Żelazo i mangan w płytkich wodach podziemnych Karpat i ich przedgórza na zachód od linii Dunajca

Abstract

Omówiono występowanie żelaza i manganu w wodach utworów czwartorzędowych Karpat i ich przedgórza (na zachód od linii Dunajca), w powiązaniu z poszczególnymi środowiskami hydrogeochemicznymi, oraz dla porównania w wodach utworów starszych (miocenu, paleogenu i kredy). Określono przeciętne i maksymalne zawartości tych pierwiastków oraz wskaźnik Mn/Fe. Zawartość Fe i Mn w obrębie danego środowiska oraz w zależności od jego charakteru hydrogeochemicznego wykazuje duże zróżnicowanie.

IRON AND MANGANESE IN SHALLOW GROUND WATERS WITHIN THE CARPATHIANS AND THEIR FORELAND WEST OF THE DUNAJEC RIVER

The following presents the results of chemical analyses of water samples collected from the first ground-water horizon within the Carpathians and their Foreland west of the Dunajec River. The horizon under consideration is the first usable one and occurs predominantly in the Quaternary formation. Under some circumstances, when the Quaternary formation occurs to be unfavourable for water storage or in case of its thickness limited, the first usable horizon exists in older formations: in Miocene .within the Foreland or in Palaeogene and Cretaceous within the Carpathian Mountains. When considering hydrogeochemical environments representative for the Quaternary horizon then the ground waters in the alluvial formation can be pointed out in the Carpathian Mts; respectively the alluvial and the fluviogiacial formation appear as the other two environments representative in the Foreland.

The iron and the manganese content vary widely with respect to hydrogeochemical environments. They show, in particular environment, considerable variations running with a parallel line.

From regional point of view, a higher content of Fe and Mn is observed in the Foreland than in the Carpathians. In alluvial waters of the Carpathian iron occurs in higher amount as compared with the Foreland; however, their manganese content is lower. In general, alluvial waters of the Carpathian Mts. contain iron in the range of 0.0-0.5 mg/dm³ and manganese does not exceed 0.1 mg/dm³; tha latter can, from time to time, reach a considerable value of several mg/dm³.

Alluvial waters from the Foreland predominantly contain iron in excess of 2 mg/dm³, but the manganese content is, for the most part, less than 1 mg/dm³. Considerable amounts of iron are found in waters from fluvioglacial formation and this refers to tens mg/dm³. On the contrary, manganese is found in low amounts and many times the analyses prove the water samples manganese-free.

The Mn/Fe index has similar distribution in all hydrogeochemical environments, Its upper limit reaches 0.2 and nearly in 30% of cases the index value is zero.

Variability of the Mn/Fe index has been also studied in terms of depth to water table encountered while drilling through the Quaternary formation. Results of such a trial have not occurred to be of significant value, as the water table has been encountered at the shallow depths.