| Abstract [eng] |
Bottom sediments of water bodies are an important sink for pollutants from the environment. As environmental conditions in water bodies change – pH, oxidation-reduction potential, salinity, etc., pollutants can be released from the surface layers of sediments into the aquatic environment. Heavy metals (referred to as HMs) found in bottom sediments are pollutants of great importance due to their stability in the environment, toxicity to living organisms and bioaccumulation. In order to assess the potential HM pollution in water bodies and the risk posed by such pollution to the environment and humans there is a need to conduct studies of bottom sediment contamination by HMs. The aim of this work is to assess and evaluate the contamination of relatively natural Lake Avinėlis and artificial Kalesninkai reservoir bottom sediments by heavy metals. 4 cores (250 samples) were collected from Lake Avinėlis; 5 cores (45 samples) were collected from Kalesninkai reservoir. HMs in bottom sediment samples were determined using the X-ray fluorescence spectrometry method, Niton™ XL2, 700 device. The concentrations of HMs detected in the sediments of Kalesnikai reservoir did not exceed the limit values established in the hygiene standards of Lithuania. Contamination by As was detected in the central part of Lake Avinėlis, As concentrations in the surface layers of the bottom sediments exceeded the limit value of 20 mg/kg by 4 to 15 times. The results of the study show a greater diversity of HMs in the bottom sediments of Kalesnikai reservoir compared to the bottom sediments of Lake Avinėlis. The average As concentrations determined in the surface sediments of Lake Avinėlis (up to 50 cm depth) are 19 times higher than in the bottom sediments of Kalesninkai Pond; the Zn concentrations determined in the bottom sediments of Kalesninkai Pond are 1.4 times higher than in the bottom sediments of Lake Avinėlis. Cr concentrations in the bottom sediments of Lake Avinėlis are below the detection limit; average Cr concentration in Kalesninkai Pond is (31.2 ± 14.3) mg/kg. As contamination was detected in the central part of lake Avinėlis. No As concentrations exceeding the limit values were detected in samples collected on the inflow and outflow parts of the lake. Obtained data indicates a point source of As pollution in the central part of lake Avinėlis that is not related to the natural water inflow into the lake, and likely is an anthropogenic source of As contamination. |
