Spatial distribution of metallic trace elements in soils contaminated by atmospheric fallouts. Case study: Sclaigneaux (Belgium)

The valleys of Sambre and Meuse in Wallonia hosted numerous metal ore treatment factories. They engendered a contamination of soils by metallic trace elements that may migrate in the landscape through erosion, lixiviation, biological transportation, aso. We investigated the spatial distribution of some metallic trace elements in soils around a former zinc-ore treatment plant to a distance of 3km. The sampling strategy aimed at (i) verifying that the main source of trace elements was the plant chimney, (ii) assessing the impact of the wind directions on fallout dispersion and (iii) evaluating whether there were differences of contents according to soil types and to soil occupation. Two hundred and fifty topsoil samples were collected according to a stratified design dealing with distance to the chimney, direction of dominant winds, soil type, and land use. Pseudo-total contents in inorganic elements, pH, TOC, and N were determined in the laboratory. Besides, classical statistical analysis (i) ANCOVA (three-way ANOVA with the distance as a co-variate) and (ii) Principal Component Analysis were also performed. First results show that (i) zinc, lead and cadmium contents are closely correlated to each other and (ii) negatively correlated with the distance. If the geographical location is the major driving factor of trace elements contents in soils, significant differences were also found between soil type and land use (p-value