Polychlorinated biphenys in sediments of selected coastal environments in Northern Morocco

PCBs were analysed in number of sediment samples from key aquatic environments of northern Morocco. Results show that significantly high PCB concentrations (108-210 ng g-1 in surficial samples and up to 450 ng g-1 at 32-35 cm depth) can be found only in ports and, in particular, the port of Tangier whose values, which exceed NOAA ERL guidelines and, in one case, the ERM limit, can cause adverse effects in biota. However, the PCB depth distribution suggests that the situation is improving. The other values span the intervals 4.8-13.4 ng g-1 in sediments and 0.80-8.04 in marsh and soil samples. The PCB content in marine samples appears surprisingly high, being 4.9 and 10.0 ng g-1 at the Mediterranean and Atlantic sites, respectively. All these other values are not harmful, being lower than ERL values. PCB homologue profiles appear rather different from place to place and not always referable to specific commercial products. This can be the result of a multiplicity of the sources or to fractionation processes caused by differential transport and interaction rates before the incorporation into the sediments.