A survey of the thermodynamic of evaporate salts in ODe oftbe Yazd playas based 00 a grouod sampUog aad remotesensing

This study was done in ehe wet marginal part of the Siahkooh playa (Kevir) in Yauf. Iran. which is located in the northwest of Ardakan. The abundance of Ca and SO. iones led to gypsum crystallization ncar the water table in the soil. From depeh to the soil surface, the caC~- CaSO .. ,2H,O -NaCI-H,<)-PCo, soil and water system change to CaSO •• 2H,<)Na1SO .. ·NaCI· Hz{). From water table (I00cm under soil surface) to the soil surface. ionic power was decreased and activty coefteient was incrased respctivcly. Therefore. ncar ground table, gypsum fonn and high concentration of Ca iones from gypsum lead to low amounts of exchangeable Na. This influence has been continued up to soil surface to achieve a relative balance. Replacement ofNa with Ca on the exchangeble surfaces of soil and ex~ of SO .. ioncs formed NaSO .. ineraJs. The precipitation of 1800ton per hectar natrium salts(sulfatic &. coloridic) was estimated wjth respect to the mean of annual evaporation (roughly 900mm) in the studied site. The result also showed that the seventh bands ofI .. odsal7 are more important to diferentiate between sulfate and chloride salts as well as sodium and calcium salts.