Monitoring and assessment of oil pollution in the Danube River during the transnational Joint Danube Survey.

An extensive river basin monitoring exercise of 2581 km of the river Danube was carried out in 2001 under of the aegis of the transnational Joint Danube Survey (JDS). Water, suspended and bottom sediment, and biota samples were collected from 76 cross-sections in the Danube main stream and 22 major tributaries during the 39-day cruise, and analysed for chemical and biological variables. During the JDS, oil pollution was characterised with GC-FID and fluorescence measurements. Fluorescence fingerprints of the cyclohexane extracts of water, suspended and bottom sediment samples allowed characterization and quantification of the type and level of oil pollution. The results revealed that the oil pollution in the water varied in the range 1-300 microg/l. Gasoline type contamination was found at the higher concentration levels and diesel oil type in the lower concentrations. Oil contamination was similar in the suspended and bottom sediment (the less than 63 microm grain-size fraction) and varied between 2-140 mg/kg. A higher contamination level was found along the middle Danube reach. The highest concentrations were observed in the suspended sediment upstream of the Danube delta. Weathered crude oil characteristics were observed in the upper Danube basin, whereas between crude and diesel oil characteristics were dominant along most of the middle and the lower Danube reaches.