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Use of Zebra mussel (Dreissena polymorpha) to assess trace metal contamination in the largest Italian subalpine lakes
No full textTrace metal (Cd, Co, Cr, Cu, Hg, Ni, Pb and Zn) contamination was evaluated in zebra mussels from the lakes Maggiore, Lugano, Como, Iseo and Garda, which are located in the most highly populated and industrialised area in Italy. Zebra mussels from Lake Maggiore contained the highest concentrations (3.44, 1.51, 4.97, 0.158, 5.87, 346 μg g−1 for Cd, Co, Cr, Hg, Pb, Zn, respectively) of all metals analysed except Cu and Ni. The lowest levels of most metals were in animals from Garda and Lugano (0.78 and 0.60 μg g−1 for Cd, 2.87 and 2.03 μg g−1 for Cr, 0.065 and 0.049 μg g−1 for Hg, 12.1 and 11.9 μg g−1 for Ni, 1.96 and 2.46 μg g−1 for Pb, 158 and 163 μg g−1 for Zn). The most contaminated sites and possible local sources of metals were identified for each lake, and the lakes classified into quality classes concerning metal pollution
Assessment of river Po sediment quality by micropollutants analysis
No full textTrace metals, PCB congeners and DDT homologues were determined in composite sediment samples collected from 10 representative sites along the river Po in two separate seasons. The aim was to identify the most anthropogenically impacted areas for future monitoring programmes and to aid development of Italian sediment quality criteria. The surface samples were collected during low flow conditions. Trace metal concentrations were assayed by electrothermal (Cd Co, Cr, Cu, Ni, Pb), flame (Fe, Mn, Zn) or hydride generation (As) atomic absorption spectrometry after microwave assisted acid digestion. Hg was determined on solid samples by automated analyser. Organic microcontaminants were determined by gas-chromatography with 63 Ni electron capture detector after Soxhlet extraction. Concentrations of trace metals, total PCB and DDT homologues showed two distinct peaks at the sites immediately downstream of Turin and Milan, respectively, and in each case decreased progressively further downstream. Principal component analysis identified three major factors (from a multi-dimensional space of 35 variables) which explained 85-90% of the total observed variance. The first and second factors corresponded to anthropogenic inputs and geological factors on sediment quality; the third included seasonal processes of minor importance. Sediment quality assessment identified Cd, Cu, Hg, Pb, Zn and organic microcontaminants as posing the most serious threats to river sediment quality. A reference site within the Po basin provided Useful background values. Moderate pollution by organochlorine compounds was ascribed both to local Sources and to atmospheric deposition
Modellazione numerica del comportamento meccanico del sottosuolo torinese per lo studio dell'applicabilità del microtunnelling
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