Heavy metals uptake and excretion in different plant species of Kushk arid ecosystem, Yazd province

This research was followed after few introductory surveys of heavy metals distribution in the mining zone of the Central Iran. The research was carried out in the territory of Kushk Mining Company, located at45km northeast from Bafgh city and 145 km from Yazd city. The morphology of the area is mountainous. The major desert shrubs in the polluted area are Artemisia siberia and Salsola vermiculata. The surface soils (depth:0-25cm) and 10 samples from each plant species with root, juicy stems and second years old stems were randomly collected to a distance of about 8 km (where metal concentrations in soil were decreased to a minimum amounts) from mining waste dam. Because of the lead and zinc mining operation in Kushk, the lead, zinc and cadmium in soil and plant samples were measured. Also due to secondary formation of gypsum in mine formations, calcium in the samples was measures as an essential element for plants. Desert shrubs in despite the impressions have an special living pattern and so different behaviors in uptake and excretion of heavy metals. The accumulation of metals (lead, zinc, cadmium and calcium) in juicy and fresh shoot organs were increased about 2.5 times more than roots and were decreased from a mean concentration of 85.82 ppm in juicy stems to a minimum mean concentration in dry stems with the mean of 0.0 ppm in A. sieberi less accumulation of heavy metals in fresh shoots relative to root with a more accumulation of Ca have been shown in A. sieberi and S. vermiculata showed any significant difference in means of metals in its organs but the mean of heavy metals were increased in its shoots (from 4.6 ppm in root to 12.91ppm in shoot) and the mean of metals were decreased in shoots (from 153.52ppm in root to 134.69ppm in shoot).