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The effect of geochemical processes on groundwater in the Velenje coal basin, Slovenia: insights from mineralogy, trace elements and isotopes signatures

Authors
  • Kanduč, Tjaša1
  • Šlejkovec, Zdenka1
  • Vreča, Polona1
  • Samardžija, Zoran2
  • Verbovšek, Timotej3
  • Božič, Darian4
  • Jamnikar, Sergej4
  • Solomon, D. Kip5
  • Fernandez, Diego P.5
  • Eastoe, Christopher6
  • McIntosh, Jennifer7
  • Mori, Nataša8
  • Grassa, Fausto9
  • 1 Jožef Stefan Institute, Department of Environmental Sciences, Jamova cesta 39, Ljubljana, 1000, Slovenia , Ljubljana (Slovenia)
  • 2 Jožef Stefan Institute, Department of Nanostructured Materials, Jamova cesta 39, Ljubljana, 1000, Slovenia , Ljubljana (Slovenia)
  • 3 University of Ljubljana, Department of Geology, Faculty of Natural Sciences and Engineering, Aškerčeva 12, Ljubljana, Slovenia , Ljubljana (Slovenia)
  • 4 Velenje Coal Mine d.o.o., Partizanska 78, Velenje, 3320, Slovenia , Velenje (Slovenia)
  • 5 The University of Utah, Department of Geology and Geophysics, 115 S 1460, E RM 308, Salt Lake City, USA , Salt Lake City (United States)
  • 6 University of Arizona, Department of Geosciences, 1040 E 4th St., Tucson, AZ, 85721, USA , Tucson (United States)
  • 7 University of Arizona, Department of Hydrology and Atmospheric Sciences, 1133 E. James E, Rogers Way, Tucson, AZ, 85721, USA , Tucson (United States)
  • 8 National Institute of Biology, Department of Organisms and Ecosystems Reserach, Večna pot 111, Ljubljana, 1000, Slovenia , Ljubljana (Slovenia)
  • 9 Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Palermo, Via Ugo La Malfa, 153, Palermo, 90146, Italy , Palermo (Italy)
Type
Published Article
Journal
SN Applied Sciences
Publisher
Springer International Publishing
Publication Date
Oct 31, 2019
Volume
1
Issue
11
Identifiers
DOI: 10.1007/s42452-019-1561-6
Source
Springer Nature
Keywords
License
Yellow

Abstract

This study investigated the mineralogical and isotopic composition of groundwater and precipitation to identify and constrain geochemical processes within stacked Pliocene and Triassic aquifers in the Velenje coal basin. Scanning electron microscopy combined with energy-dispersive X-ray spectroscopic analysis revealed that suspended matter in the Pliocene aquifer consists of feldspars and quartz, while dolomite, calcite and feldspars are present in the aquifer dewatering Triassic strata. The concentrations of trace elements in Triassic and Pliocene aquifers range from highest to lowest Zn > Fe > Ni > Al > Ba > Mn > B>Li > Mo > As with the majority of trace element concentrations below international drinking water health guidelines. Multivariate principal component analysis indicated that concentrations of Mn, Ba, Eu, Cs, Y, Li and T, pH, conductivity and dissolved oxygen in samples were the best chemical parameter for distinguishing the two aquifers. A significant positive correlation (p < 0.05) was found between Ni, Mn, Co, Zn, As and Mo. Groundwater in the Pliocene aquifer likely has an external source of carbon based on the δ13CCO2 values (− 12.3 to − 3.6‰). The groundwater also has detectable levels of dissolved methane with isotopic values (− 77.7 to − 51.4‰ δ13CCH4; − 247 to − 162‰ δ2HCH4) consistent with microbial methanogenesis. The groundwater in the Triassic aquifer has tritium values (up to 4.1 TU 3H) characteristic of modern recharge (< 50 years), while the lack of detectable 3H (0 TU) in the Pliocene aquifer is consistent with longer residence times.

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