Terry F. Bidleman

Arctic contaminants: sources, occurrence and pathways

Potentially toxic organic compounds, acids, metals and radionuclides in the northern polar region are a matter of concern as it becomes evident that long-range transport of pollution on hemispheric to global scales is damaging this part of the world. In this review and assessment of sources, occurrence, history and pathways of these substances in the north, the state of knowledge of the transport media--the ocean and atmospheric circulation--is also examined. A five-compartment model of the northern region is developed with the intent of assessing the pathways of northern contaminants. It shows that we know most about pathways of acids, metals and radionuclides and least about those of complex synthetic organic compounds. Of the total annual inputs of anthropogenic acidic sulphur and the metals lead and cadmium to the Arctic via the atmosphere, an estimated 10-14% are deposited. A water mass budget for the surface layer of the Arctic Ocean, the most biologically active part of that sea, is constructed to examine the mass budget for one of the major persistent organochlorine compound groups found in remote regions, hexachlorocyclohexanes (HCH), one isomer of which is lindane. It is concluded that both the atmosphere and the ocean are important transport media. Even for the HCH substances which are relatively easily measured and simple in composition compared to other synthetic organics, we know little about the occurrence and environmental physical/chemical characteristics that determine pathways into the food chain. More environmental measurements, chemical characterization studies and environmental chemical transport modelling are needed, as is better knowledge of the circulation of the Arctic Ocean and the marine food web.

Interdependence of the slopes and intercepts from log-log correlations of measured gas-particle paritioning and vapor pressure—I. theory and analysis of available data

Gas-particle partitioning is examined using a partitioning constant Kp = (F/TSP)/A, where F (ng m−3) and A (ng m−3) are the particulate-assiociated and and concentrations, respectively, and TSP is the total suspended particulate matter level (μg m−3). At a given temperature and for a given sample of particulate matter, compound-dependent values of Kp tend to be correlated with the sub-cooled liquid vapor pressure (pL0, toor according to log Kp = mr log pL0+bm. Theory predicts that br values should be somewhat similar, and that mr values should be near −1. This is supported by field and laboratory work. However, there is still noticeable variability in reported mr and br values, even when obtained by the same researchers sampling in the same location. Three possible thermodynamic sources of variability include variability in the compound-to-compound differences in the thermodynamics of adsorption, event-to-event variability in the specific surface area of the aerosol and event-to-event variability in the ambient temperature. Non-thermodynamic sources of variability include sorption of gaseous analytes to the filters used in differentiating between F and A, the presence of non-exchangeable component in the measured F values, within-event adsorption/desorption kinetics, within-event changes in contaminant levels, and within-event changes in temperature. Each of these sources of variability operate in their own way to cause variability in mr and br. In general, one can expect there to be a correlation in the obseved mr and br of the form br = msmr+bs. For the study of Yamasaki et al. (1982, Envir. Sci. Technol. 16, 189–194), one obtains ms = 5.77 and bs = −2.18, with r2 = 0.91. In the presence of such a correlation, one can expect that all log (F/TSP)/A vs log pL0 plot will tend to intersect at the same (x,y) poitn given by (−ms, bs. Exisiting field and laboratory data show this tendency.

Global hexachlorocyclohexane use trends and their impact on the arctic atmospheric environment

The relationship between the global technical HCH use trends and their impact on the arctic atmospheric environment has been studied. Two significant drops in global technical HCH usage were identified. In 1983, China banned the use of technical HCH. This represented the largest drop ever in global use rates. In 1990 India stopped technical HCH usage in agriculture and the former Soviet Union banned the use of technical HCH. Since 1990, India has been the biggest user of technical HCH in the world. Significant drops in atmospheric α-HCH in the arctic were observed between 1982 and 1983, and again between 1990 and 1992. The rapid response in atmospheric concentrations to usage is encouraging; however, since α-HCH concentrations in the arctic waters have remained relatively unchanged, the decline in atmospheric α-HCH has reversed the net direction of air-sea gas flux. The accumulated mass in oceans and large lakes may represent a new source of HCH to the arctic atmosphere.

Collection of airborne polycyclic aromatic hydrocarbons and other organics with a glass fiber filter-polyurethane foam system

High volume air samples were collected in an urban (Columbia, SC) and rural (Savannah River Plant, SC) location using a glass fiber filter followed by two plugs of polyurethane foam (PUF). Total organics ⩾ n-C19 were analyzed by flame ionization GC, and PAH were determined by reversed phase HPLC with fluorescence detection. Most of the 3- and 4-ring PAH were found on the PUF trap, while the higher-ring PAH were retained by the filter. For total organics, fluoranthene, and pyrene, the adsorbentretained: filter-retained ratio was related to the suspended particle concentration and the average sampling temperature through an equation derived from the Langmuir isotherm. Movement of organic vapors through the PUF bed was related to the temperature-weighted air volume, where the temperature weighting factor was calculated from the Antoine equation for phenanthrene vapor pressure. At 20°C and 600m3 air, breakthrough from the first to the second PUF trap was 15% for phenanthrene and anthracene, and 25 % for total organics ⩾n-C19. The same volume of air sampled at 25°C produced 40% or more breakthrough.

Effects of temperature, TSP and per cent non-exchangeable material in determining the gas-particle partitioning of organic compounds

The temperature dependence of the measured, gas-particle partitioning ratio (FT/TSP)/AT has been examined for the case when a constant fraction x (%) of a compound is assumed to be bound within the particulate matter, and non-exchangeable with the gas phase. The parameter FT is the total (exchangeable + non-exchangeable) measured concentration in the atmosphere (ng m−3), AT is the gaseous concentration (ng m−3), and TSP is the level of suspended atmospheric particulate matter (μg m−3). It is assumed that the true thermodynamic constant Kp depends upon 1/T according to log Kp = mp/T + bp where mp depends on the enthalpy of desorption of the compound of interest, bp depends in part on other properties of the compound as well as the specific surface area of the particulate matter, and T is the temperature (Kelvin). When Kp or TSP are low, the difference between the measured quantity (FT/TSP)/AT and Kp can be significant even when the non-exchangeable fraction x is as low as a few per cent. This approach has been used to examine the PAH data set of Yamasaki et al. [(1982) Env. Sci. Technol.16, 189–194]. It was found that the Yamasaki data set does not allow estimates of x that are consistent with the current understanding of the temperature dependence of log Kp values. A likely reason for this result is some dependence of mp and bp on the exact nature of the particulate matter and atmospheric conditions such as relative humidity. It is concluded that estimates of x values for a given compound on actual particulate matter may only be possible by the direct examination of individual particulate matter samples.

Polycyclic aromatic and organochlorine compounds in the atmosphere of northern Ellesmere Island, Canada

In February–April 1988 we collected air samples at Alert in the Canadian Arctic (82.5°N, 62.3°W) to determine the types, concentrations, and vapor-particle relationships for polycyclic aromatic hydrocarbons (PAH) and oxygenated compounds, Organochlorine (OC) pesticides, and polychlorinated biphenyls (PCB). Samples were taken using a glass fiber filter-polyurethane foam train and were analyzed by capillary gas chromatography using mass selective and electron capture detection. PAH and oxygenated compounds included dibenzofuran, biphenyl, fluorene, phenanthrene, 9-fluorenone, fluoranthene, benzofluoranthenes, pyrene, chrysene, benzopyrenes, indeno[cd]pyrene, benzo[ghi]perylene, 2-methyl phenanthrene, benz[a]anthracene, and anthracene (given in order of relative abundance, highest to lowest). OC compounds included hexachlorocyclohexanes (HCH), hexachlorobenzene, pentachlorobenzene, PCB, polychlorocamphenes, chlordanes, and the dichlorodiphenyl-trichloroethane (DDT) group (given as above). The concentration ratios of α-HCH/γ-HCH (5.2–9.8) and trans- to cis-chlordane (0.78–1.29) are reported. Compounds having estimated liquid-phase saturation vapor pressure (pL0) ≥ 10-3 Pa at the average sampling temperature (245 K) were almost entirely gaseous. Those from 10-6 ≤ pL0 ≤ 10-3 Pa were distributed between the particle and gas phases, whereas little or no gaseous component was evident for compounds having pL0 ≤ 10-6 Pa. The particle-vapor distribution of PAH and OC compared favorably to the Junge-Pankow model.

Determination of Henry's law constants for hexachlorocyclohexanes in distilled water and artificial seawater as a function of temperature

Henrys law constants were determined for α- and γ-hexachlorocyclohexane (HCH) as a function of temperature (0.5–45°C) in artificial seawater (SW; 30‰) and distilled water (DW) using the gas stripping method. Water samples (1–5 ml) were withdrawn from the stripping vessel during the stripping process (30–360 h), solvent extracted and analyzed by gas chromatography—electron-capture detection. The effect of bubbling depth was checked to ensure that bubbles leaving the system were at equilibrium with HCHs in the aqueous phase. Henrys law constants determined at 35 and 45°C in SW were significantly higher (P≤ 0.05) than in DW for both α- and γ-HCH, but not at lower temperatures. The slopes (m) and intercepts (b) of log H vs. 1T plots were: α-HCH (DW, 0.5–45°C); m = −2810 ± 110, b = 9.31 ± 0.38; α-HCH (SW, 0.5–23°C); m = −2969 ± 218, b = 9.88 ± 0.76; γ-HCH (DW, 0.5–45°C); m = −2382 ± 160, b = 7.54 ± 0.54; γ-HCH (SW, 0.5–23°C); m = −2703 ± 276, b = 8.68 ± 0.96. Henrys law constants determined in this study compared well with those calculated from reported vapor pressure and solubility data.

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.

Estimating the atmospheric deposition of organochlorine contaminats to the Arctic

Abstract This work predicts the flux of several OC compounds: α- and γ-HCH, hexachlorobenzene (HCB), chlordane (cis- + trans- chlordane), diedlrin, p,p′-DDT and toxaphene, to the Arctic in the summer and winter. These estimates are based on known deposition mechanisms using atmospheric OC concentrations, gas-aerosol partition data, and OC physical properties typical of the polar environment.

Semivolatile organic compounds in the ambient air of Denver, Colorado

Abstract A filter-polyurethane foam plug high volume air sampler was used to collect the particle (P) and vapor (V) phases of four classes of semivolatile organic compounds (SOC) in Denver, CO: n -alkanes. polychlorinated biphenyls (PCB), polycyclic aromatic hydrocarbons (PAH), and organochlorine pesticides. The carbon preference index (CPI) of n -alkanes in the V or P phases alone was skewed by temperature-dependent V/P partitioning; a combined gaseous + particulate CPI was preferred. The CPI suggested that the alkanes in Denver air were predominently petrogenic. Total PCB were calculated as the sum of individual congeners and also as Aroclor equivalents, with good agreement between the two methods. Apparent V/P distributions of these compound classes were expressed as A(TSP)/F , were A and F are the adsorbent- and filter-retained SOC concentrations (ng m −3 ) and TSP is the total suspended particle concentration (μg m −3 ). Values of A(TSP)/F were related to the average sampling temperature ( T , K) through: log [ A ( TSP )/ F ] = m / T + b . Fitted log A(TSP)/F at 5°C correlated well with p L 0 at 5°C, the SOC liquid vapor pressure. No differences were observed in partitioning behavior among the four SOC types.