engleski

Use of Geochemical Methods in the Research of Groundwater Systems

The chemical composition of groundwater is controlled by dissolution and by chemical reactions with solids, liquids and gases with which they come into contact during the various phases of the hydrological cycle (Stumm & Morgan, 1995). Over the past 50 years, the geochemical parameters such as basic chemical composition, REE (rare earth elements), stable (deuterium, oxygen-18 & -17, carbon-13, nitrogen-15 etc) and radioactive isotopes (carbon-14, tritium, radon-222, uranium-238, chloride-36 etc) gases (methane, carbon dioxide, etc) and noble gases (helium, argon, krypton, neon) and geochemical modelling, are often used to investigate groundwater origin, residence time and to improve understanding of how structural, geological, mineralogical, and hydrological features affect flow and chemistry in the groundwater system. The variation of the chemical composition of groundwater along a flow path is influenced by the spatial variation of minerals and rocks, the initial composition of the recharge solution and geochemical reactions such as oxidation-reduction reactions, sorption and exchange reactions and transformation of organic matter etc. Geochemical modelling is used for quantifying the geochemical reactions occurring along the flow paths within groundwater systems using geochemical software such as NETPATH, PHREEQC, GWB etc. The application of above mentioned geochemical parameters as a tool in the hydrogeological investigation of thermal and ‘’cold’’ groundwaters will be demonstrated at the few examples from Croatia, to show how can be geochemical methods in combination with other methods useful in determination of groundwater origin, residence time and hydrological features affect flow. Although the use of geochemical parameters is not perfect and some improvements are needed in the interpretation of the obtained information, and in the construction and interpretation of numerical models using geochemical data, the best approach will ensure an optimized iterative process between field data collection and analysis, interpretation, and the application of forward, inverse, and statistical modelling tools.

geochemical parameters, isotopes, geochemical modelling, groundwater

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