Tufas are increasingly gaining attention as potential environmental indicators, since their morphological, geochemical and isotopic characteristics reflect climatic conditions in the period of their growth, as well as discharge, precipitation, insulation, nutrient balance and anthropogenic influences. Mercury is one of the most toxic and hazardous pollutant which occurs in the environment in different chemical forms, which fundamental ecological characteristic is lack of biodegradability. The aim of the study was to first time compare environmental records (total mercury concentrations) obtained from the recent tufa with those from ambient water where tufa precipitated. Ratio found can be useful tool to estimate former mercury concentrations in water using tufa as a paleo-record. Krka River is situated in the karst region of Croatia and tufa is precipitated on the entires course of the river, forming several barriers and cascades. The uniqueness of these tufa barriers and waterfalls is base natural phenomenon of the “Krka” National Park. Despite the hydrological situation of the entire catchment are not yet fully explained, we sampled tufa from Krka River and 3 major tributaries (Krčić, Čikola & Zrmanja Rivers). Samplings of tufa on 28 sites were performed during three years (2006-2008). Mercury measurements were performed by cold vapour atomic absorption spectrometry (CVAAS) and concentrations are presented as average total concentrations in tufa: Krka (0.019 mg/kg at spring and 0.040 mg/kg in freshwater stream), Krčić (0.015 mg/kg), Zrmanja (0.047 mg/kg) and Čikola (0.026 mg/kg). Concentrations in tufa were approximately 2*104 times higher comparing with water concentrations.

Geoznanosti,Kemija