Liisa M. Jantunen

Contaminants in the Canadian Arctic: 5 years of progress in understanding sources, occurrence and pathways

Recent studies of contaminants under the Canadian Northern Contaminants Program (NCP) have substantially enhanced our understanding of the pathways by which contaminants enter Canadas Arctic and move through terrestrial and marine ecosystems there. Building on a previous review (Barrie et al., Arctic contaminants: sources, occurrence and pathways. Sci Total Environ 1992:1-74), we highlight new knowledge developed under the NCP on the sources, occurrence and pathways of contaminants (organochlorines, Hg, Pb and Cd, PAHs, artificial radionuclides). Starting from the global scale, we examine emission histories and sources for selected contaminants focussing especially on the organochlorines. Physical and chemical properties, transport processes in the environment (e.g. winds, currents, partitioning), and models are then used to identify, understand and illustrate the connection between the contaminant sources in industrial and agricultural regions to the south and the eventual arrival of contaminants in remote regions of the Arctic. Within the Arctic, we examine how contaminants impinge on marine and terrestrial pathways and how they are subsequently either removed to sinks or remain where they can enter the biosphere. As a way to focus this synthesis on key concerns of northern residents, a number of special topics are examined including: a mass balance for HCH and toxaphene (CHBs) in the Arctic Ocean; a comparison of PCB sources within Canadas Arctic (Dew Line Sites) with PCBs imported through long-range transport; an evaluation of concerns posed by three priority metals--Hg, Pb and Cd; an evaluation of the risks from artificial radionuclides in the ocean; a review of what is known about new-generation pesticides that are replacing the organochlorines; and a comparison of natural vs. anthropogenic sources of PAH in the Arctic. The research and syntheses provide compelling evidence for close connectivity between the global emission of contaminants from industrial and agricultural activities and the Arctic. For semi-volatile compounds that partition strongly into cold water (e.g. HCH) we have seen an inevitable loading of Arctic aquatic reservoirs. Drastic HCH emission reductions have been rapidly followed by reduced atmospheric burdens with the result that the major reservoir and transport agent has become the ocean. In the Arctic, it will take decades for the upper ocean to clear itself of HCH. For compounds that partition strongly onto particles, and for which the soil reservoir is most important (e.g. PCBs), we have seen a delay in their arrival in the Arctic and some fractionation toward more volatile compounds (e.g. lower-chlorinated PCBs). Despite banning the production of PCB in the 1970s, and despite decreases of PCBs in environmental compartments in temperate regions, the Arctic presently shows little evidence of reduced PCB loadings. We anticipate a delay in PCB reductions in the Arctic and environmental lifetimes measured in decades. Although artificial radionuclides have caused great concern due to their direct disposal on Russian Shelves, they are found to pose little threat to Canadian waters and, indeed, much of the radionuclide inventory can be explained as remnant global fallout, which was sharply curtailed in the 1960s, and waste emissions released under license by the European reprocessing plants. Although Cd poses a human dietary concern both for terrestrial and marine mammals, we find little evidence that Cd in marine systems has been impacted by human activities. There is evidence of contaminant Pb in the Arctic, but loadings appear presently to be decreasing due to source controls (e.g. removal of Pb from gasoline) in Europe and North America. Of the metals, Hg provokes the greatest concern; loadings appear to be increasing in the Arctic due to global human activities, but such loadings are not evenly distributed nor are the pathways by which they enter and move within the Arctic well understood.

Reversal of the Air-Water Gas Exchange Direction of Hexachlorocyclohexanes in the Bering and Chukchi Seas: 1993 versus 1988.

In the summer of 1993, water and air samples were collected in the Bering and Chukchi Seas (BERPAC-93) to determine the air-water gas exchange of hexachlorocyclohexanes (HCHs). Average concentrations in the ocean surface water, 2.00 and 0.45 ng L -1 for α-HCH and γ-HCH, were 18% and 24% lower than values found on a 1988 cruise. Mean concentrations in ocean air were 91 pg m -3 α-HCH and 23 pg m -3 γ-HCH, a decrease since 1988. The water/air fugacity ratio of α-HCH averaged 1.86 over all stations, compared to 0.74 from 1988 measurements. Afugacity ratio greater than unity implies volatilization and reversal of the net gas exchange direction since 1988. The 1993 fugacity ratios for γ-HCH indicated volatilization in the Bering Sea (1.25), deposition in the Gulf of Anadyr and Chirikov Basin region (0.72), and near equilibrium in the Chukchi Sea (0.90-0.98). In 1988, the net exchange of γ-HCH was depositional at all stations. Mean fluxes on BERPAC-93 estimated from the two-film model were 30 for α-HCH and -1.5 for γ-HCH (ng m -2 day -1 , positive indicates volatilization).

Air-water gas exchange of hexachlorocyclohexanes (HCHs) and the enantiomers of α-HCH in Arctic regions

In the summers of 1993 and 1994, air and water samples were taken in the Bering and Chukchi Seas and on a transect across the polar cap to the Greenland Sea to measure the air-sea gas exchange of hexachlorocyclohexanes (HCHs) and the enantiomers of α-HCH. Atmospheric concentrations of α- and γ-HCH have decreased threefold or more since the mid-1980s, whereas concentrations in surface water have shown little change. The saturation state of surface water (water/air fugacity ratio) was determined from the air and water concentrations of HCHs and their Henrys law constants as a function of temperature. Fugacity ratios >1.0 indicated net volatilization of α-HCH in all regions except the Greenland Sea, where concentrations in air and water were close to equilibrium. Net deposition of γ-HCH in the Chukchi Sea was indicated by fugacity ratios <1.0. In other regions, γ-HCH was volatilizing or near air-water equilibrium. Enantioselective degradation of (−)α-HCH was found in surface water of the Bering and Chukchi Seas. The ER was reversed in the Canada Basin and Greenland Sea, where (+)α-HCH was preferentially lost. The same order of enantioselective degradation was seen in air within the marine boundary layer of these regions, which provides direct evidence for sea-to-air transfer of α-HCH.

The transport of β-hexachlorocyclohexane to the western Arctic Ocean: a contrast to α-HCH

Abstract A large database for α-hexachlorocyclohexane (α-HCH), together with multimedia models, shows this chemical to have exhibited classical ‘cold condensation’ behavior. The surface water of the Arctic Ocean became loaded between 1950 and 1990 because atmospheric transport of α-HCH from source regions to the Arctic was rapid and because α-HCH partitioned strongly into cold water there. Following emission reductions during the 1980s, α-HCH remained trapped under the permanent ice pack, with the result that the highest oceanic concentrations in the early 1990s were to be found in surface waters of the Canada Basin. Despite a much stronger partitioning into water than for α-HCH, β-HCH did not accumulate under the pack ice of the Arctic Ocean, as might be expected from the similar emission histories for the two chemicals. β-HCH appears to have loaded only weakly into the high Arctic through the atmosphere because it was rained out or partitioned into North Pacific surface water. However, β-HCH has subsequently entered the western Arctic in ocean currents passing through Bering Strait. β-HCH provides an important lesson that environmental pathways must be comprehensively understood before attempting to predict the behavior of one chemical by extrapolation from a seemingly similar chemical.

Decline of hexachlorocyclohexane in the Arctic atmosphere and reversal of air‐sea gas exchange

Hexachlorocyclohexanes (HCHs) are the most abundant organochlorine pesticides in the arctic atmosphere and ocean surface water. A compilation of measurements made between 1979–93 from stations in the Canadian and Norwegian Arctic and from cruises in the Bering and Chukchi seas indicates that atmospheric concentrations of α-HCH have declined significantly (p < 0.01), with a time for 50% decrease of about 4 y in summer-fall and 6 y in winter-spring. The 1992–93 levels of about 100 pg m−3 are 2–4 fold lower than values in the mid-1980s. The trend in γ-HCH is less pronounced, but a decrease is also suggested from measurements in the Canadian Arctic and the Bering-Chukchi seas. HCHs in ocean surface water have remained relatively constant since the early 1980s. The decline in atmospheric α-HCH has reversed the net direction of air-sea gas exchange to the point where some northern waters are now sources of the pesticide to the atmosphere instead of sinks.

Air—Water Exchange of Anthropogenic and Natural Organohalogens on International Polar Year (IPY) Expeditions in the Canadian Arctic

Shipboard measurements of organohalogen compounds in air and surface seawater were conducted in the Canadian Arctic in 2007-2008. Study areas included the Labrador Sea, Hudson Bay, and the southern Beaufort Sea. High volume air samples were collected at deck level (6 m), while low volume samples were taken at 1 and 15 m above the water or ice surface. Water samples were taken within 7 m. Water concentration ranges (pg L(-1)) were as follows: α-hexachlorocyclohexane (α-HCH) 465-1013, γ-HCH 150-254, hexachlorobenzene (HCB) 4.0-6.4, 2,4-dibromoanisole (DBA) 8.5-38, and 2,4,6-tribromoanisole (TBA) 4.7-163. Air concentration ranges (pg m(-3)) were as follows: α-HCH 7.5-48, γ-HCH 2.1-7.7, HCB 48-71, DBA 4.8-25, and TBA 6.4 - 39. Fugacity gradients predicted net deposition of HCB in all areas, while exchange directions varied for the other chemicals by season and locations. Net evasion of α-HCH from Hudson Bay and the Beaufort Sea during open water conditions was shown by air concentrations that averaged 14% higher at 1 m than 15 m. No significant difference between the two heights was found over ice cover. The α-HCH in air over the Beaufort Sea was racemic in winter (mean enantiomer fraction, EF = 0.504 ± 0.008) and nonracemic in late spring-early summer (mean EF = 0.476 ± 0.010). This decrease in EF was accompanied by a rise in air concentrations due to volatilization of nonracemic α-HCH from surface water (EF = 0.457 ± 0.019). Fluxes of chemicals during the southern Beaufort Sea open water season (i.e., Leg 9) were estimated using the Whitman two-film model, where volatilization fluxes are positive and deposition fluxes are negative. The means ± SD (and ranges) of net fluxes (ng m(-2) d(-1)) were as follows: α-HCH 6.8 ± 3.2 (2.7-13), γ-HCH 0.76 ± 0.40 (0.26-1.4), HCB -9.6 ± 2.7 (-6.1 to -15), DBA 1.2 ± 0.69 (0.04-2.0), and TBA 0.46 ± 1.1 ng m(-2) d(-1) (-1.6 to 2.0).

Henry's law constants for α-, β-, and γ-hexachlorocyclohexanes (HCHs) as a function of temperature and revised estimates of gas exchange in Arctic regions

Abstract Henrys law constants (H, Pa m3 mol−1) were determined for α-, β-, and γ-HCH in deionized water over a temperature range of 5–35°C using bubble stripping (BS) and dynamic head space (DHS) techniques. The BS method was improved from previous work in the same laboratory by adjusting for loss of water from the stripping chamber over the experiment. This correction resulted in H values that were ∼15% lower than those calculated without volume adjustments. Good agreement between the BS and DHS methods was found for α- and γ-HCHs, with an average ratio of BS/DHS values = 0.99. H values at 20°C for α- and γ-HCH were 86–89% of those determined by Jantunen and Bidleman (Chemosphere, Global Change Science 2 (2000) 225), but only 62–69% of the results reported by Kucklick et al. (Marine Chem. 34 (1991) 197). The BS rate of β-HCH was much slower than for the other HCHs and its H was determined only by the DHS method. Enthalpies of water-to-air transfer, ΔHwa, were 59.3±1.6, 65.1 ± 1.3 and 61.4 ± 3.1 kJ mol−1 for α-, β- and γ-HCH, respectively. A reassessment of air–water gas exchange in the western Arctic Ocean and its regional seas was made, based on measurements in 1992–1994. α-HCH was significantly (p

From the city to the Lake: loadings of PCBs, PBDEs, PAHs and PCMs from Toronto to Lake Ontario.

Loadings from Toronto, Canada to Lake Ontario were quantified and major sources and pathways were identified, with the goal of informing opportunities for loading reductions. The contaminants were polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), polycyclic aromatic hydrocarbons (PAHs) and polycyclic musks (PCMs). Loadings were calculated from measured concentrations for three major pathways: atmospheric processes, tributary runoff, and wastewater treatment plant (WWTP) effluents. Although atmospheric deposition to the Great Lakes has received the greatest attention, this was the dominant loading pathway for PCBs only (17 ± 5.3 kg/y or 66% of total loadings). PCB loadings reflected elevated urban PCB air concentrations due to, predominantly, primary emissions. These loadings contribute to consumption advisories for nearshore fish. PBDE loadings to the lake, again from mainly primary emissions, were 48% (9.1 ± 1.3 kg/y) and 42% (8.0 ± 5.7 kg/y) via tributaries and WWTPs, respectively, consistent with emissions deposited and subsequently washed-off of urban surfaces and emissions to the sewage system. PAHs loadings of 1600 ± 280 kg/y (71%) from tributaries were strongly associated with vehicle transportation and impervious surfaces. PCM loadings were 83% (±140 kg/y) from WWTP final effluent, reflecting their use in personal care products. Opportunities for source reduction lie in reducing the current inventories of in-use PCBs and PBDE-containing products, reducing vehicle emissions of PAHs and use of PAHs in the transportation network (e.g., pavement sealants), and improving wastewater treatment technology.

Chiral persistent organic pollutants as tracers of atmospheric sources and fate: review and prospects for investigating climate change influences

Elimination of persistent organic pollutants (POPs) under national and international controls reduces “primary” emissions, but “secondary” emissions continue from residues deposited in soil, water, ice and vegetation during former years of high usage. Secondary sources are expected to dominate in the future, when POPs transport and accumulation will be controlled by air–surface exchange and the biogeochemical cycle of organic carbon. Climate change is likely to affect mobilization of POPs through, e.g., increased temperature, loss of ice cover in polar regions, melting glaciers and changes in soil and water microbiology which affect degradation and transformation. Chiral compounds offer advantages for following transport and fate pathways because of their ability to distinguish racemic (newly released or protected from microbial attack) and nonracemic (microbially altered) sources. Here we explain the rationale for this approach and suggest applications where chiral POPs could aid investigation of climate–mediated exchange and degradation processes. Examples include distinguishing agricultural vs. non–agricultural and recently used vs. residual pesticides, degradation and sequestration processes in soil, historical vs. recent atmospheric deposition, sources in arctic air and influence of ice cover on volatilization.

Temperature dependent Henry’s law constant for technical toxaphene

Abstract Toxaphene is an abundant organochlorine (OC) pesticide in Great Lakes and Arctic ecosystems and the Henrys Law constant (HLC, Pa m3/mol) is a critical factor in describing its gas exchange between air and water. The HLCs for technical toxaphene and two hexachlorocyclohexane (HCHs) isomers (α- and γ-HCH) were determined by the gas stripping method over a temperature range of 10–40°C. The relationship to temperature (K) was described by log H=m/T+b . Parameters of this equation were: toxaphene m=−3209, b=10.42; α-HCH m=−3298, b=10.88; γ-HCH m=−3005 and b=9.51. The HLCs (Pa m3/mol) at 293.15 K were: toxaphene=0.30, α-HCH=0.43 and γ-HCH=0.18.