New approaches to studying heavy metals in soils by X-ray absorption spectroscopy (XANES)) and extractive fractionation

Abstract

A comprehensive approach to studying the nature of interaction between heavy-metal ions and the organic–mineral matrix of soils involves application of modern physical analytical techniques and chemical methods of extractive fractionation. XANES was used to obtain the first data on the near-edge fine structure of X-ray spectra for a number of heavy-metal species in ordinary chernozem. Data on the structure of soil samples saturated with Zn²⁺ and Cu²⁺ obtained by XANES (X-ray absorption near-edge structure) make it possible to elucidate the interaction mechanisms of the metals and the types of chemical bonds formed thereby. As contamination doze of with Cu and Zn is increased (from 2000 to 10 000 mg/kg soil), particularly if the metals are introduced in the form of readily solubility salts, bonding between the metals and soil components weakens. Data of extractive fractionation of metal compounds from samples saturated with Cu and Zn compounds testify that the Cu²⁺ ion is preferably retained in the organic matter of the soil, whereas the Zn²⁺ ion is bound mostly to silicates, carbonates, and Fe and Mn (hydro)oxides.