Assessment of heavy metal pollution in bottom sediments of small water reservoirs with different catchement management

The main purpose of this work was to determine the degree of negative impact of heavy metals accumulated in the water sediments to aquatic organisms. Samples of sediments were collected in winter 2013, from 4 layers of sediment (0-5, 5-10, 10-20 and 20-30 cm) at three points along the water reservoir. Sediments were prepared for analysis in accordance with the procedures applied in soil science. The analysis was carried out for the fraction with a particle diameter less than 1 mm. The total content of such elements as Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn, was determined by atomic absorption spectrometry (using the Thermo Scientific iCE 3000 series spectrometer) after digestion in a mixture (5:1) of concentrated acid HNO3 (65 %) and HClO4 (60%). The total Hg content was obtained by using the AMA 254 analyzer. Only the lead content in the analyzed samples of bottom sediments exceeded the contamination value given by polish law (the Regulation of the Minister of Environment). According to the classification of PGI samples of sediments are classified mainly as medium polluted sediments (Class II), with the exception of zinc and lead concentrations (Class III). Due to the value of the indicator of sediments ecological risk (Er) for cadmium, the examined sediments from small water reservoirs no. 1 and 2 should be classified as deposits with a higher rate of environmental contamination risk. The sediments from small water reservoirs no. 3 and 4 belong to the class of a much higher index of contamination risk. On the basis of the PER indicator (a degree of potential envi ronmental risk) the sediments from small water reservoirs located within the area of organic farming can be classified as contaminated by heavy metals to a moderate degree. On the other hand, the analyzed sediments of small water reservoirs no. 3 and 4 were classified as deposits with a severe degree of heavy metal contamination. On the basis of the LAW classification one can say that the bottom sediments of examined ponds were classified into different classes depending on the analyzed chemical element.