Toxic Metals in Urban Reservoirs in the Prague Metropolitan Area (Czech Republic)

Abstract

Levels of selected toxic metals (Cd, Cu, Cr, Ni, Pb, Zn, Mn, Fe and Al) were determined in water, sediment and different species of fish in twelve reservoirs of the Prague metropolitan area. These reservoirs are affected by different types of urban drainage systems, which alter the level and fate (properties, availability, accumulation, toxicity) of toxic metals in the aquatic environment. Measurements of toxic metals were complemented by analysis of basic water quality parameters. Environmental quality standards (EQS) were exceeded in more than 50% of the studied reservoirs for the following chemical parameters: total organic carbon (TOC), chemical oxygen demand (COD) and phosphate (PO 4 3-). These parameters indicate a significant organic pollution and a high eutrophication level. Copper was identified as the most hazardous pollutant among the selected toxic metals in water. Other metals (Zn, Fe, Mn) exceeded the EQS only exceptionally. High concentrations of copper and zinc resulting in exceeded EQS were also identified in the sediment of most reservoirs. In a few cases increased concentrations of chromium, cadmium and lead were exceeded the EQS. A high variability of metal levels was detected in fish species, according to their age and food habits. The highest levels of toxic metals were found in the Kyjský reservoir (Zn, Cu, Ni, Cd and Pb), Strnad reservoir (Zn, Cu, Cr and Fe) and the retention reservoirs Stodůlecký N3 (Zn, Cu and Cr) and Hájecký RN3 (Zn, Cu, Cr and Pb). These reservoirs are highly affected by different anthropogenic activities, such as printing industry, traffic (Prague's ring road) and wastewater treatment plants.