دکتر حمیدرضا پاکزاد

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. © 2014, Springer-Verlag Berlin Heidelberg.

2014

Distribution and origin of heavy metals in the sand sediments in a sector of the Oman Sea (the Sistan and Baluchestan province, Iran)

( Article . )

Pakzad, H.R., Pasandi, M., Soleimani, M., Kamali, M.

Quaternary International (10406182)345pp. 138-147

Distribution of heavy metals in the clastic fine-grained sediments of Gavkhuni playa lake (Southeast of Isfahan, Iran)

( Article . )

Pakzad, H.R., Pasandi, M., Rahimi, H.

Environmental Earth Sciences (18666299)71(11)pp. 4683-4692

The sedimentary basin of Gavkhuni playa lake includes two sedimentary environments of delta and playa lake. These environments consist of mud, sand and salt flats. There are potentials for concentration of heavy metals in the fine-grained sediments (silt and clay) of the playa due to existence of Pb/Zn ore deposits, industrial and agricultural regions in the water catchment of Zayandehrud River terminating to this area. In order to study the concentration of heavy metals and the controlling factors on their distribution in the fine-grained sediments, 13 samples were taken from the muddy facies and concentration of the heavy metals were determined. The results showed that the heavy metal concentrations range in the sediments (in ppm) are Mn (395.5-1,040), Sr (100.4-725.76), Pb (14.66-91.06), Zn (23.59-80.9), Ni (37-73.66), Cu (13.83-29.83), Co (5.73-13.78), Ag (3.03-4.76) and Cd (2.3-5.5) in their order of abundances. The concentration of Ag is noticeable in the sediments relative to the average concentration of this element in mud sediments. The amounts of Pb and Zn are relatively high in all the samples in comparison with the other elements. The concentration of Ni is relatively high in the oxidized samples. The distribution of Pb is directly related to organic matter content of the sediments. The concentrations of Zn, Sr, Cu, Co and Cd in the samples of the playa are lower than those in the delta. The amount of illite is another factor influencing Zn and Pb concentrations. Sr is more concentrated in the sediments with the high content of calcium carbonate. The distribution pattern of Cu, Co, Pb and Mn resembles to that of the clay content of the sediments. The clay content shows positive correlations with Co, Cu and Mn concentrations and negative correlation with Ag. The Sr and Ag concentrations are positively correlated with the amount of CaCO3. The amounts of Co, Cu, Ni and Mn show negative correlations with the calcium carbonate content. Pb and Co are noticeably correlated with Mn. © 2013 Springer-Verlag Berlin Heidelberg.

2007

Geomorphological features in the Gavkhoni playa lake, SE Esfahan, Iran

( Article . )

Pakzad, H.R., Kulke h.,

Carbonates and Evaporites (08912556)22(1)pp. 1-5

Sedimentology and stratigraphic sequence of the Gavkhoni playa lake, SE Esfahan, Iran

( Article . )

Pakzad, H.R., Fayazi, F.

Carbonates and Evaporites (08912556)22(2)pp. 93-100

The provenance of the Varzaneh aeolian sand field regarding to lithology and texture, SW Esfahan, Iran

( Article . Green )

Pakzad, H.R., Ajalloeian, R.

American Journal of Applied Sciences (discontinued) (15469239)4(8)pp. 547-553

2004

Geochemistry of the Gavkhoni Playa Lake brine

( Article . )

Pakzad, H.R., Ajalloeian, R.

Carbonates and Evaporites (08912556)19(1)pp. 67-74

The Gavkhoni Playa Lake is located to the southeast of Esfahan, Iran. It is surrounded by the Varzaneh aeolian sand field to the west and alluvial/fluvial sediments to all other directions. It is typical of the few permanent lakes within closed drainage basins in Iran. The properties of intermittent fine-grained and coarse-grained siliciclastic and finally fine-grained evaporite sediments suggest that the basin was influenced repeatedly by wet and dry periods. During periods of flooding, it had been a shallow permanent lake. With increasing aridity, the middle of the lake became increasingly restricted and shallower which resulted in the formation of a salt pan, contributing to the nature of the lake brine. Due to the enclosed nature of the lake system, the water chemistry of Gavkhoni Playa Lake is dominated by sodium and chloride ions but shows wide variations in composition and concentration through time and location. The percentage of Na+(1,012 to 10,3040 ppm), Cl(4,118 to 19,9365 ppm), Mg2+ (360 to 25,691 ppm), and K+(78 to 3,570 ppm) is highest toward the south and at a minimum in the north. Calcium content, ranging from 160 to 3,480 ppm, appears highest in the north. The percentage of strontium (5 to 292 ppm) with the highest value to the north, is extremely low in comparison to other elements. Sulfate is another abundant anion in the brines with the highest content of 22,051 ppm. Bicarbonate is a minor anion ranging from 73 to 450 ppm with the highest values to the north and west. The concentration of sulfate and bicarbonate does not change regularly in the brines from north to south, nor does it vary seasonally. The chemical analysis of the brine shows that it becomes progressively depleted in carbonate and sulfates from the margins to the center of the lake. It ultimately became a Na+, (Mg2+), Cl-brine type in the northern section and a Na+, Mg2+, Cl-brine type in the central part of the lake. After complete desiccation, the mineral assemblage exhibited halite, camallite, bischofite, and tachyhydrite in abundance.