AN ISOTOPIC SURVEY OF SOME MINERAL WATER RESOURCES IN THE CARPATHIAN CHAIN (ROMANIA)
Abstract
Popular since ancient times, the mineral waters from Carpathian Chain (Romania) have gained a well-deserved reputation due to
their quality and health benefits. This study provides a description of the chemical and isotopic composition (δ2H, δ18O) of
mineral waters (CO2 - rich and CO2 - free water) located in six of the most popular areas, in order to improve the overall
knowledge about their genesis and recharge mechanisms. The hydro-chemical facies of groundwater vary spatially, the analysed
mineral waters falling predominantly in the Ca2+-HCO3- type, except for those on Bodoc area that highlights a Na+-HCO3- type
water, which can be related with the calc-alkaline volcanic activity that has dominated the Harghita Mountains, Bodoc springs
being located nearby. The water chemistry is largely controlled by rock weathering and ion exchange processes. Monthly
variation of water stable isotopes 2H and 18O was measured over one year in both precipitation and groundwater, in order to
evaluate the possible relationship between rainfall composition and groundwater. All the water samples display values from -89
to -67‰ for 2H and from -11.7 to -8.1‰ for 18O, most samples having values within the range from -80 to -70‰ for 2H, and -
11 to -9‰ for 18O. For most of the investigated springs, 2H and 18O values were below GMWL (Global Meteoric Water
Line), featuring O-shifts. The enrichment in 18O reveals an exchange reaction between the water aquifers with the specific
geological structure containing rocks (igneous rocks, carbonates, etc.) with high content of 18O, on its pathway to the surface.