Technical Note: Large overestimation of &amp;lt;i&amp;gt;p&amp;lt;/i&amp;gt;CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; calculated from pH and alkalinity in acidic, organic-rich freshwaters

Abril, Gwénaël; Bouillon, Steven; Darchambeau, François; Teodoru, CR; Marwick, Trent R.; Tamooh, Fredrick; Omengo, Fred; Geeraert, Naomi; Deirmendjian, Loris; Polsenaere, Pierre; Borges, Alberto

doi:10.5194/bgd-11-11701-2014

Cited by 89 publications

(142 citation statements)

References 42 publications

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“…The pCO 2 was measured with an infra-red gas analyser (Li-Cor Li-840) within minutes after sampling, with head-space equilibration technique (Abril et al, 2015) by creating a headspace with ambient air in the polypropylene syringes (1:1 ratio of air and water). The Li-840 was calibrated with a suite of CO 2 :N 2 mixtures (Air Liquide Belgium) with mixing ratios of 388, 813, 3788 and 8300 ppm CO 2 .…”

Section: Methodsmentioning

confidence: 99%

Effects of agricultural land use on fluvial carbon dioxide, methane and nitrous oxide concentrations in a large European river, the Meuse (Belgium)

Borges

Darchambeau

Lambert

et al. 2018

Science of The Total Environment

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146

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• Large data-set of CO 2 , CH 4 , and N 2 O in the surface waters of the Meuse River We report a data-set of CO 2 , CH 4 , and N 2 O concentrations in the surface waters of the Meuse river network in Belgium, obtained during four surveys covering 50 stations (summer 2013 and late winter 2013, 2014 and 2015), from yearly cycles in four rivers of variable size and catchment land cover, and from 111 groundwater samples. Surface waters of the Meuse river network were over-saturated in CO 2 , CH 4 , N 2 O with respect to atmospheric equilibrium, acting as sources of these greenhouse gases to the atmosphere, although the dissolved gases also showed marked seasonal and spatial variations. Seasonal variations were related to changes in freshwater discharge following the hydrological cycle, with highest concentrations of CO 2 , CH 4 , N 2 O during low water owing to a longer water residence time and lower currents (i.e. lower gas transfer velocities), both contributing to the accumulation of gases in the water column, combined with higher temperatures favourable to microbial processes. Inter-annual differences of discharge also led to differences in CH 4 and N 2 O that were higher in years with prolonged low water periods. Spatial variations were mostly due to differences in land cover over the catchments, with systems dominated by agriculture (croplands and pastures) having higher CO 2 , CH 4 , N 2 O levels than forested systems. This seemed to be related to higher levels of dissolved and particulate organic matter, as well as dissolved inorganic nitrogen in agriculture dominated systems compared to forested ones. Groundwater had very low CH 4 concentrations in the shallow and unconfined aquifers (mostly fractured limestones) of the Contents lists available at ScienceDirectScience of the Total Environment j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / s c i t o t e n vMeuse basin, hence, should not contribute significantly to the high CH 4 levels in surface riverine waters. Owing to high dissolved concentrations, groundwater could potentially transfer important quantities of CO 2 and N 2 O to surface waters of the Meuse basin, although this hypothesis remains to be tested.

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Section: Methodsmentioning

confidence: 99%

Effects of agricultural land use on fluvial carbon dioxide, methane and nitrous oxide concentrations in a large European river, the Meuse (Belgium)

Borges

Darchambeau

Lambert

et al. 2018

Science of The Total Environment

Self Cite

146

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“…The dissolved gases were measured with a uniform method based on the headspace technique, either directly in the field by infrared gas analysis (IRGA; for CO 2 ), or on return in the laboratory by gas chromatography (GC; for CH 4 and N 2 O). Our analysis excludes p CO2 data computed from pH and total alkalinity, because of strong biases due to the interference from organic acids, in particular in organic C rich black waters 15,16 .…”

Section: Methodsmentioning

confidence: 99%

“…In the Amazon basin, CO 2 emissions from floodplain lakes 11 and from river channels 12,13 have been attributed to organic and inorganic C from wetlands (flooded forest and macrophytes). Finally, recently recognized biases in computed CO 2 data traditionally used in inland water studies 15,16 highlight the requirement for careful data-quality checking and future emphasis on high-quality direct CO 2 measurements.In this study, we report an extensive compilation of dissolved CO 2 , CH 4 and N 2 O concentrations (Supplementary Table 1) gathered in 12 river basins in sub-Saharan Africa (SSA; Fig. 1 and Supplementary Fig.…”

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confidence: 99%

Globally significant greenhouse-gas emissions from African inland waters

et al. 2015

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Carbon dioxide emissions to the atmosphere from inland waters-streams, rivers, lakes and reservoirs-are nearly equivalent to ocean and land sinks globally. Inland waters can be an important source of methane and nitrous oxide emissions as well, but emissions are poorly quantified, especially in Africa. Here we report dissolved carbon dioxide, methane and nitrous oxide concentrations from 12 rivers in sub-Saharan Africa, including seasonally resolved sampling at 39 sites, acquired between 2006 and 2014. Fluxes were calculated from published gas transfer velocities, and upscaled to the area of all sub-Saharan African rivers using available spatial data sets. Carbon dioxide-equivalent emissions from river channels alone were about 0.4 Pg carbon per year, equivalent to two-thirds of the overall net carbon land sink previously reported for Africa. Including emissions from wetlands of the Congo river increases the total carbon dioxide-equivalent greenhouse-gas emissions to about 0.9 Pg carbon per year, equivalent to about one quarter of the global ocean and terrestrial combined carbon sink. Riverine carbon dioxide and methane emissions increase with wetland extent and upland biomass. We therefore suggest that future changes in wetland and upland cover could strongly a ect greenhouse-gas emissions from African inland waters.C limate predictions necessitate a full and robust account of natural and anthropogenic greenhouse-gas (GHG) fluxes, especially for CO 2 (refs 1-3), CH 4 (ref. 4) and N 2 O (ref. 5), which together accounted for 94% of the anthropogenic global radiative forcing by well-mixed GHGs in 2011 relative to 1750 (ref. 6). Inland waters (streams, rivers, lakes and reservoirs) are increasingly recognized as important sources of GHGs to the atmosphere, with global CO 2 and CH 4 emissions estimated at 2.1 PgC yr −1 (ref.3) and 0.7 PgC yr −1 (CO 2 -equivalents; CO 2 e) (ref. 4) (1 Pg = 10 15 g), respectively. Considering that the oceanic and land carbon (C) sinks correspond to ∼1.5 and ∼2.0 PgC yr −1 (ref. 7), respectively, the GHG flux from inland waters is significant in the global C budget.In a recent global compilation of inland CO 2 data 3 , <20 data points (out of 6,708, that is, <0.3%) represented African inland waters (with the exception of South Africa, which has been densely sampled), even though they account for ∼12% of both global freshwater discharge 8 and riverine surface area 3 , and include some of the largest rivers and lakes in the world. Equally for the global CH 4 database, there is a strong under-representation of tropical inland waters, whereby a recent synthesis 4 resorted to extrapolating CH 4 fluxes from temperate rivers.The prevailing large uncertainty involved in GHG flux estimates for inland waters, essentially due to the paucity of available data, is coupled to a poor understanding of underlying processes, both of which preclude gauging of future fluxes in response to human pressures. In particular, there is a need to further understand the link between inland water GHG fluxes and ...

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“…The pCO 2 was measured with an infra-red gas analyzer (Licor Li-840) after headspace equilibration in the syringe (Abril et al, 2015;Borges et al, 2015). The Li-840 was calibrated with N 2 and certified CO 2 :N 2 mixtures (Air Liquide, Belgium) of 388, 813, 3788 and 8300 ppm CO 2 .…”

Section: Ch 4 Oxidation Measurements and Water Column Chemical Analysesmentioning

confidence: 99%

Emission and oxidation of methane in a meromictic, eutrophic and temperate lake (Dendre, Belgium)

et al. 2017

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h i g h l i g h t sThe studied lake was meromictic and characterized by high methane, nutrients and sulfate concentrations in the water column. High aerobic and anaerobic methane oxidation rates were observed in the water column, and were dependent on the season. Anaerobic methane oxidation was linked to sulfate reduction, and potentially to nitrate reduction. Despite high methane oxidation rates, methane fluxes to the atmosphere were high. a r t i c l e i n f o a b s t r a c tWe sampled the water column of the Dendre stone pit lake (Belgium) in spring, summer, autumn and winter. Depth profiles of several physico-chemical variables, nutrients, dissolved gases (CO 2 , CH 4 , N 2 O), sulfate, sulfide, iron and manganese concentrations and d 13 C-CH4 were determined. We performed incubation experiments to quantify CH 4 oxidation rates, with a focus on anaerobic CH 4 oxidation (AOM), without and with an inhibitor of sulfate reduction (molybdate). The evolution of nitrate and sulfate concentrations during the incubations was monitored. The water column was anoxic below 20 m throughout the year, and was thermally stratified in summer and autumn. High partial pressure of CO 2 and CH 4 and high concentrations of ammonium and phosphate were observed in anoxic waters. Important nitrous oxide and nitrate concentration maxima were also observed (up to 440 nmol L À1 and 80 mmol L À1 , respectively). Vertical profiles of d 13 C-CH 4 unambiguously showed the occurrence of AOM. Important AOM rates (up to 14 mmol L À1 d À1 ) were observed and often co-occurred with nitrate consumption peaks, suggesting the occurrence of AOM coupled with nitrate reduction. AOM coupled with sulfate reduction also occurred, since AOM rates tended to be lower when molybdate was added. CH 4 oxidation was mostly aerobic (~80% of total oxidation) in spring and winter, and almost exclusively anaerobic in summer and autumn. Despite important CH 4 oxidation rates, the estimated CH 4 fluxes from the water surface to the atmosphere were high (mean of 732 mmol m À2 d À1 in spring, summer and autumn, and up to 12,482 mmol m À2 d À1 in winter).

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Technical Note: Large overestimation of <i>p</i>CO<sub>2</sub> calculated from pH and alkalinity in acidic, organic-rich freshwaters

Cited by 89 publications

References 42 publications

Effects of agricultural land use on fluvial carbon dioxide, methane and nitrous oxide concentrations in a large European river, the Meuse (Belgium)

Effects of agricultural land use on fluvial carbon dioxide, methane and nitrous oxide concentrations in a large European river, the Meuse (Belgium)

Globally significant greenhouse-gas emissions from African inland waters

Emission and oxidation of methane in a meromictic, eutrophic and temperate lake (Dendre, Belgium)

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