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Abstract:

Corbu I Lake, analyzed between July 24^th and 29^th, 2019, had a brackish water that from a physico-chemical point of view, presented oxygen supersaturation, a high degree of mineralization, a rather alkaline pH and a subunitary index of water transparency. Also, the water of Corbu I Lake corresponded to a moderate ecological status (III) at the time of taking the surface samples, due to the pointlike and local diffuse anthropogenic influences. From a chemical point of view, the biogenic elements containing nitrogen and phosphorus, sulphates and detergents, were not conforming with the maximum permitted levels specified by the Order No. 161/2006, published in the Official Journal of Romania by the Ministry of Environment and Water Management. Regarding the eutrophication degree, the indicators of total mineral nitrogen and total phosphorus corresponded to the eutro-hypertrophic and, respectively, hypertrophic stages. The N_{T mineral}/P_T ratio ranged between 5.72 and 68.53, indicating the more pronounced incidence of eutrophication in this lake, which also had a high content of organic matter (>20 mg/l), due to the zonal diffuse sources of pollution. The ecological status of the studied aquatic environment was from good to weak classes for nitrites, ammonium and phosphates, moderate for sulphates and weak for detergents. It had a low content of silica, as well as anaerobic fermentation products (H₂S and S^2-) that were undetectable and quantitatively insignificant. The granulometry of the bottom-sediment samples of Corbu I Lake has identified muds, with the clay fraction subordinated to the silt. Due to the accumulated and decomposed biogenic material, black and unctuous muds with a specific odor were found. The interpretation of the data resulting from the grain size analysis highlighted the deposition of the sediments by suspensions in calm water with poor circulation, a different and poorly sorting and an excess of fine clastic material.