Development, Evaluation and Application of a Nested Exposure Assessment Model for Organic Contaminants in the Nordic and Arctic Region

It is well established Nordic and Arctic environments suffer from long-range environmental transport (LRT) of various organic contaminants, e.g. Persistent Organic Pollutants (POPs). At the same time, some areas in our region are experiencing elevated levels of such contaminants, assumed mainly attributed to local / domestic emissions. In this project, we have studied how various sources and source regions affect environmental exposure in northern Europe by using a combination of modelling and measuring techniques. Specifically, we have developed, evaluated and applied a novel Nested Exposure Model (NEM) for both the physical and biotic environment to expand on the insights obtained from observations alone. Our scientific vision has been to establish an operational exposure modelling tool for organic contaminants to support both future research and chemical management strategies under realistic climatic and environmental conditions. A key goal of this project was to describe the fate and transport of organic contaminants within the physical (abiotic) environment of the target region. NEM includes compartments describing a two-layer atmosphere, soils, fresh water and freshwater sediment, coastal water and coastal sediment, as well as open seawater. Through nesting up to five different model domains, NEM offers increasing resolution with increasing proximity (in space and time) to a study region of interest. Chemical transport between neighboring grid cells may occur by air, fresh water and seawater. Through sequential simulations, chemical inflow from the outside world into the next user-defined domain of NEM is based on model outputs stored from simulations of the preceding domain. This is made possible as spatially and temporally variable environmental input data are derived from global data sets, processed and stored at a spatial resolution of 0.5°x0.5° (latitude/longitude). Evaluating NEM by comparing model predictions for PCB-153 in air with measurements at nine long-term monitoring sites of the European Monitoring and Evaluation Programme (EMEP) shows that differences between observations and model predictions are comparable to the variability anticipated from differences in sampling and analytical methods used across laboratories involved. The added capability of NEM to target any user-defined region of the globe ensures flexibility and future opportunities, extending well beyond this project. The project has carried out extensive measurement campaigns of persistent organic pollutants (POPs) in air across Europe and Norway. The measurements from Norway represent the most comprehensive national survey carried out until now. The measurement data from this project allows for a critical evaluation of the NEM with respect to its capability to reproduce measured concentrations, main pathways as well as spatial and temporal variabilities. Research on the biotic part of the model has had a focus on the aquatic food web. A relatively simple pelagic food-chain has been extended to include a benthic component. An evaluation of the new bentho-pelagic model suggests it provides a more realistic description of selected PCBs in comparison to the original pelagic model. The new model has already been evaluated and applied to obtain a better understanding of the bioaccumulation behavior of selected cyclic volatile methylsiloxanes (D4, D5 and D6) within a northern aquatic food-chain. Additionally, an Arctic bioaccumulation model was adapted to represent Norwegian-Arctic ecosystems. The marine part of the model now includes three types of zooplankton (copepods, krill and amphipods), four fish species (herring, Atlantic cod, capelin and polar cod), two marine mammals (ringed seal and beluga whale), and one migratory seabird (black-legged kittiwake). The model also has a terrestrial module consisting of lichen and reindeer, and a module for human exposure via the environment. Moreover, the model has been further developed to enable simulations in both space and time. Evaluation of the model shows that it is able to successfully predict concentrations of PCB-153 across time, space and species. When the integrated NEM model is run on global, historical emission estimates of PCB-153 from 1930-2020, simultaneously accounting for the transport and fate in the physical environment, the model successfully predicts concentrations throughout the food web, when compared to measurements from Kongsfjorden, Svalbard. The NEM model is also able to satisfactorily predict concentrations of PCB-153 in cod and herring in Norwegian marine areas, accounting for variability in space and time. This shows that NEM model is able to model the whole link from global historical emissions to ecosystem exposure in Norwegian and Arctic areas. Further research will be required to delineate the boundaries of applicability towards organic contaminants with divergent fate properties beyond those studied in this project.

Prosjektet har ledet til økt tverrfaglig forskningssamarbeid, både nasjonalt og internasjonalt. Prosjektresultatene har også vært en forutsetning for flere nye forskningsprosjekter som allerede har startet. Resultatene vil kunne ha potensielle effekter på videreutvikling av rasjonelle kjemikaliestratagier for å beskytte mennesker og miljø mot helseskadelig stoffer.

It is well established Nordic and Arctic environments may be significantly exposed by long range transport (LRT) of various organic contaminants, e.g. Persistent Organic Pollutants (POPs). At the same time, several areas in our region are experiencing elevated levels of such contaminants, mainly attributed to local emissions (LE). Key examples are some coastal environments / lakes with consumption advisories on seafood / fish. To complicate matters, organic contaminants measured in the environment today may in part be due to primary emissions (PE) amenable to further control strategies, and in part be due to secondary emissions (SE) from contaminated reservoirs as polluted in the past. So far, no devoted and comprehensive study has been carried out to assess the relative significance of both LRT, LE, SE and PE in controlling exposure of both the physical and biotic environment, including potential shifts in burdens due to changes environmental and climatic conditions. This makes it difficult to provide decision makers with scientific advice concerning rational control strategies. In this project, we aim to elucidate how these factors affect environmental exposure in northern Europe by using a combination of modelling and measuring techniques. Specific, we aim to develop, apply and evaluate a nested exposure model for both the physical and biotic environment to confront, complement and expand on the insights obtained from observations alone. Passive air samplers will be used to map the influence of LRT vs LNE for a wide range of substances across Norway and we will also expand on the world's longest time trends of POPs in air and use data from environmental surface media to assess SE vs PE in controlling air trends within Norway and the UK. Our vision is to establish an operational exposure modelling tool for organic contaminants which could support both future research and chemical management strategies under changing climatic and environmental conditions.