ALIPHATIC AND POLYCYCLIC AROMATIC-HYDROCARBONS IN BLACK-SEA SEDIMENTS

Concentrations of aliphatic hydrocarbons (AHC) in sediments of the Bla ck Sea ranged from 153,000 ng g(-1) dw near the mouth of the Danube Ri ver to about 10,000 ng g(-1) dw in abyssal plain sediments. Compound d istributions were dominated by long-chain n-alkanes except at the Danu be station where a significant petrogenic component with an unresolved complex mixture was also present. Polycyclic aromatic hydrocarbon (PA H) concentrations ranged from 1,250 ng g(-1) dw to about 200 ng g(-1) dw at the same locations and compound distributions were dominated by PAH of pyrolytic origin. The flux of hydrocarbons to the central Black Sea sediments over the past 25 years is estimated to be similar to 58 0 mu g AHC m(-2) yr(-1) and similar to 80 mu g PAH m(-2) yr(-1). Long- range aeolian transport is invoked as the primary mechanism for delive ring terrigenous higher plant AHC and pyrogenic PAH in abyssal Black S ea sediments although petrogenic hydrocarbons and retene appear to be delivered via fluvial transport and as a result are preferentially dep osited in sediments along the continental margin. Analysis of a sedime nt core showed a rapid decrease in AHC and PAH concentrations with inc reasing depth in the sediment, reaching background levels of about 100 0 ng g(-1) dw and 10 ng g(-1) dw, respectively, by about 4 cm depth or about 150 years BP. AHC fluxes in these sediments deposited before th e industrial revolution were similar to 50 mu g m(-2) yr(-1), PAH flux es were similar to 0.5 mu g m(-2) yr(-1). Differences between the dist ributions of AHC and PAH in surface sediments and the core sediments i ndicate an uncoupling of the source and transport processes affecting various components of the two hydrocarbon classes.