Heavy metals in river sediments ? A chemometrical evaluation

Abstract

First results are presented to support decisions within projects of recultivation in the Merseburg region. From two places of the river Luppe eight sediment samples were taken at four different days. The total concentrations of Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn were determined by ICP-AES after digestion with aqua regia both in the gross samples and in four particle size fractions obtained by wet sieving. Subsequently each fraction was split into six classes by a sequential extraction to characterise the pattern of heavy metal binding form. Questions about the difference of the regions, the importance of the particle size fractions, the mobility of the metals, and the influence of the seasonal factor were tried to answer by the help of chemometrical methods. It was possible to show that the two sampling places situated only about 7 km from each other have different total metal concentrations as well as different binding form patterns. The trend of the heavy metal enrichment in the smallest particle size fraction can easily be seen in two-dimensional diagrams, but could in general not be confirmed statistically for all metals. The consideration of all four factors together (region, particle size fraction, mobilisation class, and time) shows the significant influence caused by all factors and all interactions. Multivariate covariance analysis is used to include also the influence of sampling conditions.