A stable isotope investigation of the Classical Karst aquifer: evaluating karst groundwater components for water quality preservation
Doctor Daniel H., Sonja Lojen , Milena Horvat - (29/1,2000)
The karst aquifer resurgence zone that is located along the western border of the Classical Karst region of southwestern Slovenia and to the north of Trieste, Italy is comprised of several distinct groundwater components. The purpose of this ongoing study is to examine the varying influence of these groundwater components on the karstic outflow under changing hydrologic conditions, using natural stable isotopes as tracers. In particular, the influence of the Soča river on the groundwater of this region was examined using mercury, a pollutant of elevated concentration in the Soča, as an additional tracer of Soča river water. The results of the isotopic measurements confirm the division of karstic groundwaters into three main categories: (1) springs and the estavelles of an ephemeral karstic lake (Sablici springs, Moschenizze North spring, Doberḍ Lake), which are largely influenced by the Soča and Vipava rivers during periods of low flow, (2) the group of the Timavo springs that is subject to main influences of the Reka River and water derived from local precipitation, and (3) the grouping of Sardos spring and Moschenizze South spring, which form an intermediate category between the first two groups, exhibiting characteristics that indicate variable contributions from the other two end-members. Mercury levels in these karstic groundwaters are generally quite low, however significant variablity in mercury levels with varying hydrologic conditions have been observed, indicating also a varying influence of the Soča river.