fernández-puga, M.C.

García-Martínez, M.C. (María del Carmen)

Moya-Ruiz, F. (Francisca)

Palomino, D. (Desirée)

Sánchez-Guillamón, O. (Olga)

Vázquez, J.T. (Juan Tomás)

English

Fernández-Puga, M.C. (María Carmen)

Repositorio Institucional Digital del IEO

A preliminary characterization of greenhouse gas (CH4 and CO2) emissions from Gulf of Cadiz mud volcanoesO. Sánchez-Guillamón (1), M.C. García (1), F. Moya (1), J.T. Vázquez (1), D. Palomino (1), M.C. Fernández-Puga (2) & A. Sierra (3)(1) Instituto Español de Oceanografía. CO de Málaga, Puerto Pesquero s/n, 29640 Fuengirola, Málaga. España.(2) Departamento de Ciencias de la Tierra. Facultad de Ciencias del Mar y Ambientales. Universidad de Cádiz, Puerto Real (Cádiz), España.(3) Departamento de Química-Física. Facultad de Ciencias del Mar y Ambientales. Universidad de Cádiz, Puerto Real (Cádiz), España.ACKNOWLEDGEMENTSThis work is a contribution to SUBVENT project. We thank Dr. J.Forja, Dr. T. Ortega & M.Burgos for their support in GC analyses.REFERENCESHoughton & Woodwell (1990). TISGLOW 1, 1-8.Naqvi et al. (2010). Biogeosciences, 7, 2159-90.Pérez et al. (2010). Biogeosciences 7, 1789-1807.Sierra, A. (2014). Tesis de MasterSommer at al. (2009). Mar. Eco. Prog. Ser, 382: 69-86.Submarine mud volcanism represents an important migration pathway for CH4 and other long-lived greenhouse gases as CO2 from deeper reservoirs to the surface. The high levels of methane (150 to 200 nM) in bottom waters imply that there are sites withlocalized, probably periodic, enhanced methane release in these mud volcanoesGases concentrations from :Physico – chemical analyses indicate that 9 of the 11 sampling sites above MVs were seeping gases at the time of surveying, predominantly at Algacel, Mercator and Rosco MVs. Our observations suggest that the emission of methane and carbon dioxide from the mud volcanoes structures studied here may be relevant at the present as a part of the carbon global cycle and to the global methane budget of the hydrosphere and possibly also to the atmosphere.MVs of this study are widely located at the Moroccan field, along the middle and upper slope of the Moroccan margin at water depths between 300 to 1600 m whereas Bonjardim is located at the deep-south Portuguese margin at 3100 m depth CO2 is the most abundant greenhouse gas whereas CH4 is more “virulent”, approximately 300 more effectively than CO2 (Naqvi et al., 2010).Methane contribution to current global warning is estimated to be about 15 %to the anthropogenic greenhouse effect (Houghton & Woodwell, 1990). Ocean-AtmosphereexchangesWe have been focused on 11 MVs as a carbon source of degassing deeply reservoirsto offer an approach of the amount of gas releases to the hydrosphere in these active fluid flow environments.ROV-LUSONiskin bottlesSeabird 911 CTD-Rosette Niskin bottlesGas chromatography withflame ionization detectionPotentiometricTitration (TA) Fig.2. Mud volcanoes location and water samples collected during SUBVENT2 cruiseare shown.Fig. 1. Mud volcano schema illustrating fluid seepagesprocesses and ocean – atmosphere exchanges.Shallower to deeper mud volcanoesSurface to bottom watersSHALLOWESTThe lowest values of methane (50 nM) in bottom waters and fCO2 (265 µatm) are relatedwith the distance to geological active Moroccan area : DEPTH FLUCTUATIONSBonjardim MV DEEPESTThe regional background measured in other MVs in the Gulf ofCadiz appoints that the methane release from this study isremarkably highCaptain Arutyunov MVSan Petersburgo MVSommer et  al. (2009)Sierra, A. (2014)Bottom dissolved CO2 concentrations in three MVs are very high(1540 µ atm) and corresponds to values founded at depthshigher than 1000m in other regions.Pérez et al. (2010)8 nM in vertical profiles20 nM in bottom waters12,59 nM in vertical profiles14.29 nM in bottom watersCAMVSPMVBONJARDIM MVROSCO MVMERCATOR MVALGACELMVECMVRosco MVAlgacel MVMercator MVDuring SUBVENT2 cruise, water column over mud volcanoes and their tops were surveyed for gas seepage characterization500 mL SW forCO2 analysis20 mL SW forCH4 analysisFugacityof CO2TªS%0PRSDIC   pH TADissolvedCH4Fig. 3. Water samplers and Analytical equipments used in thegas seepage and water column characterization.192 nMin D11Fig.4. Water column profiles of methane concentrations in CTD stations and ROV sampling sites.Fig.5. Temperature, salinity and Carbon Dioxideconcentration (fugacity of CO2) vertical profiles in CTD-Rosette stations.Fig.6. Carbon Dioxide concentrations in ROV sampling sites and CTD-Rosette stations. Samples where fugacity is higher than 700 µatm are enhancedFig.7. Schema of Gulf of Cadiz location of MVs studied in different biogeochemicalstudies related with greenhouse gases characterization.CO2SIGNIFICANTLYROV  samples present HIGHEST CONCENTRATIONS and very similar /higher valueswhere CTD-Rosette samples in 5 -10 m above seafloor were also collected.CTD- Rosette present higher bottom than surface concentrations excepting at Bonjardim MVdecreasedValues varied widely within 50 to 200 nM for CH4 and between 400 to 1500 µatm for fCO2700Dissolved CO2 concentrations from ROV samplesare higher than CTD- Rosette samplesfCO2 concentrations in Algacel MV, Mercator MV and El Cid MV are higher that the standard limit.Vertical  CTD- Rosette profiles show greater fCO2 values at the bottomEl Cid MVAlgacel MVMercator MVGreenhouse CO2 concentration is large influenced bywater column depth, temperature, salinity and geological processes.

A preliminary characterization of greenhouse gas (CH4 and CO2) emissions from Gulf of Cadiz mud volcanoes

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A preliminary characterization of greenhouse gas (CH4 and CO2) emissions from Gulf of Cadiz mud volcanoes

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