People living a subsistence lifestyle in the Arctic are highly exposed to persistent organic pollutants, including polychlorinated biphenyls (PCBs). Formerly Used Defense (FUD) sites are point sources of PCB pollution; the Arctic contains thousands of FUD sites, many co-located with indigenous villages. We investigated PCB profiles and biological effects in freshwater fish (Alaska blackfish [Dallia pectoralis] and ninespine stickleback [Pungitius pungitius]) living upstream and downstream of the Northeast Cape FUD site on St. Lawrence Island in the Bering Sea. Despite extensive site remediation, fish remained contaminated with PCBs. Vitellogenin concentrations in males indicated exposure to estrogenic contaminants, and some fish were hypothyroid. Downstream fish showed altered DNA methylation in gonads and altered gene expression related to DNA replication, response to DNA damage, and cell signaling. This study demonstrates that, even after site remediation, contaminants from Cold War FUD sites in remote regions of the Arctic remain a potential health threat to local residents – in this case, Yupik people who had no influence over site selection and use by the United States military.

The spatial distribution, compositional profiles, and enantiomer fractions (EFs) of organochlorine pesticides (OCPs), including hexachlorocyclohexanes (HCHs), dichlorodiphenyltrichloroethanes (DDTs), and chlordanes (CHLs), in the surface sediments in the Bering Sea, Chukchi Sea and adjacent areas were investigated. The total concentrations of DDTs, HCHs and CHLs varied from 0.64 to 3.17 ng/g dw, 0.19–0.65 ng/g dw, and 0.03–0.16 ng/g dw, respectively. No significant difference was observed between the Bering Sea and Chukchi Sea for most pollutants except for trans-CHL, ΣCHLs (sum of trans- and cis-chlordane) and p,p'-DDD. Concentration ratios (e.g., α-HCH/γ-HCH, o,p'-DDT/p,p'-DDT) indicated that the contamination in the studied areas may result from inputs from multiple sources (e.g., historical usage of technical HCHs as well as new input of dicofol). Chiral analysis showed great variation in the enantioselective degradation of OCPs, resulting in excess of (+)-enantiomer for α-HCH in thirty of the 32 detectable samples, preferential depletion of (−)-enantiomer for o,p'-DDT in nineteen of the 35 detectable samples, and nonracemic in most samples for trans- and cis-chlordane. The ecological risks of the individual OCPs as well as the mixture were assessed based on the calculation of toxic units (TUs), and the results showed the predominance of DDT and γ-HCH in the mixture toxicity of the sediment. Overall, the TUs of OCPs in sediments from both the Bering and Chukchi Seas are less than one, indicating low ecological risk potential.

Mercury concentration ([Hg]), δ¹⁵N, and δ¹³C values were measured in eggs from common murres (Uria aalge), thick-billed murres (U. lomvia), glaucous gulls (Larus hyperboreus), and glaucous-winged gulls (L. glaucescens) collected in Alaska from 1999 to 2005. [Hg] was normalized to a common trophic level using egg δ¹⁵N values and published Hg trophic magnification factors. Egg [Hg] was higher in murres from Gulf of Alaska, Cook Inlet, and Norton Sound regions compared to Bering Sea and Bering Strait regions, independent of trophic level. We believe the Yukon River outflow and terrestrial Hg sources on the southern Seward Peninsula are responsible for the elevated [Hg] in Norton Sound eggs. Normalizing for trophic level generally diminished or eliminated differences in [Hg] among taxa, but temporal variability was unrelated to trophic level. Normalizing murre egg [Hg] by trophic level improves the confidence in regional comparisons of Hg sources and biogeochemical cycling in Alaska.

The western stock of the Steller sea lion (Eumetopias jubatus) in the northern Pacific Ocean has declined by approximately 80% over the past 30 years. This led to the listing of this sea lion population as an endangered species in 1997. Chemical pollution is a one of several contributing causes. In the present study, 145 individual PCBs were determined in tissues of male sea lions from Tatitlek (Prince William Sound) and St. Paul Island (Bering Sea), and placentae from the Aleutian Islands. PCBs 90/101, 118, and 153 were abundant in all the samples. The mean toxic equivalents (TEQ) were 2.6, 4.7 and 7.4pg/g lw in the kidney, liver, and blubber samples, respectively. The mean TEQ in placentae was 8pg/g lw. Total PCBs concentrations (2.6–7.9μg/g lw) in livers of some males were within a range known to cause physiological effects. Further suggesting the possibility of adverse effects on this stock.

After the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, radionuclides released by this event were observed in the Pacific Ocean. Models predicted that these radionuclides would be transported to the Bering Sea; however, limited evidence currently reveals the transportation of these radionuclides to the Arctic Ocean. Here, we provide the first direct observation showing that FDNPP-derived 134Cs and 137Cs were present in subarctic regions and the Arctic Ocean (Chukchi Sea) in 2017. Furthermore, we conclude that these radionuclides were transported from the Pacific Ocean into the Bering and Chukchi Seas by ocean currents. Additionally, the 137Cs activity concentrations in the Bering Sea exceed those in all previous reports. Due to the continuous leaking of radionuclides from the FDNPP, we hypothesize that FDNPP-derived radionuclides will be continuously transported to the Arctic Ocean in the next several years. Our results suggest that though far away from Fukushima, the accident-derived anthropogenic radionuclides also influenced the Arctic Ocean by ocean currents.

Eighteen polycyclic aromatic hydrocarbons (PAHs) were measured in surficial sediments along a marine transect from the North Pacific into the Arctic Ocean. The highest average Σ18PAHs concentrations were observed along the continental slope of the Canada Basin in the Arctic (68.3 ± 8.5 ng g−1 dw), followed by sediments in the Chukchi Sea shelf (49.7 ± 21.2 ng g−1 dw) and Bering Sea (39.5 ± 11.3 ng g−1 dw), while the Bering Strait (16.8 ± 7.1 ng g−1 dw) and Central Arctic Ocean sediments (13.1 ± 9.6 ng g−1 dw) had relatively lower average concentrations. The use of principal components analysis with multiple linear regression (PCA/MLR) indicated that on average oil related or petrogenic sources contributed ∼42% of the measured PAHs in the sediments and marked by higher concentrations of two methylnaphthalenes over the non-alkylated parent PAH, naphthalene. Wood and coal combustion contributed ∼32%, and high temperature pyrogenic sources contributing ∼26%. Petrogenic sources, such as oil seeps, allochthonous coal and coastally eroded material such as terrigenous sediments particularly affected the Chukchi Sea shelf and slope of the Canada Basin, while biomass and coal combustion sources appeared to have greater influence in the central Arctic Ocean, possibly due to the effects of episodic summertime forest fires.

Assessing the fate of both legacy and newer persistent organic pollutants (POPs) is an ongoing challenge. Top predators, including seabirds, are effective monitors of POPs because they forage over a range of marine habitats, integrating signals over space and time. However, migration patterns can make unravelling contaminant sources, and potentially assessments of the effectiveness of regulations, challenging if chemicals are acquired at distant sites. In 2014, we fitted geolocators on ancient murrelets (Synthliboramphus antiqueus) at four colonies on the Pacific Coast of Canada to obtain movement data throughout an annual cycle. All birds underwent a post-breeding moult in the Bering Sea. Around one-third then returned to overwinter on the British Columbia (BC) coast while the rest migrated to overwinter in waters along the north Asian coast. Such a stark difference in migration destination provided an opportunity to examine the influence of wintering location on contaminant signals. In summer 2015, we collected blood samples from returned geo-tagged birds and analyzed them for a suite of contaminants, including polybrominated diphenyl ethers (PBDEs), non-PBDE halogenated flame retardants, perfluoroalkyl substances (PFASs), organochlorines, and mercury. Feathers were also collected and analyzed for stable isotopes (δ¹³C, δ¹⁵N, and δ³⁴S). We found no significant differences in blood concentrations of any contaminant between murrelets from the two different overwinter areas, a result that indicates relatively rapid clearance of POPs accumulated during winter. Spatial variation in diet (i.e., δ¹³C) was associated with both BDE-47 and -99 concentrations. However, individual variation in trophic level had little influence on concentrations of any other examined contaminants. Thus, blood from these murrelets is a good indicator of recent, local contaminants, as most signals appear independent of overwintering location.

The bioaccumulative, persistent and toxic properties of long-chain perfluoroalkyl acids (PFAAs) resulted in strict regulations on PFAAs, especially in developed countries. Consequently, the industry manufacturing of PFAAs shifts from long-chain to short-chain. In order to better understand the pollution situation of PFAAs in marine environment under this new circumstance, the occurrence of 17 linear PFAAs was investigated in 30 surface seawater samples from the North Pacific to Arctic Ocean (123°E to 24°W, 32 to 82°N) during the sixth Chinese Arctic Expedition in 2014. Total concentrations of PFAAs (∑PFAAs) were between 346.9 pg per liter (pg/L) to 3045.3 pg/L. The average concentrations of ∑PFAAs decreased in the order of East China Sea (2791.4 pg/L, n = 2), Sea of Japan (East Sea) (832.8 pg/L, n = 6), Arctic Ocean (516.9 pg/L, n = 7), Chukchi Sea (505.2 pg/L, n = 4), Bering Sea (501.2 pg/L, n = 8) and Sea of Okhotsk (417.7 pg/L, n = 3). C4 to C9 perfluoroalkyl carboxylic acids (PFCAs) were detected in more than 80% of the surface water samples. Perfluorobutanoic acid (PFBA) was the most prevalent compound and perfluorooctanoic acid (PFOA) was the second abundant homolog. The concentration of individual PFAAs in the surface seawater of East China Sea was much higher than other sampling seas. As the spatial distribution of PFAAs in the marine environment was mainly influenced by the river inflow from the basin countries, which proved the large input from China. Furthermore, the marginal seas of China were found with the greatest burden of PFOA comparing the pollution level in surface seawater worldwide. PFBA concentration in the surrounding seas of China was also high, but distributed more evenly with an obvious increase in recent years. This large-scale monitoring survey will help the improvement and development of PFAAs regulations and management, where production shift should be taken into consideration.

Seventy-four surface sediment samples were collected from the Arctic Ocean and Bering Sea to determine the content of metal(loid)s (As, Cu, Cd, Ni, Pb, Zn and Cr). Metal(loid)s content in these sediments varied from 2.36–41.90 mg/kg for As, 8.63–82.28 mg/kg for Cu, 0.14–0.71 mg/kg for Cd, 11.86–100.60 mg/kg for Ni, 8.30–27.58 mg/kg for Pb, 39.93–391.43 mg/kg for Zn, and 40.96–106.49 mg/kg for Cr. The pH and water-soluble organic carbon content had considerable impacts on the content of metal(loid)s in sediment, but the texture of sediment has limited influence on metal(loid)s content in sediment. In addition, the hotspots of most of these metal(loid)s appeared in the Beaufort Sea region. The geoaccumulation index (Igₑₒ) indicated that Cd was the metal with the highest contamination in these sediments, with 55.41% of the sample sites posing moderate pollution. The ecological risk for As, Cu, Ni, Pb, Zn and Cr indicates low ecological risk (100%), while Cd posed moderate risk (35.14%), considerable risk (54.05%) and high risk (10.81%) and attributed more than 76.45% of the total potential ecological risk of these metal(loid)s.

Trace metals in Laptev and East Siberian Sea sediments were analyzed to examine the element distribution pattern and to assess sediment contamination using contamination indices. The maximum Cr, Zn, Ni, Cu, and As concentrations occurred in the deeper parts of the East Siberian and Laptev Seas and the estuarine shelves of the Lena and Yana Rivers, and a high Cd content was observed in the sediment of the eastern part of the East Siberian Sea. The increased Cd concentration could be a result of the large number of phytoplankton supplied by the highly productive waters of the Bering Sea and the sorption capacity of Cd precipitation on Fe and Mn oxyhydroxides in seawater. The mean enrichment factors and geoaccumulation index values for Cr, Ni, Cu, Zn, Pb, and Cd showed no contamination by these metals at any sampling locations; however, slight As enrichment was found, possibly originating from natural sources.