Jan C. Duinker

A structure-activity relationship (SAR) approach towards metabolism of PCBs in marine animals from different trophic levels

Abstract A qualitative structure-activity relationship (SAR) to estimate the influence of biotransformation on the degree of bioaccumulation of chlorinated biphenyl (CB) congeners under field conditions, is presented. The CB patterns of different animal species from the western part of the Dutch Wadden Sea are used to illustrate the SAR. The CB pattern in a particular species was compared with that of the bivalve mollusc Macoma balthica . It is assumed that no biotransformation occurs in this species, the CB pattern being determined only by equilibrium partitioning between tissues and the ambient water. When no significant differences in the pattern of a group of persistent congeners existed between a given species and Macoma balthica , significantly lower relative concentrations of congeners with vicinal H-atoms in the meta - and para -positions in that species were attributed to biotransformation. The contribution of metabolizable congeners decreased in the order Macoma balthica > Nereis diversicolor > Pleuronectes platessa , Haematopus ostralegis (male juv.) > H . ostralegis (male (sub-)adult), Phoca vitulina . No significant differences in the patterns of persistent congeners were observed between the latter four species. Phoca vitulina was the only species with a lowered relative concentration of CB-118. Biotransformation of congeners with this configuration, i.e. possessing vicinal H-atoms only in the o, m position and (at maximum) one ortho -chlorine, may be significant from a toxicological point of view, as a number of toxic congeners belong to this group.

Chlorobiphenyls: model compounds for metabolism in food chain organisms and their potential use as ecotoxicological stress indicators by application of the metabolic slope concept.

A model is described to explain the compositional similarities and differences in chlorobiphenyls (CBs) in members of marine food chains, including water. Four groups of CBs are distinguished based on the presence/absence of vicinal H-atoms in o,m and/or m,p vicinal H-atoms, according to structure-activity relations for their biotransformation by cytochrome P-450 1A and 2B isozymes. Contents of CBs (X) in water, diatom, mussel, copepod, worm, shrimp, flounder, herring, and harbor porpoise were transformed into molar X/153 ratios (CB-153 is persistent) and plotted against X/153 ratios in diatom, lacking metabolic efficiency. For each metabolic group, a linear plot results. Their slopes indicate relative metabolic efficiencies of cytochrome P-450 isozymes. Indication of PB-type enzyme activity in harbor porpoise, flounder, and herring that was not observed before biochemically is new. Metabolic slopes of CBs can also be used as environmental stress indicators by comparison of slopes in a selected organism in areas with different degrees of contamination.

At-sea intercomparison of two newly designed underway pCO2 systems — encouraging results

Two newly designed underway systems for the measurement of CO2 partial pressure (pCO2) in seawater and the atmosphere are described. Results of an intercomparison experiment carried out in the North Sea are presented. A remarkable agreement between the two simultaneously measured (pCO2) data sets was observed even though the spatial variability in surface pCO2 was high. The average difference of all l -min averages of the seawater pCO2 was as low as 0.15 μatm with a standard deviation of 1.2 μatm indicating that no systematic difference is present. A closer examination of the profiles shows that differences tend to be highest during maxima of the pCO2 gradient (up to 14 μatm/min). The time constants of both systems were estimated from laboratory experiments to 45 s, respectively, 75 s thus quantitatively underlining their capability of a fast response to pCO2 changes

Chlorobiphenyls (PCB) and PAHs in water masses of the northern North Atlantic

Concentrations of 23 individual chlorobiphenyls (CBs) and 6 polyaromatic hydrocarbons (PAHs) were determined in different water masses of the North Atlantic Ocean around Iceland. The study was carried out in the framework of the second Intergovernmental Oceanographic Commission (IOC) baseline studies of contaminants in the North Atlantic Ocean, involving trace organics and trace elements. Concentrations of individual CBs were extremely low. In solution, they varied between <2 and 126 fg dm−3 and in suspension between <2 and 1400 fg dm−3. The values for their sum (∑CB) were between 10 and 1048 in solution, and 286–11 241 fg dm−3 in suspension. ∑PAHs were present in the <5–65 pg dm−3 range, p,p′-DDE and hexachlorobenzene were <2 fg dm−3. The concentrations of CBs and PAHs decreased from the surface towards the bottom at each station. The lowest concentrations were found in Norwegian Sea Deep Water (∑CB 10 fg dm−3), concurrent with the lowest halocarbon concentrations found during the cruise. Values in near-surface waters were considerably lower than those determined at mid-latitudes of the North Atlantic. These findings reflect the mixing of water bodies with higher CB concentrations from the central North Atlantic with less contaminated waters from the Arctic Ocean. Concentrations in suspension exceeded those in solution in most samples, as a result of the relatively high suspended matter concentrations in the waters around Iceland. Particulate CB and PAH concentrations were positively correlated with particulate organic carbon concentrations. This suggests that suspended organic material is a carrier for these relatively apolar organic compounds in the water column. The data do not support the co-distillation concept suggested in the literature.

Distribution of individual chlorobiphenyls (PCB) in solution and suspension in the Baltic Sea

Single and multidimensional GC-ECD techniques were applied to determine individual chlorobiphenyls (CBs) in solution and in suspended particles in the Baltic Sea (some data were also obtained for the adjacent German Bight in the North Sea). Large volumes (up to 1100 dm3) were analysed in transects in November 1988 and 1989 and in spring 1991. Salinity and temperature were measured continuously along the sampling tracks in all three cruises; nutrients and pH only in the latter two cruises. Concentrations of individual CBs in solution were in the sub- and low pg dm−3 range (detection limit being 0.05 pg dm−3), and of their sum between 2 and 237 pg dm−3. These concentrations are considerably lower than previously reported data. This is mainly the result of the elimination of contamination and interference problems in the sampling, clean-up and GC-ECD procedures. It may also partly reflect the reduction in the production and use of PCBs in the last decade. The highest concentrations in solution originated from local sources in the Belt Sea and the Gulf of Finland. Regional differences were found for the compositions of the CB mixtures in solution. The lowest concentrations of CBs in solution were found in areas and periods of plankton production (spring 1991), with ΣCB concentrations between 2 and 14 pg dm−3. The compositions of the CB mixtures showed regional differences in each cruise. These could be interpreted in terms of mixing between different water bodies. The classification of transects on the basis of these CB patterns agreed well with the distinction of water bodies on the basis of T-S diagrams and hydrochemical data. Concentrations of individual CBs in suspension were generally 0.1–0.5 pg dm−3, those of their sum (ΣCB) between 4 and 6 pg dm−3 during the autumn cruises. Extremely high values were found in the Belt Sea-Kattegat area in spring 1991 (up to 589 pg dm−3 for individual CBs and up to 2859 pg dm−3 for ΣCB). This probably reflects the uptake of CBs into particulates during a plankton bloom. Primary production may effectively remove CBs from the water column into the sediments. The amounts of chlorobiphenyls presently stored in the sediments of the Baltic Sea exceed the amounts in the water column by several orders of magnitude. The compositions of the CB mixtures differed considerably between solution and suspension. The relations between log K′d (apparent particle/water partition coefficient) and log Kow (octanol-water distribution coefficient) suggest the existence of (quasi-)equilibrium conditions in autumn. Deviations from this behaviour arise from biological activity in spring. The contribution of toxic congeners to the CB mixtures was dominated by the mono- and di-ortho-Cl substituted derivatives of the most toxic non-ortho-Cl CBs. The toxicity of the CB mixtures in solution was between 0.01 and 12fg dm−3 TEQs (TCDD toxic equivalents). CBs-77, -118, -105 and -156 had the largest contributions to TEQs.

An in-situ filtration/extraction system for the recovery of trace organics in solution and on particles tested in deep ocean water

A system for in-situ filtration and extraction of organics in natural waters has been developed and tested down to 4000 m in the Atlantic Ocean. Up to 2000 dm3 water can be filtered and extracted at low suspended matter concentrations. The sampling equipment has new features for the analysis of trace organic compounds: contamination is extremely low, this can be checked and cured, if necessary, and water flow can be selected and maintained at a constant rate. Various resins can be applied, with different optimum flow rates for the efficient extraction of the compounds of interest. The properties of the resin (here XAD-2) do not change with depth. The operation of the unit is controlled by menu-driven software. All relevant data are stored for later evaluation. Tests in the deep Atlantic resulted in total procedural blanks, including sampling, as low as 0/003 pg dm−3 for individual chlorobiphenyls (CBs), HCB and DDE and 0.5 pg dm−3 for individual PAHs. Actual dissolved concentrations were in the range 0.005–0.1 pg dm−3 for CBs, HCB and DDE and 0.5–140 pg dm−3 for PAHs.

Seasonal variability of the long-chain alkenone flux and the effect on the U37k′-index in the Norwegian Sea

A seasonally-varying sedimentation pattern was observed for the alkenone flux measured with sediment traps in the northern North Atlantic. In the Norwegian Sea (traps were set at 500, 1000 and 3000 m) the alkenone flux varied between 0.1 and 7.1 μg m−2 d−1 and followed the seasonal pattern of the bulk parameters. Maximum fluxes occurred from mid-October until mid-November and were also high in May. A surprising result was that considerably higher particle fluxes were observed at 3000 m. For the alkenone flux, the highest additional input of 250% was observed during the period when sediment resuspension was greatest in summer. At the Barents Sea continental margin (traps at 1840 and 1950 m) the alkenone fluxes follow the sedimentation pattern of the bulk parameters, with a less visible signal of distinct seasonality observed in the 1950 m trap. The sedimentation of total alkenones varied between 0.8 and 144 μg m−2 d−1 at 1840 m and between 0.5 and 31.0 μg m−2 d−1 at 1950 m. Resuspension and lateral advection contributed significantly to measured fluxes in the two near-bottom traps. Alkenone concentrations were determined in faecal pellets of Appendicularia, ostracods and euphausids from selected samples at the Barents Sea site. The alkenone flux in pellets (4% to 24% of total) was 5 to 6 times higher at 1950 m depth than at 1840 m and the major part (77–78%) of the total flux of C37:3 reaching the near-bottom trap at 1950 m was associated with faecal pellets of the meso-zooplankton. Spatial and temporal variations of the U37k′ signals were observed, indicating that the imprint in the alkenone signal depends on the origin and transport pathway of the organic material. Strong deviations occur in areas where nepheloid layers contribute particles of long residence times to the primary flux.

On the penetration of anthropogenic CO2 into the North Atlantic Ocean

The penetration of anthropogenic or “excess” CO2 into the North Atlantic Ocean was studied along WOCE-WHP section A2 from 49°N/11°W to 43°N/49°W using hydrographic data obtained during the METEOR cruise 30–2 in October/November 1994. A backcalculation technique based on measurements of temperature, salinity, oxygen, alkalinity, and total dissolved inorganic carbon was applied to identify the excess CO2. Everywhere along the transect surface water contained almost its full component of anthropogenic CO2 ( ∼62 μmol kg−1). Furthermore, anthropogenic CO2 has penetrated through the entire water column in the western basin of the North Atlantic Ocean. Even in the deepest waters (5000 m) of the western basin a mean value of 10.4 μmol kg−1 excess CO2 was calculated. The maximum penetration depth of excess CO2 in the eastern basin of the North Atlantic Ocean was ∼3500 m with values falling below 5 μmol kg−1 in greater depths. These results compare well with distributions of carbontetrachloride. They are also in agreement with the current understanding of the role of the “global ocean conveyor belt” for the uptake of anthropogenic CO2 into the deep ocean.

Polychlorinated biphenyls in North Sea water

Thirty-one individual chlorobiphenyl congeners (CBs) were analysed in water from the North Sea. Single column gas chromatographic and multidimensional gas chromatographic techniques were used to separate the constituents of the complex mixtures. Characteristic concentrations of individual CBs in off-shore water were between <0.05 and 2 pg dm−3, and up to 40 pg dm−3 in near-coastal waters. ΣCB values in off-shore waters were two to three times higher than values measured in the open Atlantic. Most concentrations in suspended matter were below the limit of detection (0.05 pg dm−3 in 100 dm3 samples). The most toxic (non-ortho-Cl substituted) CBs and their ortho-chlorine substituted derivatives were also determined. The sum of their concentrations was two to four times smaller than that of the non- or less toxic CBs. High concentrations and different compositions of the CB mixtures were found in the region where oil platforms are located. The much lower concentration levels reported here compared with older data reflect the improved measures to avoid contamination during sampling and laboratory procedures, as well as the analysis of a large volume of sea water (at least 100 dm3 for off-shore waters).

A comparison between activated charcoals and multidimensional GC in the separation and determination of (non-ortho Cl substituted) toxic chlorobiphenyls

Abstract Six activated charcoals were tested, using a multidimentional GC separation technique, for their efficiencies to isolate the most toxic, non-ortho Cl substituted biphenyls (CBs) from ortho Cl CBs in order to allow their reliable determination by single column GC-ECD. The tested charcoals failed to meet the requirement of complete separation of these groups of CBs. In addition interfering non-CB compounds were found to elute from charcoals.