Abstract

The aim of this study is investigate the distribution of selected heavy metals (zinc, copper, lead, cadmium) and metal-resistant bacteria in water and bottom sediments of drinking water reservoir for Gdańsk (Poland). The research area - Straszyn Lake is a dam reservoir on Radunia river, of the total volume of 3 mln m3. Sediment and water sampling took place between May and October 2013 (eight series). Regarding metal concentration in sediments the following sequence of metals can be written down: Zn>Pb>Cu>Cd. These metal concentrations were slightly higher than the average ones for Pommeranian Region. Evaluation of metals accumulation was performed using Müller index, which is arranged from the numbers 0 to 6 to indicate the bottom sediment’s contamination and geochemical classification of sediment quality according to Polish standards. Müller geochemical index was changing in a wide range: the lowest values for each metal were observed in the sampling point located near the inflow of Radunia river, and the highest – near the dam. The maximum value of Müller’s geochemical index was determined for copper: 4.1 which means that the sediment is ‘strongly contaminated’. However, the analysed bottom sediments were classified as the I and II category according to Polish geochemical standards. A significant part of heterotrophic bacteria isolated from the bottom sediment and surface water (raw and treated water) showed a resistance to 0.2 mM and 2 mM concentrations of zinc, copper and lead. The highest percentages of metal- resistant bacteria were recorded in the sediments of the reservoir (60% - 88%). The share of metal-resistant strains in the raw water was significantly lower (34% - 61%). The results indicate also that water treatment processes may contribute to the selection of resistant strains.

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