[en] As part of a broader study on the riverine biogeochemistry in the Athi-Galana-Sabaki (A-G-S) River catchment (Kenya), we present data constraining the sources, transit and transformation of multiple nitrogen (N) species as they flow through the A-G-S catchment (~47 000 km2). The data set was obtained in August-September 2011, November 2011, and April-May 2012, covering the dry season, short rain season and long rain season respectively. Release of (largely untreated) wastewater from the city of Nairobi had a profound impact on the biogeochemistry of the upper Athi River, leading to low dissolved oxygen (DO) saturation levels (36-67%), high ammonium (NH4+) concentrations (123-1193 μmol L-1), and high dissolved methane (CH4) concentrations (3765-6729 nmol L-1). Riverine dissolved inorganic nitrogen (DIN; sum of NH4+ and nitrate (NO3-); nitrite was not measured) concentration at the most upstream site on the Athi River was highest during the dry season (1195 μmol L-1), while DIN concentration was an order of magnitude lower during the short and long rain seasons (212 and 193 μmol L-1, respectively). During the rain seasons, low water residence time led to relatively minimal in-stream N cycling prior to discharge to the ocean, whereas during the dry season we speculate that prolonged residence time creates two differences comparative to wet season, where (1) intense N cycling and removal of DIN is possible in the upper to mid-catchment and leads to significantly lower concentrations at the outlet during the dry season, and (2) as a result this leads to the progressive enrichment of 15N in the particulate N (PN) pool, highlighting the dominance of untreated wastewater as the prevailing source of riverine DIN. The rapid removal of NH4+ in the upper reaches during the dry season was accompanied by a quantitatively similar production of NO3- and nitrous oxide (N2O) downstream, pointing towards strong nitrification over this reach during the dry season. Nitrous oxide produced was rapidly degassed downstream, while the elevated NO3- concentrations steadily decreased to levels observed elsewhere in more pristine African river networks. Low pelagic primary production rates over the same reach suggest that benthic denitrification was the dominant process controlling the removal of NO3-, although large cyanobacterial blooms further downstream highlight the significant role of DIN assimilation by primary producers also. Consequently, the intense nitrification and uptake of N by algae leads to significant enrichment of 15N in the PN pool during the dry season (mean: +16.5 ± 8.2‰ but reaching as high as +31.5‰) compared to the short (+7.3 ± 2.6‰) and long (+7.6 ± 5.9‰) rain seasons. A strong correlation between the seasonal N stable isotope ratios of PN (δ15NPN) and oxygen stable isotope ratios of river water (δ18OH2O; as a proxy of freshwater discharge) presents the possibility of employing a combination of proxies - such as δ15NPN of sediments, bivalves and near-shore corals - to reconstruct how historical land use changes have influenced nitrogen cycling within the catchment, whilst potentially providing foresight on the impacts of future land management decisions.
Research Center/Unit :
FOCUS - Freshwater and OCeanic science Unit of reSearch - ULiège
Disciplines :
Aquatic sciences & oceanology
Author, co-author :
Marwick, T. R.
Tamooh, F.
Ogwoka, B.
Teodoru, C.
Borges, Alberto ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Unité d'Océanographie chimique (UOC)
Darchambeau, François ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Unité d'Océanographie chimique (UOC)
Bouillon, S.
Language :
English
Title :
Dynamic seasonal nitrogen cycling in response to anthropogenic N loading in a tropical catchment, Athi–Galana–Sabaki River, Kenya
Abril G. and Frankignoulle M.: Nitrogen-alkalinity interactions in the highly polluted Scheldt basin (Belgium) Water Res. 35 844-850 2001.
Aravena R., Evans M. L., Cherry J. A.: Stable isotopes of oxygen and nitrogen in source identification of nitrate from septic systems Ground Water 31 180-186 1993. (Pubitemid 23623570)
Ayres R. U., Schlesinger W. H., Socolow R. H.: Human impacts on the nitrogen cycle in: Industrial Ecology and Global Change edited by: Socolow R., Andrews C., Berkhout F., Thomas V., Cambridge University Press Cambridge United Kingdom 121-155 1994.
Bartlett K. B., Crill P. M., Bonassi J. A., Richey J. E., Harris R. C.: Methane flux from the Amazon River floodplain: emissions during rising water J. Geophys. Res., 95 16773-16778 doi:10.1029/JD095iD10p16773 1990.
Barnes J. and Upstill-Goddard R. C.: N2O seasonal distributions and air-sea exchange in UK estuaries: implications for the tropospheric N2O source from European coastal waters J. Geophys. Res., 116 G01006 doi:10.1029/ 2009JG001156 2011.
Baulch H. M., Schiff S. L., Maranger R., Dillon P. J.: Nitrogen enrichment and the emission of nitrous oxide from streams Global Biogeochem. Cy., 25 GB4013 doi:10.1029/2011GB004047 2011.
Beaulieu J. J., Tank J. L., Hamilton S. K., Wollheim W. M., Hall Jr., 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., Thomas S. M.: Nitrous oxide emission from denitrification in stream and river networks P. Natl. Aca. Sci., 108 214-219 2011.
Beaulieu J. J., Shuster W. D., Rebholz J. A.,: Controls on gas transfer velocities in a large river J. Geophys. Res., 117 G02007 doi:10.1029/ 2011JG001794 2012.
Bouillon S., Abril G., Borges A. V., Dehairs F., Govers G., Hughes H. J., Merckx R., Meysman F. J. R., Nyunja J., Osburn C., Middelburg J. J.: Distribution origin and cycling of carbon in the Tana River (Kenya): a dry season basin-scale survey from headwaters to the delta Biogeosciences 6 2475-2493 doi:10.5194/bg-6-2475-2009 2009.
Bouillon S., Yambélé A., Spencer R. G. M., Gillikin D. P., Hernes P. J., Six J., Merckx R., Borges A. V.: Organic matter sources fluxes and greenhouse gas exchange in the Oubangui River (Congo River basin) Biogeosciences 9 2045-2062 doi:10.5194/bg-9-2045-2012 2012.
Bouwman A. F., Van Drecht G., Knoop J. M., Beusen A. H. W., Meinardi C. R.: Exploring changes in river nitrogen export to the world's oceans Global Biogeochem. Cy., 19 GB1002 doi:10.1029/2004GB002314 2005. (Pubitemid 40801453)
Brewer P. G. and Goldman J. C.: Alkalinity changes generated by phytoplankton growth Limnol. Oceanogr., 21 108-117 1976.
Canfield D. E., Glazer A. N., Falkowski P. G.: The evolution and future of Earth's nitrogen cycle Science 330 192-196 doi:10.1126/science.1186120 2010.
Cao H., Auguet J.-C., Gu J.-D.: Global ecological pattern of ammonia-oxidizing archaea PLoS ONE 8 e52853. doi:10.1371/journal.pone.0052853 2013.
Caraco N. F. and Cole J. J.: Human impact on nitrate export: an analysis using major world rivers Ambio 28 167-170 1999. (Pubitemid 29194653)
Carpenter S. R., Caraco N. F., Correll D. L., Howarth R. W., Sharpley A. N., Smith V. H.: Nonpoint pollution of surface waters with phosphorus and nitrogen Ecol. Appl., 8 559-568 1998. (Pubitemid 28381987)
Clark I. D. and Fritz P.: Environmental Isotopes in Hydrogeology Lewis Publishers Boca Raton FL., 1997.
Cole M. L., Valiela I., Kroeger K. D., Tomasky G. L., Cebrian J., Wigand C., McKinney R. A., Grady S. P., Carvalho da Silva M. H.: Assessment of a -15N isotopic method to indicate anthropogenic eutrophication in aquatic ecosystems J. Environ Qual., 33 124-132 2004. (Pubitemid 38095563)
Costanzo S. D., O'donohue M. J., Dennison,W. C., Loneragan N. R., Thomas M.: A new approach for detecting and mapping sewage impacts Mar. Pollut. Bull., 42 149-156 2001. (Pubitemid 32178231)
Dafe F.: No business like slum business? The political economy of the continued existence of slums: a case study of Nairobi DESTIN: Development Studies Institute Working Paper Series No. 09-98 2009.
De Brabandere L., Dehairs F., Van Damme S., Brion N., Meire P., Daro N.: 15N and 13 C dynamics of suspended organic matter in freshwater and brackish waters of the Scheldt estuary J. Sea Res., 48 1-15 2002. (Pubitemid 34979198)
de Villiers S.: The deteriorating nutrient status of the Berg River South Africa Water SA 33 659-664 2007 (Pubitemid 350085347)
di Persia D. H. and Neiff J. J.: The Uruguay river system in: The ecology of river systems edited by: Davies B. R., Walker K. F., Junk W., Dordrecht the Netherlands 599-662 1986.
Dortch Q.: The interaction between ammonium and nitrate uptake in phytoplankton Marine ecology progress series Oldendorf 61 183-201 1990.
Downing J. A., McClain M., Twilley R., Melack J. M., Elser J., Rabalais N. N., Lewis Jr., W. M., Turner R. E., Corredor J., Soto D., Yanez-Arancibia A., Kopaska J. A., Howarth R.W.: The impact of accelerating land-use change on the N-cycle of tropical aquatic ecosystems: current conditions and projected changes Biogeochemistry 46 109-148 1999. (Pubitemid 29347865)
Dudgeon D.: The ecology of rivers and streams in tropical Asia in: River and stream ecosystems edited by: Cushing C. E., Cummins K. W., Minshall G. W., Elsevier Science B. V., Amsterdam 615-657 1995.
Elliot E. M. and Brush G. S.: Sedimented organic nitrogen isotopes in freshwater wetlands record long-term changes in watershed nitrogen source and land use Environ. Sci. Technol., 40 2910-2916 2006. (Pubitemid 43673291)
Elser J. J., Fagan W. F., Denno R. F., Dobberfuhl D. R., Folarin A., Huberty A., Interlandi S., Kilham S. S., McCauley E., Schulz K. L., Siemann E. H., Sterner R.W.: Nutritional constraints in terrestrial and freshwater food webs Nature 408 578-580 2000.
Faniran J. A., Ngceba F. S., Bhat R. B., Oche C. Y.: An assessment of the water quality of the Isinuka springs in the Transkei region of the Eastern Cape Republic of South Africa Water SA 27 241-250 2001. (Pubitemid 32453779)
Fianko J. R., Lowor S. T., Donkor A., Yeboah P. O.: Nutrient chemistry of the Densu River in Ghana The Environmentalist 30 145-152 2010.
Fleitmann D., Dunbar R. B., McCulloch M., Mudelsee M., Vuille M., McClanahan T. R., Cole J. E., Eggins S.: East African soil erosion recorded in a 300 year old coral colony from Kenya Geophys. Res. Lett., 34 L04401 doi:10.1029/2006GL028525 2007. (Pubitemid 47272067)
Frankignoulle M., Bourge I., Wollast R.: Atmospheric CO2 fluxes in a highly polluted estuary (The Scheldt) Limnol. Oceanogr., 41 365-369 1996. (Pubitemid 26311213)
French E., Kozlowski J. A., Mukherjee M., Bullerjahn G., Bollmanna A.: Ecophysiological characterization of ammoniaoxidizing archaea and bacteria from freshwater Appl. Environ. Microb., 78 5773-5780 2012.
Galloway J. N. and Cowling E. B.: Reactive nitrogen and the world: 200 years of change AMBIO 31 64-71 2002.
Galloway J. N., Schlesinger W. H., Hiram Levy I. I., Michaels A., Schnoor J. L.: Nitrogen fixation: anthropogenic enhancement-environmental response Global Biogeochem. Cy., 9 235-252 1995. (Pubitemid 26435748)
Galloway J. N., Aber J. D., Erisman J. W., Seitzinger S. P., Howarth R. W., Cowling E. B., Cosby B. J.: The nitrogen cascade BioScience 53 341-356 2003. (Pubitemid 36453247)
Gillikin D. P. and Bouillon S.: Determination of -18O of water and -13C of dissolved inorganic carbon using a simple modification of an elemental analyser-isotope ratio mass spectrometer: an evaluation Rapid Commun. Mass Sp., 21 1475-1478 2007. (Pubitemid 46663687)
Goldberg,W. M.: Comparative study of the chemistry and structure of gorgonian and antipatharian coral skeletons Mar. Biol., 35 253-267 1976.
Goldberg W. M. and Hamilton R. D.: The sexual cycle in Plexaura homomalla in: Prostoglandins from Plexaura homomalla: ecology utilization and conservation of a major medical marine resource. A Symposium edited by: Bayer M. and Weinheimer A. J., University of Miami Press Miami FL 58-61 1974.
Goreau T. J., Kaplan W. A., Wofsy S. C., McElroy M. B., Valois F. W., Watson S. W.: Production of NO? 2 and N2O by nitrifying bacteria at reduced concentrations of oxygen Appl. Environ. Microbiol., 40 526-532 1980. (Pubitemid 11203420)
Grigg R. W.: Growth rings: annual periodicity in two gorgonian corals Ecology 55 876-881 1974.
Hama T., Miyazaki T., Ogawa Y., Iwakuma T., Takahashi M., Otsuki A., Ichimura S.: Measurement of photosynthetic production of a marine phytoplankton population using a stable 13C isotope Mar. Biol., 73 31-36 1983.
Harrison J. A., Maranger R. J., Alexander R. B., Giblin A. E., Jacinthe P. A., Mayorga E., Seitzinger S. P., Sobota D. J., Wollheim W. M.: The regional and global significance of nitrogen removal in lakes and reservoirs Biogeochemistry 93 143-157 2009.
Holland E. A., Dentener F. J., Braswell B. H., Sulzman J. M.: Contemporary and pre-industrial global reactive nitrogen budgets Biogeochemistry 46 7-43 1999. (Pubitemid 29347861)
Howarth R.W.: Coastal nitrogen pollution: a review of sources and trends globally and regionally Harmful Algae 8 14-20 2008.
Howarth R. W., Billen G., Swaney D., Townsend A., Jaworski N., Lajtha K., Downing J. A., Elmgren R., Caraco N., Jordan T., Berendse F., Freney J., Kudeyarov V., Murdoch P., Zhao-Liang Z.: Regional nitrogen budgets and riverine N and P fluxes for the drainages to the North Atlantic Ocean: natural and human influences Biogeochemistry 35 75-139 1996.
Hugoni M., Etien S., Bourges A., Lepère C., Domaizon I., Mallet C., Bronner G., Debroas D., Mary I.: Dynamics of ammonia oxidizing archaea and bacteria in contrasted freshwater ecosystems Res. Microbiol., 164 360-370 doi:10.1016/j.resmic.2013. 01.004 2013.
IAEA: GNIP Maps and Animations International Atomic Energy Agency Vienna http://isohis.iaea.org(last accessed: 25 November 2013) 2001.
K.N.B.S.: Kenya: 2009 population and housing census highlights Kenyan National Bureau of Statistics 2009.
Kithiia S. M.: Land use changes and their effects on sediment transport and soil erosion within the Athi drainage basin Kenya IAHS-AISH P., 245 145-150 1997.
Kithiia S. M.: Effects of Sediments Loads on Water Quality within the Nairobi River Basins Kenya International Journal of Environmental Protection 2 16-20 2012.
Kithiia S. M. and Wambua B. N.: Temporal changes of sediment dynamics within the Nairobi River sub-basins between 1998-2006 time scale Kenya Annals of Warsaw University of Life Sciences - SGGW Land Reclamation 42 17-22 2010.
Koné Y. J. M., Abril G., Kouadio K. N., Delille B., 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., Borges A. V.: Seasonal variability of methane in the rivers and lagoons of Ivory Coast (West Africa) Biogeochemistry 100 21-37 2010.
Kreitler C. W.: Nitrogen-isotope ratio studies of soils and groundwater nitrate from alluvial fan aquifers in Texas J. Hydrol., 42 147-170 1979. (Pubitemid 10254639)
Lapointe B. E., Barile P. J., Littler M. M., Littler D. S.: Macroalgal blooms on southeast Florida coral reefs: II. Crossshelf discrimination of nitrogen sources indicates widespread assimilation of sewage nitrogen Harmful Algae 4 1106-1122 2005. (Pubitemid 41562274)
Lehmann M. F., Sigman D. M., Berelson W. M.: Coupling the 15N/14N and 18O/16O of nitrate as a constraint on benthic nitrogen cycling Mar. Chem., 88 1-20 2004.
Lévêque C.: River and stream ecosystems of northwestern Africa in: River and Stream Ecosystems edited by: Cushing C. E., Cummins K. W., Minshall G. W., Elsevier Science B. V., Amsterdam 519-536 1995.
Marion G. S., Dunbar R. B., Mucciarone D. A., Kremer J. N., Lansing J. S., Arthawiguna A.: Coral skeletal -15N reveals isotopic traces of an agricultural revolution Mar. Pollut. Bull., 50 931-944 2005. (Pubitemid 41270596)
Mayorga E., Seitzinger S. P., Harrison J. A., Dumont E., Beusen A. H. W., Bouwman A. F., Fekete B. M., Kroeze C., Van Drecht A.: Global nutrient export from WaterSheds 2 (NEWS 2): model development and implementation Environ. Modell. Softw., 25 837-853 2010.
McGuire K. and McDonnell J.: Stable isotope tracers in watershed hydrology in: Stable isotopes in ecology and environmental science 2nd edited by: Michener R. and Lajtha K., Blackwell Publishers Boston Massachusetts 334-374 2007.
Mengis M., Gachter R., Wehrli B.: Sources and sinks of nitrous oxide (N2O) in deep lakes Biogeochemistry 38 281-301 doi:10.1023/A:1005814020322 1997. (Pubitemid 27324522)
Mogaka H., Gichere S., Davis R., Hirji R.: Climate variability and water resources degradation in Kenya: improving water resources development and management World Bank Working Papers 69 2006.
Mook W. G. and De Vries J. J.: Environmental isotopes in the hydrological cycle: principles and applications Vol. 3 Surface Water 2000.
Moynihan M. A., Baker D. M., Mmochi A. J.: Isotopic and microbial indicators of sewage pollution from Stone Town Zanzibar Tanzania Mar. Pollut. Bull., 64 1348-1355 2012.
Mutisya D. K. and Tole M.: The impact of irrigated agriculture on water quality of rivers Kongoni and Sirimon Ewaso Ng'iro North Basin Kenya Water Air Soil Poll., 213 145-149 2010.
Ohowa B. O.: Seasonal variations of the nutrient fluxes into the Indian Ocean from the Sabaki river Kenya Discov. Innovat., 8 265-274 1996. (Pubitemid 126490650)
Olima W.: Dynamics and implications of sustaining urban spatial segregation in Kenya - experiences from Nairobi metropolis in: International Seminar on Segregation in the City Lincoln Institute of Land Policy Cambridge USA World Health Organization (WHO) 2001.
Ongwenyi G. S., Kithiia S. M., Denga F. O.: An overview of the soil erosion and sedimentation problems in Kenya IAHS Press Wallingford United Kingdom 1993.
Oosterom A. P.: The geomorphology of southeast Kenya Ph.D. thesis Agricultural University Wageningen the Netherlands 1988.
Owens N. J. P.: Natural variations in 15N in the marine environment Adv. Mar. Biol., 24 390-451 1987.
Rajkumar A. N., Barnes J., Ramesh R., Purvaja R., Upstill- Goddard R.: Methane and nitrous oxide fluxes in the polluted Adyar River and estuary SE India Mar. Pollut. Bull., 56 2043-2051 doi:10.1016/j.marpolbul.2008. 08.005 2008.
Ravishankara A. R Daniel J. S., Portmann R. W.: Nitrous oxide (N2O): the dominant ozone-depleting substance emitted in the 21st century Science 326 123-125 2009.
Richey J. E., Devol A. H., Wofy S. C., Victoria R., Riberio M. N. G.: Biogenic gases and the oxidation and reduction of carbon in Amazon River and floodplain waters Limnol. Oceanogr., 33 551-561 1988.
Risk M. J., Sayer B. G., Tevesz M. J., Karr C. D.: Comparison of the organic matrix of fossil and recent bivalve shells Lethaia 29 197-202 1997.
Risk M. J., Lapointe B. E., Sherwood O. A., Bedford B. J.: The use of -15N in assessing sewage stress on coral reefs Mar. Pollut. Bull., 58 793-802 2009.
Sebilo M., Billen G., Grably M., Mariotti A.: Isotopic composition of nitrate-nitrogen as a marker of riparian and benthic denitrification at the scale of the whole Seine River system Biogeochemistry 63 35-51 2003. (Pubitemid 36639327)
Sebilo M., Billen G., Mayer B., Billiou D., Grably M., Garnier J., Mariotti A.: Assessing nitrification and denitrification in the Seine River and estuary using chemical and isotopic techniques Ecosystems 9 564-577 2006. (Pubitemid 43883096)
Seitzinger S. P. and Kroeze C.: Global distribution of nitrous oxide production and N inputs in freshwater and coastal marine ecosystems Global Biogeochem. Cy., 12 93-113 1998.
Seitzinger S. P., Mayorga E., Bouwman A. F., Kroeze C., Beusen A. H. W., Billen G., Van Drecht G., Dumont E., Fekete B. M., Garnier J., Harrison J. A.: Global river nutrient export: a scenario analysis of past and future trends Global Biogeochem. Cy., 24 GB0A08 doi:10.1029/2009GB003587 2010.
Sherwood O. A., Scott D. B., Risk M. J., Guilderson T. P.: Radiocarbon evidence for annual growth rings in the deep-sea octocoral Primnoa resedaeformis Mar. Ecol.-Prog. Ser 301 129-134 2005. (Pubitemid 41608880)
Tamooh F., Van den Meersche K., Meysman F., Marwick T. R., Borges A. V., Merckx R., Dehairs F., Schmidt S., Nyunja J., Bouillon S.: Distribution and origin of suspended matter and organic carbon pools in the Tana River Basin Kenya Biogeosciences 9 2905-2920 doi:10.5194/bg-9-2905-2012 2012.
Taylor P. G. and Townsend A. R.: Stoichiometric control of organic carbon-nitrate relationships from soils to the sea Nature 464 1178-1181 2010.
Thomas H., Schiettecatte L.-S., Suykens K., Koné Y. J. M., Shadwick E. H., Prowe A. E. F., Bozec Y., de Baar H. J. W., Borges A. V.: Enhanced ocean carbon storage from anaerobic alkalinity generation in coastal sediments Biogeosciences 6 267-274 doi:10.5194/bg-6-267-2009 2009.
Tiffen M., Mortimore M., Gichuki F.: More people less erosion: environmental recovery in Kenya ACTS Press Nairobi Kenya 33-43 1994.
Townsend S. A., Webster I. T., Schult J. H.: Metabolism in a groundwater-fed river system in the Australian wet/dry tropics: tight coupling of photosynthesis and respiration J. N. Am. Benthol. Soc., 30 603-620 2011.
Trimmer M., Grey J., Heppell C. M., Hildrew A. G., Lansdown K., Stahl H., Yvon-Durocher G.: River bed carbon and nitrogen cycling: state of play and some new directions Sci. Total Environ., 434 143-158 2012.
Van Katwijk M., Meier N. F., Loon R. V., Hove E. V., Giesen W. B. J. T., Velde G. V. D., Hartog C. D.: Sabaki river sediment load and coral stress: correlation between sediments and condition of the Malindi-Watamu reefs in Kenya (Indian Ocean) Mar. Biol., 117 675-683 1993. (Pubitemid 24417129)
Vitoria L., Otero N., Soler A., Canals A.: Fertilizer characterization: isotopic data (N S O C and Sr) Environ. Sci. Technol., 38 3254-3262 2004.
Vitousek P. M., Aber J. D., Howarth R. W., Likens G. E., Matson P. A., Schindler D. W., Schlesinger W. H., Tilman D. G.: Human alteration of the global nitrogen cycle: sources and consequences Ecol. Appl., 7 737-750 1997.
Weiner S., Lowenstam H. A., Taborek B., Hood L.,: Fossil mollusk shell organic matrix components preserved for 80 million years Paleobiology 5 144-150 1979.
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)
Wetzel R. G.: Limnology 3rd Edn., Lake and river ecosystems Academic Press San Diego 2001.
Widory D., Petelet-Giraud E., Negrel P., Ladouche B.: Tracking the sources of nitrate in groundwater using coupled nitrogen and boron isotopes: a synthesis Environ. Sci. Technol., 39 539-548 2005. (Pubitemid 40129873)
Wrage N., Velthof G. L., van Beusichem M. L., Oenema O.: Role of nitrifier denitrification in the production of nitrous oxide Soil Biol. Biochem., 33 1723-1732 doi:10.1016/S0038-0717(01)00096-7 2001. (Pubitemid 32961521)
Yamamoto S., Alcauskas J. B., Crozier T. E.: Solubility of methane in distilled water and seawater J. Chem. Eng. Data 21 78-80 1976.
Yasin J. A., Kroeze C., Mayorga E.: Nutrients export by rivers to the coastal waters of Africa: past and future trends Global Biogeochem. Cy., 24 GB0A07 doi:10.1029/2009GB003568 2010.
Zhang G.-L., Zhang J., Liu S.-M., Ren J.-L., Zhao Y.-C.: Nitrous oxide in the Changjiang (Yangtze River) Estuary and its adjacent marine area: Riverine input sediment release and atmospheric fluxes Biogeosciences 7 3505-3516 doi:10.5194/bg-7-3505-2010 2010.
Zurbrügg R., Suter S., Lehmann M. F., Wehrli B., Senn D. B.: Organic carbon and nitrogen export from a tropical dam-impacted floodplain system Biogeosciences 10 23-38 doi:10.5194/bg-10-23-2013 2013.
