Source to sink river pollution assessment in northern Bulgaria: Preliminary results on contaminant delivery in the lower danube basin

Bulgaria occupies a unique position in south-east Europe in terms of river basin management and control because contamination from metal extraction and processing industries not only has a potential significant trans-border impact but also affects both the Mediterranean and Black Seas. However, to date, no whole basin source to sink study of metal contamination has yet been conducted in the country. This paper begins to address this issue by presenting preliminary results from a survey conducted in August 2004 of water and sediment quality in the river basins that drain into the Danube River in northern Bulgaria. A total of 294 surface water, channel sediment, floodplain sediment and mine waste samples were collected from 103 sites in northern Bulgaria and concentrations of heavy metals and arsenic (As) were determined using ICP-MS. Comparison of metal and As levels with EU (water) and Dutch (sediment) threshold values shows that waters and sediments in the Ogosta and Isǩr catchments are the most seriously polluted; other rivers in the Danubian Region generally have very low metal and As concentrations. Metal and As concentrations in the Danube River itself generally comply with EU and Dutch threshold values suggesting that, at present, the Ogosta and Isǩr Rivers are not significantly degrading the environmental health of the Danube. Finally, an assessment is made of the potential impact that climate and land use related changes in flood frequency and magnitude might have on the dispersal and remobilisation of sediment-associated contaminant metals in the Danube Basin.