Organic geochemistry of Danube River sediments from Pančevo (Serbia) to the Iron Gate dam (Serbia-Romania)

The type and source of natural organic matter was investigated in Danube River sediments from the Hungarian Plain near Belgrade to the Carpathian-Balkan Mountains near the Iron Gate dam by means of pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). In addition, the input of anthropogenic organic matter to the river was traced using sewage markers (linear alkyl benzenes and alkyl phenolic compounds). The VGI ratio employs the most abundant lignin marker (4-vinylguaiacol) and the most abundant organonitrogen compound (indole) in the sediment pyrolysis products and is proposed as an index of the relative contributions of land plant vs. aquatic biomass to sediments. Sewage marker analysis revealed their enhanced accumulation in sediments close to metropolitan/industrial areas and at the mouth of the Velika Morava tributary, as well as their overall decrease in concentration downstream towards the Iron Gate dam.