Identifying the controlling mechanism of geogenic origin chromium release in soils.

A laboratory study was conducted to assess the mobility and mechanisms of chromium release from soils obtained from an area of wide spread geogenic contamination. The agricultural soil sample used in this study was taken from the Schimatari area in Asopos River basin in Greece. In order to refine the isolation of minerals contained in the soil, two types of separation analysis were conducted. First, a size fractionation with hydrocyclone and second, a weight fractionation with heavy liquids. The separated fractions were characterized using chemical, mineralogical and surface analysis. The results provided consistent evidence that the heavy fraction of the soil is related directly to the mobile fraction of chromium. At acidic pHs, the clay-sized fraction also plays an additional important role in the mobility of Cr, due to the fact that this fraction has high surface area and chromium reactivity index. In addition, pH-edge leaching studies showed a high correlation between Cr-Ni, Cr-Mn and Cr-Y released from the soil which also suggests that the mobility of chromium is controlled by chromite weathering which is the case observed in Asopos river basin.