Water and dissolved gas geochemistry at Coatepeque, Ilopango and Chanmico volcanic lakes (El Salvador, Central America)

Coatepeque (on the E slope of Santa Ana Volcano), Ilopango (inside Ilopango Caldera) and Chanmico (associated
with San Salvador Volcano) are volcanic lakes in El Salvador, showing a thermocline at a relatively shallowdepth
(from 30 to 40 m, from 20 to 40 m and from 5 to 15 m depth, respectively) and anoxic conditions below 33, 24
and 4 m depth, respectively. The Na+–Cl− composition of the Coatepeque and Ilopango lakes, displaying TDS
values up to 1226 and 1216 mg/L, respectively, is likely due to hydrothermal fluids that feed these two lakes,
as also confirmed by Cl−/Br− molar ratios ≤ 650, high As, B, Li and Si contents and Cl−/SO4 2− ratio N 1. The Mg2
+–HCO3
− water composition of Lake Chanmico, whose TDS values were between 566 and 856 mg/L, suggests
water-rock interaction processes with mafic/ultramafic rocks variably affected by serpentinization processes,
which produced high Mg2+, Si and B concentrations. Waters at depth were characterized by the presence of
CO2 from an extra-lacustrine source, as suggested by δ13C-CO2 values significantly less negative than those typically
related to biogenic processes, albeit this gas was found in smaller quantities when compared to those recorded
in other meromictic lakes hosted in quiescent volcanic systems (e.g. Lake Kivu in DRC, Monticchio,
Albano and Averno lakes in Italy, Hule and Rio Cuarto lakes in Costa Rica, Lake Pavin in France). The occurrence
of CH4, whose concentrations in Lake Chanmicowere up to two orders of magnitude higher than those recorded
in Coatepeque and Ilopango lakes, suggests bacterial methanogenesis.

Aggarwal, J.K., Palmer, M.R., Bullen, T.D., Arnosson, S., Ragnarsdottir, K.V., 2000. The boron
isotope systematic of Icelandic geothermal waters: 1. Meteoric water charged systems.
Geochim. Cosmochim. Acta 64, 579–585.
Agostini, S., Corti, G., Doglioni, C., Carminati, E., Innocenti, F., Tonarini, S., Manetti, P., Di
Vincenzo, G., Montanari, D., 2006. Tectonic and magmatic evolution of the active volcanic
front in El Salvador: insight into the Berlin and Ahuachapan geothermal areas.
Geothermics 35, 368–408.
Aiuppa, A., Avino, R., Brusca, L., Caliro, S., Chiodini, G., D'Alessandro, W., Favara, R.,
Federico, C., Ginevra, W., Inguaggiato, S., Longo, M., Pecoraino, G., Valenza, M., 2006.
Mineral control of arsenic content in thermalwaters fromvolcano-hosted hydrothermal
systems: insights fromIsland of Ischia and Phlegrean Fields (Campanian Volcanic
Province, Italy). Chem. Geol. 229, 313–330.
Aleman Alberto, E.M., Guerrero Nolasco, E.N., 2007. Evaluación de la calidad del agua en el
Lago de Coatepeque en el periodo de Junio-Agosto de 2006.
Alvarado, G.E., Dengo, C., Martens, U., Bundschuh, J., Aguilar, T., Bonis, S.B., 2007. Stratigraphy
and geologic history. In: Bundschuh, J., Alvarado, G.E. (Eds.), Central America:
Geology, Resources and Hazards. vol. 1. Taylor & Francis, London, pp. 345–394.
Ambury, L., 2017. Correlating the vertical water column temperature to water color
change event of Caldera Lake Coatepeque, El Salvador. US Hydro 2017 Conference,
Galveston, TX.
Anzidei, M., Carapezza, M.L., Esposito, A., Giordano, G., Tarchini, L., Lelli, M., 2008. The
Albano Maar lake high resolution bathymetry and dissolved CO2 budget (Colli Albani
District, Italy): constrains to hazard evolution. J. Volcanol. Geotherm. Res. 171,
258–268.
Apollaro, C., Marini, L., Critelli, T., Barca, D., Bloise, A., De Rosa, R., Liberi, F., Miriello, D.,
2011. Investigation of rock-to-water release and fate of major, minor, and trace elements
in the metabasalt–serpentinite shallow aquifer of Mt. Reventino (CZ, Italy)
by reaction path modelling. Appl. Geochem. 26 (9–10), 1722–1740.
Ayenew, T., 2005. Major ions composition of the groundwater and surface water systems
and their geological and geochemical controls in the Ethiopian volcanic terrain. SINET
Ethiop. J. Sci. 28 (2), 171–188.
Barnes, I., LaMarche Jr., V.C., Himmelberg, G.R., 1967. Geochemical evidence of presentday
serpentinization. Science 56, 830–832.
Bernard, A., Escobar, C.D., Mazot, A., Guttiérrez, R.E., 2004. The acid crater lake of Santa
Ana volcano, El Salvador. Geol. Soc. Am. Spec. Pap. 375, 121–133.
Bonatti, E., Lawrence, J.R., Morandi, N., 1984. Serpentinization of oceanic peridotites: temperature
dependence of mineralogy and boron content. Earth Planet. Sci. Lett. 70,
88–94.
Boschetti, T., Etiope, G., Pennisi, M., Romain, M., Toscani, L., 2013. Boron, lithium and
methane isotope composition of hyperalkaline waters (Northern Apennines, Italy):
terrestrial serpentinization or mixing with brine? Appl. Geochem. 32, 17–25.
Boström, K., Valdes, S., 1969. Arsenic in ocean floors. Lithos 2 (4), 351–360.
Brondi, M., Dall'Aglio, M., Vitrani, F., 1973. Lithium as pathfinder element in the large scale
hydrothermal exploration for hydrothermal systems. Geothermics 2, 142–153.
Bruni, J., Canepa, M., Chiodini, G., Cioni, R., Cipolli, F., Longinelli, A., Marini, L., Ottonello, G.,
Vetuschi Zuccolini,M., 2002. Irreversiblewater–rock mass transfer accompanying the
generation of the neutralMg–HCO3 and high-pH, Ca–OH spring waters of the Génova
province Italy. Appl. Geochem. 17, 455–474.
Buresh, R.J., Patrick, W.H., 1981. Nitrate reduction to ammonium and organic nitrogen in
an estuarine sediment. Soil Biol. Biochem. 13, 279–283.
Cabassi, J., Tassi, F., Vaselli, O., Fiebig, J., Nocentini, M., Capecchiacci, F., Rouwet, D.,
Bicocchi, G., 2013. Biogeochemical processes involving dissolved CO2 and CH4 at
Albano, Averno, Monticchio meromictic volcanic lakes (Central-Southern Italy).
Bull. Volcanol. 75, 683.
Cabassi, J., Tassi, F., Mapelli, F., Borin, S., Calabrese, S., Rouwet, D., Chiodini, G., Marasco, R.,
Chouala, B., Avino, R., Vaselli, O., Pecoraino, G., Capecchiacci, F., Bicocchi, G., Caliro, S.,
Ramirez, C., Mora-Amador, R., 2014. Geosphere-biosphere interactions in bio-activity
volcanic lakes: evidences from Hule and Rio Cuarto (Costa Rica). PLoS One 9 (7),
e102456.
Caliro, S., Chiodini, G., Izzo, G., Minopoli, C., Signorini, A., Avino, R., Granieri, D., 2008. Geochemical
and biochemical evidence of lake turnover and fish kill at Lake Averno, Italy.
J. Volcanol. Geotherm. Res. 178, 305–316.
Christenson, B., 2000. Geochemistry of fluids associated with the 1995/96 eruption of Mt.
Ruapheu, NewZealand: signatures and processes in themagmatic-hydrothermal system.
J. Volcanol. Geotherm. Res. 97, 1–30.
Christenson, B., Tassi, F., 2015. In: Rouwet, D., Christenson, B., Tassi, F.,
Vandemeulebrouck, J. (Eds.), Gases in volcanic lake environments. “Volcanic Lakes,
Advances in Volcanology”. Springer-Heidelberg, pp. 125–153 https://doi.org/
10.1007/978-3-642-36833-2_2.
Cinti, D., Poncia, P.P., Brusca, L., Tassi, F., Quattrocchi, F., Vaselli, O., 2015. Spatial distribution
of arsenic, uranium and vanadium in the volcanic-sedimentary aquifers
of the Vicano-Cimino Volcanic District (Central Italy). J. Geochem. Explor. 152,
123–133.
Cinti, D., Tassi, F., Procesi, M., Brusca, L., Cabassi, J., Capecchiacci, F., Delgado Huertas, A.,
Galli, G., Grassa, F., Vaselli, O., Voltattorni, N., 2017. Geochemistry of hydrothermal
fluids from the eastern sector of the Sabatini Volcanic District (central Italy). Appl.
Geochem. 84, 187–201.
Colvin, A., Rose, W.I., Varekamp, J.C., Palma, J.L., Escobar, D., Gutiérrez, E., Montalvo, F.,
Maclean, A., 2013. Crater lake evolution at Santa Ana volcano following the 2005
eruption. In: Rose, W.I., Palma, J.L., Delgado Granados, H., Varley, N. (Eds.), Understanding
Open Vent Volcanism and Related Hazards. Geol Soc America Special
Paper 498(2), pp. 23–44 https://doi.org/10.1130/2013.2498(00).
Corti, G., Carminati, E., Mazzarini, F., Oziel Garcia, M., 2005. Active strike-slip faulting in El
Salvador, Central America. Geology 33 (12), 989–992. https://doi.org/10.1130/
G21992.1.
Costa, A., Chiodini, G., 2015. Modelling air dispersion of CO2 from limnic eruptions. In:
Rouwet, D., Christenson, B., Tassi, F., Vandemeulebrouck, J. (Eds.), Volcanic Lakes, Advances
in Volcanology. Springer-Heidelberg, pp. 451–465 https://doi.org/10.1007/
978-3-642-36833-2_2.
Davis, S.N., Cecil, L.D., Zreda, M., Moysey, S., 2001. Chlorine-36, bromide, and the origin of
spring water. Chem. Geol. 179, 3–16.
Dotsika, E., Poutoukis, D., Tzavidopoulos, I., Maniatis, Y., Ignatiadou, D., Raco, B., 2009. A
natron source at Pikrolimni Lake in Greece? Geochemical evidence. J. Geochem.
Explor. 103, 133–143.
Dull, R., Southon, J.R., Kutterolf, S., Freundt, A., Wahl, D., Sheets, P., 2010. Did the TBJ
Ilopango eruption cause the AD 536 event? American Geophysical Union, Fall Meeting
2010, Abstract #V13C-2370
Esquivel, I., 2016. Levantamiento batimétrico y medición de parámetros físico-químicos
en el Lago de Ilopango, El Salvador. Bachelor thesis. Universidad de El Salvador.
Etiope, G., Schoell, M., Hosgörmez, H., 2011. Abiotic methane flux fromthe Chimaera seep
and Tekirova ophiolites (Turkey): understanding gas exhalation from low temperature
serpentinization and implications for Mars. Earth Planet. Sci. Lett. 310 (1–2),
96–104.
Etiope, G., Ehlmann, B.L., Schoell,M., 2013. Low temperature production and exhalation of
methane from serpentinized rocks on Earth: a potential analog for methane production
on Mars. Icarus 224 (2), 276–285.
Evans, W.C., White, L.D., Rapp, J.B., 1998. Geochemistry of some gases in hydrothermal
fluids from the southern Juan de Fuca ridge. J. Geophys. Res. 15, 305–313.
Fantoni, D., Brozzo, G., Canepa, M., Cipolli, F., Marini, L., Ottonello, G., Vetuschi Zuccolini,
M., 2002. Natural hexavalent chromium in groundwaters interacting with ophiolitic
rocks. Environ. Geol. 42, 871–882.
Faure, G., 1986. Inorganic Geochemistry. Macmillan Pub Com, p. 627.
Ferrés, D., Delgado Granados, H., Hernández, W., Pullinger, C., Chávez, H., Castillo
Taracena, C.R., Cañas-Dinarte, C., 2011. Three thousand years of flank and central
vent eruptions of the San Salvador volcanic complex (El Salvador) and their effects
on El Cambio archeological site: a review based on tephrostratigraphy. Bull. Volcanol.
73, 833. https://doi.org/10.1007/s00445-011-0465-0.
Ferrés, D., Delgado Granados, H., Gutiérrez, R.E., Farraz, I.A., Hernández, E.W., Pullinger,
C.R., Escobar, C.D., 2013. Explosive volcanic history and hazard zonation maps of
Boquerón Volcano (San Salvador volcanic complex, El Salvador). In: Rose, W.I.,
Palma, J.L., Delgado Granados, H., Varley, N. (Eds.), Understanding Open-vent Volcanism
and Related Hazards: Geological Society of America Special Paper. vol. 498,
pp. 201–230. https://doi.org/10.1130/2013.2498(12).
Fontes, J.C., Matray, J.M., 1993. Geochemistry and origin of formation brines fromthe Paris
Basin, France. Chem. Geol. 109, 177–200.
FORGAES & SNET, 2006. Investigaciones hidrogeológicas, hidrológicas e hidroquímicas en
el Lago Coatepeque. Unión Europea (Resumen ejecutivo).
Göb, S., Loges, A., Nolde, N., Bau, M., Jacob, D.E., Markl, G., 2013. Major and trace element
compositions (including REE) of mineral, thermal, mine and surface waters in SW
Germany and implications for water–rock interaction. Appl. Geochem. 33, 127–152.
Grassa, F., Capasso, G., Oliveri, Y., Sollami, A., Carreira, P., Carvalho, M.R., Marques, J.M.,
Nunes, J.C., 2010. Nitrogen isotopes determination in natural gas: analytical method
and first results on magmatic, hydrothermal and soil gas samples. Isot. Environ.
Health Stud. 46 (2), 141–155.
Hernández, P.A., Pérez, N.M., Varekamp, J.C., Henriquez, B., Hernández, A., Barrancos, J.,
Padron, E., Calvo, D., Melian, G., 2007. Crater lake temperature changes of the 2005
eruption of Santa Ana Volcano, El Salvador, Central America. Pure Appl. Geophys.
164, 2507–2522.
Hoefs, J., 2009. Stable Isotope Geochemistry. 6th edn. Springer, Berlin, p. 288.
IAEA/WMO, 2018. Global Network of Isotopes in Precipitation. The GNIP Database Accessible
at:. https://nucleus.iaea.org/wiser.
Kling, G.W., Evans, W.C., Tanyileke, G.Z., 2015. The comparative limnology of Lakes Nyos
and Monoun, Cameroon. In: Rouwet, D., Christenson, B., Tassi, F., Vandemeulebrouck,
J. (Eds.), Volcanic Lakes, Advances in Volcanology. Springer-Heidelberg, pp. 401–425
https://doi.org/10.1007/978-3-642-36833-2_2.
Kojima, T., Nagamine, A., Ueno, N., Uemiya, S., 1997. Absorption and fixation of carbon dioxide
by rock weathering. Energy Convers. Manag. 38, S461–S466.
Kusakabe M (2015) Evolution of CO2 content in Lakes Nyos and Monoun, and sublacustrine
CO2-recharge system at Lake Nyos as Envisaged from CO2/3He ratios and
noble gas signatures. “Volcanic Lakes, Advances in Volcanology,”. Ed: D. Rouwet, B.
Christenson, F. Tassi, J. Vandemeulebrouck, DOI https://doi.org/10.1007/978-3-642-
36833-2_2, Springer-Heidelberg, 427–450.
Laiolo, M., Coppola, D., Barahona, F., Benítez, J.E., Cigolini, C., Escobar, D., Funes, R.,
Gutierrez, E., Henriquez, B., Hernandez, A., Montalvo, F., Olmos, R., Ripepe, M.,
Finizola, A., 2017. Evidences of volcanic unrest on high-temperature fumaroles by
satellite thermal monitoring: the case of Santa Ana volcano, El Salvador. J. Volcanol.
Geotherm. Res. 340, 170–179.
Langelier,W., Ludwig, H., 1942. Graphical methods for indicating the mineral character of
natural waters. J. Am. Water Assoc. 34, 335–352.
Langone, A., Baneschi, I., Boschi, C., Dini, A., Guidi, M., Cavallo, A., 2013. Serpentinite-water
interaction and chromium(VI) release in spring waters: examples from Tuscan
ophiolites. Ofioliti 38 (1), 41–57. https://doi.org/10.4454/ofioliti.v38i1.415.
Lefkowitz, J.N., Varekamp, J.C., Reynolds, R.W., Thomas, E., 2017. A tale of two lakes: the
Newberry Volcano twin crater lakes, Oregon, USA. Geol. Soc. Lond., Spec. Publ. 437
(1), 253–288.
Lexa, J., Šebesta, J., Chavez, J., Hernandez,W., Pécskay, Z., 2011. Geology and volcanic evolution
in the southern part of the San Salvador Metropolitan Area. J. Geosci. 56,
105–140.
Lopez, D.L., Ransom, L., Pérez, N.M., Hernández, P.A.,Monterrosa, J., 2004. Dynamics of diffuse
degassing at Ilopango Caldera, El Salvador. In: Rose, W.I., Bommer, J.J., Lopez, D.L.,
Carr, M.J., Major, J.J. (Eds.), Natural Hazards in El Salvador. Boulder, Colorado. Geological
Society of America Special Paper 375, pp. 191–202.
Lopez, D.L., Ransom, L., Monterrosa, J., Soriano, T., Barahona, F., Olmos, R., Bundschuh, J.,
2009. Volcanic arsenic and boron pollution of Ilopango Lake, El Salvador. In: Natural
Arsenic in Groundwaters of Latin America. Arsenic in the Environment, 1. Taylor &
Francis (CRC Press), London, United Kingdom, pp. 129–143.
Lopez, D.L., Bundschuh, J., Birkle, P., Armienta, M.A., Cumbal, L., Sracek, O., Cornejo, L.,
Ormachea, M., 2012. Arsenic in volcanic geothermal fluids of Latin America. Sci.
Total Environ. 429, 57–75.
Mah, R.A., Ward, D.M., Baresi, L., Glass, T.L., 1977. Biogenesis of methane. Annu. Rev.
Microbiol. 31, 309–341.
Mann, C.P., Stix, J., Vallance, J.W., Richer, M., 2004. Subaqueous intracaldera volcanism,
Ilopango Caldera, El Salvador, Central America. In: Rose, W.I., Bommer, J.J., Lopez,
D.L., Carr, M.J., Major, J.J. (Eds.), Natural Hazards in El Salvador. Geological Society
of America, Boulder, Colorado, pp. 159–174 Special Paper 375.
Margiotta, S., Mongelli, G., Summa, V., Paternoster, M., Fiore, S., 2012. Trace element
distribution and Cr(VI) speciation in Ca-HCO3 and Mg-HCO3 spring waters from
the northern sector of the Pollino massif, southern Italy. J. Geochem. Explor. 115,
1–12.
MARN, 2017. Informe técnico sobre cambio de color en las aguas del Lago de Coatepeque.
Technical report. Ministerio de Medio Ambiente y Recursos Naturales de El Salvador.
Marques, J.M., Carreira, P.M., Carvalho, M.R., Matias, M.J., Goff, F.E., Basto, M.J., Graça, R.C.,
Aires-Barros, L., Rocha, L., 2008. Origins of high pH mineral waters from ultramafic
rocks, Central Portugal. Appl. Geochem. 23, 3278–3289.
Martin, C., Flores, K.E., Harlow, G.E., 2016. Boron isotopic discrimination for subductionrelated
serpentinites. Geology 44 (11), 899–902.
Martínez-Hackert, B., Bajo Sanchez, J.V., Figueroa, C., 2017. Active volcanoes under water
and inland: using hydrography on Coatepeque Caldera Lake, El Salvador. US Hydro
2017 Conference, Galveston, TX.
Molongoski, J.J., Klug, M.J., 1980. Anaerobic metabolism of particulate organic matter in
the sediments of a hypereutrophic lake. Freshw. Biol. 10, 507–518.
Mook, W.G., Bommerson, J.C., Staverman, W.H., 1974. Carbon isotope fractionation between
dissolved bicarbonate and gaseous carbon dioxide. Earth Planet. Sci. Lett. 22,
169–176.
O'Leary, M.H., 1988. Carbon isotopes in photosynthesis. BioScience 38, 328–336.
Pabst, S., Zack, T., Savov, I., et al., 2015. Evidence for boron incorporation into the serpentine
crystal structure. Am. Mineral. 96 (7), 1112–1119. https://doi.org/10.2138/
am.2011.3709.
Palme, H., O'Neill, H., 2014. Cosmochemical estimates of mantle composition. Treatise on
Geochemistry, 2nd edition Elsevier.
Parkhurst, D.L., Appelo, C.A.J., 1999. User's Guide to PHREEQC, Version 2: A Computer Program
for Speciation, Batch-reaction, One-dimensional Transport, and Inverse Geochemical
Calculations. U.S. Geol. Surv.: Earth Sci. Information Center, Open-File
Reports Section (Distributor).
Pasternack, G.B., Varekamp, J.C., 1997. Volcanic lake systematic I. Physical constraints.
Bull. Volcanol. 58, 528–538.
Paternoster,M., Mongelli, G., Caracausi, A., Favara, R., 2016. Depth influence on the distribution
of chemical elements and saturation index of mineral phases in twins maar
lakes: the case of the Monticchio lakes (southern Italy). J. Geochem. Explor. 163,
10–18.
Po, H.N., Senozan, N.M., 2001. The Henderson-Hasselbalch equation: its history and limitations.
J. Chem. Educ. 78 (11), 1499.
Pullinger, C., 1998. Evolution of the Santa Ana Volcanic Complex, El Salvador. Michigan
Technological University (M. Sc. in Geology).
Ransom, L., 2002. Volcanic Diffuse Soil Degassing and Lake Chemistry of the Ilopango Caldera
System, El Salvador, Central America. MSc Thesis. Ohio University, Athens (OH).
Rapprich, V., Hradecký, P., 2005. The Cinotepeque Range of central El Salvador: geology,
magma origin, and volcanism. Bull. Geosci. 80, 277–286.
Richer, M., Mann, C.P., Stix, J., 2004. Mafic magma injection triggers eruption at Ilopango
Caldera, El Salvador, Central America. In: Rose, W.I., Bommer, J.J., Lopez, D.L., Carr,
M.J., Major, J.J. (Eds.), Natural Hazards in El Salvador. Boulder, Colorado, Geological
Society of America Special Paper vol. 375, pp. 175–189.
Risacher, F., Fritz, B., Hauser, A., 2011. Origin of components in Chilean thermal waters.
J. S. Am. Earth Sci. 31, 153–170.
Rodriguez, R., Olmos, R., Payes, J., 2014. Medición de gas Radón (Rn222) en aguas termales
del Cerro Pacho, Caldera Coatepeque, El Salvador. Rev. Geol. Am. Central 50, 71–82.
Rouwet, D., 2013. VOLADA - a collaborative data base on Volcanic Lakes. https://vhub.org/
resources/2437.
Rouwet, D., Tassi, F., 2014. An overview of the structure, hazards, and methods of investigation
of Nyos-type lakes from the geochemical perspective. J. Limnol. 73 (1).
https://doi.org/10.4081/jlimnol.2014.836.
Rouwet, D., Tassi, F., Mora-Amador, R., Sandri, L., Chiarini, V., 2014. Past, present and future
of volcanic lake monitoring. J. Volcanol. Geotherm. Res. 272, 78–97.
Rowe, G.L., Ohsawa, S., Takano, B., Brantley, S.L., Fernandez, J.F., Barquero, J., 1992. Using
crater lake chemistry to predict volcanic activity at Poás volcano, Costa Rica. Bull.
Volcanol. 54, 494–503.
Rysgaard, S., Risgaard-Petersen, N., Sloth, N.P., Jensen, K., Nielsen, L.P., 1994. Oxygen regulation
of nitrification and denitrification in sediments. Limnol. Oceanogr. 39,
1643–1652.
Salata, G.G., Roelke, L.A., Cifuentes, L.A., 2000. A rapid and precise method for measuring
stable carbon isotope ratios of dissolved inorganic carbon. Mar. Chem.
69, 153–161.
Salazar, J.M.L., Hernández, P.A., Pérez, N.M., Olmos, R., Barahona, F., Cartagena, R., Soriano,
T., López, D.L., Sumino, H., Notsu, K., 2004. Spatial and temporal variations of diffuse
CO2 degassing at Santa Ana-Izalco-Coatepeque volcanic complex, El Salvador, Central
America. In: Rose, W.I., Bommer, J.J., Lopez, D.L., Carr, M.J., Major, J.J. (Eds.), Natural
Hazards in El Salvador. Boulder, Colorado, Geological Society of America Special
Paper vol. 375, pp. 129–149.
Saxby, J., Gottsmann, J., Cashman, K., Gutiérrez, E., 2016. Magma storage in a strike-slip
caldera. Nat. Commun. 7, 12295. https://doi.org/10.1038/ncomms12295.
Schoell, M., 1980. The hydrogen and carbon isotopic composition of methane from natural
gases of various origins. Geochim. Cosmochim. Acta 44, 646–661.
Schoell,M., Tietze, K., Schoberth, S., 1988. Origin of themethane in Lake Kivu (east-central
Africa). Chem. Geol. 71, 257–265.
Schwarzenbach, E.M., Gazel, E., Caddick, M.J., 2014. Hydrothermal processes in partially
serpentinized peridotites from Costa Rica: evidence from native copper and complex
sulfide assemblages. Contrib. Mineral. Petrol. 168, 1079. https://doi.org/10.1007/
s00410-014-1079-2.
Scolamacchia, T., Pullinger, C., Caballero, L.,Montalvo, F., Beramendi Orosco, L.E., González
Hernández, G., 2010. The 2005 eruption of Llamatepec (Santa Ana) volcano, El
Salvador. J. Volcanol. Geotherm. Res. 189, 291–318.
SNET, 2000. Cuerpos de Agua Continentales de El Salvador. Report. Servicio Nacional de
Estudios Territoriales, El Salvador.
Sofield, D.J., 1998. History and Hazards of San Salvador Volcano, El Salvador. Thesis of
Master of Science in Geology. Michigan Technological University.
Sriwana, T., van Bergen, M.J., Varekamp, J.C., Sumarti, S., Takano, B., Van Os, B.J.H., Leng,
M.J., 2000. Geochemistry of the acid Kawah Putih Lake, Patuha volcano, West Java,
Indonesia. J. Volcanol. Geotherm. Res. 97, 77–104.
Su, C., Suarez, D., 2004. Boron release from weathering illites, serpentine, shales, and illitic/
palygorskitic soils. Soil Sci. Soc. Am. J. 68 (1), 96–105.
Tassi, F., Rouwet, D., 2014. An overview of the structure, hazards, and methods of investigation
of Nyos-type lakes from the geochemical perspective. J. Limnol. 73 (1),
39–54.
Tassi F, Vaselli O, Luchetti G, Montegrossi G, Minissale A (2008) Metodo per la
determinazione dei gas disciolti in acque naturali. Int Rep CNR-IGG, Florence, n°
10450, pp. 11. (In Italian).
Tassi, F., Vaselli, O., Tedesco, D., Montegrossi, G., Darrah, T., Cuoco, E., Mapendano, M.,
Poreda, R., Delgado Huertas, A., 2009. Water and gas chemistry at Lake Kivu (DRC):
geochemical evidence of vertical and horizontal heterogeneities in a multi-basin
structure. Geochem. Geophys. Geosyst. 10 (2). https://doi.org/10.1029/
2008GC002191.
Tassi, F., Fazi, S., Rossetti, S., Pratesi, P., Ceccotti, M., Cabassi, J., et al., 2018a. The biogeochemical
vertical structure renders a meromictic volcanic lake a trap for geogenic
CO2 (Lake Averno, Italy). PLoS One 13 (3), e0193914. https://doi.org/10.1371/journal.
pone.0193914.
Tassi, F., Cabassi, J., Andrade, C., Callieri, C., Silva, C., Viveiros, F., Corno, G., Vaselli, O.,
Selmo, E., Gallorini, A., Ricci, A., Giannini, L., Cruz, J.V., 2018b. Mechanisms regulating
CO2 and CH4 dynamics in the Azorean volcanic lakes (São Miguel Island, Portugal).
J. Limnol. https://doi.org/10.4081/jlimnol.2018.1821.
Thauer, R.K., Badziong, W., 1980. Respiration with sulfate as electron acceptor. In:
Knowles, C.J. (Ed.), Diversity of Bacterial Respiratory Systems. CRC, Boca Raton,
pp. 65–85.
Tonarini, S., Agostini, S., Doglioni, C., Innocenti, F., Manetti, P., 2007. Evidence for
serpentinite fluid in convergent margin systems: the example of El Salvador (Central
America) arc lavas. Geochem. Geophys. Geosyst. 8, Q09014. https://doi.org/10.1029/
2006GC001508.
US EPA, 2001. National Primary Drinking Water Standards. United States Environmental
Protection Agency (EPA 816-F-01-007).
Varekamp, J.C., 2015. The chemical composition and evolution of volcanic lakes. In:
Rouwet, D., Christenson, B., Tassi, F., Vandemeulebrouck, J. (Eds.), Volcanic Lakes, Advances
in Volcanology. Springer-Heidelberg, pp. 93–123 https://doi.org/10.1007/978-
3-642-36833-2_2.
Varekamp, J.C., Kreulen, R., 2000. The stable isotope geochemistry of volcanic lakes, with
examples from Indonesia. J. Volcanol. Geotherm. Res. 97, 309–327.
Vaselli, O., Tassi, F., Montegrossi, G., Capaccioni, B., Giannini, L., 2006. Sampling and analysis
of fumarolic gases. Acta Vulcanol. 1–2, 65–76.
Venturi, S., Tassi, F., Bicocchi, G., Cabassi, J., Capecchiacci, F., Capasso, G., Vaselli, O., Ricci, A.,
Grassa, F., 2017. Fractionation processes affecting the stable carbon isotope signature
of thermal waters from hydrothermal/volcanic systems: the examples of Campi
Flegrei and Vulcano Island (southern Italy). J. Volcanol. Geotherm. Res. 345, 46–57.
Walther, C.H.E., Flueh, E.R., Ranero, C.R., von Huene, R., Strauch, W., 2000. Crustal structure
across the Pacific margin of Nicaragua: evidence for ophiolitic basement and a
shallow mantle sliver. Geophys. J. Int. 141 (3), 759–777.
Webster, J.G., Nordstrom, D.K., 2003. Geothermal Arsenic. The source, transport and fate
of arsenic in geothermal systems. In: Welch, A.H., Stollenwerk, K.G. (Eds.), Arsenic
in Groundwater: Geochemistry and Occurrence. Kluwer Academic Publishers,
pp. 101–126.
Weiss, R., 1970. The solubility of nitrogen, oxygen and argon in water and seawater.
Deep-Sea Res. 17, 721–735.
WHO, 2003. Boron in drinking-water. Background Document for Development of WHO
Guidelines for Drinking-water Quality. World Health Organization, Geneva,
Switzerland.
Wilhelm, E., Battino, R., Wilcock, R.J., 1977. Low-pressure solubility of gases in liquid
water. Chem. Rev. 77 (2), 219–262.
Zehnder, A.J.B., 1978. Ecology of methane formation. In: Michell R (ed) Water Pollution
Microbiology. Wiley, New York, pp. 349–376.
Zhang, J., Quay, P.D., Wilbur, D.O., 1995. Carbon isotope fractionation during gas–water
exchange and dissolution of CO2. Geochim. Cosmochim. Acta 59, 107–114.
Zimmer, M., Tassi, F., Vaselli, O., Kujawa, C., Cabassi, J., Erzinger, J., 2015. The gas membrane
sensor (GMS) method: a new analytical approach for real-time gas concentration
measurements in volcanic lakes. Geol. Soc. Lond., Spec. Publ. 437 (1), 223–232