Time-dependent copper extraction in different soil orders as influenced by soil to extractant Ratio

Abstract:In order to study and compare patterns of time-dependent copper (Cu) extraction in different soil orders and to investigate the effect of soil to extractant ratio (SER) on the rate of Cu release in different soil orders, a laboratory experiment was designed with ten soils from five orders. Soil samples were extracted using DTPA extractant for periods of 1, 10, 30, 60, 120, 240, 480, and 1440 min. Overall patterns of Cu extracted was characterized by a fast release reaction during the first two hours followed by a slower reaction and the pattern well fitted to power function, parabolic diffusion, and Elovich models. At SER = 1: 2 (SER1/2) Cu release rates were in order: Vertisols › Alfisols › Inceptisols › Histosols › Mollisols. At SER = 1: 10 (SER1/10), however, Cu release rates were in order: Histosols › Vertisols › Alfisols › Inceptisols › Mollisols. Results showed that the amounts of Cu released at SER1/10 were 76 to 316% higher than those of SER1/2 in different soil orders. The difference in the extraction capacity of the extractant between two SER was more considerable in Mollisols and Histosols and in all soils decreased with time. According to results of correlation coefficients between soil properties and percent increase in Cu extraction at SER1/10 than those of SER1/2, it is assumed that the higher extractant distributed to the soil per unit weight at SER1/10 might be responsible for higher dissolution of Cu bound to carbonates and OM which are potentially available forms, besides other available forms.