HYDROCHEMICAL FEATURES OF THE SOUTH DOBROGEA'S LAKES

Telteu Camelia-Eliza, University of Bucharest, Romania

Abstract

The present paper presents some hydrochemical features of the South Dobrogea's lakes. The study includes the lakes on the Black Sea shore (Siutghiol, Tăbăcărie, Techirghiol and Tatlageac) and on the right side of the Danube River (Bugeac, Oltina, Mârleanu, Iortmac, Vederoasa and Baciu).
The analyze is based on the processing of data concerning the hydrochemical parameters for the years 2006-2008 (the data were provided by the "Romanian Waters" National Administration) and the data regarding the pH, the dissolved oxygen (mg/l), the total dissolved solids (g/l) and the salinity (‰), obtained during summer 2011 (with Hanna instrument-HI 9828-).
The concentration of the chlorine (51.78 – 33737 mg/l) and sulfate (50.93 – 6296 mg/l) is higher than magnesium (38.30 – 2470.42 mg/l) and calcium cations (25.93 – 206.40 mg/l). The values of the total mineral nitrogen (0.925 – 3.384 mg/l), of the total phosphorus (0.069 – 0.673 mg/l), of the phytoplankton biomass (5.99 – 19.46 mg/l) and of the chlorophyll "a" (44.590 – 601.449 µg/l) include, generally, the lakes to the hypertrophic status.
In case of the Bugeac, Oltina and Siutghiol lakes, the analyze highlights statistically significant correlations, α=0.05, between the precipitation (for 10 days, 20 days and 30 days), the daily air temperature and some hydrochemical parameters.
In the summer of 2011, in case of the Bugeac, Baciu, Mârleanu, Oltina and Tatlageac lakes, the pH ranged between 7.97 (Bugeac lake) and 8.28 (Baciu lake), the dissolved oxygen between 8.27 mg/l (Baciu lake) and 9.29 mg/l (Tatlageac lake), the total dissolved solids between 0.29 g/l (Bugeac lake) and 1.29 g/l (Tatlageac lake) and the salinity between 0.28 (‰) (Bugeac lake) and 1.33 (‰) (Tatlageac lake).
Following the application of Carlson's Trophic State Index, based on the lakes's transparency values during summer 2011 which was estimated with the Secchi disk, the Bugeac, Oltina, Mârleanu and Tatlageac lakes belong to the hypertrophic status.

Keywords: lake, eutrophication, physico-chemical parameters, South Dobrogea