The Environmental Significance of Cadmium in Contaminated Soils

The increased input of heavy metals from the widespread disposal of industrial wastes has led to a growing public concern on the issue of their fate, bioavailability and significance in the environment. This study was carried out mainly to study the solid-solution phase distribution, chemical speciation and plant uptake of cadmium in soils amended with Cd nitrate salt at rates of 5 -40 mmol/kg for incubation times varying between 3 -15 months. The solid phase speciation of Cd in soils amended with Cd nitrate at rate of 5 mmol/kg was estimated using Inductively Coupled Plasma-Mass Spectrometry (lCP-MS) after the soils were sequentially extracted with IM NH4OAc, 0.125 M Cu (OAC)2 and 1M HNO3. MINTEQA2 version 3.0 which is used to explore the speciation of cadmium in the solution of the three soils revealed the majority of metal as the free ionic Cd2+. Greenhouse experiments were conducted to study Cd uptake by plant grown on soils amended with cadmium nitrate at levels from 0 -20mmollkg soils, using Lettuce (Lactuce sativa) as the bio-monitor. Significant positive correlations were obtained between the bioconcentration of Cd by plant and the Cd amendments, exchangeable chemical fraction and residence time.