Application of geochemical modeling for analysis of changes in groundwater chemistry in karst area (case study from gypsum karst in the Czarny Potok valley, SW Ukraine)

One of the most up to date scientific problems in recognition of karst processes is quantitave evaluation their activity. Basic and distinctive indicators that describe karst processes activity are intensity and magnitude of chemical denudation (Aksiom S.D., 2002). Not only a tool for describing changes taking place in the observed hydrogeological system will be presented in the paper but tools that allow to predict changes that may take place on the spur of the natural and anthropogenic factors. Only a few methods widely used in hydrogeology are also used in geography. In this paper authors present basis of geochemical modeling that can be widely used. Geochemical modeling can be divided into two main issues: Measurement, assessment and generalization of kinetic and thermodynamic data for solid phases (e.g. minerals), gases and solutions; Use of above data in numerical algorithms describing natural and anthropogenicly changed systems of interaction between water and matrix (Macioszczyk, Dobrzyński, 2006). The practical aspects of geochemical modeling concentrate mainly on creating geochemical models of the environment and its changes. Geochemical modeling has been recently widely used for describing chemical composition of groundwater as well as factors and processes shaping it. A geochemical model is a tool that allow for understanding hydrogeochemical processes taking place in the environment. It is a basis for further analysis of system`s susceptibility for modifications conducted by human as well as it might be an element of the forecast of the risk of environment contamination. The main advantage of geochemical modeling is simplicity of received data interpretation, possibility of groundwater chemistry origin interpretation, predicting chemistry modifications and also forecasting changes in water quality. Geochemical models can be divided into three main groups: Speciation model – it doesn`t include any information about temporal or spatial distribution of processes, it only describe the effect of water – rock – gases interaction in a single point of hydrogeological space; Reaction path model – it delivers information about succeeding changes of the hydrogeological system (spatial variability) that take place as an effect of providing a load of mass and/or energy. The time effect can be modeled with use of reaction rate constant; Reactive transport model – it include data describing temporal and spatial variability of chemical reactions in the system