Several field campaigns have been carried out as a part of the ArcRisk project. Data from these campaigns have been used for validation of models and to investigate transport processes, especially the link between abiotic and biotic environment. Transfer of POPs from abiotic matrices into biota is an important process, but there are few studies available. This page gives some of the ArcRisk results, and provides links to databases, not only from reviews conducted in the ArcRisk project, but also links to databases where large data sets and information are stored.

Databases of contaminants

Several field campaigns have been conducted in Arctic areas during the last decade. Within the ArcRisk project, an overview over POP levels has been established in 2010. It contains abiotic compartments such as air, snow, ice and water, as well as flux of contaminants within snowpacks and ice caps. In addition, low trophic level animals (plankton) have been included. Hence, this database provides an overview over recent data available. More studies are available, especially from the years after this overview was constructed.

An ISI ‘Web of Science’ and PubMed Literature survey (12.01.2012) revealed that about 1200 publications are available in peer-reviewed international journals on POPs in Arctic environments (since 1979). The ArcRisk project has compiled an overview of recent (1999-2011) and relevant reviews on fate and distribution of POPs and mercury in Arctic and Antarctic biota. The list can be downloaded here lænk till listan “relevant reviews on fate and distribution of POPs and mercury in Arctic and Antarctic biota” in D26. Information about analytical methods and sampling strategies are available in several peer reviewed articles.

Environment Canada provides regular reports on POPs levels in the North American Arctic as a part of the Northern Contaminants Program (NCP). These data are available on the internet – Canadian Arctic Contaminants Assessment Report. The written reports can be ordered directly from the NCP secretariat.

Environmental fate of organic contaminants

POPs can be transported from the primary source to remote areas. How far, when and how they will be transported is determined by their physical-chemical properties.

Changed temperatures and precipitation patterns can affect the abiotic transport processes as well as and their uptake in biota. Snow and ice melt brings “stored” POPs to the receiving rivers and oceans. Invading species might bring pollutants into the ecosystem, species composition might change in the ecosystems and the primary production can be affected as well. These are all examples of factors and processes that the ArcRisk project aimed to elucidate.

Fate processes in snowpack

In areas of high latitude (and altitude) snow is a significant source of atmospherically derived contaminants to catchment areas as well as marine waters (Blais et al., 2001; Daly and Wania, 2004; Bergknut et al., 2010; Pućko et al., 2011). However, the release of contaminants from the snowpack and their geochemistry following periods of thaw are not well understood, particularly for chemicals that are generally more polar, ionizable and/or largely non-volatile compared to semi-volatile “legacy” POPs. To date, there is a lack of measurement data for these chemicals in the remote snowpack.

Because snow accumulation on terrestrial surfaces or sea ice is controlled by several snowpack temperature- and wind-associated processes (e.g. wind pumping) that influence its structure and moisture content (Halsall, 2004; Herbert et al., 2006), chemical phase partitioning between vapour, particles, water and ice is crucial to understand the fate of contaminants in the snowpack. When melting commences with a seasonal increase in air temperature, chemical repartitioning can occur within the snowpack, which in turn will influence their elution order and release with meltwater (Halsall, 2004; Durnford and Dastoor, 2011; Meyer and Wania, 2010).

The geochemical behaviour of substances such as mercury and PFAS in the ageing snowpack is controlled by the physical properties of the snow and chemical processes (e.g., reduction and oxidation of Hg, and ice-based chemical partitioning coefficients for POPs), as well as particle type and amount. These interactions “decides” the fate of chemicals within the snowpack and control their elution during melt, either in a “first flush” (e.g., reactive gaseous mercury (RGM) and some shorter chain PFAs, such as perfluorobutane sulfonate (PFBS)), or later for particle-associated chemicals e.g. PHg). Despite the fact that PFAS are more water soluble than hydrophobic POPs, their various chain lengths and surfactant properties ensure a variable elution order during the onset of melt, although recent fieldwork conducted as part of the ArcRisk project shows that over time these chemicals will accumulate and undergo enrichment in snow layers prior to final melt.

Highest POPs concentrations in Arctic environments have been found in marine organisms due to bioaccumulation along the Arctic marine food webs. However, the transfer from the abiotic into the biotic compartment of the Arctic ecosystems depend on physical-chemical properties of the compound, the composition of the abiotic medium, as well as exchange processes with the organisms and surrounding environment (usually at low trophic levels).

Biologically available fractions of contaminants

The amount of POPs associated with the fraction of the abiotic medium transferred into an organism is considered as the bioavailable fraction for the specific abiotic medium investigated. Previous investigations have shown that the particulate composition in marine waters (distribution between dissolved and particulate phase) directly influences the partitioning of POPs. Temperature change has a direct influence on these processes and alters the partitioning of organic compounds between the dissolved and particulate phases in water and air. In addition, because many contaminants are strongly particle-associated, contaminated sediments can function as important secondary pollution sources for a long time after the primary sources have been stopped (Saloranta et al., 2011).

Within the framework of the ArcRisk project, food items, such as salmon, smoked halibut, whale and seal meat were purchased from the local market in Nuuk, Western Greenland, and examined for POP concentrations and distribution patterns. The concentrations for all pesticides were in the lower to medium (ng/g) range. The narwhal mattak (a local delicacy; blubber and skin from narwhal) samples showed the highest PCB and pesticide concentrations. These samples were analysed for chiral pesticides (α-HCH, trans- and cis-chlordane and the metabolite oxychlordane) as well. Chiral environmental pollutants are excellent indicators for the estimation of bioavailability and biotransformation potential in biological systems, even on an individual basis for top predator organisms (Kallenborn and Hühnerfuss, 2001; Wong and Bidleman, 2011). If the enantiomeric fraction (EF=EF1/(EF1+EF2) deviates from racemic distribution of enantiomers (EF=0.5), it is mainly caused by direct enantioselective biodegradation and/or accumulation. Enantioselective analytical methods can therefore help to estimate the bioavailability and biotransformation potential for chiral organic pollutants. The largest deviation from racemic distribution among the Greenlandic food items was found for all chiral compounds in narwhal. Many marine mammals (e.g., narwhal) have a notable metabolic capacity for biotransformation of POPs. Thus, potentially harmful transformation products are found in marine mammal tissues as a considerable contaminant contribution. These findings are considered as an indication of the above-average metabolic capacity of narwhals for biotransformation of the selected chiral organic pollutants.

Factors affecting bioavailability

Bioaccumulation factors (BAFs) determine the potential for accumulation of POPs in species. Factors presented within a suite of different studies are listed, see table below, for toxaphene, chlorinated benzenes, HCHs, DDTs, chlorobornanes, PCBs and PBDEs in plankton (Calanus spp) and beluga – ringed seal (PCB and PBDE). How much of a POP that is taken up in animals are determined by different factors, where the bioconcentration factor (BCF) is one of them. Bioconcentration factors means that POPs are up-concentrated from water to animals – like zooplankton at low trophic levels. The higher Kow (partitioning coefficient octanol-water), the higher BCF.

Human exposure to environmental pollutants occurs via the air, water and not the least, via the food we eat. How much pollutant one is exposed to depend on factors such as where we live and our habits. Seafood and fish from high up in the food web is an important exposure route for many contaminants.

If environmental pollutants will give negative effects and what those effects would depend on the exposure route and the properties of the pollutant. The potency of environmental pollutants differs widely and while one pollutant may give effect already at very low concentrations, others need to accumulate and maybe be transformed in the human body quite extensively before any effect may occur.

AMAP human health reports provide the baseline information on the health status of the populations living in the circumpolar area. Within the AMAP area, ten key areas have been identified that are a special focus for coordinated and harmonized monitoring and research activities. The main AMAP areas are: Chukotka Peninsula; the Mouth of Lena River; Taymir Peninsula, Norilsk area; Novaya Zemlya, Kara and Pechora Seas, the Mouth of Pechora River area; Kola Peninsula and Northern Fennoscandia area; Svalbard and East Greenland area; Baffin Island, West Greenland area; Canadian Arctic Islands and Arctic Archipelago; Lower Mackenzie River and Delta area; and Northern Alaska, North Slope area, see figure below.

A) The AMAP boundary of the Arctic (red line). The map shows ten key areas important to the AMAP monitoring program. B) Example of study sites from which data have been entered into the ArcRisk meta Database. The majority of the places are AMAP monitoring program sites (AMAP).
The work conducted within the ArcRisk project was focused on Europe and the European Arctic. Cohorts from the following areas in Europe were included in the ArcRisk: Croatia, Czech Republic, Finland, Greece, Greenland, Italy, Norway, Spain, Slovenia, and Russia. The areas were chosen to represent different climate zones, diets and exposure.

Scenario analyses of contamination in human populations due to environmental exposure and the fate of contamination are feasible only in areas where the population is monitored systematically for years. Within the AMAP area, human population contamination exposure has been monitored since 1992 with a varying number of follow-ups.

Effects of climate change on the food-web structure can have large consequences for the bioaccumulation of POPs. These can be bottom-up effects, in which changes in the abundance of primary producers influence the relative abundance of biota at higher trophic levels. They can also be top-down effects, where changes in the abundance of predators influence the relative abundance of organisms at lower trophic levels. Some top-down effects may be more evident, as changes in ice cover will have devastating effects on the abundance of top predators that depend on ice, such as polar bears and seals. Other top-down effects, such as predators switching to different prey and species moving to new regions, are more difficult to predict. Climate change effects on processes related to the intake of POPs could be enhanced intake in gills and intestines due to warmer temperatures and increased metabolism which may decrease internal concentrations or lead to increased exposure to toxic metabolites. Enforced fasting for e.g. polar bear may lead to increased residue levels.

Impacts on bioaccumulation modelling

There could be three primary mechanisms through which climate change can affect the bioaccumulation of environmental contaminants (Gouin et al., 2013):

climate change induced changes in environmental exposure (M1)
dietary exposure (M2) and
species-to-species uptake and loss rates (M3)
To date, only few modelling studies have investigated these mechanisms to some extent in the Arctic and Baltic Sea regions. In general, the physical environment played a relatively small role in determining the susceptibility to chemical exposure compared to the food web properties.

Hence, the global climate change induced direct changes (temperature and precipitation) would have little influence on the bioaccumulation of POPs in foods consumed by humans. Climate change induced effects were most likely to be indirect, such as changes in the dietary composition of food chains (M2). The direct effects on temperature-dependent uptake and loss rates are not likely to be significant compared to the indirect effects (M3).

Marine Food Web Modelling

A marine food web was chosen from the Svalbard region for initial model development. The Svalbard food web model contains plankton and fish samples taken within the ArcRisk project. A review of the marine ecosystem of Kongsfjorden in Svalbard by Hop et al. (2002) was utilized to help shape the initial structure of the Svalbard marine food web. The species included in the food web were algae, copepods (Calanus hyperboreus), amphipods (Onisimus spp., Apherusa glacialis and Themisto libellula), polar cod (Boreogadus saida), three seal species (Erignathus barbatus, Phoca hispida and P. groenlandica), and polar bears (Ursus maritimus). Levels of PCB in Svalbard waters in 2001 were used in the model (Sobek and Gustafsson, 2004).

Feeding relationships in the Svalbard marine food web (the linkage between developed food web and human cohorts of interest is missing in this food web; number means species specific trophic level).
The food web model underestimates the measured concentrations, which vary with the species and the PCB congener. PCB concentrations predicted in polar cod were most sensitive to the digestion factor, which suggests biomagnification as a very important factor. The herbivorous Apherusa glacialis are more affected by PCB concentrations in the water.

Humans living on Svalbard are relatively few in number (~2500), have a short residence time there and their diet does not include large contribution from local marine fish or mammals. Hence, studies of human exposure were done in other Arctic areas instead. The food web model from Svalbard is still highly relevant for human exposure in other Arctic areas, e.g. since the surrounding Barents Sea is important for the Norwegian and Russian fishing industry and the consumers. Bioaccumulation key processes are similar around the Arctic. Hence, results and tools developed within the Svalbard food web model can be applied on other Arctic food web systems that are more relevant for human exposure. However, even while using state-of-the-art modelling tools, the estimations of bioaccumulation in Arctic marine food webs under a changing climate is very difficult. Potential changes in the ecosystem, impact of invading species and ocean acidification are yet not fully understood.

Due to the slow uptake and elimination rates of many POPs at higher trophic levels (marine mammals), a dynamic model could provide improved predictions compared to a static model. A dynamic model is also expected to be more suitable compared to a steady-state model regarding PFAS, since the PFAS exposure changes rapidly over time.

To develop a relevant future climate change scenarios for food web modelling is challenging. A review by Cousins et al. (2011) demonstrated that predicting changes in food web structure due to future climate change is not yet possible. Information about possible scenarios and already on-going changes observed are needed before models can be further developed for food webs in change. ArcRisk have developed bioaccumulation models for Arctic food webs. However, data of POPs in sea water is still scarce, although needed to improve the models.

Environmental contaminants are emitted un-/intentionally. Pesticides are a classic example of intentional release of a toxic chemical to the environment. Other chemicals are released unintentionally to the environment e.g. by-products from industries. Furthermore, contamination from historical use may still be a source of emissions, e.g. via contaminated sediments and land.

The further fate of the contaminant depends both on properties of the substance and to which media the emissions took place. Some chemicals are long-lived as they persist degradation. Such chemicals can be transported long distances in air and water, accumulate in food webs and pollute areas and animals far from the original source.

Transport of POPs can be illustrated by “global fractionation”. They evaporate from the source – e.g. pesticides used in a southern agriculture. The pesticides are then transported with air further north (in the northern hemisphere), precipitate/scavenges out from the air. Eventually, the POPs repeat this process in several steps (“grasshopping”) until they reach the Arctic (Wania and Mackay 1996).

Emissions

Past, current and future emission patterns of contaminants

Emissions of legacy POPs such as DDTs, PCBs and HCHs have decreased during the last decades due to extensive regulatory action, including complete ban in several countries. Metal emissions, such as mercury, are also expected to decrease.

However, Pacyna et al. (2010) estimated an increase of Asian mercury emissions unless emission controls will be implemented. This is of high importance in a global perspective, since the emissions in Asia are estimated to be higher than any of the other continents. If emissions will continue to increase largely depend on economic development and advances in industrial techniques and emission control techniques. For the metals and unintentionally formed POPs, such as the dioxins, a complete ban is not possible as the contaminants are naturally occurring and unintentionally generated in processes not aiming to emit these contaminants.

Regional sources

As permafrost thaws in the Arctic, waste sites may leak contaminants to the receiving water systems. Less ice cover in Arctic facilitates shipping and off shore activities in a vulnerable area, where sea charts and search & rescue systems not always are well developed/within acceptable reach. These factors need to be taken into account for future work with contaminant risks in the Arctic, especially environmental pollutants related to transport, oil and gas. The North West and North East passage have already been used for shipping traffic. Shipping and offshore in the Arctic was one of the themes at the Arctic Frontiers 2014 conference in Tromsø, Norway.

Pathways and long-range transport of pollutants

POPs and mercury reach the Arctic mainly via atmospheric long range transport. Some substances are also transported via ocean currents and rivers.

DDT and PCB are examples of atmospheric transported compounds, while α-HCH can also be transported by water currents. Atmospheric transport of semivolatile POPs to the Arctic takes place via repeated evaporation and deposition events, resulting in the pollutant “hopping” to its final destination in the Arctic (Wania and Mackay 1996). Mercury is also transported from lower latitudes to the Arctic via the atmosphere. The transport mechanism involves different forms of mercury, both gaseous elemental mercury (Hg(0)), Hg(II) and particle bound species, and involve an oxidation process.