METHYLMERCURY IN TISSUES OF FISH FROM THE SVRATKA RIVER, CZECH REPUBLIC

Mercury is a global pollutant with a disturbing occurrence and fate in aquatic ecosystem where it is accumulated especially in fish through a transformation process to create its most toxic form - methylmercury. This study is focused on the evaluation of contamination of fish (muscle and skin tissue) from the Svratka River (South Moravian Region, Czech Republic) by methylmercury. The fish were caught at two sampling sites - upstream and downstream from the municipal wastewater treatment plant (WWTP) Brno-Modrice. Extraction of methylmercury was performed according to a method based on methylmercury digestion in hydrochloric acid and its subsequent extraction with toluene. The subsequent analysis was carried out using a gas chromatograph equipped with a DB-17 capillary column and a micro electron capture detector. Selected samples were also analysed to determine total mercury concentrations using a special single-purpose atomic absorption spectrometer for determination of mercury. Obtained data were statistically evaluated. The normality of the data was rejected in most cases, and thus nonparametric statistical methods were used for further analysis. The highest levels of methylmercury were observed in muscle tissue of fish caught upstream from the WWTP - 77.89-865.7 mu g times kg super(-1). Generally, methylmercury levels were significantly higher in muscle than in skin. Levels of total mercury in selected muscle samples varied from 96.06 to 194.6 mu g times kg super(-1) and from 73.5 to 144.8 mu g times kg super(-1) for fish caught upstream and downstream from the WWTP, respectively. None of the samples exceeded the limit for total mercury in fish muscle tissue applied by the Czech Republic.