Technical Note: Mesocosm approach to quantify dissolved inorganic carbon percolation fluxes

Abstract. Dissolved inorganic carbon (DIC) fluxes across the vadose zone are influenced by a complex interplay of biological, chemical and physical factors. A novel soil mesocosm system was evaluated as a tool for providing information on the mechanisms behind DIC percolation to the groundwater from unplanted soil. Carbon dioxide partial pressure (pCO2), alkalinity, soil moisture and temperature were measured with depth and time, and DIC in the percolate was quantified using a sodium hydroxide trap. Results showed good reproducibility between two replicate mesocosms. The pCO2 varied between 0.2 and 1.1%, and the alkalinity was 0.1–0.6 meq L−1. The measured cumulative effluent DIC flux over the 78-day experimental period was 185–196 mg L−1 m−2 and in the same range as estimates derived from pCO2 and alkalinity in samples extracted from the side of the mesocosm column and the drainage flux. Our results indicate that the mesocosm system is a promising tool for studying DIC percolation fluxes and other biogeochemical transport processes in unsaturated environments.

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Inorganic carbon fluxes across the vadose zone of planted and unplanted soil mesocosms

Biogeosciences Discussions ◽

10.5194/bgd-11-4251-2014 ◽

2014 ◽

Vol 11 (3) ◽

pp. 4251-4299 ◽

Cited By ~ 2

Author(s):

E. M. Thaysen ◽

D. Jacques ◽

S. Jessen ◽

C. E. Andersen ◽

E. Laloy ◽

...

Keyword(s):

Carbon Dioxide ◽

Vadose Zone ◽

Inorganic Carbon ◽

Plant Biomass ◽

Dissolved Inorganic Carbon ◽

Carbon Fluxes ◽

Atmospheric Co2 ◽

Carbon Dioxide Partial Pressure ◽

Post Harvest ◽

Unplanted Soil

Abstract. The efflux of carbon dioxide (CO2) from soils influences atmospheric CO2 concentrations and thereby climate change. The partitioning of inorganic carbon fluxes in the vadose zone between emission to the atmosphere and to the groundwater was investigated. Carbon dioxide partial pressure in the soil gas (pCO2), alkalinity, soil moisture and temperature were measured over depth and time in unplanted and planted (barley) mesocosms. The dissolved inorganic carbon (DIC) percolation flux was calculated from the pCO2, alkalinity and the water flux at the mesocosm bottom. Carbon dioxide exchange between the soil surface and the atmosphere was measured at regular intervals. The soil diffusivity was determined from soil radon-222 (222Rn) emanation rates and soil air Rn concentration profiles, and was used in conjunction with measured pCO2 gradients to calculate the soil CO2 production. Carbon dioxide fluxes were modelled using the HP1 module of the Hydrus 1-D software. The average CO2 effluxes to the atmosphere from unplanted and planted mesocosm ecosystems during 78 days of experiment were 0.1 ± 0.07 and 4.9 ± 0.07 μmol carbon (C) m−2 s−1, respectively, and largely exceeded the corresponding DIC percolation fluxes of 0.01 ± 0.004 and 0.06 ± 0.03 μmol C m−2 s−1. Post-harvest soil respiration (Rs) was only 10% of the Rs during plant growth, while the post-harvest DIC percolation flux was more than one third of the flux during growth. The Rs was controlled by production and diffusivity of CO2 in the soil. The DIC percolation flux was largely controlled by the pCO2 and the drainage flux due to low solution pH. Plant biomass and soil pCO2 were high in the mesocosms as compared to a standard field situation. Our results indicate no change of the cropland C balance under elevated atmospheric CO2 in a warmer future climate, in which plant biomass and soil pCO2 are expected to increase.

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Inorganic carbon fluxes across the vadose zone of planted and unplanted soil mesocosms

Biogeosciences ◽

10.5194/bg-11-7179-2014 ◽

2014 ◽

Vol 11 (24) ◽

pp. 7179-7192 ◽

Cited By ~ 8

Author(s):

E. M. Thaysen ◽

D. Jacques ◽

S. Jessen ◽

C. E. Andersen ◽

E. Laloy ◽

...

Keyword(s):

Carbon Dioxide ◽

Plant Growth ◽

Vadose Zone ◽

Inorganic Carbon ◽

Dissolved Inorganic Carbon ◽

Carbon Dioxide Partial Pressure ◽

Co2 Production ◽

Post Harvest ◽

Unplanted Soil ◽

Soil Mesocosms

Abstract. The efflux of carbon dioxide (CO2) from soils influences atmospheric CO2 concentrations and thereby climate change. The partitioning of inorganic carbon (C) fluxes in the vadose zone between emission to the atmosphere and to the groundwater was investigated to reveal controlling underlying mechanisms. Carbon dioxide partial pressure in the soil gas (pCO2), alkalinity, soil moisture and temperature were measured over depth and time in unplanted and planted (barley) mesocosms. The dissolved inorganic carbon (DIC) percolation flux was calculated from the pCO2, alkalinity and the water flux at the mesocosm bottom. Carbon dioxide exchange between the soil surface and the atmosphere was measured at regular intervals. The soil diffusivity was determined from soil radon-222 (222Rn) emanation rates and soil air Rn concentration profiles and was used in conjunction with measured pCO2 gradients to calculate the soil CO2 production. Carbon dioxide fluxes were modeled using the HP1 module of the Hydrus 1-D software. The average CO2 effluxes to the atmosphere from unplanted and planted mesocosm ecosystems during 78 days of experiment were 0.1 ± 0.07 and 4.9 ± 0.07 μmol C m−2 s−1, respectively, and grossly exceeded the corresponding DIC percolation fluxes of 0.01 ± 0.004 and 0.06 ± 0.03 μmol C m−2 s−1. Plant biomass was high in the mesocosms as compared to a standard field situation. Post-harvest soil respiration (Rs) was only 10% of the Rs during plant growth, while the post-harvest DIC percolation flux was more than one-third of the flux during growth. The Rs was controlled by production and diffusivity of CO2 in the soil. The DIC percolation flux was largely controlled by the pCO2 and the drainage flux due to low solution pH. Modeling suggested that increasing soil alkalinity during plant growth was due to nutrient buffering during root nitrate uptake.

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Technical note: mesocosm approach to quantification of carbon dioxide fluxes across the vadose zone

Biogeosciences Discussions ◽

10.5194/bgd-10-9947-2013 ◽

2013 ◽

Vol 10 (6) ◽

pp. 9947-9967

Author(s):

E. M. Thaysen ◽

S. Jessen ◽

P. Ambus ◽

C. Beier ◽

D. Postma ◽

...

Keyword(s):

Carbon Dioxide ◽

Vadose Zone ◽

Water Flux ◽

Lower Boundary ◽

Agricultural Practices ◽

Small Variation ◽

Technical Note ◽

Carbon Dioxide Partial Pressure ◽

Physical Factors ◽

Promising Tool

Abstract. Carbon dioxide (CO2) fluxes in the vadose zone are influenced by a complex interplay of biological, chemical and physical factors. A soil mesocosm system was designed to assess the effect of agricultural practices on carbon fluxes within and out of the vadose zone at controlled environmental conditions. Carbon dioxide partial pressure (pCO2), alkalinity, soil moisture and temperature were measured with depth and time, and DIC in the percolate was quantified using a sodium hydroxide trap. Results showed good reproducibility between two replicate mesocosms. The pCO2 varied between 0.2–1.1% and alkalinity was 0.1–0.6 meq L−1. The measured effluent DIC flux was 185–196 mg L−1 m−2 and in the same range as estimates derived from pCO2 and alkalinity in samples extracted from the side of the mesocosm column, and the water flux. The relatively small variation provides confidence that the mesocosm system is a promising tool for studying a~range of processes in unsaturated environments. Meanwhile, high suction at the mesocosm bottom applied to reduce water ponding during intensive irrigation caused degassing of dissolved CO2 from the water phase just below the outlet, leading to diffusion of dissolved CO2 across the lower boundary. Though not influencing DIC flux measurements to the groundwater, this lead to a lowering of the pCO2 in the stagnant water at the mesocosm bottom. A free-drainage boundary is suggested in order to avoid this effect.

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Technical Note: Precise quantitative measurements of total dissolved inorganic carbon from small amounts of seawater using a gas chromatographic system

Biogeosciences ◽

10.5194/bg-10-6601-2013 ◽

2013 ◽

Vol 10 (10) ◽

pp. 6601-6608 ◽

Cited By ~ 13

Author(s):

T. Hansen ◽

B. Gardeler ◽

B. Matthiessen

Keyword(s):

Inorganic Carbon ◽

Dissolved Inorganic Carbon ◽

Biological Effects ◽

Total Sample ◽

Measurement Range ◽

Technical Note ◽

Infrared Detection ◽

Detection Methods ◽

Total Dissolved Inorganic Carbon ◽

Ct Measurement

Abstract. Total dissolved inorganic carbon (CT) is one of the most frequently measured parameters used to calculate the partial pressure of carbon dioxide in seawater. Its determination has become increasingly important because of the rising interest in the biological effects of ocean acidification. Coulometric and infrared detection methods are currently favored in order to precisely quantify CT. These methods however are not sufficiently validated for CT measurements of biological experiments manipulating seawater carbonate chemistry with an extended CT measurement range (~1250–2400 μmol kg–1) compared to natural open ocean seawater (~1950–2200 μmol kg−1). The requirement of total sample amounts between 0.1–1 L seawater in the coulometric- and infrared detection methods potentially exclude their use for experiments working with much smaller volumes. Additionally, precise CT analytics become difficult with high amounts of biomass (e.g., phytoplankton cultures) or even impossible in the presence of planktonic calcifiers without sample pre-filtration. Filtration however, can alter CT concentration through gas exchange induced by high pressure. Addressing these problems, we present precise quantification of CT using a small, basic and inexpensive gas chromatograph as a CT analyzer. Our technique is able to provide a repeatability of ±3.1 μmol kg−1, given by the pooled standard deviation over a CT range typically applied in acidification experiments. 200 μL of sample is required to perform the actual CT measurement. The total sample amount needed is 12 mL. Moreover, we show that sample filtration is applicable with only minor alteration of the CT. The method is simple, reliable and with low cumulative material costs. Hence, it is potentially attractive for all researchers experimentally manipulating the seawater carbonate system.

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Technical Note: Highly precise quantitative measurements of total dissolved inorganic carbon from small amounts of seawater using a common gas chromatographic system: an alternative method compared to established detection systems

Biogeosciences Discussions ◽

10.5194/bgd-10-4439-2013 ◽

2013 ◽

Vol 10 (3) ◽

pp. 4439-4460 ◽

Cited By ~ 3

Author(s):

T. Hansen ◽

B. Gardeler ◽

B. Matthiessen

Keyword(s):

Carbon Dioxide ◽

Partial Pressure ◽

Inorganic Carbon ◽

Dissolved Inorganic Carbon ◽

Biological Effects ◽

Total Sample ◽

Technical Note ◽

Infrared Detection ◽

Detection Methods ◽

Total Dissolved Inorganic Carbon

Abstract. Total dissolved inorganic carbon (CT) is one of the most frequently measured parameters in order to calculate the partial pressure of carbon dioxide in seawater. Its measurement has become increasingly important because of the rising interest in the biological effects of acidification. The coulometric- and infrared detection methods are favoured to precisely quantify CT. However, these methods were not validated for CT samples from acidification experiments investigating biological responses to manipulated partial pressure of carbon dioxide (pCO2), which need an extended CT measurement range (~1250–2400 μmol kg−1) compared to natural open ocean seawater samples (~1950–2200 μmol kg−1). Additionally, the requirement of total sample amounts between 0.25–1 L seawater in the coulometric- and infrared detection methods exclude their use for experiments working with smaller volumes. Precise CT analytics also become difficult with high amounts of biomass (e.g. phytoplankton cultures) or even impossible in the presence of planktonic calcifiers without sample pre-filtration. However, filtration can alter CT concentration through gas exchange. Addressing these problems, we present precise quantification of CT using a small, basic and inexpensive gas chromatograph as a highly sensitive CT-analyzer. Our technique is able to provide a measurement precision of ± 3.7 μmol kg−1 and an accuracy of ± 1.2 μmol kg−1 in a CT range typically applied in acidification experiments. It requires sample sizes of only 200 μL taken from 10 mL pre-filtered samples or from a 10 mL sub-sampled seawater reference (Dickson standard). Our method is simple, reliable and with low cumulative analytical costs. Hence, it is potentially attractive for all scientists experimentally manipulating the seawater carbonate system.

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Impact of peatlands on carbon dioxide (CO<sub>2</sub>) emissions from the Rajang River and Estuary, Malaysia

10.5194/bg-2018-391 ◽

2018 ◽

Cited By ~ 1

Author(s):

Denise Müller-Dum ◽

Thorsten Warneke ◽

Tim Rixen ◽

Moritz Müller ◽

Antje Baum ◽

...

Keyword(s):

Carbon Dioxide ◽

Inorganic Carbon ◽

Dissolved Inorganic Carbon ◽

Co2 Flux ◽

Southeast Asian ◽

Dry Season ◽

Carbon Dioxide Partial Pressure ◽

Wet Season ◽

Peat Deposits ◽

Carbon Dioxide Co2

Abstract. Tropical peat-draining rivers are known as potentially large sources of carbon dioxide (CO2) to the atmosphere due to high loads of carbon they receive from surrounding soils. However, not many seasonally resolved data are available, limiting our understanding of these systems. We report the first measurements of carbon dioxide partial pressure (pCO2) in the Rajang River and Estuary, the longest river in Malaysia. The Rajang River catchment is characterized by extensive peat deposits found in the delta region, and by human impact such as logging, land use and river damming. pCO2 averaged 2919 ± 573 µatm during the wet season and 2732 ± 443 µatm during the dry season. This is at the low end of reported values for Southeast Asian peat-draining rivers, but higher than values reported for Southeast Asian rivers that do not flow through peat deposits. However, dissolved inorganic carbon (DIC) and δ13C-DIC data did not suggest that peatlands were an important source of inorganic carbon to the river, with an average DIC concentration of 203.9 ± 59.6 µmol L−1 and an average δ13C-DIC of −8.06 ± 1.90 ‰. Also, compared to rivers with similar peat coverage, the pCO2 in the Rajang was rather low. Thus, we suggest that peat coverage is, by itself, insufficient as sole predictor of CO2 emissions from peat-draining rivers, and that other factors, like the spatial distribution of peat in the catchment and pH, need to be considered as well. In the Rajang River, peatlands probably do not contribute much to the CO2 flux due to the proximity of the peatlands to the coast. CO2 fluxes to the atmosphere were 2.28 ± 0.52 gC m−2 d−1 (wet season) and 2.45 ± 0.45 gC m−2 d−1 (dry season), making the Rajang River a moderate source of carbon to the atmosphere.

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Dissolved inorganic carbon and alkalinity fluxes from coastal marine sediments: model estimates for different shelf environments and sensitivity to global change

Biogeosciences ◽

10.5194/bg-10-371-2013 ◽

2013 ◽

Vol 10 (1) ◽

pp. 371-398 ◽

Cited By ~ 85

Author(s):

V. Krumins ◽

M. Gehlen ◽

S. Arndt ◽

P. Van Cappellen ◽

P. Regnier

Keyword(s):

Organic Carbon ◽

Marine Sediments ◽

Reactive Transport ◽

Inorganic Carbon ◽

Dissolved Inorganic Carbon ◽

Transport Processes ◽

Coastal Marine Sediments ◽

Coastal Marine ◽

Depositional Flux ◽

Particulate Inorganic Carbon

Abstract. We present a one-dimensional reactive transport model to estimate benthic fluxes of dissolved inorganic carbon (DIC) and alkalinity (AT) from coastal marine sediments. The model incorporates the transport processes of sediment accumulation, molecular diffusion, bioturbation and bioirrigation, while the reactions included are the redox pathways of organic carbon oxidation, re-oxidation of reduced nitrogen, iron and sulfur compounds, pore water acid-base equilibria, and dissolution of particulate inorganic carbon (calcite, aragonite, and Mg-calcite). The coastal zone is divided into four environmental units with different particulate inorganic carbon (PIC) and particulate organic carbon (POC) fluxes: reefs, banks and bays, carbonate shelves and non-carbonate shelves. Model results are analyzed separately for each environment and then scaled up to the whole coastal ocean. The model-derived estimate for the present-day global coastal benthic DIC efflux is 126 Tmol yr−1, based on a global coastal reactive POC depositional flux of 117 Tmol yr−1. The POC decomposition leads to a carbonate dissolution from shallow marine sediments of 7 Tmol yr−1 (on the order of 0.1 Pg C yr−1. Assuming complete re-oxidation of aqueous sulfide released from sediments, the effective net flux of alkalinity to the water column is 29 Teq. yr−1, primarily from PIC dissolution (46%) and ammonification (33%). Because our POC depositional flux falls in the high range of global values given in the literature, the reported DIC and alkalinity fluxes should be viewed as upper-bound estimates. Increasing coastal seawater DIC to what might be expected in year 2100 due to the uptake of anthropogenic CO2 increases PIC dissolution by 2.3 Tmol yr−1and alkalinity efflux by 4.8 Teq. yr−1. Our reactive transport modeling approach not only yields global estimates of benthic DIC, alkalinity and nutrient fluxes under variable scenarios of ocean productivity and chemistry, but also provides insights into the underlying processes.

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Dissolved inorganic carbon and alkalinity fluxes from coastal marine sediments: model estimates for different shelf environments and sensitivity to global change

Biogeosciences Discussions ◽

10.5194/bgd-9-8475-2012 ◽

2012 ◽

Vol 9 (7) ◽

pp. 8475-8539 ◽

Cited By ~ 3

Author(s):

V. Krumins ◽

M. Gehlen ◽

S. Arndt ◽

P. van Cappellen ◽

P. Regnier

Keyword(s):

Organic Carbon ◽

Marine Sediments ◽

Reactive Transport ◽

Inorganic Carbon ◽

Dissolved Inorganic Carbon ◽

Transport Processes ◽

Coastal Marine Sediments ◽

Coastal Marine ◽

Depositional Flux ◽

Particulate Inorganic Carbon

Abstract. We present a one-dimensional reactive transport model to estimate benthic fluxes of dissolved inorganic carbon (DIC) and alkalinity (AT) from coastal marine sediments. The model incorporates the transport processes of sediment accumulation, molecular diffusion, bioturbation and bioirrigation, while the reactions included are the redox pathways of organic carbon oxidation, re-oxidation of reduced nitrogen, iron and sulfur compounds, pore water acid-base equilibria, and dissolution of particulate inorganic carbon (calcite, aragonite, and Mg-calcite). The coastal zone is divided into four environmental units with different particulate inorganic carbon (PIC) and particulate organic carbon (POC) fluxes: reefs, banks and bays, carbonate shelves and non-carbonate shelves. Model results are analyzed separately for each environment and then scaled up to the whole coastal ocean. The model-derived estimate for the present-day global coastal benthic DIC efflux is 126 Tmol yr−1, based on a global coastal reactive POC depositional flux of 117 Tmol yr−1. The POC decomposition leads to a~carbonate dissolution from shallow marine sediments of 7 Tmol yr−1 (on the order of 0.1 Pg C yr−1). Assuming complete re-oxidation of aqueous sulfide released from sediments, the effective net flux of alkalinity to the water column is 29 Teq yr−1, primarily from PIC dissolution (46%) and ammonification (33%). Because our POC depositional flux falls in the high range of global values given in the literature, the reported DIC and alkalinity fluxes should be viewed as upper-bound estimates. Increasing coastal seawater DIC to what might be expected in year 2100 due to the uptake of anthropogenic CO2 increases PIC dissolution by 2.3 Tmol yr−1 and alkalinity efflux by 4.8 Teq yr−1. Our reactive transport modeling approach not only yields global estimates of benthic DIC, alkalinity and nutrient fluxes under variable scenarios of ocean productivity and chemistry, but also provides insights into the underlying processes.

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