Hydrocarbons (normal alkanes) in the surface microlayer of seawater

The authors conducted a detailed quantitative analysis of dissolved and particulate hydrocarbons in the surface microlayer of the oceans, sampled by a metallic screen, with respect to the underlying water. The n-alkane content varies from 0.11 to 5.66 μg 1⁻¹ in the underlying water: much higher concentrations are encountered in the microlayer, reaching as high as 1200 μg 1⁻¹. On the average, the n-alkanes account for 10% of total hydrocarbons in the underlying water and 15% of these in the surface microlayer. The hydrocarbons are in general of biological origin (distribution of n-alkanes centred around n C₂₇ to n C₂₉, approaching that of algae). Of note is the contribution of petroleum pollution. The remarkable fact is the accumulation of hydrocarbons in the surface microlayer, with an enrichment factor averaging 50.