Distribution of different forms of copper in freshwater pond soils of Orissa, India

The distribution of native copper fractions in freshwater pond soils of Orissa and their relationship to important soil properties were studied. Total Cu and diethylene triamine penta acetic acid (DTPA) extractable Cu ranged 7.0-24.0 and 2.0-4.9 mg/kg soil, respectively, with mean values of 12.7 and 3.1 mg/kg. The amounts of exchangeable, weakly adsorbed, moderately adsorbed, strongly adsorbed and organic matter associated Cu ranged 1.7-2.6%, 3.5-6.0%, 3.3-6.6%, 0.7-2.2% and 0.8-7.2% of the total Cu, respectively. Cu occluded or bound by carbonates or other acid-soluble mineral fractions was 1.5-6.1% of the total Cu. Most of the Cu (58-91%) was in the residual fraction. All the chemical fractions of Cu significantly correlated with each other and with the organic carbon status of the soils.