OCCURRENCE AND DYNAMICS OF POLYCHLORINATED DIBENZO-PARA-DIOXINS AND DIBENZOFURANS AND POLYCYCLIC AROMATIC-HYDROCARBONS IN THE MIXED SURFACE-LAYER OF REMOTE COASTAL AND OFFSHORE WATERS OF THE BALTIC

The particulate and the apparently dissolved fraction of water samples, collected from three remote coastal and six offshore stations in the Baltic Sea, were GC/MS analyzed for polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and polycyclic aromatic hydrocarbons (PAHs). The distribution of compounds mainly associated with particulate matter was dependent on the concentrations of particulate lipids (P(L)) but showed no correlation with particulate organic carbon (POC). The compounds found mainly in the dissolved fraction correlated weakly to the concentrations of dissolved organic carbon (DOC). The apparent log particulate organic carbon-water partition coefficients (log (p)K(oc)a) were in the range of 6.6-8.5 for PCDD/Fs and 6.3-8.3 for PAHs. Predicted log dissolved organic carbon-water partition coefficients (log pred(DOC)K(oc)) were approximately 2-3 orders of magnitude lower than log (p)K(oc)a indicating that the average 'truly' dissolved concentrations were in the order of 70 pg of PCDD/Fs.m-3 and 500 ng-m-3 PAH. Calculated log octanol-water partition coefficients (log (calc)k(ow)), which correlated well with literature log K(ow) and log S(w) data, were in the range of 7.1-8.7 for PCDD/Fs and 6.5-8.5 for PAHs. The average concentration of particle-associated PCDD/Fs was 230 pg.m-3 (1.8 pg.m-3 TEQ) and the apparently dissolved concentration was 120 pg.m-3 (1.0 pg of TEQ.m-3). Corresponding figures for the 11 PAHs were 190 and 530 ng.m-3, respectively. This gave a total momentarily content of 2.6 kg of (21 g of TEQ) PCDD/Fs and 5.4 ton of PAHs in the mixed surface layer of the whole open Baltic. The fugacity ratio between air and water is < 1 for both the PAHs and PCDD/Fs, indicating a net transport from the air to the water. A multivariate classification method (SIMCA) showed that the particulate chemical profile compositions are relatively similar to other particulate water and air environmental samples.