In 2014 we carried out a study on the stream sediments of the Calore river (a tributary of the Volturno, the biggest south-Italian river) to assess the environmental conditions of a basin that covers 3058 Km2 (Fig.1) of the Campania region and that, until now, has been only marginally studied from this point of view.
Our study showed that, despite evidence from concentrations of many elements for enrichment over natural background values, the spatial distribution of major and trace elements in Calore river basin is determined mostly by geogenic factors. Figure 2 shows the main lithological features of the study area, while Figure 3 shows the spatial distribution of elemental association factor scores.
The south-western area of the basin highlighted an enrichment of many elements potentially harmful for human health and other living organisms (Al, Fe, K, Na, As, Cd, La, Pb, Th, Tl, U); but these anomalies are due to the presence of pyroclastics and alkaline volcanic lithologies.
Even where sedimentary lithologies occur (in northern area), many harmful elements (Co, Cr, Mn, Ni) have shown high concentration levels due to a natural origin.
On the other hand, a strong heavy metal contamination (Pb, Zn, Cu, Sb, Ag, Au, Hg), due to an anthropic contribution, is highlighted in many areas characterised by the presence of road junctions, urban settlements and industrial areas. Figure 4 highlights the enrichment factors of these elements: 3 - 4 time higher than the background values. The south-western area of the basin is characterised by a moderate/high degree of contamination (Fig.5), just where the two busiest roads of the area run and the highest concentration of industries occurs.
We assessed the distribution of the potentially harmful elements (PHE) and the related interpretations using geochemical indexes, chemometric approach and mapping of the other relevant information, all linked to PHE distribution.
First of all, 562 stream sediment samples were collected, air-dried, sieved to < 100 mesh fraction and analyzed for 37 elements after an aqua regia extraction by a combination of ICP-AES and ICP-MS.
Univariate and multivariate statistical analyses of data were performed to show the single element distribution and the distribution of elemental association factor scores resulting from R-mode factor analyses, in order to interpret the hypothetical origin of elements’ distribution (natural, anthropogenic or mixed).
The degree of contamination of the area was evaluated through analysing the Contamination Factor index and the production of a Contamination Degree map.
This approach proved successful as it achieved meaningful results and interpretations of complex datasets. It represents a useful tool to evaluate the hypothetical origin of geochemical anomalies of stream sediments; it also allows a quantitative assessment of the metal pollution threat to ecosystem and human health.
by Daniela Zuzoloa*, Domenico Cicchellaa, Lucia Giaccioa, Ilaria Guagliardib, Libera Espositoa
a - Department of Science and Technology, University of Sannio, via dei Mulini 59/A, 82100 - Benevento, Italy
b - Department of Biology, Ecology and Earth Sciences, University of Calabria, Via Ponte Bucci 4, cubo 15B, I-87036 Arcavacata di Rende (CS), Italy