Vertical fluxes of polycyclic aromatic hydrocarbons and organochlorine compounds in the western Alboran Sea (southwestern Mediterranean)

Time-series samples of sinking particles were collected in the Alboran Sea with sediment traps moored at three water column depths (250, 500 and 750 m) between February and May 1992. The samples were analyzed for individual polychlorobiphenyl congeners (i.e. PCBs IUPAC no.: 28, 52, 101, 118, 153, 138 and 180), chlorinated pesticides (DDE and Lindane) and individual polycyclic aromatic hydrocarbons (PAHs; 3-6 aromatic rings), Average concentrations of PCB and total PAHs were 78.9 ng g(-1) (range: 27.3-212) as Clophen A40 equivalents and 1176 ng g(-1) (range: 104-2780), respectively. The 1,1-dichloro-2,2-bis(p-chlorophenyl)ethene (4,4'-DDE) and 1,2,3,4,5,6-hexachlorocyclohexane (gamma-HCH) were the only chlorinated pesticides identified throughout the sampling period, with respective concentrations of 6.6 ng g(-1) (range 1.1-15) and 16.8 ng g(-1) (range 5.4-48). Corresponding fluxes of PCBs (as Clophen A40 equivalents) and PAHs were 15.1 ng m(-2) d(-1) (range: 6.9-24.9) and 225 ng m(-2) d(-1) (range: 15-625). Contaminant fluxes were analyzed with other collective fluxes obtained from the same samples (i.e. fecal pellets, mass and organic carbon); while higher molecular weight PAHs (MW > 228 daltons) exhibited a strong correlation with the mass fluxes (r(2) = 90.7%, p < 0.001, n = 18), the lower molecular weight compounds (MW < 202 daltons) covaried with organic carbon and fecal pellet fluxes (r(2) = 76.4%, p < 0.001, n = 18). The Sigma PCB fluxes covaried with organic carbon, and fecal pellet fluxes and depth (r(2) = 97.6%, p < 0.001, n = 9). The 4,4'-DDE only covaried with fluxes of organic carbon (r(2) = 85.87%, p < 0.001) and gamma-HCH with the fecal pellets fluxes and depth (r(2) = 85.2% and p = 0.001, n = 9). Comparison with similar data from the northwestern Mediterranean and other oceans suggests that the Alboran Sea is a relatively clean environment primarily due to its relative remoteness from input terrigenous sources.