Speciation of sewage derived phosphorus in coastal sediments from Rio de Janeiro, Brazil

Phosphorus speciation was performed in sediments and waters from an area of 20 km2 under the influence of untreated sewage released via a submarine outfall. Results showed that the pool of organic and non-apatite P made up the major fraction of sewage derived P. A good correlation between Pnapat and FeDBC indicated that sorption on iron oxides is an important mechanism for removal of P to the sediments. Mass balances revealed that most of the sewage derived P had been exported from the observation area but, in spite of this, concentrations of labile forms of P reaching 1900 μg P g−1 were amongst the highest reported for polluted estuarine sediments. The supply over 20 yr of high nutrient loads would have been sufficient to produce 500 000 t of fixed carbon, of which 2% lies presently in the sediments of the surveyed area.