Heavy metals Analysis: Water samples were preserved
immediately after collection by acidifying with
concentrated HNO3 to pH < 2; by using 5 ml for 1 liter of
water sample. Heavy metals were extracted from the
collected water samples using nitric acid digestion method
according to APHA [22]. Fish samples (1.0 g dry weight)
were digested with 6 ml of HNO3 (65%) and 2 ml of H2O2
(30%) at 280°C on a hot plate for 4 h. Finally, 2 ml of 1 N
HNO3 was added to the residue and the solution
evaporated again on the hot plate, continuing until every
sample was completely digested. After cooling, a further
10 ml of 1 N HNO3 was added. The solution was then
diluted and filtered through a 0.45-µ nitrocellulose
membrane filter [24]. The metal concentrations were
measured using Atomic Absorption spectrometer Varian
Spectr AA (220) with graphite furnace accessory and
equipped with deuterium arc background corrector.