Resumen de Heavy metal distribution in the salt pan of Gavkhuni playa lake (southeast of Isfahan, Iran)
Hamid Reza Pakzad, Mehrdad Pasandi, Masoumeh Zaheri
The Gavkhuni playa lake consists of sand, mud, and salt flats. The salt pan covers extensive part of the playa. Its color is usually clear and white, but black, pink and green colors also occur. The black color of halite has been caused by impurities of detrital sediments. The sand detrital sediments have been derived from the aeolian sands located in the west of the playa lake. The pink to light red color of the halite is due to the existence of iron oxides or/ and microbial effects. There are potentials for natural concentrations of heavy metals in the evaporite sediments of this lake especially due to the occurrence of sedimentary Pb/Zn ore deposits in its drainage basin. To study the concentration of the heavy metals in the salt pan, 18 samples were taken from the salt pan and analyzed. The results show that average concentrations (ppm) of the heavy metals in the salt pan are Ni (56.46), Sr (26.46), Pb (11.42), Ag (10.70), Mn (6.15), Co (2.86), Cd (1.98), Zn (1.48) and Cu (1.14) in their order abundances. The amounts of Zn, Mn, Sr, Cu, Cd and Pb are relatively high in samples containing calcium minerals. The concentrations of Mn and Cu in the pink and green salts are relatively higher than the white ones, because these metals tend to be adsorbed by organic matter. Manganese oxides are important factors influencing the Ni concentration in the sediments. The Mn and Sr concentrations increase in the samples containing iron silicate minerals and carbonate grains. The Co and Ni concentrations are high in the samples containing Fe/Mg-bearing clastic grains. The Ag concentration is high in the samples containing sulfide minerals. Strong adsorption of Mn2+, Co2+ and Zn2+ to clay minerals and precipitation of Cu as Cu, Cu2S, CuS and Pb as PbCO3 and PbS in the mud sediments can be the reasons for the lower concentrations of these elements in the pure salt sediments than the mud deposits. Enrichment factor indicates that Ag is moderately enriched and other elements are weakly enriched in the evaporite deposits.
