engleski

Changes of the geochemical parameters in water of the Plitvice Lakes over the past 30 years

Within this work we represent the results of analyses of water temperatures and chemical parameters (pH, c(Ca2+), c(HCO3 - ), c(Mg2+), c(CO2), calcite saturation index (SIcalc), calcite dissolution ionic ratio (IRcalc) and Mg/Ca ratio) in period 1981-2014 on eight locations at the Plitvice Lakes (two springs, two rivers and four lakes). Statistical analyses considered that the data was not collected systematically and evenly for all seasons by using a two principles: by observing changes in each calendar month over the whole period and by comparing the mean annual values in two end periods, 1981-1986 and 2010-2014. In accordance with the trend of global and local air warming (recorded increase of air temperature in Gospić in 1981-2014 was ~2 °C), a warming of spring (~0.5 °C) and lake waters (~1.5 °C) is observed in the past 30 years. An increase is also observed for c(Ca2+) and c(HCO3 - ), 7% and 15% respectively, but no change in c(Mg2+), resulting in Mg/Ca decrease. This implies that the increase in water temperature caused an increase in geochemical dissolution of calcite, but not of dolomite, also making Mg/Ca useless as a temperature proxy. The temporal water warming could have caused increased degassing of CO2, but this does not seem to be the case since the trend of downstream c(HCO3 - ) decrease has not changed for the observed period. SIcalc and IRcalc show an increase on dolomite based lake locations indicating a local increase of bioactivity in the last 30 years. There is no statistically significant changes observed for pH and c(CO2). The work in detail has been described in A. Sironić, J. Barešić, N. Horvatinčić, A. Brozinčević, M. Vurnek, S. Kapelj Applied Geochemistry 78 (2017) 12-22. doi: 10.1016/j.apgeochem.2016.11.013

Plitvice Lakes ; geochemical parameters ; past 30 years

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