William M. J. Strachan

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.

Melting Glaciers: A Major Source of Persistent Organochlorines to Subalpine Bow Lake in Banff National Park, Canada

Abstract Organochlorine pesticides and polychlorinated biphenyls (PCBs) are ubiquitous and persistent in the environment. They are known to concentrate in cold environments as a result of progressive evaporation from warm regions, and condensation in colder regions. In this study we show that melting glaciers supply 50 to 97% of the organochlorine inputs to a subalpine lake in Alberta, Canada, while contributing 73% of input water. Tritium analyses indicated that during the mid- to late summer warm period, at least 10% of the glacial melt originated from ice that was deposited in 1950–1970, when it was more contaminated with organochlorines. This finding suggests that climate warming may cause melting glaciers to become increasing sources of contaminants to freshwaters. Organochlorines from glacial streams were largely in dissolved form because the organic-poor glacial clays had a limited sorption capacity for the more hydrophobic chemicals.

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.

Atmospheric pollution by persistent organic compoumds: Monitoring with pine needles

Abstract Pine needles (P. sylvestris ) were used to observe the geographic and temporal patterns of atmospheric organic pollutants. Samples collected in 1986 (growth years 1984–1986) across Europe were analysed for DDT residues, the hexachlorocyclohexane isomers (alpha-HCH and lindane), pentachlorophenol (PCP), polychlorinated biphenyls (PCBs) and hexachlorobenzene (HCB). DDT was related to a 1984 spraying event in Germany; the HCHs, PCBs and HCB were ubiquitous with elevated levels of lindane in southern France; PCP was elevated in Swedish samples. Methodology is described.

Persistent organic pollutants (POPs) in a small, herbivorous, arctic marine zooplankton (Calanus hyperboreus): trends from April to July and the influence of lipids and trophic transfer.

Samples of Calanus hyperboreus, a herbivorous copepod, were collected (n = 20) between April and July 1998, and water samples (n = 6) were collected in May 1998, in the Northwater Polynya (NOW) to examine persistent organic pollutants (POPs) in a high Arctic marine zooplankton. Lipid content (dry weight) doubled, water content (r2 = 0.88) and delta15N (r2 = 0.54) significantly decreased, and delta13C significantly increased (r2 = 0.30) in the C. hyperboreus over the collection period allowing an examination of the role of these variables in POP dynamics in this small pelagic zooplankton. The rank and concentrations of POP groups in C. hyperboreus over the entire sampling was sum of PCB (30.1 +/- 4.03 ng/g, dry weight) > sum of HCH (11.8 +/- 3.23) > sum of DDT (4.74 +/- 0.74), sum of CHLOR (4.44 +/- 1.0) > sum of CIBz (2.42 +/- 0.18), although these rankings varied considerably over the summer. The alpha- and gamma-HCH and lower chlorinated PCB congeners were the most common POPs in C. hyperboreus. The relationship between bioconcentration factor (BCF) and octanol-water partition coefficient (Kow) observed for the C. hyperboreus was linear and near 1:1 (slope = 0.72) for POPs with a log Kow between 3 and 6 but curvilinear when hydrophobic POPs (log Kow > 6) were included. Concentrations of sum of HCH. Sum of CHLOR and sum of CIBz increased over the sampling period, but no change in sum of PCB or sum of DDT was observed. After removing the effects of time, the variables lipid content, water content, delta15N and delta13C did not describe POP concentrations in C. hyperboreus. These results suggest that hydrophobic POP (log Kow = 3.86.0) concentrations in zooplankton are likely to reflect water concentrations and that POPs do not biomagnify in C. hyperboreus or likely in other small, herbivorous zooplankton.

The effect of water temperature and composition on Henry's law constant for various PAH's

Henrys Law Constants (H) for benzene, naphthalene, phenanthrene and anthracene were experimentally determined at various water temperatures (5°C to 35°C) in distilled water using an on-line monitoring technique. The results from these experiments were compared to the values available in the literature and to the ratio of vapor pressure and solubility data using experimental and calculated data. The effect of salt concentration on H for naphthalene was measured at 25°C. H values increased with salt concentration and were proportional to the decrease in solubility of naphthalene in water. A good correlation between the observed H for naphthalene in sea water as a function of temperature and the ratio of vapor pressure and solubility was observed.

Microbial degradation is a key elimination pathway of hexachlorocyclohexanes from the Arctic Ocean

Microbial degradation is a key elimination pathway of hexachlorocyclohexanes from the Arctic Ocean

Automated rain sampler for trace organic substances

An automated rain sampler was designed, built, and evaluated as a collecting device for persistent organic chemicals in rain. It consists of large Teflon-coated funnel (0.209 m/sup 2/) with an automated lid and a Teflon column containing XAD-2 or -7 resin. The sampler was tested for recoveries and field precision with a number of organochlorine substances and PCBs frequently found at the nanogram per liter level in rain. Recoveries averaged 86%, and the mean coefficient of variation for ..cap alpha..-benzene hexachloride, lindane, and polychlorinated byphenyl was 33% under field conditions where samples of 0.4-22 L of rain were collected.

Prediction of seawater solubility of aromatic compounds

Abstract The salting-out effect by seawater constituents on the water solubilities of 11 aromatic compounds, anthracene, pyrene, phenanthrene, biphenyl, naphthalene, p-nitrotoluene, p-toluidine, o-nitrophenol, m-nitrophenol, p-nitrophenol and phenol was investigated. A best fit equation (r = 0.965) for the salting-out parameters, K, and distilled water solubilities, So, at 20°C was found to be K = −0.0298 log So + 0.114. Seawater solubilities, S, predicted for solutions of ionic strength, I, using the equation log S = (0.0298 I + 1) log So − 0.114 I were in agreement with observed values within 13 % (average 4.8 %) and there were no significant differences between values from the Pacific Ocean seawater and those from 35 o/oo NaCl solutions. It was concluded that dissolved organic matter in seawater had an insignificant effect for the test chemicals.

Organochlorine Pesticide and Trace Metal Monitoring of Russian Rivers Flowing to the Arctic Ocean: 1990–1996

Information is presented on the concentrations of organochlorine pesticides (HCHs and DDT residues) and trace metals (Fe, Cu, Zn and Ni) in waters of 15 large Russian rivers flowing to the Arctic Ocean during 1990-1996. Estimates of the corresponding annual fluxes are made. Other contaminants (Hg, Pb, Cr, Mn, beta-HCH and dihydroheptachlor) were examined briefly. Concentration data are presented as averaged annual means for each of the seven years with the ranges, standard deviations and numbers of samples. Also given are data on locations, the methods of analysis and limited quality assurance data. Data on discharges to the Northern Seas for the more frequently monitored contaminants are given for rivers accounting for >70% of the total northerly flows. Scaled-up fluxes to account for unmonitored rivers as well are given for each sea; totals over the period were: Fe, 1452; Cu, 15; Zn, 59 (x 10(3) t yr(-1)); alpha-HCH, 25; gamma-HCH, 44 (t yr(-1)). Ni was monitored at too few rivers to estimate its total Russian flux. The fluxes for the HCHs considerably exceed previous estimates and indicate that the Arctic Ocean is not in balance as much as was previously believed.