Geochemical phases of aluminum in the river sediments as indicators of its environmental availability

Abstract

Natural fluvial sediments are predominantly composed of river transported debris resulting from weathering and erosion of the basin. Understanding both the concentration and the distribution of metals in the river bed sediments in headwaters is essential to provide a scientific reference for the protection of water resources and the control of water pollution downstream. Sequential chemical fractionation studies of elements in various phases in the environment are widely used in investigating the effects of a particular element in the ecosystem. In this study, determination of aluminum (Al) bound to six phases operationally defined (soluble/exchangeable/specifically adsorbed, bound to manganese oxides, associated with amorphous compounds, bound to oxidizable organic matter, associated with crystalline iron oxides, and residual fraction) in the river bed sediment samples was performed in order to evaluate its potential environmental availability in the monitoring area. Aluminum contents were determined by flame atomic absorption spectrophotometry. The pattern of fractionation of Al in the sediments that are studied suggests that this element does not pose a risk to the aquatic environment under the current environmental conditions since it is mainly part of the potentially less bioavailable geochemical fractions.