Modes of occurrence of tungsten in alluvial soils and river sediments in the area of the Grantcharitsa tungsten deposit, Western Rhodopes, Bulgaria

A distinct increase in the concentration of W in the topsoil (from 19-20 to 71 ppm) is found in the vertical profile of the alluvial soil at the Grantcharitsa deposit. The distribution of W, Fe, and C is well correlated, which indicates a significant role of organic material and iron oxides/hydroxides formed in the soil in the chemical behavior of W. The role in these processes of scheelite, W-containing goethite and rutile identified in the soil is insignificant.