|
Zoltan Siklosy, Institute for Geochemical Research, Hungarian Academy of Sciences (Hungary)
Attila Demeny, Institute for Geochemical Research, Hungarian Academy of Sciences (Hungary)
Sebastien Pilet, University of Lausanne (Hungary)
Szabolcs Leel-Ossy, Eotvos Lorand University (Hungary)
Magdolna Virag, Eotvos Lorand University (Hungary)
|
|
Until recent years, only a few research studies have dealt with the potential of cave systems for monitoring environmental pollution. Caves situated in major urban settlements would be ideal objects of such studies, but their use is hampered by the rare occurrence of such sites and the general protection of show caves. This study deals with an 1) actively growing stalagmite in which trace element concentration variations suggest anthropogenic contamination and 2) hydrochemical and isotopic analyses of dripping water in an urban karstic area indicating different degrees of anthropogenic wastewater influx into the karst recharge system.
1) The Trio Cave is located in S-Hungary, approx. 1.5 km east from the nearest entrance and the air-shaft of the uranium mine. A stalagmite located about 150 m away from the entrance was drilled and the core investigated for stable isotope and trace element compositions. The youngest 1 cm of the drill core may represent the last ∼100 years. The pre-mining period is characterized by systematic co-variations of trace elements (e.g. U and P) that can be related to soil activity. The youngest 1.3 mm, however, records a sudden rise in the U content (from 0.2-0.3 ppm to about 2 ppm) uncorrelated with any other variables. The significant increase in U concentration suggested a causal relationship with uranium ore mining that started in the 1950's in the area. The area's morphology exclude the possibility of direct fluvial U transport to the cave, however, wind transport of dust released from air shafts and dust deposition have been detected by earlier studies.
2) Budapest, the capital of Hungary, is famous for its hydrothermal cave system and active thermal spas. The Szemlohegy Cave is one of the well-known show caves of the Buda thermal karst region, situated underneath of a densely populated area. The extensive surface coverage and the existence of drainpipe and water-conduit systems significantly reduced the catchment area of the infiltrating water. To study the effect of a metropolis for the karst system and water body, in situ measurements of electric conductivity, temperature and pH, hydrochemical analyses of dripping water, and stable H and O isotope analyses were carried out. The studied drip sites revealed significant differences in terms of the studied parameters related to the degree of surface coverage, the type of vadose flow towards the dripping site, and - what warned us most - the contribution of external water that was pumped from the Danube river as drinking water. This indicates leakage from the pipe systems that may also contain polluted waste water. As infiltration of polluted waters and the influx of urban atmospheric air represent real dangers for these caves.
This study was financially supported by the Hungarian Scientific Research Fund (OTKA T 049713) and the Hungarian Scholarship Board (travel grants to Z.S.). This paper is a contribution to the Millennium Project (EU-017008).
|
