title: Estimation of groundwater residence time using environmental radioisotopes (14C,T) in carbonate aquifers, southern Poland.
abstract: Triassic carbonate aquifers in the Upper Silesia region, affected by intense withdrawal, have been investigated by means of isotopic analyses of (14)C, δ(13)C, δ(2)H, δ(18)O and (3)H. The isotopic examinations were carried out in the 1970s and in the early 1980s, and it was the first application of tracers to estimate age and vulnerability for the contamination of groundwater in this region. Similar isotopic analyses were conducted in 2007 and 2008 with the same Triassic carbonate formation. The isotopic examinations were performed within the confined part of the carbonate formation, wherein aquifers are covered by semi-permeable deposits. The direct recharge of the aquifer occurs in the outcrop areas, but it mainly takes place due to percolation of the water through aquitards and erosional windows. The Triassic aquifer has been intensively drained by wells and by lead-zinc mines. Nowadays, the declining water demand and closure of some mines have induced a significant increase in the water table level. The detailed analysis of the results, including the radiocarbon age corrections and the comparison of radioisotope activities, has made it possible to estimate the range of residence time within the carbonate Triassic aquifer. This range from several tens to several tens of thousands indicates that the recharge of aquifers might have occurred between modern times and the Pleistocene. The apparent age of the water estimated on the basis of (14)C activity was corrected considering the carbon isotope exchange and the diffusion between mobile water in fractures and stagnant water in micropores. The obtained corrected period of recharge corresponds to the result of investigations of noble gases, which were carried out in the 1990s. In almost half of the cases, groundwater is a mixture of young and old water. The mixing processes occur mainly in areas of heavy exploitation of the aquifer.
authors.affiliation: Institute for Ecology of Industrial Areas, Katowice, Poland. samborska@ietu.katowice.pl
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Samborska
authors.forename: Andrzej
authors.initials: A
authors.lastname: Różkowski
authors.forename: Piotr
authors.initials: P
authors.lastname: Małoszewski
mesh_terms: D002254:Carbonates; D004784:Environmental Monitoring; D060587:Groundwater / Q000737:chemistry; D007554:Isotopes / Q000032:analysis; D011044:Poland; D014872:Water Movements
chemical_list: D002254:Carbonates; D007554:Isotopes