Publicación: Hydrochemistry of karstic waters in a low-energy cave (Castañar de lbor, Spain)
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2006
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info:eu-repo/semantics/openAccess
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Instituto Geológico y Minero de España
Resumen
La Cueva de Castañar de lbor (Cáceres, España) es una cueva de baja energía presentando, bajo condiciones naturales, una elevada estabilidad microambiental a lo largo del ciclo anual con una oscilación térmica anual de 0,09ºC. Se realizaron nueve campañas de muestreo desde diciembre de 2003 a agosto de 2005 para la caracterización hidroquímica de las aguas kársticas en este microambiente estable. Un total de 61 muestras de agua fueron recogidas en siete puntos de la cavidad incluyendo lagos, gours y goteos. Las características fisicoquímicas de las aguas kársticas están principalmente controladas por: (a) la composición mineralógica y características petrológicas de la roca encajante de la cueva y (b) las propiedades hidrogeológicas del macizo rocoso que tienen una fuerte influencia en la tasa de interacción agua-roca. La composición química de las aguas kársticas es muy estable a lo largo de todo el año, siendo esencialmente de tipo Mg2·-Ca1·-HCO3· como consecuencia de su percolación a través de materiales dolomíticos. Durante el verano se produce un descenso de la relación Mg2•/Cci• vinculado a procesos de evaporación y precipitación mineral en la zona del epikarst. Todas las aguas analizadas están muy próximas al estado de saturación o sobresaturadas en calcita y aragonito. En un ambiente termohigrométricamente muy estable el estado de saturación y la tasa de precipitación mineral están controladas esencialmente por los ligeros desequilibrios entre la Pcoz del aire y del agua de infiltración. En cuevas de bajo rango energético como Castañar de lbor el agua juega un papel decisivo en los intercambios entre la atmósfera y el sistema kárstico.
Castañar de lbor ((aceres, Spain) is a low energy cave showing very high micro-environmental stability throughout the annual cycle under natural conditions. After the continuous automatic recording of climatic parameters during a whole year the annual variation is 0.09°( for the temperature and 1120 ppm for C01 . Nine sampling campaigns were carried out from December 2003 to August 2005 for the hydrochemical characterization of the karstic waters in this stable micro-environment. A total of 58 water samples have been collected at 7 locations in the cave, such as lakes, gours and drippings. Physical-chemical features of karstic waters are mainly controlled by (a) petrologic and mineralogic composition of the host rock of the cave and (b) hydrogeologic properties of rocks that have a strong influence on the extent of water/rock interaction. The chemical composition of the karstic water is highly stable during the year, being essentially of Mg1·-Ca2·-HCOi (calcium-magnesium bicarbonate) type as the water percolates through dolomitic limestones. A decrease of the ratio Mg2·/Ca1 • occurs during the summer probably related with evaporation and mineral precipitation processes at the exterior soil (and/or epikarst). Karstic waters are very near to equilibrium throughout the annual cycle or eventually slightly saturated in calcite and aragonite. Saturation state and mineral precipitation both are determined essentially by small differences in partial pressure of C02 between air and infiltration water. In low energy caves the water has a crucial role in the interchanges of mater and energy between atmosphere and karst system.
Castañar de lbor ((aceres, Spain) is a low energy cave showing very high micro-environmental stability throughout the annual cycle under natural conditions. After the continuous automatic recording of climatic parameters during a whole year the annual variation is 0.09°( for the temperature and 1120 ppm for C01 . Nine sampling campaigns were carried out from December 2003 to August 2005 for the hydrochemical characterization of the karstic waters in this stable micro-environment. A total of 58 water samples have been collected at 7 locations in the cave, such as lakes, gours and drippings. Physical-chemical features of karstic waters are mainly controlled by (a) petrologic and mineralogic composition of the host rock of the cave and (b) hydrogeologic properties of rocks that have a strong influence on the extent of water/rock interaction. The chemical composition of the karstic water is highly stable during the year, being essentially of Mg1·-Ca2·-HCOi (calcium-magnesium bicarbonate) type as the water percolates through dolomitic limestones. A decrease of the ratio Mg2·/Ca1 • occurs during the summer probably related with evaporation and mineral precipitation processes at the exterior soil (and/or epikarst). Karstic waters are very near to equilibrium throughout the annual cycle or eventually slightly saturated in calcite and aragonite. Saturation state and mineral precipitation both are determined essentially by small differences in partial pressure of C02 between air and infiltration water. In low energy caves the water has a crucial role in the interchanges of mater and energy between atmosphere and karst system.
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Categorías UNESCO
Palabras clave
aguas kársticas, cueva de baja energía, presión parcial de C02, saturación mineral, C02 partial pressure, karstic waters, low-energy cave, mineral saturation
Citación
Centro
Facultades y escuelas::Facultad de Ciencias
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Ciencias Analíticas
Grupo de investigación
Geología Aplicada al Medio Ambiente (GAMA)