DISTRIBUTION OF AS, CR AND V SPECIES IN THE PO-ADRIATIC MIXING AREA, (ITALY)

The distribution of dissolved and particulate concentrations of As, Cr and V was investigated in the mixing area of the Po river in five sur veys over the period March 1992-March 1995. The data obtained indicate noticeable contamination of coastal waters of the northern Adriatic w ith Cr but not As or V. Total dissolved concentrations for As and V we re comparable with oceanic levels but were higher by a factor of 4 for Cr. These results suggest either low anthropogenic inputs of As and V , from tenigenous and atmospheric sources, or efficient removal mechan isms. The investigated metals had low reactivity during freshwater-sea water mixing and the distribution of concentrations in the dissolved a nd solid phases suggests that the dilution process is the main factor controlling the transport of these metals to the sea in low-to-medium solid transport conditions. Further investigations an required to eluc idate the behavior of these metals during high solid transport conditi ons. Significant changes in the speciation of As occurred during the t ransition between the two end-member matrices, In the coastal waters o f the northern Adriatic, the arsenite fraction in winter, and the arse nite and dimethylarsinate fractions in summer increased with respect t o riverine waters. Changes in the speciation of chromium were minor, b ut also showed a small increase in reduced species in marine waters. ( C) 1997 Elsevier Science B.V.