Composition and sources of dissolved and particulate PAH in surface waters from the Rhone delta (NW Mediterranean)

PAH were determined in surface waters from the Rhone delta in winter and summer 1987. Both particulate and dissolved phases were analyzed by GC and GC/MS. Concentrations of major unsubstituted compounds associated with particles varied from a few to 20 ng l⁻¹, or from 0.42 to 6.0 μg g⁻¹. The seasonal variations reflected higher inputs in winter resulting from the presence of highly PAH-enriched particles. Tetra- and penta-cyclic PAH with MW 202 and 252 predominated, which reflected a significant origin from pyrolytic processes. A rapid decrease of the level of higher MW PAH was observed seawards in both seasons. Study of the tricyclic compounds and their alkylated homologues demonstrated a mainly fossil origin in winter, whereas in summer a high heterogeneity of particles was observed. PAH in the dissolved phase were found at concentrations up to 31 and 50 ng l⁻¹ in summer and winter, respectively. These levels were much higher than those encountered in the corresponding particulate phases. PAH with MW 178 and 202 predominated, and the alkylated homologues of the tricyclic compounds showed a major fossil orgin in winter and a mixed origin in summer. In winter dissolved PAH were transported through the delta into the marine environment without significant losses.