Przykład znacznego wzbogacenia siarczanów wód gruntowych w ciężkie izotopy siarki i tlenu w wyniku bakteryjnej redukcji

Andrzej Trembaczowski

Abstract


EXAMPLE OF CONSIDERABLE EMICHMENT OF SULFATES OCCURRING IN GROUNDWATER INTO HEAVY ISOTOPES OF SULFUR AND OXYGEN DUE TO BACTERIAL REDUCTION

Summary
This paper presents the patterns of groundwaters, which contain vestigial amount of hydrogen sulphide and sulphate(less than I mg/I). These sulphates are strongly enriched in heavy isotopes 34S and 180 (δ34 S>+ 60‰). The dissimilatoryreduction of the sulphate by bacteria, is the cause of this great enrichment. The question is the origin of these sulphates - it is unknown. The Miocene sulphates have been found in the groundwater at the distance about 9 km to the South (see Fig. 1, 2). These sulphates are enriched in heavy isotopes by reducing bacteria too (δ34S=+40‰) (see Fig.2 and Tab. 1). The assessment of δ34S of primarysulphate is presented in Table 2. Calculations of δ-values depend on the amount of primary sulphate and fractionation factor α. Both these parameters are unknown, and may be variable. The results of these calculations are not unequivocal, and they cannot testify the origin of the sulphates. Sulphates may come from forestmarshy-waters as well, where they are reduced by bacteria, and enriched in heavy sulphur too (δ34S>+40‰). It is possible, that shallow groundwaters flow from E to W, like the Sanna river (see Fig. 3). So, the participation of forest-marshy- sulphates in the shallow groundwater at Zaklików is possible. The investigation of another well allows to solve this question. The second well is situated towards the forest (seeFig. 3). The amount of sulphate in this groundwater is verysmall too (l mg/l), and the sulphate is enriched in heavy isotopes (δ34S>+56‰, see Tab. 3). The above considered patterns confirm, that high values of 834S and 8180 of sulphates do not necessarily testify to marine-evaporitic origin. However, it confirms the results of dissimilatory reduction processes.

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