Unusual patterns of organohalogenated compounds in fillet, liver, and brain of dab (Limanda limanda) from the North and Baltic Seas

Thirty-two pools as well as individual samples of fillet, liver and brain of dab (Limanda limanda) from seven marine regions in the North and Baltic Seas were analyzed on halogenated natural products (HNPs) and anthropogenic persistent organic pollutants (POPs). The residue pattern was dominated by the well-known HNP 2,4,6-tribromophenol (TBP, 27-420 ng/g lipid, fillet) and the man-made PCB 153 (29-100 ng/g lipid, fillet). Indications on the presence of polybrominated dibenzo-p-dioxins (PBDDs) could be verified in ten of 12 samples by two independent gas chromatography with mass spectrometry (GC/MS) methods. Synthesis of a PBDD mixture, followed by enrichment of individual PBDD congeners by countercurrent chromatography and their calibration by GC with flame ionization detection (GC/FID) enabled the (semi-)quantitation of individual PBDD congeners, ranging from 2 to 1100 ng/g lipids. The PBDDs which were most likely naturally produced were even the most abundant substance class in some of the samples. A new approach of considering the total weights of the entire fillet, liver, and brain samples, respectively, enabled determining the total amounts of compounds for the distribution within the fish. This data treatment indicated differences between HNPs and POPs. Namely, >60% of the determined HNPs but only 36-53% of the POPs were stored in the fillet of the fish. Spatial differences between HNPs (TBP) and POPs (PCBs) were also found with TBP becoming more abundant with increasing distance from the coast.