Effect of soil erosion and topography on distribution of cadmium (Cd) in Sumani watershed, west Sumatra, Indonesia

The purpose of this study was to characterize and present the distribution of heavy metals especially Cd on agricultural and non-agricultural lands and river sediments in relation to soil erosion and topography status in watersheds. The study was conducted for a detailed soil survey by collecting 146 soil sample based on land use, soil family and topography position and 23 river sediments sample. The Cd was extracted by 0.1 M HCl and determined by ICP. The result showed that the concentration of Cd in soil and river sediment were low in toxicity based on FAO recommendation (Cd 0.4 mg/kg) with only 4 out of 169 sampling sites contained Cd exceeding the toxicity level. Volcanic ash from Mount Talang Volcano is a natural source of Cd in Sumani watershed. Cd concentration was low in areas with high soil erosion, which indicate material translocation caused by high soil erosion that accumulates sediment in plains and rivers. Agricultural soil was found to be low in soil pH and clay accompanied by high R factor and upland topography hence the increase in Cd concentration of the soil. The study concluded that Cd abundance in soils may be influenced by soil pH, texture, total carbon, erosion factors, and topography