Lipid geochemistry of surficial sediments from the coastal environment of Egypt I. Aliphatic hydrocarbons — characterization and sources

Abstract

Samples of surficial bottom sediments collected from six main zones along the Alexandria coast (Egypt) have been analyzed and characterized in terms of their contents of biogenic and anthropogenic hydrocarbon biomarkers. The distributions, structures, and applicability of these compounds in determining sample sources are discussed using the biomarker multi-tracer approach. By means of multivariate statistical analyses (Q-mode cluster analysis, extended Q-mode factor analysis, and linear programming technique), the hydrocarbon tracers were grouped according to their probable input sources and the sampling stations according to the relative importance of each source contribution. Homologous long chain n-alkanes (C15C38), CPI, UCM, and biomarkers such as pristane, phytane, tricyclic (C19C29) and tetracyclic (C24, C28 and C29) terpanes, 17α(H),21β(H)-hopanes (C27C35), 5α(H),14β(H),17β(H)-steranes (C27C29) with minor amounts of 5α(H),14α(H),17α(H)-steranes and 13α(H),17β(H)-diasteranes were found to be the most suitable indicators to differentiate between sewage/industrial pollution and natural background sources. Several ratios of the terrestrial and anthropogenic biomarkers were calculated for every station in each zone. These ratios, the aliphatic hydrocarbon concentrations (relative to TOC), and the statistical findings from the multivariate techniques indicate strong signals of petroleum/industrial and biogenic/terrestrial aliphatic hydrocarbons in the Alexandria coastal region.