Camilla Teixeira

Empirical and modeling evidence of regional atmospheric transport of current-use pesticides.

Water samples from 30 lakes in Canada and the northeastern United States were analyzed for the occurrence of 27 current-use pesticides (CUPs). Eleven CUPs were frequently detected in lakes receiving agricultural inputs as well as in remote lakes hundreds of kilometers from known application areas. These included the triazine herbicide atrazine and its desethylated degradation product; the herbicides alachlor, metolachlor, and dacthal; the organophosphate insecticides chlorpyrifos, diazinon, and disulfoton; the organochlorine insecticides alpha-endosulfan and lindane; and the fungicides chlorothalonil and flutriafol. For six of the pesticides, empirical half-distances on the order of 560 to 1,820 km were estimated from the water-concentration gradient with latitude. For most of the pesticides, a suite of assessment models failed to predict such atmospheric long-range transport behavior, unless the effect of periods of lower hydroxyl radical concentrations and dry weather were taken into account. Observations and model results suggest that under the conditions prevailing in south-central Canada (relatively high latitude, low precipitation rates), many CUPs will be able to undergo regional-scale atmospheric transport and reach lakes outside areas of agricultural application. When assessing the potential of fairly reactive and water-soluble substances to undergo long-range transport, it is imperative to account for periods of no precipitation, to assure that degradation rate constants are correct, and to apply oxidant concentrations that are valid for the region and time period of interest.

Enantioselective Breakdown of .alpha.-Hexachlorocyclohexane in a Small Arctic Lake and its Watershed.

Water and snow samples were collected at Amituk Lake on Cornwallis Island to investigate the enantioselective degradation of α-hexachlorocyclohexane (α-HCH)in the Arctic. The two enantiomers were separated by gas chromatography on permethylated cyclodextrin capillary columns. The enantiomeric ratio (ER=(+)α-HCH)(-)α-HCH) for an α-HCH standard was 1.00±0.005, which is in excellent agreement with a theoretical ER of 1.00 for unmetabolized α-HCH. ERs of snow samples were racemic (0.9810.03). Degradation was found in Amituk Lake at 15-21 m where ERs were 0.7710.004; however, stream runoff and lake outflow ERs varied considerably during the study. ERs of the outflow traced the meltwater running over the surface of the lake, being close to streamwater values during peak runoff and returning to deep lake water values during low flow. Streamwater ERs decreased within a few weeks of snowmelt and showed a large variability (0.970.62), which may be due to the differences in temperature and amount of suspended sediments. The rapid enantioselective breakdown of a-HCH suggests that the ability of arctic microbial systems to degrade organic contaminants is greater than commonly thought

Deposition History of Brominated Flame Retardant Compounds in an Ice Core from Holtedahlfonna, Svalbard, Norway

Brominated flame retardants (BFRs) have been found in Arctic wildlife, lake sediment, and air. To identify the atmospheric BFR deposition history on Svalbard, Norway, we analyzed 19 BFRs, including hexabromocyclododecane (HBCD), 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE), decabromodiphenyl ethane (DBDPE), pentabromoethylbenzene (PBEB), and 15 polybrominated diphenyl ether congeners (PBDE) in the upper 34 m of an ice core (representing 1953-2005) from Holtedahlfonna, the western-most ice sheet on Svalbard. All of the non-PBDE compounds were detected in nearly continuous profiles in the core. Seven PBDEs were not observed above background (28, 47, 66, 100, 99, 154, 153), while 4 were found in 1 or 2 of 6 segments (17, 85, 138, 183). BDEs-49, 71, 190, 209 had nearly continuous profiles but only BDE-209 in large amounts. The greatest inputs were HBCD and BDE-209, 910, and 320 pg cm(-2) yr(-1) from 1995-2005. DBDPE, BTBPE, and PBEB show nearly continuous input growth in recent core segments, but all were <6 pg cm(-2) yr(-1). Long-range atmospheric processes may have moved these particle-bound BFRs to the site, probably during the Arctic haze season. Average air mass trajectories over 10 years show >75% of atmospheric flow to Holtedahlfonna coming from Eurasia during haze periods (March and April).

The historical residue trend of PCBs in the Agassiz Ice Cap, Ellesmere Island, Canada

Current detailed measurements of contaminant deposition cannot provide a historical perspective except through long-term monitoring programs. In the Aretic, ice caps provide an alternative to lake sediments, in that the annual snow layers reflect atmospheric deposition. As a result of the remoteness of the ice cap and the limited summer melt, annual layers undergo little chemical change, especially after the first summer season, and therefore provide a well-defined historical record. Initial work was undertaken at the Agassiz Ice Cap (80°49′50″ N, 72°56′30″ W) beginning in 1986, but a major effort was undertaken in 1993, during which snow samples covering 30 years were taken from a snow pit. Large volume snow samples were obtained for the determination of PCB congeners. Mean ΣPCB deposition to the ice cap ranged from 930 ng/m2/year in the winter of 1967–1968 to a minimum of 91 ng/m2/year in 1980–1981. Since 1980–1981, deposition has again increased to a local maximum of 848 ng/m2/year (in 1989–1990). The mean deposition for the 30 years of record was 406 ng/m2/year, with no evidence of a consistent long-term trend.

The recent depositional trend of polycyclic aromatic hydrocarbons and elemental carbon to the Agassiz Ice Cap, Ellesmere Island, Canada

Polar ice caps can provide long-term records of atmospheric deposition. Owing to the prevalent conditions, the layers of accumulated snow are subject to little chemical or physical change and are temporally well defined. Sampling of the Agassiz Ice Cap on Ellesmere Island was undertaken in early 1993 to investigate the potential of polar ice caps for use in determining recent historical trends in the deposition of anthropogenic contaminants to the Arctic. Discrete annual snow and ice layers representing the last 30 years of accumulation were sampled from a deep pit to obtain large volume samples for the determination of polycyclic aromatic hydrocarbons (PAHs) and elemental carbon (EC). The flux of PAHs to the ice cap has remained relatively constant for the past 20 years, with a mean value of 11 (± 6) μg/m2/year. This equates to a total annual loading of PAH to the Arctic of 37 t/year for the same period. Prior to this period, a greater flux of 74 (± 20) μg/m2/year is observed. Mean values for EC concentration and flux were found to be 2.6 (± 2.8) μg/l and 310 (± 370) μg/m2/year, respectively. However, analytical complications were encountered with the analysis of EC, and these data should be considered as preliminary baseline values only.

Polybrominated diphenyl ethers and alternative flame retardants in air and precipitation samples from the northern Lake Victoria region, East Africa.

High volume air and precipitation samples were collected close to the shore of Lake Victoria at Entebbe, Uganda, between October 2008 and July 2010 inclusive. Polybrominated diphenyl ethers (PBDEs) and alternative flame retardants (AFRs) were analyzed by GC-MS. BDEs 47, 99, and 209 were the predominant PBDEs with mean concentrations (in air) of 9.84, 4.38, 8.27 pg m(-3) and mean fluxes in precipitation of 3.40, 6.23, and 7.82 ng m(-2) sample(-1), respectively. 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE), and hexabromocyclododecane (HBCDD), anti- and syn-Dechlorane plus were detected at levels comparable with those of PBDEs. Both PBDEs and AFRs in air generally increased from 2008 to 2010. Elevated PBDE concentrations in air were associated with slow moving low altitude air masses from the region immediately adjacent to the lake, while low concentrations were mostly associated with fast moving westerly and southwesterly air masses. Analysis of the octa- and nona-BDE profiles suggested photolysis and pyrolytic debromination of BDE-209 in the air samples. The highly halogenated and most abundant PBDEs and AFRs in air also predominated in precipitation samples. This is the first study to report flame retardants in high volume air samples and precipitation in Equatorial Africa.

Deposition of Brominated Flame Retardants to the Devon Ice Cap, Nunavut, Canada

Brominated flame retardants (BFRs) can be transported to Arctic regions via atmospheric long-range transport, however, relatively little is known about their deposition to terrestrial environments. Snow cores from the Devon Ice Cap in Nunavut, Canada served to determine the recent depositional trends of BFRs. Snow pits were dug in 2005, 2006, and 2008. Dating using annual snow accumulation data, ion chemistry, and density measurements established that the pits covered the period from approximately 1993 to spring 2008. Samples were extracted under clean room conditions, and analyzed using GC-negative ion MS for 26 tri- to decabromodiphenyl ethers (BDEs), as well as other BFRs, nonbrominated flame retardants, and industrial chemicals. Decabromodiphenyl ether (BDE-209) was the major congener present in all samples followed by nona-BDEs (BDE-207, BDE-206, and BDE-208), both accounting for 89% and 7% of total BDE, respectively. BDE-209 concentrations were in most cases significantly correlated (P < 0.05) to tri- to nona-BDE homologues, and the strength of the correlations increased with increasing degree of bromination. Prior to or after deposition BDE-209 may be subject to debromination to lighter congeners. Deposition fluxes of BDE-209 show no clear temporal trend and range between 90 and 2000 pg·cm(-2)·year(-1). Back trajectory origin in densely populated areas of northeastern North America is significantly correlated (P < 0.005) with the BDE-209 deposition flux. Several other high production volume and/or alternative BFRs such as hexabromocyclododecane (HBCD), 1,2-bis(2,4,6-dibromophenoxy)ethane (BTBPE), pentabromo ethyl benzene (PBEBz), and pentabromobenzene (PBBz), as well as the industrial chemical 1,3,5-tribromobenzene (135-TBBz) were found consistently in the snow pits.

Bioaccumulation of Toxaphene Congeners in the Lake Superior Food Web

The bioaccumulation and biotransformation of toxaphene was examined in the food webs of Lake Superior and Siskiwit Lake (Isle Royale) using congener specific analysis as well as stable isotope ratios of carbon and nitrogen to characterize food webs. Toxaphene concentrations (calculated using technical toxaphene) in lake trout (Salvelinus namaycush) from the western basin of Lake Superior (N = 95) averaged (±SD) 889 ± 896 ng/g wet wt and 60 ± 34 ng/g wet wt in Siskiwit Lake. Major congeners in lake trout were B8-789 (P38), B8-2226 (P44), B9-1679 (P50), and B9-1025 (P62). Toxaphene concentrations were found to vary seasonally, especially in lower food web organisms in Lake Superior and to a lesser extent in Siskiwit Lake. Toxaphene concentrations declined significantly in lake herring (Coregonus artedii), rainbow smelt (Omerus mordax), and slimy sculpin (Cottus cognatus) as well as in zooplankton (> 102 μm) and Mysis (Mysis relicta) between May and October. The seasonal variation may reflect seasonal shifts in the species abundance within the zooplankton community. Trophic magnification factors (TMF) derived from regressions of toxaphene congener concentrations versus δ15N were > 1 for most octa- and nonachlorobornanes in Lake Superior except B8-1413 (P26) and B9-715. Log bioaccumulation factors (BAFs) for toxaphene congeners in lake trout (ng/g lipid/ng/L dissolved) ranged from 4.54 to 9.7 and were significantly correlated with log octanol-water partition coefficients. TMFs observed for total toxaphene and congener B9-1679 in Lake Superior were similar to those in Arctic lakes, as well as to previous studies in the Great Lakes, which suggests that the bioaccumulation behavior of toxaphene is similar in pelagic food webs of large, cold water systems. However, toxaphene concentrations were lower in lake trout from Siskiwit Lake and lakes in northwestern Ontario than in Lake Superior possibly because of shorter food chains and greater reliance on zooplankton or other pelagic invertebrates.

Deposition of atmospherically transported polychlorinated biphenyls in the Canadian arctic

Abstract Snow collectors were installed in 1990 at two Canadian high arctic weather stations (Mould Bay {MB} and Eureka {EU}) in an effort to estimate annual deposition of PCBs, compare these estimates to annual snowpack measurements and to investigate the timing of the deposition. The collectors operated successfully but tended to over collect when two snow fences were used. The daily flux of ΣEPCBs in the snowpack for 1990/91 generally compared well to that of the snow collector at MB. The snowpack sample at EU for the same period was considered to be unrepresentative, due to low snow accumulation on the ground and high winds, with resulting low concentrations and fluxes. The congener makeup of snowpack and snow collector samples was similar for both sites. Mean ΣEPCB fluxes for the collectors for the winter season were 2.0 and 3.8 ng· m −2 · day −1 for MB and EU respectively. Due to the tendency of the collectors to overcatch, especially late in the season, the fluxes were corrected relative to the shielded Nipher Gauge used to measure snowfall at the weather stations. The corrected ΣEPCB fluxes for MB reduced the overall contribution of a high concentration event in the winter, in favour of the fall season, the time of greatest snow accumulation. Initial assessment of the collectors for measuring the timing of and composition of PCB deposition to the arctic is very encouraging. Work is continuing to improve the collectors and to provide a better estimate of deposition of organic contaminants to the arctic environment.

Current-use pesticides in inland lake waters, precipitation, and air from Ontario, Canada

Concentrations of current-use pesticides (CUPs) in water, zooplankton, precipitation, and air samples as well as stereoisomer fractions (SF; herbicidally active/total stereoisomers) of metolachlor were determined in water samples collected from 10 remote inland lakes in Ontario, Canada, between 2003 and 2005. The most frequently detected chemicals in lake water, precipitation, and air were α-endosulfan, atrazine, metolachlor, chlorpyrifos, chlorothalonil, and trifluralin, and α-endosulfan and chlorpyrifos were the chemicals detected frequently in zooplankton. Air concentrations of these CUPs were within the range of previously reported values for background sites in the Great Lakes basin. High detection frequency of CUPs in lake water and precipitation was attributed to high usage amounts, but some CUPs such as ametryn and disulfoton that were not used in Ontario were also detected. Mean bioaccumulation factors (wet wt) in zooplankton for endosulfan ranged from 160 to 590 and from 20 to 60 for chlorpyrifos. The overall median SF of metolachlor in precipitation samples (0.846) was similar to that of the commercial S-metolachlor (0.882). However, the median SF of metolachlor in water from all sampled inland lakes (0.806) was significantly lower compared with Ontario rivers (0.873) but higher compared with previous measurements in the Great Lakes (0.710). Lakes with smaller watershed areas showed higher SFs, supporting the hypothesis of stereoselective processing of deposited metolachlor within the watersheds, followed by transport to the lakes.