Cadmium availability in calcareous soils of agricultural lands in Hamadan, western Iran

Determination of various chemical forms of cadmium in soils is important to evaluate its mobility and adverse effects on soil quality. We have assessed availability and partitioning of Cd in selected calcareous soils varying widely in physicochemical properties under different management practices. Surface soils were collected from the main agricultural areas in Hamadan, western Iran. The DTPA-extractable Cd was in the range of 0.010 to 0.042 mg kg(-1). The background value (typical range of concentration) for Cd was 0.01 to 0.02 mg kg(-1). Land use had a significant effect on DTPA-extractable Cd. The distribution of Cd in soils was as follows: NaOH (35.6-72.7%) > HNO3 (7.8-41.7%) > EDTA (16.1-32.6%) > KNO3+H2O (0.38-2.1%). The proportion of mobile fraction in the soils under vegetables field was higher compared to the other management practices, suggesting greater contribution of anthropogenic metals. Statistical analysis of the DTPA-extractable Cd with different Cd fractions showed that the DTPA-extractable Cd was most significantly correlated (r =0.82; P < 0.01) with the exchangeable fraction.