In this paper stable isotopes of carbon were used to trace organic and inorganic carbon cycles and biogeochemical processes, especiially methanogenesis within different geologic substrates of the Pliocene lignite-bearing Velenje Basin in northern Slovenia. Lithotypes of lignite, coalbed gases, calcified woods (xylites), carbonate-rich sediments, and groundwaters were investigated. In the lignite seam, CO2 and CH4 were the major gas components with small amounts of N2. Carbon dioxide is likely sourced from a mixture of in situ microbial activity and external CO2, while CH4 is dominantly sourced from microbial methanogenesis, with possible addition of thermogenic gas from deeper formations, and the influence of microbial oxidation of methane.
COBISS.SI-ID: 24995623
Temporal changes in chemical and isotopic composition of “free” seam gases were observed as a function of the advancement of the working face –120/B, G2/C and –50/B within boreholes jpk-28/10, jpk-30/10, jpk-31/10, jpk-22/09 and jpk-23/09. Mass spectrometry and isotope mass spectrometry methods were used to determine gas composition and perform gas characterization. Coalbed gases in the Velenje basin are highly variable in both their concentrations and stable isotope composition. Major gas components are CO2 and methane. Concentrations and isotopic studies revealed several genetic types of coalbed gases: endogenic CO2 (including CO2 originating from dissolution of carbonates), microbial methane and CO2.
COBISS.SI-ID: 25317159
The geochemical and isotopic composition of surface and groundwaters in the Velenje Basin, Slovenia, were investigated to gain a better understanding of the origin of surface and groundwaters. Surface waters are controlled by calcite dissolution, while groundwaters from Triassic aquifer are controlled by dolomite dissolution. Groundwaters from Pliocene and Lithotamnium aquifers have isotopic composition of carbon suggestive of biogenic CO2 reduction and degradation of organic matter. The partial pressure of CO2 in surface waters and groundwaters is well above atmospheric concentrations, indicating that these waters are a potential source of CO2 to the atmosphere. This paper represents geochemical characterization of waters and therefore basis for further modeling of groundwater flow in Velenje sedimentary basin.
COBISS.SI-ID: 23711527
The methodology of investigation of groundwaters from Velenje Basin was transferred to researches of alpine springs, which are important for water supply in Slovenia. At the same time scientific reserach with other research organizations in Slovenia and abroad was established. The investigated Alpine springs in Slovenia represent waters strongly influenced by chemical weathering of Mesozoic limestone and dolomite, only one spring was located in Permo-Carboniferous shales. Waters were generally close to saturation with respect to calcite, and dissolved CO2 was up to fortyfold supersaturated relative to the atmosphere. Isotopic composition of carbon of dissolved inorganic carbon indicates the portion of soil CO2 contributed in water and is related with soil thickness of infiltrating water in aquifer and could be therefore used as a tool for vulnerability assessment. Stable oxygen isotope composition of water, and tritium values indicate recharge from modern precipitation.
COBISS.SI-ID: 25562663