazawa

Keyword(s):

North Pacific ◽

Inorganic Carbon ◽

Dissolved Inorganic Carbon ◽

Temporal Variations ◽

Atmospheric Co2 ◽

Total Dissolved Inorganic Carbon

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Groundwater data improve modelling of headwater stream CO<sub>2</sub> outgassing with a stable DIC isotope approach

Biogeosciences ◽

10.5194/bg-15-3093-2018 ◽

2018 ◽

Vol 15 (10) ◽

pp. 3093-3106 ◽

Cited By ~ 6

Author(s):

Anne Marx ◽

Marcus Conrad ◽

Vadym Aizinger ◽

Alexander Prechtel ◽

Robert van Geldern ◽

...

Keyword(s):

Inorganic Carbon ◽

Dissolved Inorganic Carbon ◽

Stream Water ◽

Temporal Variations ◽

Headwater Stream ◽

Integral Approach ◽

Gas Transfer ◽

Transfer Velocity ◽

Outgassing Rate ◽

Carbon Dioxide Co2

Abstract. A large portion of terrestrially derived carbon outgasses as carbon dioxide (CO2) from streams and rivers to the atmosphere. Particularly, the amount of CO2 outgassing from small headwater streams is highly uncertain. Conservative estimates suggest that they contribute 36 % (i.e. 0.93 petagrams (Pg) C yr−1) of total CO2 outgassing from all fluvial ecosystems on the globe. In this study, stream pCO2, dissolved inorganic carbon (DIC), and δ13CDIC data were used to determine CO2 outgassing from an acidic headwater stream in the Uhlířská catchment (Czech Republic). This stream drains a catchment with silicate bedrock. The applied stable isotope model is based on the principle that the 13C ∕ 12C ratio of its sources and the intensity of CO2 outgassing control the isotope ratio of DIC in stream water. It avoids the use of the gas transfer velocity parameter (k), which is highly variable and mostly difficult to constrain. Model results indicate that CO2 outgassing contributed more than 80 % to the annual stream inorganic carbon loss in the Uhlířská catchment. This translated to a CO2 outgassing rate from the stream of 34.9 kg C m−2 yr−1 when normalised to the stream surface area. Large temporal variations with maximum values shortly before spring snowmelt and in summer emphasise the need for investigations at higher temporal resolution. We improved the model uncertainty by incorporating groundwater data to better constrain the isotope compositions of initial DIC. Due to the large global abundance of acidic, humic-rich headwaters, we underline the importance of this integral approach for global applications.

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