Effects of seabird vectors on the fate, partitioning, and signatures of contaminants in a High Arctic ecosystem

Seabirds bioaccumulate contaminants from prey, transport them to their nesting sites, and deposit them in their excreta and carcasses, thereby focusing marine-derived contaminants into remote, terrestrial receptor sites. In the case of organochlorine chemicals transported by northern fulmars (Fulmarus glacialis) to a High Arctic seabird colony on Devon Island, Nunavut, Canada (76°13'N, 89°14'W), this contaminant pathway dominates all others. In freshwater ponds below the nesting cliffs, concentrations of organochlorine contaminants characteristic of fulmar input were 2- to 45-fold higher in sediments and water (depending on seabird input to the particular pond) than in ponds remote from the colony. Air-water fugacity quotients for the ponds decreased with seabird input, indicating that fulmar contaminant input shifts air-water partitioning to increasingly favor volatilization to air. Although contaminant evasion from water was favored, direct evidence of it was not detected in air samples. For PCBs, congener profiles of pond sediments or water became more similar to seabird sources as seabird input increased, and less similar to air profiles. Based on measurements of contaminants in fulmars and other local environmental media, this study presents the first application of fugacities and multivariate source apportionment statistics to resolve seabird biological vectors.     

Development of a multichemical food web model: application to PBDEs in Lake Ellasjoen, Bear Island, Norway

A multichemical food web model has been developed to estimate the biomagnification of interconverting chemicals in aquatic food webs. We extended a fugacity-based food web model for single chemicals to account for reversible and irreversible biotransformation among a parent chemical and transformation products, by simultaneously solving mass balance equations of the chemicals using a matrix solution. The model can be applied to any number of chemicals and organisms or taxonomic groups in a food web. The model was illustratively applied to four PBDE congeners, BDE-47, -99, -100, and -153, in the food web of Lake Ellasj?en, Bear Island, Norway. In Ellasj?en arctic char (Salvelinus alpinus), the multichemical model estimated PBDE biotransformation from higher to lower brominated congeners and improved the correspondence between estimated and measured concentrations in comparison to estimates from the single-chemical food web model. The underestimation of BDE-47, even after considering bioformation due to biotransformation of the otherthree congeners, suggests its formation from additional biotransformation pathways not considered in this application. The model estimates approximate values for congener-specific biotransformation half-lives of 5.7,0.8,1.14, and 0.45 years for BDE-47, -99, -100, and -153, respectively, in large arctic char (S. alpinus) of Lake Ellasj?en.     

Time trends of Arctic contamination in relation to emission history and chemical persistence and partitioning properties

How long does ittake for organic contaminant concentrations to decline in the Arctic after regulatory measures have succeeded in reducing emissions globally? This question is explored by using a zonally averaged global distribution model to estimate the lag-time between the period when emissions begin to decrease and when a decline in a chemical's Arctic Contamination Potential is observed. A long lag is problematic, as contaminant concentrations can continue to increase well after a potential hazard is recognized. Using three different emission scenarios, the chemical property combinations that are most likely to experience a lag on the order of decades were identifed among 96 hypothetical chemicals with different partitioning and reactivity properties. The first such property combination comprises the persistent "swimmers" that reach the Arctic by slow long-range oceanic transport. They require a half-life (t(1/2)) in water of more than 10 years for a significant lag to occur. The second group of compounds experiencing a long lag includes semivolatile chemicals that are in dynamic exchange between atmosphere and ocean. These "multihoppers", with air-water partition coefficients, K(AW) of approximately 0.01, need to be highly persistent in air (t(1/2) >3 years) and surface media (t(1/2) >10 years). Their lag depends both on the oceans' large storage capacity and relatively low stickiness, i.e., a high likelihood of return to the atmosphere. Notably, no lag is predicted for less water soluble multihoppers (K(AW) >1), which are more likely to distribute into soils and foliage, because the terrestrial environment is "stickier" than the oceans, greatly reducing the number of hops these chemical will experience. The oceans thus play a crucial role in facilitating delayed Arctic contamination, either by transporting dissolved contaminants slowly to higher latitudes, or by providing a relatively nonsticky temporary storage reservoir which is in constant exchange with the atmosphere. Precaution advises a swift regulatory response to increasing concentrations in remote marine organisms of substances that have property combinations that are predicted to result in a significant delay between emission reductions and concentration declines.     

Perfluoroalkyl contaminants in the Canadian Arctic: evidence of atmospheric transport and local contamination

Perfluorosulfonates (PFSAs) and perfluorocarboxylates (PFCAs) have been hypothesized to reach remote locations such as the Canadian Arctic either indirectly as volatile precursor chemicals that undergo atmospheric transport and subsequent degradation, or directly via oceanic and atmospheric transport of the PFSAs and PFCAs themselves. Water, sediment, and air samples were collected from three Arctic lakes (Amituk, Char, and Resolute) on Cornwallis Island, Nunavut, Canada. Samples were analyzed for PFSAs and PFCAs, precursor chemicals including the fluorotelomer alcohols (FTOHs) and polyfluorinated sulfonamides (FSAs), and precursor degradation products such as the fluorotelomer unsaturated carboxylates (FTUCAs). PFSAs and PFCAs were detected in water and sediment of all three Arctic lakes (concentrations ranged from nondetect to 69 ng/L and nondetect to 85 ng/g dry weight, respectively). FTOHs and FSAs were observed in air samples (mean concentrations ranged from 2.8 to 29 pg/m3), and confirm that volatile precursors are reaching Arctic latitudes. The observation of degradation products, including FTUCAs observed in sediment and atmospheric particles, and N-ethyl perfluorooctanesulfonamide (NEtFOSA) and perfluorooctanesulfonamide (PFOSA) in air samples, indicate that degradation of the FTOHs and FSAs is occurring in the Arctic environment. PFSAs and PFCAs were also observed on atmospheric particles (mean concentrations ranged from < 0.1 to 5.9 pg/m3). In addition, results of this study also indicate that local perfluoroalkyl contamination of Resolute Lake, which is located downstream of an airport wastewater input, has occurred.     

Modeling global-scale fate and transport of perfluorooctanoate emitted from direct sources

The long-term (1950-2050) global fate of perfluorooctanoate (PFO) is investigated using the global distribution model, GloboPOP. The model is used to test the hypotheses that direct PFO emissions can account for levels observed in the global oceans and that ocean water transport to the Arctic is an important global distribution pathway. The model emission scenarios are derived from historical and projected PFO emissions solely from direct sources. Modeled ocean water concentrations compare favorably to observed PFO concentrations in the world's oceans and thus ocean inventories can be accounted for by direct sources. The model results support the hypothesis that long-range ocean transport of PFO to the Arctic is important and estimate a net PFO influx of approximately 8-23 tons per year flowing into the model's Northern Polar zone in 2005, an amount at least 1 order of magnitude greater than estimated PFO flux to the Arctic from potential indirect sources such as atmospheric transport and degradation of fluorotelomer alcohols. Modeled doubling times of ocean water concentrations in the Arctic between 1975 and 2005 of approximately 7.5-10 years are in good agreement with doubling times of PFO in Arctic biota estimated from monitoring data. The model is further applied to predict future trends in PFO contamination levels using forecasted (2005-2050) direct emissions, including substantial reductions committed to by industry. Modeled ocean water concentrations in zones near to sources decline markedly after 2005, whereas modeled concentrations in the Arctic are predicted to continue to increase until approximately 2030 and show no significant decrease for the remaining 20 years of the model simulation. Since water is the primary exposure medium for Arctic biota, these model results suggest that concentrations in Arctic biota may continue to rise long after direct emissions have been substantially reduced or eliminated.     

Combining long-range transport and bioaccumulation considerations to identify potential Arctic contaminants

The identification of potential Arctic contaminants requires an assessment of both the long-range transport and the bioaccumulation of the chemicals, most particularly in the indigenous inhabitants of the Arctic. For this purpose, a nonsteady state, zonally averaged global distribution model was linked to a nonsteady state bioaccumulation model describing Inuit exposure from a marine diet. The potential of hypothetical, perfectly persistent chemicals with varying combinations of partitioning properties to enrich in the Arctic environment following emission in the lower latitudes and, additionally, to bioaccumulate in the Arctic food chains was evaluated using the Arctic contamination and bioaccumulation potential (AC-BAP). The AC-BAP is defined as the quotient of the human body burden of the chemical and the quantity of chemical cumulatively emitted to the global environment. The highest AC-BAP values (up to 3.7 x 10(-11) person(-1)) were obtained for hypothetical multimedia chemicals with intermediate volatility and hydrophobicity. Perfectly persistent chemicals with 3.5 < log K(OW) < 8.5 and log K(OA) > 6 had AC-BAP values of at least 10% of the maximum value, indicating that a broad range of chemicals are potential Arctic contaminants if they are persistent. Moreover, the simulation results suggest that a chemical's potential to bioaccumulate has a stronger impact on the overall potential to become an Arctic contaminant in humans than its potential for long-range transport. This modeling exercise demonstrates how linking nonsteady state models of chemical bioaccumulation and of global chemical fate can provide a valuable tool for assessing a chemical's potential to be a contaminant in remote regions.     

Biogeochemical cycling of methylmercury in lakes and tundra watersheds of Arctic Alaska

The fate of atmospherically deposited and environmentally active Hg is uncertain in the Arctic, and of greatest toxicological concern is the transformation to monometh-ylmercury (MMHg). Lake/watershed mass balances were developed to examine MMHg cycling in four northern Alaska lakes near the ecological research station at Toolik Lake (68 degrees 38' N, 149 degrees 36' W). Primary features of the cycle are watershed runoff, sedimentary production and mobilization, burial, and photodecomposition in the water column. The principal source of MMHg is in situ benthic production with 80-91% of total inputs provided by diffusion from sediments. The production and contribution of MMHg from tundra watersheds is modest. Photodecomposition, though confined to a short ice-free season, provides the primary control for MMHg (66-88% of total inputs) and greatly attenuates bioaccumulation. Solid-phase MMHg and gross potential rates of Hg methylation, assayed with an isotopic tracer, vary positively with the level of inorganic Hg in filtered pore water, indicating that MMHg production is Hg-limited in these lakes. Moreover, sediment-waterfluxes of MMHg (i.e., net production at steady state) are related to sediment Hg loadings from the atmosphere. These results suggest that loadings of Hg derived from atmospheric deposition are a major factor affecting MMHg cycling in arctic ecosystems. However, environmental changes associated with warming of the Arctic (e.g., increased weathering, temperature, productivity, and organic loadings) may enhance MMHg bioaccumulation by stimulating Hg methylation and inhibiting photodecomposition.     

Perfluorinated alkyl substances in plasma, liver, brain, and eggs of glaucous gulls (Larus hyperboreus) from the Norwegian arctic

Recent environmental surveys have ascertained the widespread occurrence of perfluorinated alkyl substances (PFAS) in tissues of wildlife from the Arctic. In the present study, we investigated the distribution of a suite of PFAS in plasma, liver, brain, and egg samples from adult glaucous gulls (Larus hyperboreus), an apex scavenger-predator seabird breeding in the Norwegian Arctic. Perfluorooctane sulfonate (PFOS) was the predominant PFAS in all samples and was present at concentrations that are the highest reported thus far in any arctic seabird species and populations. Among the body compartment/ tissue samples analyzed, PFOS was highest in plasma (48.1-349 ng/g wet weight (ww)), followed by liver approximately equal to egg > brain. Perfluorocarboxylic acids (PFCAs) with 8-15 carbon (C) atoms were found, with the highest concentrations determined in plasma (sum PFCA: 41.8-262 ng/g ww), whereas 5C- and 6C-PFCAs were below the limits of detection. Perfluorobutane sulfonate, perfluorooctane sulfonamide, and four saturated (8:2 FTCA and 10:2 FTCA) and unsaturated (8:2 FTUCA and 10:2 FTUCA) fluorotelomer carboxylic acids were not detected in any samples. Perfluorohexane sulfonate was measured at concentrations up to 2.71 ng/g ww. The accumulation profiles of PFCAs were characterized by high proportions of the long and odd-numbered carbon-chain-length compounds, namely perfluoroundecanoic (11C) and perfluorotridecanoic acid (13C), although their individual contribution differed between the matrixes analyzed. Current PFAS concentrations suggest a bioaccumulation potential in Norwegian arctic glaucous gulls that needs to be assessed as part of a broad organohalogen contaminant cocktail with potential for mediating biological processes in this vulnerable top-predator marine species.     

Snowmelt sources of methylmercury to high arctic ecosystems

Mercury in humans and other top predators living in the Arctic is present at elevated levels. Since only methylmercury (MeHg) bioaccumulates in food chains, sources of MeHg need to be identified. Recently, wetlands in the High Arctic were found to produce MeHg, and this was confirmed in laboratory soil incubations. In the present study both wetlands and snowmelt water were evaluated as sources of MeHg to Arctic ecosystems in Nunavut. Three substudies took place on Cornwallis Island, and one took place on Ellesmere Island. First, the effect of wetland presence in lake watersheds was evaluated by comparing four lakes with wetlands present to four lakes without wetlands present. Next, two individual wetlands were spatially and temporally investigated. Finally, three basin tributaries were evaluated for snowmelt MeHg sources. Catchments on Cornwallis Island with wetlands did not have an observable effect on MeHg levels in downstream lake water, but the wetland on Ellesmere Island contributed significant MeHg. In contrast, calculated yields of MeHg in tributaries draining snowmelt on Cornwallis Island were higher (ca. 1.5 mg km(-2) day(-1)) than those measured in temperate catchments characterized by wetlands. Methylmercury and total Hg concentrations in lakes, wetlands, and basin tributaries showed a strong temporal trend that corresponded to inputs from snowmelt water in late spring. This study revealed that wetland export of MeHg to downstream Arctic lakes is site dependent, and snowmelt water was the most significant source of MeHg to Arctic ecosystems located on Cornwallis Island.     

PCBs, PBDEs and pesticides released to the Arctic Ocean by the Russian rivers Ob and Yenisei

The Ob and Yenisei Rivers contribute 37% of riverine freshwater inputs to the Arctic Basin and thus represent an important pathway for the land-Arctic ocean exchange of contaminants. Sampling was carried out in the Yenisei (2003) and Ob (2005) River estuaries and Kara Sea to address the general lack of reliable dissolved contaminant flux data for these major rivers. Contaminant analyses were performed by high resolution mass spectrometry on sample extracts taken from filtered large volume water samples (50-100 L) and concentrated in situ onto XAD-2 resin columns. Hexachlorocyclohexanes (HCHs), the polychlorinated biphenyl (PCB) mixtures Sovol and trichlorodiphenyl, dichlorodiphenyltrichloroethane (DDT), as well as "penta" brominated technical mixtures of polybrominated diphenyl ethers (PBDEs) are important contributors to persistent organohalogen contamination for these waterways. Dissolved fluxes to the Kara Sea were estimated at sigmaHCH 246 kg/yr, sigmaPCB 63 kg/yr, sigmaDDT 16 kg/yr, hexachlorobenzene 8 kg/yr, alpha-endosulfan 8 kg/ yr, dieldrin 5 kg/yr, sigmaPBDE 4 kg/yr, and chlordanes 4 kg/yr. Contaminant fluxes from these rivers are similar to those reported for major Canadian rivers, confirming expectations that the Ob and Yenisei are also major point sources for the Arctic basin.     

Contribution of volatile precursor substances to the flux of perfluorooctanoate to the Arctic

Perfluorooctanoate (PFO) has recently been found in remote ocean water and Arctic samples, despite not having been used in significant quantities in remote areas. Two main scenarios for the contamination of the Arctic by PFO have been suggested: (i) direct emissions of PFO and oceanic transport to the Arctic and (ii) emissions of volatile precursor substances that are transported and oxidized in the atmosphere to form PFO, which is subsequently deposited to the Arctic. Focusing on the atmospheric transport pathway, we compare the importance of fluorotelomer alcohols (FTOHs) and perfluorooctyl sulfonamidoethanols (FOSEs) for PFO deposition to the Arctic. Using a global scale multispecies mass balance model, we simultaneously calculate the transport, degradation, partitioning, and deposition of precursor substances, intermediate degradation products, and PFO and compare model results to field measurements. Prior to 2002, the modeled deposition fluxes of PFO to the Arctic originating from FOSEs and FTOHs are of a similar magnitude, and total estimated deposition compares well with deposition measurements for Arctic ice cores. However, the model underpredicts recent measurements of FOSEs in Arctic air, indicating that there may be additional emissions not taken into account. Using Monte Carlo calculations we quantify the uncertainties in our model results and identify that emission estimates, degradation yields, and degradation rate constants are the most influential input parameters controlling the estimated deposition of PFO to the Arctic.     

Characterizing water circulation and contaminant transport in Lake Geneva using bacteriophage tracer experiments and limnological methods

Multi-tracer tests with three types of marine bacteriophages (H4/4, H6/1, and H40/1), together with various limnological methods, including physicochemical depth profiling, surface drifters, deep current measurements, and fecal indicator bacteria analyses, have been applied to characterize water circulation and pathogen transport in the Bay of Vidy (Lake Geneva, Switzerland). The experimental program was carried out twice, first in November 2005, when the lake was stratified, and a second time during holomixis in February 2006. The bacteriophages were injected at three points at different depths, where contaminated waters enter the lake, including the outlet pipe of a wastewater treatment plant, a river, and a stormwater outlet. Thereafter, water samples were collected in the lake at 2 m depth during a 48 h sampling campaign. The results demonstrate that (i) contaminated river water spreads rapidly in the bay; (ii) a well-developed thermocline is highly effective in preventing contamination from the depth to rise up to the surface; (iii) rapid vertical mixing and pathogen transport occur under thermally homogeneous conditions; and (iv) repeated multi-tracertests with bacteriophages are a powerful technique to assess water circulation and contaminant transport in lakes where high dilution occurs.     

Historically and currently used Dechloranes in the sediments of the Great Lakes

Dechlorane (mirex), Dechlorane Plus (DP), Dechlorane 602 (Dec602), Dechlorane 603 (Dec603), Dechlorane 604 (Dec604), and Chlordecone (Kepone) were analyzed in 16 sediment cores collected in 2007 from the Great Lakes of North America. Results show that Lake Ontario sediments have accumulated mirex, DP, Dec602 and Dec604 in amounts 1 to 2 orders of magnitude higher than other Great Lakes. The chemical inventory decreases log-linearly with increasing latitude (N) and longitude (W) of the sampling locations, but Lake Ontario sites are outliers in the regression against latitude. The regression analyses suggest differences among the analytes with regard to source impact and long-range transport behavior. Temporal trends of input differ among lakes. Most sites in Lake Superior are still receiving increasing fluxes of DP and Dec602, while these have been declining in Lake Ontario from the peak around 1990. The relative abundance of the two DP isomers, represented by f(syn), increases with increasing distance from the potential discharge source in Niagara Falls, NY, suggesting the anti-DP isomer is more vulnerable to degradation during long-range atmospheric transport. Kepone was not detected in the sediments of Lakes Ontario, Erie, and Michigan.     

Anomalous plutonium isotopic ratios in sediments of Lake Qinghai from the Qinghai-Tibetan Plateau, China

The vertical profiles of (239+240)Pu and (137)Cs activities and (240)Pu/(239)Pu isotopic ratios are determined for three sediment cores of Lake Qinghai from the Qinghai-Tibetan Plateau, China, and compared with those in sediments of another three lakes (Lakes Bosten, Sugan, and Shuangta), the only existing ones closest to Lop Nor area, China's nuclear weapons test site in the northwestern part of the country. The mean inventory of 47.7 ± 18.7 MBq km(-2) for (239+240)Pu activity in Lake Qinghai is comparable to the average value of global fallout expected at the same latitude, yet the mean inventory of 1112.0 ± 78.0 MBq km(-2) for (137)Cs is slightly lower than that of global fallout. Anomalously low (240)Pu/(239)Pu isotopic ratios (0.038-0.125) were found in the 3-6.5 cm deep sediment layers, indicating the trace Pu input from early nuclear weapons research activities at Atomic City in the lake's watershed during the 1950-60s. Model calculation indicated that the Pu input accounted for approximately 5-16% of the total Pu inventory. The observation of low (240)Pu/(239)Pu ratio in the deep sediment layer provided a new time marker for recent sediment dating in the lake and around the area. The results are of great significance to the further understanding of sources, records, and environmental impacts of global and regional nuclear activities in the environment and provide important chronological information for further studies on the water eutrophication process and climatic change, and reconstruction of pollution history of organic contaminants and heavy metals in the watershed of Lake Qinghai.     

Evidence for control of mercury accumulation rates in Canadian High Arctic lake sediments by variations of aquatic primary productivity

Climate warming in the 20th Century has had profound effects on the limnology of High Arctic lakes, including substantial increases in autochthonous primary productivity (APP). Here, we report organic carbon and Hg core profiles from two lakes which support the hypothesis that 20th Century increases in sedimentary Hg at these latitudes were largely driven by APP increases, via Hg scavenging by algae and/or suspended detrital algal matter. Hydrocarbons quantitatively released by thermal cracking of algal-derived organic matter ("S2" carbon) were used to reconstruct past APP. Variation of S2 flux accounted for 87-91% of the variance in total Hg flux in the study lakes since 1854. Mercury and S2 carbon were also associated during the pre-Industrial Period, co-varying by as much as 30% during past warm/cool periods. As a test of the hypothesis, predicted values for 20th Century [Hg] were derived from pre-1900 Hg-S2 relationships. Measured 20th Century [Hg] was on average only 6-11% higher than that predicted in one lake, and 33% higher in the other. S2-normalization of [Hg] in the latter lake suggested that 78% of the average increase in 20th Century [Hg] could be explained by scavenging. These findings suggest that the atmospheric contribution of long-range anthropogenic Hg to High Arctic lakes may have been overestimated by several-fold because of this climate-driven process, and was responsible for no more than 22% of the 20th Century [Hg] increase in the study lakes.     

Distribution of haloacetic acids in the water columns of the Laurentian Great Lakes and Lake Malawi

Haloacetic acids (HAAs) are persistent and mildly phytotoxic compounds that have been detected in many aquatic environments, including the waters of the Great Lakes. Sources of HAAs, especially of trifluoroacetic acid (TFA), are not well understood. In this study we assessed the influence of urbanization on the concentrations and profiles of HAAs in the Laurentian Great Lakes and in Lake Malawi, an African Great Lake. Vertical depth profiles for these compounds were taken for each of the Great Lakes with additional profiles taken 2 years later for Lakes Erie and Ontario. The results showed that while TFA was relatively constant throughout the water column, the chloroacetic acids (CAAs) varied with depth. There was a trend of increasing TFA proceeding from Lake Superior to Lake Ontario (18-150 ng/L). Total CAA concentrations were relatively constant throughout the lakes (approximately 500 ng/L) with dichloroacetic acid being the most abundant. No bromoacetic acids were detected. In the Detroit River, a connecting channel between Lakes Huron and Erie, the TFA values were similar to those in Lake Huron, but the CAAs levels were higher than in the upstream lakes and dependent on location, indicating inputs from urban areas along the river. These results were compared to those from Lake Malawi, which has a high population density within the watershed but no heavy industry. CAAs were nondetectable, and TFA concentrations were just at the detection limit (1 ng/L). Total HAA in the water column of Lakes Superior and Huron was compared to annual precipitation inputs at a site situated near both lakes. For Lake Huron, precipitation was a minor contributor to the total HAA inventory of the lake, but for Lake Superior precipitation could be the major contributor to the mass of HAA in this lake. Generally, high HAA levels paralleled the degree of industrial activity in the adjacent waters.     

Time trends of selected persistent organic pollutants in lake sediments from Greenland

Sediments from seven lakes in West Greenland were used as natural archives to study past and present levels of PCBs (polychlorinated biphenyls, tri- to decachlorinated), tetra-BDE #47 (2,2',4,4'-bromodiphenyl ether), chlordane (cis- and trans-octachlordane) and HxCBz (hexachlorobenzene). The concentrations found are lower than or comparable to concentrations found in sediments from other Arctic regions and one to 2 orders of magnitude lower than concentrations typically found in sediments at lower latitudes. The observed temporal trends (direct and indirect dating) show a decreasing total PCB concentration. Even though local contamination sources exist, the POP deposition in the studied area is most likely a result from long-range transport. The hypothesis about "cold condensation" suggests a latitudinal fractionation to occur between different volatile compounds during the transport toward the pole. In this study a time delay in the deposition for the low-chlorinated PCBs (tri- and tetrachlorinated), compared to their emission histories and compared to higher chlorinated PCBs, was indicated. Although very low tetra-BDE #47 concentrations are observed in this study, there are indications for an increasing concentration in recent sediment layers that may reflect increasing environmental concentrations at lower latitudes. The investigated pesticides are still in use at lower latitudes, however neither chlordane nor HxCBz show any distinct temporal trend of increasing or decreasing concentration toward the sediment surface.     

Polybrominated diphenyl ethers in the sediments of the Great Lakes. 2. Lakes Michigan and Huron

Sediment cores were taken in 2002 in Lakes Michigan and Huron at six locations. A total of 75 samples were characterized, dated using 210Pb, and analyzed for 10 congeners of polybromodiphenyl ether (PBDE) including BDE209, as well as 39 congeners of polychlorinated biphenyls (PCBs). The concentrations of nine tri- through hepta-BDE congeners (Sigma9PBDE) in the surficial sediments range from 1.7 to 4 ng g(-1) for Lake Michigan and from 1.0 to 1.9 ng g(-1) for Lake Huron, on the basis of the dry sediment weight. The Sigma9PBDEs fluxes to the sediment around the year 2002 are from 36 to 109 pg cm(-2) yr(-1) in Lake Michigan and from 30 to 73 pg cm(-2) yr(-1) in Lake Huron, with spatial variations in both lakes. The flux of BDE209 ranges from 0.64 to 2.04 ng cm(-2) yr(-1) and from 0.67 to 1.41 ng cm(-2) yr(-1) in Lake Michigan and Lake Huron, respectively. Dramatic increases in PBDE concentrations and fluxes upward toward the sediment surface and the present time are evident at all locations. The inventory of PBDEs in both lakes appears to be dependent upon latitude and the proximity to populated areas, implying that north-bound air plumes from urban areas are the major sources of PBDEs found in the lake sediments at locations away from the shores. Heavier congeners are more abundant in the sediments than in air and fish samples in the region. BDE209 is about 96% and 91% of the total PBDEs on a mass basis in Lake Michigan and Lake Huron, respectively; both are higher than the 89% found in Lake Superior, although a t test shows that the value for Lake Huron is not statistically different from that for Lake Superior at the 95% confidence level.     

Organic contaminants in mountains

The study of organic contaminants at high altitudes is motivated by the potential risk that they pose to humans living in, or depending on resources derived from, mountains and to terrestrial and aquatic ecosystems in alpine areas. Mountains are also ideal settings to study contaminant transport and behavior along gradients of climate and surface cover. Information on organic contaminants in mountains is compiled from the literature and synthesized, with a focus on atmospheric transport and deposition, contaminant dynamics in alpine lakes and aquatic organisms, and concentration differences with altitude. Diurnal mountain winds, in connection with enhanced deposition at higher elevations caused by low temperatures and high precipitation rates, conspire to make mid-latitude mountains become convergence zones for selected persistent organic chemicals. In particular, the more volatile constituents of contaminant mixtures seem to become enriched, relative to the less volatile constituents at higher altitudes. For selected contaminants, concentration inversions (i.e., concentrations that increase with elevation) have been observed. A notable difference between cold trapping in high latitudes and high altitudes is the likely importance of precipitation. High rates of snow deposition in mid- and high-latitude mountains may lead to a large contaminant release during snowmelt. Regions above the tree line often have little capacity to retain the released contaminants, suggesting the potential for a highly dynamic contaminant fate situation during the snow-free season with significant revolatilization and runoff. The chemical and environmental factors that control the orographic cold trapping of organic contaminants should be examined further by measuring and comparatively interpreting concentration gradients along several mountain slopes with widely different characteristics. Future efforts should further focus on the bioaccumulation and potential effects of contaminants in the upper trophic levels of alpine food chains, on measuring more water-soluble, persistent organic contaminants, and on studying how climate change may affect contaminant dynamics in mountain settings.