The decoupling of hydrocarbons and fatty acids in the dissolved and particulate water phases of a deltaic environment

Abstract

Hydrocarbons and fatty acids have been analysed in the dissolved and particulate phases of a series of 46 water samples collected over a period of 16 months in different environments of the Ebro Delta (bays, channels and river-bed). Several qualitative and quantitative differences have regularly been observed between the particulate and the dissolved fractions, such as higher concentrations and spatial variability of lipids in the particulates, which are also enriched in unsaturated components. Furthermore, an apparent source-related decoupling between both phases has been detected by a cross-correlation study of the multivariate dataset resulting from the distributions of these components. In the dissolved fraction they have been classified into three groups. The largest, consisting mostly of hydrocarbons, reflects the anthropogenic (urban- and petroleumrelated) inputs. The second is composed of some C 15-C 20 fatty acids and represents the biogenic autochthonous inputs, especially those of algal origin. A third group is formed by the C 21-C 30 n-alkanoic acids and corresponds to the terrigenous distributions. However, the biogenic sources are better characterized in the particulate phase where groups of components reflecting algal, bacterial and terrestrial inputs have been observed.