Abstract
Abstract. Surface sediments collected from deep basins (1018–4087 m depth) of the eastern Mediterranean Sea (Ionian Sea, southern Aegean Sea and northwestern Levantine Sea) were analyzed for aliphatic and polycyclic aromatic hydrocarbons as tracers of natural and anthropogenic inputs. Concentrations of total aliphatic hydrocarbons, n-alkanes and the unresolved complex mixture (UCM) of aliphatic hydrocarbons varied significantly, ranging from 1.34 to 49.2 μg g−1, 145 to 4810 ng g−1 and 0.73 to 36.7 μg g−1, respectively, while concentrations of total polycyclic aromatic hydrocarbons (PAHs) ranged between 11.6 and 223 ng g−1. Molecular profiles of determined hydrocarbons reflect a mixed contribution from both natural and anthropogenic sources in deep-sea sediments of the eastern Mediterranean Sea, i.e., terrestrial plant waxes, degraded petroleum products, unburned fossil fuels and combustion of grass, wood and coal. Hydrocarbon mixtures display significant variability amongst sub-regions, reflecting differences in the relative importance of inputs from various sources and phase associations/transport pathways of individual hydrocarbons that impact on their overall distribution and fate. Hydrocarbon concentrations correlated significantly with the organic carbon content of sediments, indicating that the latter exerts an important control on their transport and ultimate accumulation in deep basins. Additionally, water masses' circulation characteristics also seem to influence the regional features and distribution patterns of hydrocarbons. Our findings highlight the role of deep basins/canyons as repositories of both natural and anthropogenic chemical species.
Highlights
Hydrocarbons are ubiquitous components of the organic material introduced into coastal and open sites of the world’s oceans
Aliphatic and polycyclic aromatic hydrocarbons’ profile characteristics, source-specific molecular markers and their diagnostic indices reveal mixed contributions from both natural and anthropogenic compounds accumulating in deep-sea surface sediments of the eastern Mediterranean Sea (EMS)
Anthropogenic inputs are reflected by polycyclic aromatic hydrocarbons (PAHs) of pyrolytic origin, related mainly to atmospheric inputs, and by fossil compounds both atmospherically derived and from intense maritime activities in the EMS, with the latter resulting in chronic oil pollution of surface sediments, as evidenced by the persistence of unresolved hydrocarbon mixture in all sampling sites
Summary
Hydrocarbons are ubiquitous components of the organic material introduced into coastal and open sites of the world’s oceans They enter the marine environment through both atmospheric (dry/wet deposition, gas exchange across the air–water interface) and aquatic pathways (direct discharges, continental run-offs, off-shelf export) the relative importance of which largely depends on the geographical setting of a given area. They may derive from natural sources, both marine and terrestrial, a large proportion of hydrocarbons is related to various anthropogenic activities that result in the formation and release of hazardous organic pollutants. The sources and physico-chemical properties of individual compounds determine their phase associations, dispersion pathways, pre- and post-deposition fate in the marine environment and their ultimate preservation in marine sediments (Dachs and Eisenreich, 2000; Simo et al, 1997; Wang et al, 1999; Yunker et al, 2002; and references therein)
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