Only one sediment sample could be collected in the WWTP effluent channel (W.C., Figure 1 ), since the bottom at Cl2 (Figure 1 ) and Dp consisted of small pebbles. To evaluate the degree of pollution of this sediment sample we measured the concentrations of heavy metals (chromium, copper, nickel, lead, cadmium, zinc, cobalt, and mercury), arsenic, molybdenum, mineral-oil hydrocarbons, PAHs, and PCBs.
The methods used for determining heavy metal concentrations (Cr, Cu, Ni, Pb, Cd, Zn, Co, and Hg), arsenic, mineral oil hydrocarbons, and PAHs have been previously described in detail [20 (link)]. The concentration of Mo was determined in the same way as the heavy metals. For PCB detection, the oven-dried samples (5 g) were transferred to a Soxhlet apparatus and extracted with 100 mL of n-hexane. The extracts were evaporated on a rotary evaporator (Rotavapor R-210 with Heating Bath B-491, Vacuum Pump V-700, and Vacuum Controller V-850, Büchi) and concentrated in a stream of nitrogen gas. They were then transferred into a centrifuge tube and cleaned up with concentrated sulphuric acid (min. 96%). If the samples were highly contaminated repeated acid clean-up was employed. PCBs were quantified by a gas chromatography with a 63Ni Electron capture detector (GC-17A-ECD, Shimadzu) according to EPA 8082 [21 ] standard method.
The methods used for determining heavy metal concentrations (Cr, Cu, Ni, Pb, Cd, Zn, Co, and Hg), arsenic, mineral oil hydrocarbons, and PAHs have been previously described in detail [20 (link)]. The concentration of Mo was determined in the same way as the heavy metals. For PCB detection, the oven-dried samples (5 g) were transferred to a Soxhlet apparatus and extracted with 100 mL of n-hexane. The extracts were evaporated on a rotary evaporator (Rotavapor R-210 with Heating Bath B-491, Vacuum Pump V-700, and Vacuum Controller V-850, Büchi) and concentrated in a stream of nitrogen gas. They were then transferred into a centrifuge tube and cleaned up with concentrated sulphuric acid (min. 96%). If the samples were highly contaminated repeated acid clean-up was employed. PCBs were quantified by a gas chromatography with a 63Ni Electron capture detector (GC-17A-ECD, Shimadzu) according to EPA 8082 [21 ] standard method.