Water–rock interaction induced by contaminated groundwater in a karst aquifer, Greece |
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| Authors: | G Panagopoulos N Lambrakis C Katagas D Papoulis P Tsolis-Katagas |
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| Institution: | (1) Geology Department, Section of Applied Geology and Geophysics, University of Patras, 26500 Rio, Patras, Greece;(2) Geology Department, Section of Earth Materials, University of Patras, 26500 Rio, Patras, Greece |
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| Abstract: | The karst system of SW Trifilia is composed of a thick sequence of carbonate sediments, which have experienced two types of dolomitization and dedolomitization processes and comprise an extended aquifer. The application of fertilizers in the region have not only caused the degradation of the groundwater quality but also induced hydrochemical changes exerting major control on dolomitization processes. Factor analysis indicates high correlation coefficient between NH
4
+
, NO
3
−
, Ca2+ and Mg2+, which can be attributed to cation-exchange processes involving clay minerals. The application of a conservative mixing model showed that the calculated groundwater types indicate a cation-exchange process between NH
4
+
, derived from fertilizers, and between Ca2+ and Mg2+. Mg2+ released from smectite interlayers, exchanged for NH
4
+
in the groundwater and favor a dolomitization process through the partial replacement of Ca2+ in the lattice of calcite (dedolomite) contained in precursor dolomites. This recent stage dolomitization occurred near the water level and within the phreatic zone only and had not influenced the whole karst massif; it also resulted in low Mg/Ca values found in the zone characterized by intensive application of nitrogen-based fertilizers and the absence of overlying impermeable strata. |
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| Keywords: | Cation-exchange Clay minerals Nitrogen-based fertilizers Dolomitization Karst aquifer |
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