N-Alkane Distribution in Surficial Sediments from the Aden City Coast, Yemen

The paper presents the N-alkanes distribution in recent sediments of Aden city coast. The results are the first of their kind for the region and should serve as baseline for future studies. The concentration of N-alkanes in sediment samples ranged from 3 to 1805 ng/g dry weight, expressed as Kuwait crude oil equivalent. It is evident that all the sites are contaminated to some extent with N-alkanes. N-alkanes generally constitute the major fraction of saturated hydrocarbons, and their distribution patterns are characterized by carbon-number ranges and predominance, depending on the nature of the source material and its microbial or geochemical alteration. In this respect it has been recognized that distributions exhibiting odd carbon-number predominance in the C₁₅-C₂₁ and C₂₅-C₃₁ ranges are characteristic of autochthonous and allochthonous natural inputs respectively, whereas slight even carbon-number predominance or smooth distribution in the C₂₀-C₃₀ range have been invoked for reduction or bacterial diagentic processes. Finally, fossil (petroleum) N-alkanes are characterized by a low carbon preference distribution generally concurrent with an unresolved complex mixture of branched and cyclic saturated hydrocarbons.