Hydrochemical features and their controlling factors in the Kucaj-Beljanica Massif, Serbia

Abstract

The Kucaj-Beljanica massif represents a complex hydrological karst system that possesses enormous potential for further groundwater extraction and regional water supply uses. In this paper, the influencing factors on groundwater quality in this area were discussed using hydrochemical analysis and the factor analysis method with 123 water and 20 rain/snow water samples. Hydrochemical analysis of the cation composition of cold springs, thermal springs/wells and sinkhole waters in the test area indicates that Ca2+ and Mg2+ are the dominant cations, representing 73–98% of ion equivalent. The anion composition of water indicates that HCO3− is the dominant anion, represented by 73–91% of ion equivalent. Only in the No. 30 thermal spring is characterized by K+ + Na+ and HCO3− + SO42−. The PCO2 of thermal springs/wells, cold springs and sinkhole waters decreases gradually by an average of 10,247, 3444, 319 ppmv (part per million of volume ratio), respectively. The average δ13CDIC of thermal springs/wells, cold springs and sinkhole waters is − 6.56‰, − 10.19‰ and − 13.46‰, respectively. Corresponding to δ13CDIC, the mole ratios of (Ca2+ + Mg2+)/HCO3− are 0.48, 0.55 and 0.60, respectively. Factor analysis identifies 3 sources of solutes: (a) precipitation; (b) water–rock interactions; and (c) soil leaching. Ions of Na+, K+, Cl− and SO42− indicate the predominant influence of atmospheric precipitation, but the No. 30 thermal spring sample is probably the result of deep water–rock interaction (volcanic rock) or is influenced by connate water mixed with shallow karst water. The dissolution of carbonate rocks is the primary factor affecting the Ca2+, Mg2+ and HCO3− contents of groundwater, and soil leaching is the primary factor controlling the concentration of NO3− in water. These results provide a scientific basis for rational exploitation, protection and land use planning in the test area.