Johan Axelman

A review of processes involved in the exchange of persistent organic pollutants across the air-sea interface

Abstract Atmospheric deposition across the air–sea interface is the main input route for persistent organic pollutants (POPs) to the marine environment and its ecosystems. The main processes contributing to air–sea exchange of POPs are diffusive vapour exchange, precipitation scavenging of vapours and particle-sorbed chemicals, and dry deposition with particles. Additional processes within the atmosphere and surface water affecting this exchange are aerosol–vapour partitioning, and partitioning and sedimentation in the water-column. These processes are discussed and recent findings are summarised. Commonly employed expressions used for describing these processes in models are presented, with a special focus on the influence of temperature and other seasonal parameters. Research gaps are identified which have to be addressed to gain a solid understanding of the environmental transport and distribution of POPs. This is needed to implement and evaluate the effectiveness of recent international agreements to protect the marine environment from the deleterious effects of POPs.

Time trend analysis of PAHs and PCBs in the northern Baltic proper

Abstract Laminated sediments were collected with a combined box and piston coring technique at a location in the northern Baltic proper. Twenty-two horizontal sediment layers (laminae), each with a height of approx. 1.8 mm, were analysed for carbon, nitrogen and dry weight, and ten of these layers were analysed for the amount of extractable lipids, PAHs, PCBs and the activity of 210Pb for the dating of the sediment. The results indicated a homogeneous composition of the investigated laminated sediment with respect to the parameters describing the basic sediment characteristics, i.e. density, carbon-, nitrogen- and lipid contents. The results of the chemical analyses of PAHs and PCBs in combination with the dating results of the sediment laminae showed that the PAH and PCB peaks corresponded roughly to 15 to 30 years back in time not considering the time lag between pollutant input to the Baltic aquatic environment and the deposition on this deep off shore bottom. It was also found that the relative composition of both PCBs and PAHs (chemical profiles) was fairly constant with increasing sediment depth, indicating that mineralization processes are very slow and the sediment redistribution of these compounds are of minor significance in this sediment.

Budget calculations for polychlorinated biphenyls (PCBs) in the Northern Hemisphere - a single-box approach

Numerous studies show that the environmental concentrations of PCBs have been decreasing since the production and use of PCBs in most industrialised countries was banned in the 1970s. However, most of these studies have been conducted close to historical sources. The few studies conducted in remote locations detect no trend of decreasing concentrations over the past 20–30 years. These observations suggest that PCBs may be removed more slowly from the environment, when viewed from a global or hemispheric perspective. The present study estimates the mass fluxes of individual PCB congeners in the Northern Hemisphere in order to elucidate the most important removal processes and the rate of decrease one may expect with complete cessation of emissions. Atmospheric reaction lifetimes, open-ocean settling fluxes and the pools and mobility of PCBs in the terrestrial environment are shown to be crucial parameters. However, the calculations identify important gaps of knowledge regarding predictions of environmental half-lives of PCBs. The results suggest that highly chlorinated congeners such as PCB 153 and 180 may be persistent in the global environment with annual rates of decrease of less than 1%. The compiled environmental data also highlight large differences between the different PCB congeners. Although this paper is based on more than 800 PCB measurements it should be considered a starting point for further research aiming to quantify the global fate of toxic and persistent organic substances such as the PCBs.

Vertical Flux and Particulate/Water Dynamics of Polychlorinated Biphenyls (PCBs) in the Open Baltic Sea

Abstract Concentrations of PCBs in water (dissolved), suspended particles (SPM), sediment trap material, and sediments in the Baltic Sea are discussed in relation to the dynamics of organic carbon and lipids as the sorbing matrices. Both carbon- and lipid-normalized concentrations of PCBs in SPM increase during the sedimentation giving rise to an increase in observed log Koc with more that one order of magnitude for most of the studied PCBs. It appears that hydrophobic organic compounds (HOCs) are retained within the settling particles while the organic carbon and the lipids are degraded, rather than there being a continuous uptake of PCBs during settling. However, the explanation for the high concentration maintained in the sediments over long time periods, must be an increasing capability of the organic matrix to sorb HOCs during the ageing process. The results are of importance for current models of the fate of HOCs in the environment and imply that the use of a single equation to estimate equilibrium concentrations of HOCs in SPM may significantly under-estimate concentrations in settling particles.

An evaluation of the importance of the sampling step to the total analytical variance : A four system field-based sampling intercomparison study for hydrophobic organic contaminants in the surface waters of the open Baltic Sea

An evaluation of the importance of the sampling step to the total analytical variance : A four system field-based sampling intercomparison study for hydrophobic organic contaminants in the surface waters of the open Baltic Sea

Characterisation of the PAH load outside an aluminium smelter on the Swedish Baltic coast

Abstract The load of pokycyclic aromatic hydrocarbons was investigated in a water area outside an aluminium smelter on the Swedish Baltic coast. The load was evaluated in terms of PAH content in settling particulate matter, bottom surface sediments and in two bivalves, blue mussels ( Mytilus edulis ) and Baltic tellins ( Macoma baltica ). The total PAH concentrations (15 compounds) varied between 5.3 and 41 μg/g (dry wt.) in the settling particulate matter samples and between 14 and 211 μg/g (dry wt.) in the bottom surface sediments. The two bivalves showed concentrations of 6.2 μg/g (dry wt.) for blue mussels and 167 μg/g (dry wt.) for Baltic tellins, respectively, collected outside the aluminium smelter. The PAH flux in the water area outside the aluminium smelter was estimated to approximately 1 ton of PAH/year in the 50 km 2 closest to the smelter. To characterise the PAH emissions found in the water area outside the aluminium smelter in comparison to emission profiles from other sources in Sweden, use has been made of a multivariate statistical method. The result of this analysis showed that the emission source pattern of the sediment trap samples from the area outside the smelter was significantly different from all other source areas compared in the analysis.

Compound dependence of the relationship log Kow and log BCFL

Linear relatinships between log bioconcentration factor (BCF) and log Kow for a variety of compounds have been reported many times in the literature. Analysis of the thermodynamics of the two partition processes has, however, shown that they are not analogous and that linear relationships can be expected to have different slopes for structurally unrelated compounds. In this study a set of literature lipid normalized BCF (BCFL) values of chlorbenzenes (CBs) for rainbow trout and polycyclic aromatic hydrocarbons (PAHs) forDaphnia was put together with literature Kow values. The slopes of the regression lines for log BCFL versus log Kow for the two groups of compounds proved to differ significantly in a statistical test using analysis of variance (ANOVA). The difference, which is of significance for estimates of BCFs in environmental modelling of these types of compounds, is explained by the differences in chemical structure of the two groups of compounds.

Dynamics of lipids and polychlorinated biphenyls in a baltic amphipod (Monoporeia affinis): A field study

Processes such as accumulation and elimination, which control tissue concentration of polychlorinated biphenyls (PCBs), were examined over time in an in situ study of the amphipod Monoporeia affinis. These processes were studied with respect to individual PCB congeners, percentage lipid and composition, and body weight. A secondary objective was to examine the impact of seasonal variability in percentage lipids and lipid composition on PCB concentration in two coexisting Baltic amphipods, M. affinis and Pontoporeia femorata. Polycholorinated biphenyl concentrations tended to be higher in P. femorata than in M. affinis, possibly because of P. femoratas lower respiration rate and larger size. The net accumulation of PCBs was congener dependent and negatively correlated to lipid concentration. The relation between the net concentration change rate of 16 PCB congeners over time and log Kow was not significant during the spring and summer months, a time when lipid accumulation and strong growth occur. In contrast, the net concentration change rate of the corresponding PCB congeners over time during autumn and early winter, that is, from the period before gonad maturation to the period after mating and early embryogenesis, showed a significant relation to tog Kow (r2 = 0.62, p < 0.001, n = 16). During the latter period, amphipod lipid weight was reduced while the PCB body burden increased. Results strongly indicate that elimination rather than accumulation is the main process controlling amphipod body burden. This pattern results in a transfer of PCBs from the female to the developing embryos, which is reflected in high PCB body burden in newly released offspring.

Process-diagnostic patterns of chlorobiphenyl congeners in two radiochronologically characterized sediment cores from the northern Baffin Bay

Polychlorinated biphenyl (PCB) patterns were interpreted in two radioisotopically constrained sediment cores from the Arctic ocean in order to seek clues about their large-scale environmental fates. Low but clearly measurable fluxes of individual PCB congeners were observed in deeper layer sediments, corresponding to the past 170 years, in a single dated core from the Baffin Bay shelf. Fluxes of the dominant individual congeners in the surface sediments were 20-100 pg m(-2) d(-1). Combining these data with the sediment data from the Arctic Monitoring and Assessment Program, it appears that the PCB distribution in Arctic surface sediments is governed by the organic carbon (OC) content of the sediments. The historical development of the PCB congener fingerprint suggests that the modern sediments are enriched in medium-chlorinated congeners, implying that there are at least two significant, but distinctly different, sink processes acting on the PCB pool. The relative abundance of light-to-heavy congeners, in mid-shelf marine sediments of similar ages, between 40 degrees N and 76 degrees N latitude suggests a northward dilution of PCBs which is stronger attenuated for heavier congeners, consistent with a temperature-driven global fractionation process. The significant presence of PCB in historical archives pre-dating the organochlorine society, as observed in this and several previous studies, awaits a fuller explanation.

A Multicompartmental, Multi-Basin Fugacity Model Describing the Fate of PCBs in the Baltic Sea

Persistent organic pollutants (POPs) such as polycyclic aromatic hydrocarbons and organochlorinated compounds reach lakes, estuaries and the oceans through direct discharge, riverine inflow or atmospheric deposition. These generally quite hydrophobic chemicals have a low affinity for the aqueous phase and tend to partition into the organic phases of suspended solids and bottom sediments or the lipid fraction of aquatic biota. Some POPs show a potential to biomagnify and the highest concentrations are often found in the upper trophic levels of aquatic food chains.