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RSEHN >> Publicaciones >> Bol. R. Soc. Esp. Hist. Nat. 99 (1-4), 2004 >> Trabajos presentados en la VI Reunión de la IPA España

Bol. R. Soc. Esp. Hist. Nat. 99(1-4), 2004


Trabajos presentados en la VI Reunión de la IPA España

Discriminación mediante parámetros físicoquímicos in situ, de diferentes tipos de agua presentes en un área con permafrost (península Byers, isla Livingston, Antártida occidental)


Discrimination by means of physico-chemical parameters of different waters in an area with permafrost (Byers Peninsula, Livingston Island, Western Antarctica)

José Antonio Cuchí, Juan José Durán, Pedro Alfaro, Enrique Serrano

Bol. R. Soc. Esp. Hist. Nat. 99 (1-4): 75-82, 2004

Resumen

A partir de los trabajos de campo realizados en enero-febrero de 2003 en la península Byers (isla Livingston, islas Shetland del Sur, Antártida occidental) se ha efectuado por primera vez una diferenciación de los diversos tipos de aguas presentes. Estas se han discriminado a partir de mediciones in situ de la conductividad eléctrica y la temperatura. Las 55 determinaciones realizadas presentan rangos de temperaturas entre 1,2 y 13,8 ºC y conductividades entre 4,8 y 1.441 microSiemen/cm a 25 ºC. La conductividad eléctrica, en μS/cm a 25 ºC, presenta rangos diversos según los diferentes tipos de aguas: nieve (4,8-6,1), lluvia (17,3-53,7), arroyos (51-360) lagos (76-1440), permafrost (291-371) y aguas subterráneas (246-715). Los resultados evidencian la complejidad del ciclo hidrológico durante el verano en la península Byers y ponen de manifiesto el importante papel del permafrost en el flujo hídrico.

Palabras clave: Hidrogeología, Permafrost, Conductividad eléctrica, Península Byers, Antártida.

Abstract

Byers Peninsula (aprox. 62º 37’ S, 61º 6’ W), Livingston Island, South Shetland Islands is, with a surface of aprox. 60 sq. km, the largest ice-free area in the mentioned archipelago. Rocks outcroping in the peninsula are Upper Jurassic to Lower Cretaceous sedimentary, volcano and volcano-sedimentary rocks. The oldest mentioned materials, from marine origin, cover the western part of the peninsula, while the central and eastern areas are occupied by ignimbrites and other volcanic materials. Several intrusive igneous bodies, of Cretaceous age, are also conspicuous features in the peninsula. Large platforms of marine origin with only a few peaks standing up dominate the inner area geomorphology. Holocene beaches are very developed along the coast of the peninsula. Last major deglaciation of Byers Peninsula started about 4000-5000 years BP, as pointed out by lake sediments studies. Periglacial features are common in the landscape, including among others patterned ground, solifluction lobes and rock debris. Permafrost is also present except close to sea level. Byers Peninsula contains more than 60 lakes and a developed drainage network. According to regional climatic data, mean annual precipitation in the area could be up to 800 mm and mean annual temperature about 2ºC. Hydrological and hydrogeological studies in Antarctica are scarce, although these may be interesting topics regarding environmental, limnological and geomorphological processes. The aim of this paper is to characterize and discriminate, for the first time, types of water present at Byers Peninsula by a preliminary approach to the knowledge of the hydrogeology and underground flow in the area. During the fieldwork, carried out between January 30 and February 12, 2003, 55 data of temperature and electrical conductivity from different types of water were measured in situ. Additional samples of water were colected for detailed analysis in the laboratory. In addition, 14 discharge measurements were taken at in different locations. A preliminary sketch of the hydrological cycle at Byers Peninsula reveals that winter snow is the main input of water, playing wind an important role in its distribution. Starting from springs a portion of the melting water flows superficially to the sea through the creeks and lakes network. Sudden floods occur due to the breakage of snows dams. Other portions of melting water infiltrate in the ground, showing different behaviour according to the presence or not of permafrost. At lower beaches, in absence of permafrost and with a high porosity of the materials, melted snow and summer rainfall gives a non-evaluated amount of underground recharge that flows to the sea. Frozen ground and snow or ice beds act as impervious levels. Hypodermic water flow, basically of water table type, can be confered to the presence of permafrost acting as a acuiclude under the active layer. Locally water can be confined between ice beds. Besides the scarcity of data, it is suggested that may exist an underground connection between the aquifers of the interior and the beaches ones. Permafrost plays also a role as temporary reserve of water, being the presence of springs and widespread wetlands related with its melting. Some of the springs are located near small thermokarst breakdowns. At the end of the summer, with the beginning of the frosting/melting cycles, soils become frozen and then recharge some water starting again the cycle. Electrical conductivity and water temperature measurements show a broad range of values. Electrical conductivity ranges between 4.8 and 1441 μS/cm at 25 ºC and temperature between 1.2 and 13.5 ºC. Lowest values of electric conductivity are related to snow fields: 4.μS/cm at 25 ºC. Rainfall values vary between 17.3 and 53.7 μS/cm at 25ºC, being suggested influence of wind seaborne salts. Underground water shows electric conductivity from 715 to 246 μS/cm, pointing out rock-water reactions with differences according to lithology. Underground water temperature differ according to the areas: at the interior platforms they reflect air temperature and the presence of permafrost, and at lower beaches temperatures are around 13 ºC suggesting deeper underground flow. Lakes and pools have higher electrical conductivity values than snow/rain and underground water, specially at lagoons possibly due to a washing of brackish waters, probably of marine origin, by fresh underground waters. During the summer a number of creeks drain seepage areas and lakes. Electric conductivity of their waters ranges from 51 to 360 μS/cm, being the upper values probably in connection with discharge of underground waters. An inverse relationship between discharge and electric conductivity has been pointed out in a creek near the western end of South Beaches. Higher discharges (and low electric conductivity values) are also related with rainfall episodes or high temperatures. In summary, electric conductivity, expressed in μS/cm at 25 ºC, varies according to water type: snow (4.8-6.1), rain (17.3-53.7), streams (51-360), lakes (76-1440), permafrost (291-371) and underground water (246-715). The hydrologic cycle during the end of the summer at Byers Peninsula has been described. Conditions are favourable for rock-water interactions that increase electrical conductivity of water according to rock type, temperature and time. Permafrost plays an important role in the recharge and water flow, specially in interior areas of the peninsula.

Keywords: Hidrogeology, Permafrost, Electrical conductivity, Byers Peninsula, Antarctica.





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(c) Real Sociedad Española de Historia Natural. Facultades de Biología y Geología. Universidad Complutense de Madrid. 28040-Madrid - e-mail: rsehno@bio.ucm.es