Abstract
The aim of this study is to investigate the distribution of selected heavy metals and metal–resistant bacteria in water and bottom sediments of the surface drinking water reservoir for Gdansk. The following sequence of metals in regard to metal concentration in sediments can be written down: Zn > Pb > Cu > Cd. The evaluation of metals accumulation was performed using the Muller index, to indicate the bottom sediment's contamination and geochemical classification of sediment quality according to Polish standards. The Muller geochemical index was changing in a wide range: < 1–4.1. Although the maximum value of Muller's geochemical index determined for copper indicates that the sediment is ‘strongly contaminated’, in general the analysed bottom sediments were classified as the I and II category according to Polish geochemical standards. From the microbiological side 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.
Highlights
Heavy metals are one of the most widespread contaminants in the environment
Some heavy metals are required for the normal functioning of bacteria, fungi, plants and animals [16, 17] most can be toxic to all branches of life
The maximum value of the Müller’s geochemical index was determined for copper: it was in the range 3–4 which means that the sediment was ‘strongly polluted’
Summary
Heavy metals are one of the most widespread contaminants in the environment They cause the environmental pollution from sources such as industrial effluents, mine tailings, land application of fertilizers, atmospheric deposition and leaching of metal ions from the soil into lakes and rivers by acid rain [1,2,3]. The environmental pollution as well as the widespread use of antibiotics promote the formation of the mechanisms of resistance in bacteria. Chemical disinfection contributes greatly to the control of microorganisms from treatment plant to point of use [18]. It can promote the survival of bacteria resistant to chlorine compounds, antibiotics as well as heavy metals
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