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Home > Science and research > Interaction of Geosphere-Biosphere-Atmosphere > Environmental Isotope Geochemistry

Environmental Isotope Geochemistry

Individual compounds of the bio-environment are dynamically balanced and the study of the nutrient and contaminant paths helps establish inside knowledge of these relations with respect to safeguarding the minimal man-made load on the environment. Isotopes may provide the clue for determining both the sources of those compounds, be they natural or anthropogenic and for identifying the processes that govern their transformation and ultimate deposition.

Use of the traditional and non-traditional isotope systems will be twofold: (i) for determining the sources of nutrients and toxic elements in the ecosystems and (ii) for identifying the processes in the individual environment constituents. Frequency ratios of the stable and radiogenic isotopes can be used to identify the sources of chemical elements and compounds in case those sources differ in their isotopic composition and there are no isotope fractionations. Isotope data can be also used to finding so far unknown sources and the fallout of greenhouse gases (CO2, CH4, N2O) on earth´s surface.

Selected projects

Isotope mass balance for chromium-contaminated sites based on 53Cr/52Cr ratios of solid and liquid samples

Project manager: RNDr. Martin Novák, CSc.

Carcinogenic effects of Cr(VI) in waters are of concern in many countries. In the Czech Republic, there are more than 120 Cr contaminated sites. Anthropogenic Cr pollution results from electroplating, tanning and chemical industry. Geogenic Cr pollution is associated with serpentinite bodies at convergent plate margins. In anaerobic conditions, Cr(VI) can be reduced to non-toxic, immobile Cr(III). Natural self-attenuation has been reported in some Cr(VI) contaminated aquifers. Stable isotope ratios (53Cr/52Cr) help to identify such sites. Upon Cr(VI) reduction, Cr(VI) in the residual water becomes isotopically heavy. Natural attenuation is of interest because it saves financial resources that would otherwise be needed for extraction and chemical treatment of the groundwater. We will quantify the extent of the Cr isotope effect at 5 polluted sites by analyzing solid and liquid samples. A Cr isotope mass balance will constrain the magnitude of Cr isotope fractionation. By testing 6 hypotheses, we will provide input to decision making on remediation strategy at Cr contaminated sites.

Sampling for the determination of Cr isotopic composition, USA (Author: Petra Pacherová)

Isotope constraints on microbial N2-fixation in ombrotrophic peat bogs

Project manager: RNDr. Martin Novák, CSc.

Peatlands store more N per unit area than any other ecosystem. Degradation of peat bogs can accelerate temperature increases through higher emissions of greenhouse gases. Recently, it has been suggested that sizeable N2-fixation by methanotrophs sustains C and N accumulation in pristine bogs. Similar to pristine bogs, our data from polluted bogs indicate that dated peat cores contain more N than the amount supplied by deposition of NO3-, NH4+ and DON. We hypothesize that microbial N2-fixation is triggered off even at relatively high N inputs into Sphagnum (10 kg/ha/yr), possibly toward the end of major precipitation events, bringing N-deficient water. At two sites, where deposition brings isotopically light N, we found Sphagnum containing isotopically heavier N. Atmospheric N2 could be the missing source of heavy N. In this project, we will construct N isotope mass balances for peat bogs receiving N that is isotopically heavier than N2. If Sphagnum contains isotopically lighter N than rainfall and fog, but heavier than N2, N-fixation will be again indicated as N source for the moss.

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Isotopes - Isotope Ratio Methods

The laboratory dealing with a problematic of geochemistry of light elements stabile isotopes.

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Czech Geological Survey
Geologická 577/6
152 00 Praha 5
phone: +420251085333