Seasonal variability of methane in the rivers and lagoons of Ivory Coast (West Africa)

Koné, Y. J. M.; Abril, Gwénaël; Delille, Bruno; Borges, Alberto

doi:10.1007/s10533-009-9402-0

Cited by 93 publications

(87 citation statements)

References 60 publications

(116 reference statements)

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“…For the Nyong, the CH 4 was determined with a SRI 8610C GC-FID calibrated with CH 4 :N 2 mixtures (Air Liquide France) of 2, 10 and 100 ppm CH 4 . For the Ivory Coast rivers, the CH 4 was determined by GC-FID, as described elsewhere 34 . The overall precision of measurements was ±3.9% (n = 1,057 duplicate measurements) and ±3.2% (n = 900 duplicate measurements) for CH 4 and N 2 O, respectively.…”

Section: Methodsmentioning

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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Section: Methodsmentioning

confidence: 99%

Globally significant greenhouse-gas emissions from African inland waters

et al. 2015

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“…flux densities between 0.7 and 49 mmol m −2 yr −1 in the estuaries of the Sundarban mangrove ecosystem. However, we caution that the comparison suffers from the different approaches to determining the gas exchange velocity k. Koné et al (2010), Shalini et al (2006), Biswas et al (2007), and Rao and Sarma (2013) used empirical equations relating k to wind speed, while we used estimates based on floating chamber measurements. We refer to our discussion in Müller et al (2016), where we showed that our estimates derived by floating chamber measurements yielded higher values than if we had used empirical relationships with wind speed.…”

Section: Chmentioning

confidence: 99%

Nitrous oxide and methane in two tropical estuaries in a peat-dominated region of northwestern Borneo

et al. 2016

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Abstract. Estuaries are sources of nitrous oxide (N 2 O) and methane (CH 4 ) to the atmosphere. However, our present knowledge of N 2 O and CH 4 emissions from estuaries in the tropics is very limited because data are scarce. In this study, we present first measurements of dissolved N 2 O and CH 4 from two estuaries in a peat-dominated region of northwestern Borneo. Two campaigns (during the dry season in June 2013 and during the wet season in March 2014) were conducted in the estuaries of the Lupar and Saribas rivers. Median N 2 O concentrations ranged between 7.2 and 12.3 nmol L −1 and were higher in the marine end-member (13.0 ± 7.0 nmol L −1 ). CH 4 concentrations were low in the coastal ocean (3.6 ± 0.2 nmol L −1 ) and higher in the estuaries (medians between 10.6 and 64.0 nmol L −1 ). The respiration of abundant organic matter and presumably anthropogenic input caused slight eutrophication, which did not lead to hypoxia or enhanced N 2 O concentrations, however. Generally, N 2 O concentrations were not related to dissolved inorganic nitrogen concentrations. Thus, the use of an emission factor for the calculation of N 2 O emissions from the inorganic nitrogen load leads to an overestimation of the flux from the Lupar and Saribas estuaries. N 2 O was negatively correlated with salinity during the dry season, which suggests a riverine source. In contrast, N 2 O concentrations during the wet season were not correlated with salinity but locally enhanced within the estuaries, implying that there were additional estuarine sources during the wet (i.e., monsoon) season. Estuarine CH 4 distributions were not driven by freshwater input but rather by tidal variations. Both N 2 O and CH 4 concentrations were more variable during the wet season. We infer that the wet season dominates the variability of the N 2 O and CH 4 concentrations and subsequent emissions from tropical estuaries. Thus, we speculate that any changes in the Southeast Asian monsoon system will lead to changes in the N 2 O and CH 4 emissions from these systems. We also suggest that the ongoing cultivation of peat soil in Borneo is likely to increase N 2 O emissions from these estuaries, while the effect on CH 4 remains uncertain.

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“…Other human impacts that affect carbon and nitrogen cycling in river networks that can potentially influence cycling of GHGs are river bank stabilization and floodplain drainage that disrupt the river-wetland connectivity that is important for CO 2 and CH 4 dynamics in rivers (Abril et al, 2014;Teodoru et al, 2015;Borges et al, 2015aBorges et al, , 2015bSieczko et al, 2016). The introduction of invasive animal species such as the zebra mussel (Dreissena polymorpha) in US rivers and lakes (Caraco et al, 1997;Evans et al, 2011) (Hussner, 2012), some with high production and biomass (Hussner, 2009); invasive floating macrophytes such as the water hyacinth (Eichhornia crassipes) have been documented to increase CO 2 and CH 4 levels in tropical rivers (Koné et al, 2009(Koné et al, , 2010, but this remains undocumented in temperate rivers.…”

Section: Introductionmentioning

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

159

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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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Seasonal variability of methane in the rivers and lagoons of Ivory Coast (West Africa)

Cited by 93 publications

References 60 publications

Globally significant greenhouse-gas emissions from African inland waters

Globally significant greenhouse-gas emissions from African inland waters

Nitrous oxide and methane in two tropical estuaries in a peat-dominated region of northwestern Borneo

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

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