Located in the Mediterranean Basin and close to Marseilles (France), Fos-sur-Mer is situated in the vicinity of industrial harbor and agricultural lands. Its location makes it prone to mixed pollution contributions. To characterize the background pollution and identify its multiple origins, carbonaceous particles are investigated using a coupled approach based on analyses of radiocarbon, elemental to total carbon ratio (EC/TC) and various molecular tracers such as levoglucosan. The measurements in about 30 samples collected during summer and fall/winter 2013, allow the detection of a strong seasonality of the pollution: the fall/winter PM2.5 concentration equals to three times the summer concentration and we observe a significant fluctuation of the relative contributions of fossil and non-fossil fractions (fNF is ≈ 0.83 for fall/winter samples and ≈ 0.59 for summer samples). Significant correlations between radiocarbon, levoglucosan and different methoxyphenols, allow the quantification of a major influence of biomass burning emissions during fall and winter. Biomass burning organic carbon (OCBB) and elemental carbon (ECBB) contribute to 44.5 % and 8.1 % of the TC, respectively, whereas their total contribution is only 3 % in summer samples. Biogenic emission are the main sources of carbon during summer. Significant correlations with malic acid and DL glyceric acid suggest a secondary origin. These correlations are not observed for the cold season samples, suggesting a different source for OCbio. Fossil carbons (ECF and OCF) from vehicular, shipping and industrial sources are relatively high during summer, with a predominance of the fossil origin in elemental carbon (98%). Nevertheless, the total fossil carbon concentration remains significant throughout the year, which is the signature of an important traffic and industrial activity during both seasons. Overall, our study based on radiocarbon and molecular tracers illustrates the power of a coupled approach in order to identify and quantify biomass burning, biogenic, traffic and industrial sources of carbonaceous aerosols.