Hydrocarbon distributions in sediments of the open area of the Arabian Gulf following the 1991 Gulf War oil spill

Surface sediments collected from the open area of the Arabian Gulf were analysed for total petroleum hydrocarbons and specific aliphatic hydrocarbon components in order to provide information on the extent of oil contamination and the degree of weathering of the spilled oil following the Gulf War. The concentration of petroleum hydrocarbons in the sediments ranged from 5.4–92.0 μg g−1 (dry wt) with an average of 32.6 μg g−1. The surface distribution of the petroleum hydrocarbons showed an increasing trend towards the north-east, and among the individual transects there was a pronounced increasing trend towards the north-west direction. Despite off-shore oil-related activities as well as a potential impact from the 1991 oil spill, the concentrations of petroleum hydrocarbons in the study area were relatively low. This finding may be attributed to the effectiveness of weathering processes. The distribution of the saturated hydrocarbon fractions exhibited, principally, the following: 1. the presence of n-alkanes between C15 and C33 in nearly all samples with a lack of predominance of odd/even carbon numbers; 2. the presence of an Unresolved Complex Mixture (UCM) in most of the samples; 3. the n-C18/phytane ratios reflect the limited influence of microbial degradation; 4. a relative distribution of the saturated hydrocarbons indicating weathering classification equivalent to stage I.