Speciation of native copper in some soils of Bangladesh

Abstract

The distribution of Cu among different fractions of soils was studied. Soil samples were collected from three soil series viz., Gerua, Kalma and Khilgaon, were identified from three land types such as high, medium high and medium low land in an ideal catena of Madhupur terrace soils of Gazipur District. The amount of total Cu varied significantly ranging from 10.44 to 26.92 µg g-1 at different depth of different land types. Speciation of the native Cu was done by sequential extraction to assess the exchangeable (Exch.), organic matter (Org.), Mn oxide (Mn-O), amorphous Fe oxide (Am. Fe-O), crystalline Fe oxide (Crys. Fe-O) and residual (Res.) fractions. The available concentrations of Cu were almost similar throughout the whole catena. In addition, most of the mobile fractions such as Exch. and Org. bound fractions of the elements decreased from high land to medium low land or from upper layers to lower layers of the catena. Exch. and Org. bound Cu showed significant positive relationship with organic matter. The amount of Cu in the Res. fraction increased apparently with increase in pH while low pH was responsible for the distribution of the element into mobile fractions.