This work is referred to the characterization of the environmental hydrochemistry in the broader Sapes area – Thrace region, on the basis of physico-chemical properties of surface and groundwaters occurring in the volcanosedimentary formations of this area, where gold mining activities are planned to operate. Volcanic rocks are considerably altered where they are in contact with hydrothermal solutions. Aquifers are formed within these formations. Surface and ground waters are strongly metalliferous and their hydrochemical facies present similar but complex water types. Certain characteristic chemical types are the following: Ca-Mg-HCO3-SO4, Ca-Mg-SO4-HCO3. Ca-SO4, Ca-Mg-SO4. Ca-Na-Cl-HCO3, Na-Cl. A small majority of the water samples present the following order of anion dominance HCO3− > SO42− > Cl−. Calcium is the dominant cation. Bicarbonates and sulfate ions are the dominant anions. The order of dominance for the heavy metals in surface and ground waters is as follows: Fe > Mn > Zn > Ni > Cu. The saturation index of waters regarding minerals is low. Computer simulation indicates that calcite and dolomite are common minerals in all water samples which are saturated in respect to quartz and argillaceous-siliceous minerals. The most pronounced property of waters is their acidic character. The high metal concentrations are related to water with low pH. Sulfide minerals control the low pH values of waters which is an important control factor for the evolution of the water chemical composition. The abundance of sulfates is attributed to the dissolution of the minerals pyrite (FeS2) and alunite (KAl3(SO4)2(OH)6. The water–mineral interactions are responsible for the chemical composition of waters. Water quality problems can be successfully handled by the use factor analysis. 17 chemical parameters can be substituted by five factors which successfully represent the hydrochemical processes as well as their geographic distribution. Volcanic rocks in the study area have the potential to produce acid drainage.
Keywords: Acid water - groundwater - hydrochemistry - saline water - volcanic rocks