Environmental quality of the Po River delta

The Po River collects the discharges of the most populated and industrialized area of Northern Italy and enters the Adriatic Sea with a mean flow of 1470 m 3 s -1 spreading in nine branches along the final stretch and forming a delta originating about 50 km from the sea. According to the last systematic survey carried out in 1989-1990, the Po delta waters suffer a low-moderate pollution from heavy metals and organic micropollutants. However, the Po River carries a nutrient load high enough to cause a severe marine eutrophication problem south of its delta. Provisional models have shown that even a substantial reduction on civil and industrial waste water discharges coupled with an optimal use of fertilizers in agriculture would not be sufficient to solve the problem. The Po River represents an important source also, for heavy metals and marine sediments collected at the river mouth are more polluted than are those offshore, especially for Cu, Zn and Hg. On the basis of the European guidelines the delta sediments have a medium to high contamination as far as the concentration of Ni and DDT are concerned, while data on persistent organic compounds indicate a moderate ecological risk for the biota living in the delta. These same conclusions can be obtained using the "sediment quality benchmark" procedure proposed by the NOAA in the United States.