The sample had to be diluted many folds to keep the results in the analytical range. The heavy metals (Pb, Cd, Cr, Cu and Mn) concentrations in all samples were determined by atomic absorption spectrophotometer (AAS) (Model AA-6800, Shimadzu Corporation, Japan) using an airacetylene flame with digital read-out system (Kenawy et al., 2000;Loska and Wiechuła, 2003; Tapia et al., 2012).