Sequential extraction studies on homogenized forest soil samples

Sequential extraction studies on two forest soil samples from the German Environmental Specimen Bank are presented. The reagents used in the five-step extraction scheme are: dilute ammonium acetate; 0.1 M acetic acid; 0.1 M hydroxylamine hydrochloride in 25% acetic acid; hydrogen peroxide; and hot concentrated nitric acid. Several elements in the extracts have been determined by ICP-MS and ICP-AES. The extraction behaviour of Mg, Ca, Mn, Fe, Co, Ni, Cu, Zn, As and Pb in this procedure is discussed with respect to the quantities extracted and the properties of these reagents in releasing the elements from the various solid phases usually considered in the literature. The studies indicate that reducible oxides and organics retain the major mobile fraction of the elements investigated. It has been found that the extraction time can be considerably reduced without compromising the chemical information for soil characterization.