A review of the effectiveness of vegetated buffers to mitigate pesticide and nutrient transport into surface waters from agricultural areas.

A relatively large number of studies have investigated the effectiveness of vegetated buffer strips at reducing the movement of pesticides and nutrients from agriculture fields. This review outlines the observed influence of different factors (e.g., buffer width, slope, runoff intensity, soil composition, plant community) that can influence the efficacy of vegetated buffers in pesticide and nutrient retention. The reported effectiveness of vegetated buffers reducing the movement of pesticides and nutrients ranged from 10 to 100% and 12-100%, respectively. Buffer width is the factor that is most frequently considered by various jurisdictions when making recommendations on vegetated buffer strip implementation. However, the literature clearly illustrates that there is a great deal of variation in pesticide or nutrient reduction for a given buffer width. This indicates that other factors play an important role in buffer efficacy (e.g., ratio of source area to buffer area, soil composition and structure, runoff intensity, plant community structure) in addition to the width of the vegetative buffer area. These factors need to be considered when making recommendations on vegetated buffer strip construction in agroecosystems. This review has also identified a number of other gaps in the understanding of the effectiveness of vegetated buffers at reducing the movement of pesticides and nutrients from the areas of application.

The role of vegetated buffers in agriculture and their regulation across Canada and the United States.

A vegetated buffer, barrier, or filter strip is a parcel of land that is designated to separate land used for agriculture from valued aquatic or terrestrial habitats. It exists partly with the intent to diffuse runoff and to impeded sediment, nutrients, pesticides, and other constituents from reaching off-site surface waters. Mandatory buffer implementation is regulated at various levels of government in North America - from the federal to the state and provincial levels, and by some municipalities and counties. To better understand the degree and breadth of oversight, we undertook a comprehensive search and review of vegetative buffer regulations across North America. We determined the width of buffer required, under what habitat or field conditions, for which pesticides, and application type, amongst other attributes. For ground application, margins ranged from 1 m to upwards of greater than 4000 m depending on protection goals, with some being compound specific and others being generally applied to all registered pesticides/compounds. These buffers tended to be used most often to protect surface water, groundwater (e.g. drinking water wells), and nearby sensitive crops, but the required distances are generally not consistent between jurisdictions, regardless of the stated protection goals. We recommend that a thorough science-based review take place, with input from relevant stakeholders, to harmonize vegetated buffer size for effective surface water protection where ecological, climatic, and agricultural conditions are sufficiently similar in North America.

Persistent organic pollutants and mercury in marine biota of the Canadian Arctic: an overview of spatial and temporal trends.

This review summarizes and synthesizes the significant amount of data which was generated on mercury (Hg) and persistent organic pollutants (POPs) in Canadian Arctic marine biota since the first Canadian Arctic Contaminants Assessment Report (CACAR) was published in 1997. This recent body of work has led to a better understanding of the current levels and spatial and temporal trends of contaminants in biota, including the marine food species that northern peoples traditionally consume. Compared to other circumpolar countries, concentrations of many organochlorines (OCs) in Canadian Arctic marine biota are generally lower than in the European Arctic and eastern Greenland but are higher than in Alaska, whereas Hg concentrations are substantially higher in Canada than elsewhere. Spatial coverage of OCs in ringed seals, beluga and seabirds remains a strength of the Arctic contaminant data set for Canada. Concentrations of OCs in marine mammals and seabirds remain fairly consistent across the Canadian Arctic although subtle differences from west to east and south to north are found in the proportions of various chemicals. The most significant development since 1997 is improvement in the temporal trend data sets, thanks to the use of archived tissue samples from the 1970s and 1980s, long-term studies using archeological material, as well as the continuation of sampling. These data cover a range of species and chemicals and also include retrospective studies on new chemicals such as polybrominated diphenyl ethers. There is solid evidence in a few species (beluga, polar bear, blue mussels) that Hg at some locations has significantly increased from pre-industrial times to the present; however, the temporal trends of Hg over the past 20-30 years are inconsistent. Some animal populations exhibited significant increases in Hg whereas others did not. Therefore, it is currently not possible to determine if anthropogenic Hg is generally increasing in Canadian Arctic biota. It is also not yet possible to evaluate whether the recent Hg increases observed in some biota may be due solely to increased anthropogenic inputs or are in part the product of environmental change, e.g., climate warming. Concentrations of most "legacy" OCs (PCBs, DDT, etc.) significantly declined in Canadian Arctic biota from the 1970s to the late 1990s, and today are generally less than half the levels of the 1970s, particularly in seabirds and ringed seals. Chlorobenzenes and endosulfan were among the few OCs to show increases during this period while summation operatorHCH remained relatively constant in most species. A suite of new-use chemicals previously unreported in Arctic biota (e.g., polybrominated diphenyl ethers (PBDEs), short chain chlorinated paraffins (SCCPs), polychlorinated naphthalenes (PCNs), perfluoro-octane sulfonic acid (PFOS) and perfluorocarboxylic acids (PFCAs)) has recently been found, but there is insufficient information to assess species differences, spatial patterns or food web dynamics for these compounds. Concentrations of these new chemicals are generally lower than legacy OCs, but there is concern because some are rapidly increasing in concentration (e.g., PBDEs), while others such as PFOS have unique toxicological properties, and some were not expected to be found in the Arctic because of their supposedly low potential for long-range transport. Continuing temporal monitoring of POPs and Hg in a variety of marine biota must be a priority.

Concentrations of persistent organochlorine contaminants in bowhead whale tissues and other biota from northern Alaska: implications for human exposure from a subsistence diet.

Bowhead whale (Balaena mysticetus; n = 5) blubber, liver, muscle, kidney, heart, diaphragm, tongue, and uncooked maktak (bowhead whale epidermis and blubber) were collected during subsistence hunts at Barrow, AK, USA (1997-1999) to measure concentrations of persistent organochlorine contaminants (OCs). The exposure of humans to OCs via bowhead whales and other biota [fish, ringed (Phoca hispida) and bearded seals (Erignathus barbatus), and beluga whale (Delphinapterus leucas)] as part of a subsistence diet was evaluated. Concentrations of OCs in bowhead whale tissues were correlated with lipid content (P < 0.001) and were less than levels in other marine mammals reported herein, reflecting the lower trophic status of this cetacean. The relative proportions of hexachlorobenzene (HCB) and sum (Sigma) concentrations of chlordane components (SigmaCHL), DDT-related compounds (SigmaDDT), and polychlorinated biphenyls (SigmaPCB) were not statistically different among the tissues analyzed (P < 0.05). However, relatively higher proportions of hexachlorocyclohexane isomers (SigmaHCH), particularly beta-HCH, were observed in bowhead whale heart and diaphragm (P < 0.03). Based on Canadian and World Health Organization daily intake guidelines, "safe" human consumption rates of bowhead whale tissue and other marine biota were calculated. The most restrictive limits (mean value) for daily consumption for bowhead and beluga whale were 302 and 78 g for maktak and maktaaq (beluga whale epidermis and blubber), respectively. The tolerable daily intake limits of dioxin-like compounds from the consumption of bowhead whale blubber and liver were calculated to be 199 g (approximately 600 g for maktak) and 2222 g, respectively. A detailed profile of traditional/country foods consumed by subsistence communities of northern Alaska is required to address chronic exposure in more detail. Overall, bowhead whale tissues and other biota from northern Alaska are safe to consume at, or below, the levels calculated.

Profile of persistent chlorinated contaminants, including selected chiral compounds, in wolverine (Gulo gulo) livers from the Canadian Arctic.

Wolverines (Gulo gulo) are circumpolar omnivores that live throughout the alpine and arctic tundra ecosystem. Wolverine livers were collected at Kugluktuk (Coppermine), NU (n=12) in the western Canadian Arctic to report, for the first time, the residue patterns of persistent organochlorine contaminants (OCs) in this species. The enantiomer fractions (EFs) of several chiral OCs, including PCB atropisomers, in wolverines were also determined. Results were compared to OC concentrations and EFs of chiral contaminants in arctic fox (Alopex lagopus) from Ulukhaqtuuq (Holman), NT (n=20); a closely related species that scavenges the marine and terrestrial arctic environment. The rank order of hepatic concentrations for sum ( summation operator ) OC groups in wolverines were polychlorinated biphenyls ( summation operator PCB)>chlordane-related components ( summation operator CHLOR)>DDT-related compounds ( summation operator DDT)>hexachlorocyclohexane isomers ( summation operator HCHs). The most abundant OC analytes detected in wolverine liver were PCB-153, PCB-180, and oxychlordane (OXY). Wolverine age and gender did not influence OC concentrations, which were comparable to lipid-normalized values in arctic fox. The EFs of several chiral OCs (alpha-HCH, cis- and trans-chlordane, OXY, heptachlor exo-epoxide) and PCB atropisomers (PCB-136, 149) were nonracemic in arctic fox and wolverine liver and similar to those previously calculated in arctic fox and polar bears from Iceland and the Canadian Arctic. Results suggest that these species have similar ability to biotransform OCs. As well, contaminant profiles suggest that terrestrial mammals do not represent the major source of OC exposure to wolverines and that wolverines are scavenging more contaminated prey items, such as marine mammals. While summation operator PCB did not exceed the concentrations associated with mammalian reproductive impairment, future research is required to properly evaluate the potential affect of other OCs on the overall health of wolverines.

Concentrations of selected essential and non-essential elements in arctic fox (Alopex lagopus) and wolverines (Gulo gulo) from the Canadian Arctic.

Arctic fox (Alopex lagopus) and wolverine (Gulo gulo) tissues were collected in the Canadian Arctic from 1998 to 2001 and analyzed for various essential and non-essential elements. Several elements (Ag, Al, As, B, Ba, Be, Co, Cr, Mo, Ni, Sb, Sn, Sr, Tl, U and V) were near or below the detection limits in >95% arctic fox and wolverine samples. Concentrations of Cd, Cu, Fe, total Hg (THg), Mn, Pb, Se and Zn were quantifiable in >50% of the samples analyzed and reported herein. Hepatic elemental concentrations were not significantly different among arctic foxes collected at Ulukhaqtuuq (Holman), NT (n=13) and Arviat, NU (n=50), but were significantly greater than concentrations found in wolverine liver from Kugluktuk (Coppermine), NU (n=12). The mean (+/-1 S.E.) concentrations of Cd in kidney were also significantly greater in arctic fox (1.08+/-0.19 microg g(-1) wet wt.) than wolverine (0.67+/-0.18 microg g(-1) wet wt.). However, mean hepatic Cu concentrations (Ulukhaqtuuq: 5.5+/-0.64; Arviat: 7.1+/-0.49 microg g(-1) wet wt.) in arctic foxes were significantly lower than in wolverines (32+/-3.3 microg g(-1) wet wt.). Hepatic total Hg (THg) concentrations in arctic fox from this study were not significantly different from specimens collected in 1973, suggesting that THg concentrations have not changed dramatically over the past 30 years. The mono-methylmercury (MeHg) concentrations in selected (n=10) arctic fox liver samples from Arviat (0.14+/-0.07 microg g(-1) wet wt.) comprised 14% of THg. While the molar concentrations of THg were correlated with Se in arctic foxes and wolverines, the hepatic Hg/Se molar ratios were consistently lower than unity; suggesting that Se-mediated detoxification pathways of Hg are not overwhelmed at current exposure.

Trophic transfer of persistent organochlorine contaminants (OCs) within an Arctic marine food web from the southern Beaufort-Chukchi Seas.

Stable isotope values (13C, 15N) and concentrations of persistent organochlorine contaminants (OCs) were determined to evaluate the near-shore marine trophic status of biota and biomagnification of OCs from the southern Beaufort-Chukchi Seas (1999-2000) near Barrow, AK. The biota examined included zooplankton (Calanus spp.), fish species such as arctic cod (Boreogadus saida), arctic char (Salvelinus alpinus), pink salmon (Oncorhynchus gorbuscha), and fourhorn sculpin (Myoxocephalus quadricornis), along with marine mammals, including bowhead whales (Balaena mysticetus), beluga whales (Delphinapterus leucas), ringed seals (Phoca hispida) and bearded seals (Erignathus barbatus). The isotopically derived trophic position of biota from the Beaufort-Chukchi Seas marine food web, avian fauna excluded, is similar to other coastal food webs in the Arctic. Concentrations of OCs in marine mammals were significantly greater than in fish and corresponded with determined trophic level. In general, OCs with the greatest food web magnification factors (FWMFs) were those either formed due to biotransformation (e.g. p,p'-DDE, oxychlordane) or considered recalcitrant (e.g. -HCH, 2,4,5-Cl substituted PCBs) in most biota, whereas concentrations of OCs that are considered to be readily eliminated (e.g. -HCH) did not correlate with trophic level. Differences in physical-chemical properties of OCs, feeding strategy and possible biotransformation were reflected in the variable biomagnification between fish and marine mammals. The FWMFs in the Beaufort-Chukchi Seas region were consistent with reported values in the Canadian Arctic and temperate food webs, but were statistically different than FWMFs from the Barents and White Seas, indicating that the spatial variability of OC contamination in top-level marine Arctic predators is attributed to differences in regional sources of contamination rather than trophic position.

Organochlorine contaminant and stable isotope profiles in Arctic fox (Alopex lagopus) from the Alaskan and Canadian Arctic.

Arctic fox (Alopex lagopus) is a circumpolar species distributed across northern Canada and Alaska. Arctic fox muscle and liver were collected at Barrow, AK, USA (n=18), Holman, NT, Canada (n=20), and Arviat, NU, Canada (n=20) to elucidate the feeding ecology of this species and relate these findings to body residue patterns of organochlorine contaminants (OCs). Stable carbon (delta 13C) and nitrogen (delta 15N) isotope analyses of Arctic fox muscle indicated that trophic position (estimated by delta 15N) is positively correlated with increasing delta 13C values, suggesting that Arctic fox with a predominantly marine-based foraging strategy occupy a higher trophic level than individuals mostly feeding from a terrestrial-based carbon source. At all sites, the rank order for OC groups in muscle was polychlorinated biphenyls (Sigma PCB) > chlordane-related compounds (Sigma CHLOR) > hexachlorocyclohexane (Sigma HCH) > total toxaphene (TOX) > or = chlorobenzenes (Sigma ClBz) > DDT-related isomers (Sigma DDT). In liver, Sigma CHLOR was the most abundant OC group, followed by Sigma PCB > TOX > Sigma HCH > Sigma ClBz > Sigma DDT. The most abundant OC analytes detected from Arctic fox muscle and liver were oxychlordane, PCB-153, and PCB-180. The comparison of delta 15N with OC concentrations indicated that relative trophic position might not accurately predict OC bioaccumulation in Arctic fox. The bioaccumulation pattern of OCs in the Arctic fox is similar to the polar bear. While Sigma PCB concentrations were highly variable, concentrations in the Arctic fox were generally below those associated with the toxicological endpoints for adverse effects on mammalian reproduction. Further research is required to properly elucidate the potential health impacts to this species from exposure to OCs.

Bioaccumulation of organochlorine contaminants in bowhead whales (Balaena mysticetus) from Barrow, Alaska.

Bowhead whale (Balaena mysticetus) blubber (n = 72) and liver (n = 23) samples were collected during seven consecutive subsistence harvests (1997-2000) at Barrow, Alaska, to investigate the bioaccumulation of organochlorine contaminants (OCs) by this long-lived mysticete. The rank order of OC group concentrations (geometric mean, wet weight) in bowhead blubber samples were toxaphene (TOX; 455 ng/g) > polychlorinated biphenyls (SigmaPCBs; 410 ng/g) > dichlorodiphenyltrichloroethane-related compounds (SigmaDDT; 331 ng/g) >or= hexachlorocyclohexane isomers (SigmaHCHs; 203 ng/g) >or= chlordanes and related isomers (SigmaCHLOR; 183 ng/g) > chlorobenzenes (SigmaCIBz; 106 ng/g). In liver, SigmaHCH (9.5 ng/g; wet weight) was the most abundant SigmaOC group, followed by SigmaPCBs (9.1 ng/g) >or= TOX (8.8 ng/g) > SigmaCHLOR (5.5 ng/g) > SigmaCIBz (4.2 ng/g) >or= SigmaDDT (3.7 ng/g). The dominant analyte in blubber and liver was p,p'-DDE and alpha-HCH, respectively. Total TOX, SigmaPCBs, SigmaDDT, and SigmaCHLOR concentrations in blubber generally increased with age of male whales (as interpreted by body length), but this relationship was not significant for adult female whales. Biomagnification factor (BMF) values (0.1-45.5) for OCs from zooplankton (Calanus sp.) to bowhead whale were consistent with findings for other mysticetes. Tissue-specific differences in OC patterns in blubber and liver may be attributed to variation of tissue composition and the relatively low capacity of this species to biotransform various OCs. Principal component analysis of contaminants levels in bowhead blubber samples suggest that proportions of OCs, such as beta-HCH, fluctuate with seasonal migration of this species between the Bering, Chukchi, and Beaufort Seas.

Enantiomer-specific activity of o,p'-DDT with the human estrogen receptor.

There is a growing concern that environmental xenobiotics may be affecting human and wildlife health by disrupting normal endocrine function via interaction with steroid hormone receptors. Several of these persistent contaminants are chiral and may have enantiomer-specific biological properties. Previous experiments have demonstrated that (-)-o,p'-DDT enantiomer is a more active estrogen-mimic than the (+)-enantiomer in rats. However, these results have not been extrapolated to other biological systems. This study used a yeast-based assay to assess the enantiomer-specific transcriptional activity of DDT with the human estrogen receptor (hER). (+)-17beta-estradiol, racemic DDT and individual DDT enantiomers were added to yeast cultures and hER activity was measured by quantification of beta-galactosidase. The relative activity of o,p'-DDT was weak compared to estradiol. For o,p'-DDT, the (-)-enantiomer was the active estrogen mimic whereas the hER activity of (+)-o,p'-DDT was negligible. The presence of the (+)-enantiomer at relatively greater concentration decreased the transcriptional activity of (-)-o,p'-DDT. This data demonstrates the need to consider stereochemistry of environmental contaminants and their potential influence on biological responses.