HEAVY-METAL CONCENTRATIONS IN COMMON FRESH-WATER SNAILS OF AZRAQ OASIS, JORDAN

Heavy metal concentrations in three freshwater snails, an aquatic plan t, sediment, and water from Azraq Oasis pools in the Jordanian desert were measured by atomic absorption spectrophotometry. There were signi ficant differences in metal accumulation among snail species. These sn ails are ranked according to their metal accumulation capacity in the order: Melanoides tuberculata > Melanopsis praemorsa > Theodoxus jorda ni. Although there were no significant differences among the size clas ses of these snails in metal concentrations, larger snails contained g enerally higher levels of metals than the smaller ones. The concentrat ion factors for the selected snails exceeded 10(3), while it ranged fr om 0.1-10.2 x 10(3) for Typha angustata plants. Among sampling sites, metal concentrations in M. praemorsa, T. angustata, sediment, and wate r were not significantly different, except for Fe in M. praemorsa whic h was highest at station 3, and Cd and Cr which were highest in water and sediment of station 4. The seasonal variation in metal content was found to be species and metal-dependent.