Quality Evaluation of Sediments from 24 Tributaries of the Po River, Italy

Sediment samples from 24 tributaries of the Po River (Italy) were screened for selected trace elements (Cd, Cu, Hg, Pb, and Zn) and extractable organic compounds; a proxy for contamination by organic microcontaminants. The toxicity of sediment extracts was evaluated using a battery of biotests (Dugesia gonocephala, Paracentrotus lividus, and Tamnocephalus platyurus). Contamination by trace elements (including very high Hg pollution - 4 to 16ppm total Hg - in one sub-basin) reached potentially harmful levels only in the sediments of four tributaries; while contamination by organic microcontaminants was present in most sub-basins. Sediments from most study sites did actually show signs of anthropogenic stress and were able to elicit a toxic response. A more detailed evaluation of sediment quality in the Po River tributaries seems to be urgently needed for developing the necessary remediation strategies. Research priorities should include more thorough testing of sediment toxicity, determination of metal background levels in the various sub-basins and a more detailed identification of the organic micropollutants of possible concer

Zinc-ethylene-bis-dithiocarbamate (Zineb)-mediated inhibition of monooxygenases and lipid peroxidation in bovine liver microsomes.

Hepatic bovine microsomes were incubated with Zineb concentrations ranging from 2.5 mM to 2.5 mu M. Only the higher concentrations of the fungicide (2.5 and 0.25 mM) elicited a sharp decline in cytochrome P450, cytochrome b(5) and total sulphydryl groups content as well as in the activities of NADPH cytochrome c reductase, aminopyrine N-demethylase and aniline 4-hydroxylase. The loss of cytochrome P450 was matched by a concomitant increase in the amount of cytochrome P420, which represents a catalytically inactive form of cytochrome P450. The same concentrations of the fungicide. either alone or in the presence of NADPH 1 mM, failed to increase the amount of thiobarbituric reactive substances with respect to control incubations, thereby excluding the possibility of lipid peroxidation as a contributing factor in the loss of cytochrome P450 and in the inhibition of cytochrome P450-mediated metabolism. It is concluded that Zineb can depress monooxygenase activity in bovine hepatic microsomes mainly through the denaturation of cytochrome P450 and the impaired transfer of reducing equivalents to the complex cytochrome P450-substrate. These mechanisms might also account for the inhibition in lipid peroxidation brought about by the fungicide

Characterisation of bed sediments and suspension of the river Po (Italy) during normal and high flow conditions

Grain-size distribution, major elements, nutrients and trace metals were determined in bed sediments and suspension collected at 10 representative sites along the river Po under normal and high flow conditions. Grain-size distribution and major element composition of suspension highlighted the presence of two distinct particle populations in the upper–middle Po (coarser particles, lower carbonate content) and in the lower Po (finer particles, higher carbonate content). This change partly reflects the geological differences between the two parts of the basin, and also the presence of a hydroelectric power plant at Isola Serafini (Piacenza). With respect to environmental quality issues, bed sediments and suspension provide similar results. A moderate nutrient pollution is found in all but the uppermost parts of the river basin, while the most significant inputs of trace metals appear to originate from the urban areas of Turin and Milan. Calculation of sediment enrichment factors identifies Cd, Cu, Hg and Zn as the most impacted elements by human activities. On the other hand, the high levels of Ni and Cr throughout the river seem to derive mainly from the presence of basic rocks in the upper and middle parts of the basin. Both nutrient and trace metal particulate concentrations substantially decrease under high flow conditions possibly due to “flushing” of contaminated bed sediments and resuspension of coarser material. Under normal flow conditions, water hydrochemistry and concentrations of some elements (As, Ca, Cr, Cu, K, Mg, Mn, Na, Ni, and Pb) in the dissolved phase (&lt;0.45 μm) were also determined. Calculation of trace metals partition coefficients shows that the relative importance of the particulate and water phases varies in response to water hydrochemistry and suspended solid content, but that most elements achieve a conditional equilibrium in the lower stretches of the river Po. These results are the first of this kind reported for the whole river course and highlight the factors and mechanisms controlling the origin, mobility and fate of nutrients and trace metals in the river Po.</p