series of samples (Muller et al., 1994). After acid digestion,the sample solutions were cooled and filtered using Whatman(no. 541) paper. The filtered solution was made up to
100 ml with distilled±deionized water. Samples were analyzed for Cu, Pb, Zn and Cr by a flame atomic absorption spectrophotometer (Perkin-Elmer Model 3030) using air±
acetylene flame with deuterium lamp background correction. Cd and Al were analyzed by an atomic absorption spectrophotometer Perkin-Elmer Model 3030 equipped with a graphite furnace (Perkin-Elmer Model HGA-600 Graphite Furnace and AS-60 autosampler). Quantification of the metals was based on calibration curves of standard solutions
of respective metals.