Assessment of the natural and anthropogenic sources of chemical elements in alluvial soils from the Drava River using multivariate statistical methods

The objectives of this study are as follows: (a) an assessment of the geochemical background signature of the Drava Valley before the industrial revolution; (b) an evaluation of anthropogenic geochemical influences on the alluvial plains and river terraces in the valley; and (c) a determination of the spatial distribution of trace elements in the alluvial soils of the Drava River downstream of the Austrian–Slovenian border to the confluence of Mura and Drava Rivers.Samples of topsoil (depth of 0–5 cm) and subsoil (depth of 20–30 cm) were collected from 134 sampling sites on alluvial plains and river terraces. Analysis for 41 chemical elements was performed. Based on a comparison of statistical parameters, the spatial distribution of particular elements and the results of factor analysis, one anthropogenic and three natural geochemical associations were identified. The anthropogenic association (As–Ba–Cd–Mo–Pb–Sb–Zn) is mostly a result of historical zinc and lead mining and smelting in the Drava River watershed. The natural geochemical associations (Al–Fe–K–Co–Cr–Cu–Li–Ni–Rb–Sc–Th, Ti–Ce–La–Nb–Ta and Ca–Mg–Sr) were mainly influenced by lithology. The entire assessed area of about 130 km2 is, according to Slovenian and Croatian legislation, critically polluted with trace elements, especially zinc.

► Mines and smelters contributed to the Drava alluvial sediments.
► One anthropogenic and three natural geochemical associations were identified.
► Al–Fe–K–Co–Cr–Cu–Li–Ni–Rb–Sc–Th, Ti–Ce–La–Nb–Ta and Ca–Mg–Sr are effects of lithology.
► As–Ba–Cd–Mo–Pb–Sb–Zn is influenced by historical zinc and lead mining and smelting.