Kinetics of Manganese Release from some Calcareous Soils



Manganese release kinetics was studied in six composite soil samples by using DTPA as the extracting solution in %35 of saturation moisture and in time range of 0.25- 960 hrs. In all the samples, the release of Mn was initially, relatively fast (with 25 – 55 % of total Mn released during the first 10 hrs), then the rate diminished gradually, approaching zero after a lapse of 720 hrs. Six mathematical equations (zero-order, first-order, second-order, power function, simplified Elovich and parabolic diffusion) were employed to describe and evaluate the kinetics of manganese release. A comparison of the equations, by means of comparing the coefficient of determination (r2) and the standard error of the estimate (SEE) of the equations, indicated that the power function equation best described the kinetics of Mn release, as evidenced by the highest correlation coefficient (r2) along with the lowest value of the standard error of the estimate(SEE).The first-order, second-order, and parabolic diffusion equations, because of their relatively high correlation coefficients and small standard errors, could also be used to describe Mn release kinetics. However, the zero-order and the simplified Elovich equations did not so properly describe manganese release.