Abstract
The Katangese Copperbelt Area (KCA) located south-eastern of D.R. Congo presents high concentration of Metal Trace Elements (MTE) due to a rich natural geochemical background and intense mining activities. However, the lack of data on specific baseline concentrations makes it difficult to assess and monitor the environmental quality of soils in the region. In this study, 11 MTE were measured across three land uses (croplands, forest and mining areas) to assess their baseline concentrations in topsoils of the KCA. Results showed the following (geometric) mean concentrations (mg.kg-1) in cropland soils: Al (54.6), Co (0.5), Cr (0.1), Cu (3.7), Fe (33.0), Mn (44.8), Ni (0.2), Pb (0.6), Zn (1.0), Ti (2.4), pH (5.3); in forests: Al (148.0), Cd (0.1), Co (1.9), Cr (2.2), Cu (12.3), Fe (156.4), Mn (86.9), Ni (1.1), Pb (1.9), Zn (3.7), Ti (0.4), pH (4.3); and in mining areas: Al (42.8), Cd (1.3), Co (7.0), Cr (0.1), Cu (115.5), Fe (53.3), Mn (26.1), Ni (0.5), Pb (8.2), Zn (93.1), Ti (0.3), pH (5.8). Cu and Zn were higher in mining areas compared to other land uses, demonstrating a prevalent influence of mining activities in altering the natural background of metals concentrations in the region. By contrast, croplands and forest shared a similar trend of Al and Mn contents, suggesting a mild influence of agricultural activity. This study is the first attempt to establish reference values of MTE contents in the KCA soils and thus provides valuable information for legislative purposes and for soil quality assessment.
Highlights
Ecosystem pollution with metals is of great concern due to the inherent adverse effects on living organisms including humans (Herselman, 2007)
Al was strongly associated with samples from forests and mining areas
The baseline pH in studied land uses varied from acidic to alkaline soils, with 3.8-8.0 for croplands, 3.6-5.0 for forests and 4.5-7.0 for mining areas (Fig. 4-5). These results suggest that studied soils are globally characterized as acidic, the pH at some locations can be neutral or alkaline as observed for mining areas and croplands respectively
Summary
Ecosystem pollution with metals is of great concern due to the inherent adverse effects on living organisms including humans (Herselman, 2007). The first approach for soil contamination evaluation is the determination of the total available trace element content (Ballesta et al, 2010). In this regard, the natural background concentrations of trace elements are suggested as a reference to identify polluted soils and eventually to propose a plan for their proper management (Herselman, 2007; Ballesta et al, 2010). Referred to as the natural range of concentration prior to any anthropogenic influence, the concept of geochemical background concentrations is scarcely considered and related data are quasi-inexistant for most environments.
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