At each site three to, five 5 cm deep samples were taken.And mixed evenly. Then the samples saved in prepared brown.Glass bottles were sent back to the laboratory within 24 hr and.Frozen in order to avoid contamination of the samples.Geographical information of the samples was recorded by.The Global Positioning System (GPS) (Table 1).All the collected samples were freeze-dried crushed and,,,Then sieved through a 100-mesh sieve. Approximately 0.5 g.Dried surface sediment samples were digested in 5 mLaqua.Regia (HNO3: HCl = 1: 3) and heated at 140 ° C until the samples.Turned grey. Then 3 mL HClO4 was added into the cooled.Samples (Qiao et al, 2011). The residues were diluted with.Deionized water to 25 mL for determining concentrations of.Heavy metals. Sample solutionswere stored in the refrigerator.At 4 ° C and then were analyzed for the main heavy metals.Including Cr Cd Cu,,,,, Pb Zn Ni and As with an inductively.Coupled plasma - optical emission, spectrometer (ICP-OESTeledyne Leeman Labs Hudson NH USA,,,).
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