[en] The Oubangui is a major tributary of the Congo River, draining an area of 500 000 km2 mainly consisting of wooded savannahs. Here, we report results of a one year long, 2-weekly sampling campaign in Bangui (Central African Republic) since March 2010 for a suite of physicochemical and biogeochemical characteristics, including total suspended matter (TSM), bulk concentration and stable isotope composition of particulate organic carbon (POC and 13CPOC), particulate nitrogen (PN and 15NPN), dissolved organic carbon (DOC and 13CDOC), dissolved inorganic carbon (DIC and 13CDIC), dissolved greenhouse gases (CO2, CH4 and N2O), and dissolved ignin composition. 13C signatures of both POC and DOC showed strong seasonal variations −30.6 to −25.8 ‰, and −31.8 to −27.1 ‰, respectively), but their different timing indicates that the origins of POC and DOC may vary strongly over the hydrograph and are largely ncoupled, differing up to 6‰ in 13C signatures. Dissolved lignin characteristics (carbon- ormalised yields, cinnamyl:vanillyl phenol ratios, and vanillic acid to vanillin ratios) showed arked differences between high and low discharge conditions, consistent with major seasonal ariations in the sources of dissolved organic matter. We observed a strong seasonality in pCO2, ranging between 470 ± 203 ppm for Q<1000m3 s−1 (n = 10) to a maximum of 3750 pm during the first stage of the rising discharge. The low POC/PN ratios, high %POCand low and variable 13CPOC signatures during low flow conditions suggest that the majority of the POC pool during this period consists of in situ produced phytoplankton, consistent with oncurrent pCO2 (partial pressure of CO2) values only slightly above and, occasionally, below atmospheric equilibrium. Water-atmosphere CO2 fluxes estimated using two independent pproaches averaged 105 and 204 gCm−2 yr−1, i.e. more than an order of magnitude lower than current estimates for large tropical rivers globally. Although tropical rivers are often ssumed to show much higher CO2 effluxes compared to temperate systems, we show that in situ production may be high enough to dominate the particulate organic carbon pool, and lower CO2 values to near equilibrium values during low discharge conditions. The total annual flux of TSM, POC, PN, DOC and DIC are 2.33 Tg yr−1, 0.14 TgC yr−1, 0.014 TgNyr−1, 0.70 TgC yr−1, and 0.49 Tg Cyr−1, respectively. While our TSM and POC fluxes are similar to previous stimates for the Oubangui, DOC fluxes were 30% higher and bicarbonate fluxes were 35% ower than previous reports. DIC represented 58% of the total annual C flux, and under the ssumptions that carbonate weathering represents 25% of the DIC flux and that CO2 from espiration drives chemical weathering, this flux is equivalent to 50% of terrestrial-derived riverine C transport.
Research center :
FOCUS - Freshwater and OCeanic science Unit of reSearch - ULiège
Disciplines :
Aquatic sciences & oceanology
Author, co-author :
Bouillon, S.
Yambélé, A.
Spencer, R.G.M.
Gillikin, D.P
Hernes, P.J.
Six, J.
Merckx, R.
Borges, Alberto ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Océanographie chimique
Language :
English
Title :
Organic matter sources, fluxes and greenhouse gas exchange in the Oubangui River (Congo River basin)
Publication date :
2012
Journal title :
Biogeosciences
ISSN :
1726-4170
eISSN :
1726-4189
Publisher :
European Geosciences Union, Katlenburg-Lindau, Germany
Alin, S. R., Rasera, M. F. F. L., Salimon, C. I., Richey, J. E., Holtgrieve, G. W., Krusche, A. V., and Snidvongs, A.: Physical controls on carbon dioxide transfer velocity and flux in low-gradient river systems and implications for regional carbon budgets, J. Geophys. Res.-Biogeosci., 116, GO1009, doi:10.1029/2010JG001398, 2011.
Aufdenkampe, A. K., Mayorga, E., Raymond, P. A., Melack, J. M., Doney, S. C., Alin, S. R., Aalto, R. E., and Yoo, K.: Riverine coupling of biogeochemical cycles between land, oceans, and atmosphere, Front. Ecol. Environ., 9, 53-60, doi:10.1890/100014, 2011.
Bastviken, D., Tranvik, L. J., Downing, J. A., Crill, P. M., and Enrich-Prast, A.: Freshwater methane emissions offset the continental carbon sink, Science, 331, p. 50, 2011.
Battin, T. J., Kaplan, L. A., Findlay, S., Hopkinson, C. S., Marti, E., Packman, A. I., Newbold, J. D., and Sabater, F.: Biophysical controls on organic carbon fluxes in fluvial networks, Nature Geosci., 1, 95-100, 2008.
Baulch, H. M., Schiff, S. L., Maranger, R., and Dillon, P. J.: Nitrogen enrichment and the emissons of nitrous oxide from streams, Glob. Biogeochem. Cy., 25, GB4013, doi:10.1029/2011GB004047, 2012.
Beaulieu, J. J., Shuster, W. D., and Rebholz, J. A.: Nitrous oxide emissions from a large, impounded river: The Ohio River, Environ. Sci. Technol., 44, 7527-7533, 2010.
Beaulieu, J. J., Tank, J. L., Hamilton, S. K., Wollheim, W. M., Hall, R. O., Mulholland, P. J., Peterson, B. J., Ashkenas, L. R., Cooper, L. W., Dahm, C. N., Dodds, W. K., Grimm, N. B., Johnson, S. L., McDowell, W. H., Poole, G. C., Valett, H. M., Arango, C. P., Bernot, M. J., Burgin, A. J., Crenshaw, C. L., Helton, A. M., Johnson, L. T., O'Brien, J. M., Potter, J. D., Sheibley, R. W., Sobota, D. J., and Thomas, S. M., Nitrous oxide emission from denitrification in stream and river networks, P. Natl. Acad. Sci. USA, 108, 214-219, 2011.
Bird, M. I., Robinson, R. A. J., Win Oo, N., Maung Aye, M., Lu, X. X., Higgitt, D. L., Swe, A., Tun, T., Lhaing Win, S., Sandar Aye, K., Mi Mi Win, K., and Hoey, T. B.: A preliminary estimate of organic carbon transport by the Ayeyarwady (Irrawady) and Thanlwin (Salween) rivers of Myanmar, Quaternary Int., 186, 113-122, 2008.
Borges, A. V., Delille, B., Schiettecatte, L.-S., Gazeau, F., Abril, G., and Frankignoulle, M.: Gas transfer velocities of CO2 in three European estuaries (Randers Fjord, Scheldt and Thames), Limnol. Oceanogr., 49, 1630-1641, 2004. (Pubitemid 39320755)
Bouillon, S., Korntheuer, M., Baeyens, W., and Dehairs, F.: A new automated setup for stable isotope analysis of dissolved organic carbon, Limnol. Oceanogr. Methods, 4, 216-226, 2006. (Pubitemid 44395362)
Bouillon, S., Abril, G., Borges, A. V., Dehairs, F., Govers, G., Hughes, H. J., Merckx, R., Meysman, F. J. R., Nyunja, J., Osburn, C., and Middelburg, J. J.: Distribution, origin and cycling of carbon in the Tana River (Kenya): a dry season basin-scale survey from headwaters to the δ, Biogeosciences, 6, 2475-2493, doi:10.5194/bg-6-2475-2009, 2009.
Boyer, E. W., Hornberger, G. M., Bencala, K. E., and McKnight, D.: Overview of a simple model describing variations of dissolved organic carbon in an upland catchment, Ecol. Modell., 86, 183-188, 1996.
Brunet, F., Dubois, K., Veizer, J., Nkoue Ndondo, G. R., Ndam Ngoupayou, J. R., Boeglin, J. L., and Probst, J. L.: Terrestrial and fluvial carbon fluxes in a tropical watershed: Nyong basin, Cameroun, Chem. Geol. 2, 563-572, 2009.
Bullen, T. D. and Kendall, C.: Tracing of weathering reactions and water flowpaths: a multi-isotope approach, in: Isotope tracers in catchment hydrology, edited by: Kendall, C. and McDonnell, J. J., Elsevier Science B.V., Amsterdam, 611-646, 1998.
Butman, D. and Raymond, P. A.: Significant efflux of carbon dioxide from streams and rivers in the United States, Nature Geosci., 4, 821-822, 2011.
Cerling, T. E., Hart, J. A., and Hart, T. B.: Stable isotope ecology in the Ituri Forest, Oecologia, 138, 5-12, 2004. (Pubitemid 38161930)
Chanat, J. G., Rice, K. C., and Hornberger, G. M.: Consistency in patterns in concentration-discharge plots, Water Resour. Res., 38, 1147, doi:10.1029/2001WR000971, 2002.
Ciais, P., Bombelli, A., Williams, M., Piao, S.L., Chave, J., Ryan, C.M., Henry, M., Brender, P., and Valentini, R.: The carbon balance of Africa: synthesis of recent research studies, Philos. Trans. Roy. Soc. A, 369, 2038-2057, 2011.
Coe, M. T., Costa, M. H., and Soares-Filho, B. S.: The influence of historical and potential future deforestation on the stream flow of the Amazon River - Land surface processes and atmospheric feedbacks, J. Hydrol., 369, 165-174, 2009.
Cole, J. J. and Caraco, N. F.: Carbon in catchments: connecting terrestrial carbon losses with aquatic metabolism, Mar. Freshwat. Res., 52, 101-110, 2001a. (Pubitemid 32116662)
Cole, J. J. and Caraco, N. F.: Emissions of nitrous oxide (N 2O) from a tidal, freshwater river, the Hudson River, New York, Environ. Sci. Technol., 35, 991-996, 2001b. (Pubitemid 32880814)
Cole, J. J., Prairie, Y. T., Caraco, N. F., McDowell, W. H., Tranvik, L. J., Striegl, R. G., Duarte, C. M., Kortelainen, P., Downing, J. A., Middelburg, J. J., and Melack, J.: Plumbing the global carbon cycle: integrating inland waters into the terrestrial carbon budget, Ecosystems, 10, 171-184, 2007. (Pubitemid 46825795)
Coynel, A., Seyler, P., Etcheber, H., Meybeck, M., and Orange, D.: Spatial and seasonal dynamics of total suspended sediment and organic carbon species in the Congo River, Global Biogeochem. Cy., 19, GB4019, doi:10.1029/2004GB002335, 2005. (Pubitemid 43280682)
De Angelis, M. A. and Lilley, M. D.: Methane in surface waters of Oregon estuaries and rivers, Limnol. Oceanogr., 32, 716-722, 1987.
De Angelis, M. A. and Scranton, M. I.: Fate of methane in the Hudson river and estuary, Global Biogeochem. Cy., 7, 509-523, 2003.
Devol, A. H. and Richey, J. E.: Seasonal dynamics of methane emissions from the Amazon River floodplain to the troposphere, J. Geophys. Res., 95, 417-426, 1990.
Doctor, D. H., Kendall, C., Sebestyen, S. D., Shanley, J. B., Ohte, N., and Boyer, E. W.: Carbon isotope fractionation of dissolved inorganic carbon (DIC) due to outgassing of carbon dioxide from a headwater stream, Hydrol. Process., 22, 2410-2423, 2008.
Dosskey, M. G. and Bertsch, P. M.: Forest sources and pathways of organic matter transport to a blackwater stream: a hydrological approach, Biogeochemistry, 24, 1-19, 1994. (Pubitemid 2069900)
Duarte, C. M. and Prairie, Y. T.: Prevalence of heterotrophy and atmospheric CO2 emissions from aquatic ecosystems, Ecosystems, 8, 862-870, 2005. (Pubitemid 41619391)
Duveiller, G., Defourny, P., Desclée, B., and Mayaux, P.: Deforestation in Central Africa: estimates at regional, national and landscape levels by advanced processing of systematically-distributed Landsat extracts, Remote Sens. Environ., 112, 1969-1981, 2008.
Eckard, R. S., Hernes, P. J., Bergamaschi, B. A., Stepanauskas, R., and Kendall, C.: Landscape scale controls on the vascular plant component of dissolved organic carbon across a freshwater δ, Geochim. Cosmochim. Acta, 71, 5968-5984, 2007. (Pubitemid 350161557)
Ellis, E. E., Richey, J. E., Aufdenkampe, A. K., Krusche, A. V., Quay, P. D., Salimon, C. I., and da Cunha, H. B.: Factors controlling water-column respiration in rivers of the central and southwestern Amazon Basin, Limnol. Oceanogr., 57, 527-540, 2012.
Evans, C. and Davies, T. D.: Causes of concentration/discharge hysteresis and its potential as a tool for analysis of episode hydrochemistry, Water Resour. Res., 34, 129-137, 1998. (Pubitemid 28031195)
Forster, P., Ramaswamy, V., Artaxo, P., Berntsen, T., Betts, R., Fahey, D. W., Haywood, J., Lean, J., Lowe, D. C., Myhre, G., Nganga, J., Prinn, R., Raga, G., Schulz, M., and Van Dorland, R.: Changes in Atmospheric Constituents and in Radiative Forcing, in: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, edited by: Solomon, S., Qin, D., Manning, M., Chen, Z., Marquis, M., Averyt, K. B., Tignor, M., and Miller, H. L., Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 2007.
Gadel, F., Serve, L., and Bruchet, A.: Caractérisation chimique de la fraction organique des suspensions du fleuve Congo, 97-107, Grands Bassins Fluviaux, Paris, 22-24 November 1993.
Gillikin, D. P. and Bouillon, S.: Determination of δ18O of water and δ13C of dissolved inorganic carbon using a simple modification of an elemental analyzer - isotope ratio mass spectrometer (EA-IRMS): an evaluation, Rapid Comm. Mass Spectrom., 21, 1475-1478, 2007. (Pubitemid 46663687)
Gudasz, C., Bastviken, D., Steger, K., Premke, K., Sobek, S., and Tranvik, L. J.: Temperature-controlled organic carbon mineralization in lake sediments, Nature, 466, 478-482, 2010.
Guérin, F., Abril, G., Tremblay, A., and Delmas, R.: Nitrous oxide emissions from tropical hydroelectrical reservoirs, Geophys. Res. Lett., 35, L06404, doi:10.1029/2007GL033057, 2008. (Pubitemid 351738329)
Hedges, J. I. and Ertel, J. R.: Characterization of lignin by gas capillary chromatography of cupric oxide oxidation-products, Anal. Chem., 54, 174-178, 1982.
Hedges, J. I. and Mann, D. C.: The characterization of plant tissues by their lignin oxidation products, Geochim. Cosmochim. Acta, 43, 1803-1807, 1979.
Hedges, J. I., Clark, W. A., Quay, P. D., Richey, J. E., Devol, A. H., and Santos, U. D.: Compositions and fluxes of particulate organic material in the Amazon River, Limnol. Oceanogr., 31, 717-738, 1986.
Hellings, L., Dehairs, F., Van Damme, S., and Baeyens, W.: Dissolved inorganic carbon in a highly polluted estuary (the Scheldt), Limnol. Oceanogr., 46, 1406-1414, 2001. (Pubitemid 32824616)
Hernes, P. J., Robinson, A. C., and Aufdenkampe, A. K.: Fractionation of lignin during leaching and sorption and implications for organic matter "freshness", Geophys. Res. Lett., 34, L17401, doi:10.1029/ 2007GL031017, 2007. (Pubitemid 350065255)
Kohn, M. J.: Carbon isotope compositions of terrestrial C3 plants as indicators of (paleo)ecology and (paleo)climate, P. Natl. Acad. Sci., 107, 19691-19695, 2010.
Koné, Y. J. M., Abril, G., Kouadio, K. N., Delille, B., and Borges, A. V.: Seasonal variability of carbon dioxide in the rivers and lagoons of Ivory Coast (West Africa), Estuaries and Coasts, 32, 246-260, 2009.
Koné, Y. J. M., Abril, G., Delille, B., and Borges, A. V.: Seasonal variability of methane in the rivers and lagoons of Ivory Coast (West Africa), Biogeochemistry, 100, 21-37, 2010.
Lambert, T., Pierson-Wickmann, A. C., Gruau, G., Thibault, J. N., and Jaffrezic, A.: Carbon isotopes as tracers of dissolved organic carbon sources and water pathways in headwater catchments, J. Hydrol., 402, 228-238, 2011.
Laraque, A., Mahé, G., Orange, D., and Marieu, B.: Spatiotemporal variations in hydrological regime within Central Africa during the XXth century, J. Hydrol., 245, 104-117, 2001. (Pubitemid 32386210)
Laraque, A., Bricquet, J. P., Pandi, A., and Olivry, J. C.: A review of material transport by the Congo River and its tributaries, Hydrol. Process., 23, 3216-3224, 2009.
Lewis, E. and Wallace, D. W. R.: Program developed for CO2 system calculations. ORNL/CDIAC-105. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, US Department of Energy, Oak Ridge, Tennessee, 1998.
Ludwig, W., Probst, J. L., and Kempe, S.: Predicting the oceanic input of organic carbon by continental erosion, Global Biogeochem. Cy., 10, 23-41, 1996.
Lyons, W. B., Nezat, C. A., Carey, A. E., and Hicks, D. M.: Organic carbon flux to the ocean from high-standing islands, Geology, 30, 443-446, 2002. (Pubitemid 34667937)
Mariotti, A., Gadel, F., Giresse, P., and Kinga-Mouzeo: Carbon isotope composition and geochemistry of particulate organic matter in the Congo River (Central Africa): application to the study of Quaternary sediments off the mouth of the river, Chem. Geol., 86, 345-357, 1991.
Marotta, H., Duarte, C. M., Sobek, S., and Enrich-Past, A.: Large CO 2 disequilibria in tropical lakes, Global Biogeochem. Cy., 23, GB4022, doi:10.1029/2008GB003434, 2009.
Mayorga, E., Aufdenkampe, A. K., Masiello, C. A., Krusche, A. V., Hedges, J. I., Quay, P. D., Richey, J. E., and Brown, T. A.: Young organic matter as a source of carbon dioxide outgassing from Amazonian rivers, Nature, 436, 538-541, 2005. (Pubitemid 41112924)
Meybeck, M.: Carbon, nitrogen, and phosphorus transport by world rivers, Am. J. Science 282, 401-450, 1982. (Pubitemid 12083513)
Millero, F. J.: The thermodynamics of the carbonic acid system in seawater, Geochim. Cosmochim. Acta, 43, 1651-1661, 1979.
Milliman, J. D. and Svytski, J. P. M.: Geomorphic/tectonic control of sediment discharge to the ocean: the importance of small mountaineous rivers, J. Geol., 100, 525-544, 1992. (Pubitemid 23374791)
Nkounkou, R. R. and Probst, J. L.: Hydrology and Geochemistry of the Congo River System, in: Transport of carbon and minerals in major world rivers, edited by: Degens, E. T., Kempe, S., and WeiBin, G., Mitt. Geol.-Paläont Inst. Univ. Hamburg, SCOPE/UNEP Sonderbd., 64, 483-508, 1987.
O'Connor, D. J. and Dobbins, E.: Mechanism of reaeration in natural streams, Trans. Am. Soc. Civil Engin., 123, 641-684, 1958.
Olivry, J. C. (Ed.): Opération Grands Bassins Fluviaux: premiers résultats, années 1987 à 1989, Note d'information no. 3, septembre 1989, Montpellier: ORSTOM, 124 pp., 1989.
Opsahl, S. and Benner, R.: Early diagenesis of vascular plant tissues: lignin and cutin decomposition and biogeochemical implications, Geochim. Cosmochim. Acta, 59, 4889-4904, 1995. (Pubitemid 26441420)
Orange, D., Wesselink, A. J., Mahé, G., and Feizoure, C. T.: The effects of climate changes on river baseflow and aquifer storage in Central Africa, in: Sustainability of Water Resources under increasing Uncertainty, IAHS publ. 240, 113-123, 1997. (Pubitemid 127553266)
Probst, J. L., Nkounkou, R. R., Krempp, G., Bricquet, J. P., Thiébaux, J. P., and Olivry, J. C.: Dissolved major elements exported by the Congo and the Ubangi rivers during the period 1987-1989, J. Hydrol., 135, 237-257, 1992.
Probst, J. L., Mortatti, J., and Tardy, Y.: Carbon river fluxes and weathering CO2 consumption in the Congo and Amazon river basins, Appl. Geochem., 9, 1-13, 1994.
Raymond, P. A. and Cole, J. J.: Gas exchange in rivers and estuaries: choosing a gas transfer velocity, Estuaries, 24, 312-317, 2001. (Pubitemid 32515899)
Remington, S. M., Strahm, B. D., Neu, V., Richey, J. E., and da Cunha, H. B.: The role of sorption in control of riverine dissolved organic carbon concentrations by riparian zone soils in the Amazon basin, Soil Sci., 172, 279-291, 2007. (Pubitemid 46640490)
Richey, J. E., Hedges, J. I., Devol, A. H., and Quay, P. D.: Biogeochemistry of carbon in the Amazon River, Limnol. Oceanogr., 35, 352-371, 1990.
Richey, J. E., Melack, J. M., Aufdenkampe, A. K., Ballester, V. M., and Hess, L. L.: Outgassing from Amazonian rivers and wetlands as a large tropical source of atmospheric CO2, Nature, 416, 617-620, 2002. (Pubitemid 34406758)
Richey, J. E., Krusche, A. V., Johnson, M., Cunha, H. B., and Ballester, M. V.: The role of rivers in the regional carbon balance, in: Amazonia and Climate Change, LBA Synthesis Volume - Amazonia and Global Change, edited by: Keller, M., Bustamante, M., Gash, J., and Dias, P., AGU Press, 2009.
Runge, J. and Nguimalet, C. R.: Physiogeographic features of the Oubangui catchment and environmental trends reflected in discharge and floods at Bangui 1911-1999, Central African Republic, Geomorphology, 70, 311-324, 2005. (Pubitemid 41288146)
Sanderman, J., Lohse, K. A., Baldock, J. A., and Amundson, R.: Linking soils and streams: sources and chemistry of dissolved organic matter in a small coastal watershed, Water Resour. Res., 45, W034018, doi:10.1029/2008WR006977, 2009.
Schlünz, B. and Schneider, R. R.: Transport of terrestrial organic carbon to the oceans by rivers: re-estimating flux and burial rates, Int. J. Earth Sci., 88, 599-606, 2000. (Pubitemid 30247607)
Schwartz, D.: Intérêt de la mesure du δ13C des sols en milieu naturel équatorial pour la connaissance des aspects pédologiques et écologiques des relations savane-forêt, Examples du Congo, Cah. Orstom Sér. Pédol., 26, 327-341, 1991. (Pubitemid 24400987)
Seyler, P. and Elbaz-Poulichet, F.: Biogeochemical control on the temporal variability of trace element concentrations in the Oubangui river (Central African Republic), J. Hydrol., 180, 319-332, 1996.
Seyler, P., Coynel, A., Moreira-Turcq, P., Etcheber, H., Colas, C., Orange, D., Bricquet, J. P., Laraque, A., Guyot, J. L., Olivry, J. C., and Meybeck, M.: Organic carbon transported by the equatorial rivers: example of Congo-Zäire and Amazon basins, 255-274, edited by: Lal, R. and Roose, E., Land use, erosion and carbon dynamic, Advances in Soil Science, Lewis Publishers, CRC Press, 2005.
Spencer, R. G. M., Stubbins, A., Hernes, P. J., Baker, A., Mopper, K., Aufdenkampe, A. K., Dyda, R., Mwamba, V. L., Mangangu, A. M., Wakabanghanzi, J. N., and Six, J.: Photochemical degradation of dissolved organic matter and dissolved lignin phenols from the Congo River, J. Geophys. Res., 114, G03010, doi:10.1029/2009JG000968, 2009.
Spencer, R. G. M., Hernes, P. J., Ruf, R., Baker, A., Dyda, R. Y., Stubbins, A., and Six, J.: Temporal controls on dissolved organic matter and lignin biogeochemistry in a pristine tropical river, Democratic Republic of Congo, J. Geophys. Res., 115, G03013, doi:10.1029/2009JG001180, 2010a.
Spencer, R. G. M, Aiken, G. R., Dyda, R. Y., Butler, K. D., Bergamaschi, B. A., and Hernes, P. J.: Comparison of XAD with other dissolved lignin isolation techniques and a compilation of analytical improvements for the analysis of lignin in aquatic settings, Org. Geochem., 41, 445-453, 2010b.
Spencer, R. G. M., Hernes, P. J., Aufdenkampe, A. K., Baker, A., Gulliver, P., Stubbins, A., Aiken, G. R., Dyda, R. Y., Butler, K. D., Mwamba, V. L., Mangangu, A. M., Wabakanghanzi, J. N., and Six, J.: An initial investigation into the organic matter biogeochemistry of the Congo River, Geochim. Cosmochim. Acta, 84, 614-627, 2012.
Stallard, R. F.: Terrestrial sedimentation and the carbon cycle: coupling weathering and erosion to carbon burial, Global Biogeochem. Cy., 12, 231-257, 1998. (Pubitemid 28476834)
Stubbins, A., Spencer, R. G. M., Chen, H., Hatcher, P. G., Mopper, K., Hernes, P. J., Mwamba, V. L., Mangangu, A. M., Wabakanghanzi, J. N., and Six, J.: Illuminated darkness: molecular signatures of Congo River dissolved organic matter and its photochemical alteration as revealed by ultrahigh precision mass spectrometry, Limnol. Oceanogr., 55, 1467-1477, 2010.
Stutter, M. I., Dunn, S. M., and Lumsdon, D. G.: Dissolved organic carbon dynamics in a UK podzolic moorland catchment: linking storm hydrochemistry, flow path analysis and sorption experiments, Biogeosciences Discuss., 9, 209-251, doi:10.5194/bgd9-209-2012, 2012.
Tan, K. S., Etchells, T., and Fox, D. R.: GUMLEAF v0.1alpha: generator for uncertainty measures and load estimates using alternative formulae. Environmetrics Australia, University of Melbourne, 2005.
Weiss, R. F.: Determinations of carbon dioxide and methane by dual catalyst flame ionization chromatography and nitrous oxide by electron capture chromatography, J. Chromatogr. Sci., 19, 611-616, 1981.
Weiss, R. F. and Price, B. A.: Nitrous oxide solubility in water and seawater, Mar. Chem., 8, 347-359, 1980. (Pubitemid 10150957)
Yamamoto, S., Alcauskas, J. B., and Crozier, T. E.: Solubility of methane in distilled water and seawater, J. Chem. Eng. Data, 21, 78-80, 1976.
Zappa, C. J., Raymond, P. A., Terray, E. A., and McGillis, W. R.: Variation in surface turbulence and the gas transfer velocity over a tidal cycle in a macrotidal estuary, Estuaries, 26, 1401-1415, 2003. (Pubitemid 38162124)