Assessment of the role of rock fragments in the retention of cadmium and lead in irrigated arid stony soils

In this paper we examined the possibility that the rock fragments (fraction > 2mm) of a stony cultivated arid soil from Jordan could retain Cd and Pb from a heavy metals solution. Rock fragments and fine earth were kept subme rged in heavy metal solutions for 150 days and sampled periodically. Cadmiu m and Pb adsorbtion from the solution were monitored and a selective sequen tial dissolution procedure was adapted for extracting the metals from the t reated rock fragments and fine earth. The rock fragments showed an active r ole in heavy metals retention and, with time, they sorbed Cd and Pb as much as the fine earth. Chemical processes involved in the retention are carbon ates coprecipitation and sorption by Mn and Fe oxides.