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MWC 2005 SPONSORS
U.S. Geological Survey . Senator George J. Mitchell Center . Maine DHS / Drinking Water Program . Portland Water District . Aqua Maine . Maine Coastal Program / State Planning Office . Maine Dept. of Environmental Protection . Maine Geological Survey . Maine Rural Water Association . Maine Wastewater Control Association . Maine Water Utilities Association . Maine Congress of Lake Associations . Maine Volunteer Lake Monitoring Program . Maine Rivers . University of Maine Cooperative Extension . Maine Sea Grant
Mercury, Endocrine Disruptors, and Other Emerging Contaminants
Co-Chairs: Aria Amirbahman (UMaine), Deborah Rice (Maine Bureau of Health)
Daniel B. Carr, P.E., Principal; Stephen J. Roy, P.G., Project Manager; and Erica M. Bradstreet, Project Geologist
Sanborn, Head & Associates, Inc., Portland, Maine, 207/761-9300, dcarr@sanbornhead.com
Vapor Intrusion from the Subsurface into Building Space: A Latent But Significant Pathway for Human Exposure
Although the U.S. EPA and states including Maine have long recognized the potential for human exposure through migration of volatile organic compound vapors into occupied building space, the focus has been on petroleum compounds and acute hazards. Recent work across the country has highlighted concern for chronic exposure to vapors from chlorinated solvents, which can be far more persistent in the subsurface and hence more readily transported in vapor phase. Sources of these solvents in the environment can include releases from dry cleaning, printing, machining, and other common industries that are often located in urban areas with residential properties. In recognition of the potential pervasiveness of this problem, U.S. EPA and other agencies are in the process of refining standards for screening of sites for vapor intrusion potential.
We will present an overview of the present understanding of mechanisms for vapor migration, a history of vapor intrusion as a pathway of concern, and approaches for addressing potential vapor intrusion sites. Since 2002, SHA has been the prime consultant responsible for managing one of the nation's largest vapor intrusion sites in a 350-acre urban setting with over 1,000 residential, commercial, and institutional properties. We will touch on key issues related to vapor intrusion including, but not limited to, site characterization techniques, data management, background indoor air quality, and mitigation techniques.
Teresa Thornton (student)1 and Laurie Osher2
1Senator George J. Mitchell Center for Environmental and Watershed Research, Orono, Maine, 207/581-3233, Teresa.Thornton@umit.maine.edu
2Assistant Professor of Soil and Water Quality, University of Maine, Orono, Maine, 207/581-2957, Laurie@maine.edu
Hexazinone Movement from Upland Soils to Surface Waters via Groundwater
In Maine, low bush (wild) blueberries are grown on coarse textured glacial outwash soils. Hexazinone is the most widely used broad spectrum herbicide currently available to suppress weed competition in Maine's blueberry fields. Hexazinone is highly soluble in water, has a low soil binding potential, a long half-life and is toxic to most terrestrial and aquatic plants. These chemical properties and the rapid drainage of the glacial outwash soils facilitate the swift movement of hexazinone to groundwater. Using historical application rate data, groundwater hexazinone concentration data, and hydrologic head measurements, we are mapping the movement of hexazinone from upland blueberry fields to down-gradient surface waters in downeast Maine. The multidisciplinary methods used for this project included the installation of groundwater wells, collection of water samples and hydrologic data, analysis of water for specific organic compounds, and integration of the information using a geographic information system. This presentation will include data and maps of groundwater and surface water hexazinone concentrations, and will identify the potential impact of these concentrations on aquatic plants common in downeast Maine. This work is an example of the research that addresses the complexity of measuring non-point source agricultural pollution and its impacts in Maine.
Karen Merritt (student) and Amirbahman, A.
Dept. of Civil and Environmental Engineering, University of Maine Orono, ME, 207/581-3401
Sources and Sinks: Sequestration and Transformation of Mercury in the Penobscot Estuary
The potential delivery of mercury (Hg) to the coastal ocean is mediated via the chemical, physical and biological interactions that occur within estuaries. As the zone in which river water mixes with the coastal ocean, estuaries experience significant fluctuations in system ionic strength, suspension concentrations, water temperature, pH, and the dissolved oxygen content of both the water column and benthos. Moreover, through the combined action of salinity increase and natural channel widening, estuaries function as traps for flocculated, river-borne contaminants such as Hg. This assertion is supported locally, as Hg burdens in Penobscot estuary sediments may exceed regional background concentrations by ~2 orders of magnitude (i.e., 5000 vs. 50 ng/g dry weight sediment).
With research stressing the Hg storage potential of estuaries, it is important to assess the extent to which retention affects bioavailability. The relationship between storage and availability is crucial as Hg transfer studies suggest that while inorganic Hg is biologically available, methylmercury (MeHg) biologically magnifies. Mercury methylation appears dominated by the action of a microbial consortium active in organic matter-enriched, poorly-oxygenated environments. As such, estuarine sedimentation of river-borne Hg may transport a suspension pool into an environment facilitating methylation. Furthermore, methylation may potentially be enhanced via cyclic fluctuations in inundation and redox conditions that typify an estuary's tidally flooded reaches. Our current research utilizes reactive membranes to assess the extent to which tidal exchange affects mobility of sediment solid phase and porewater Hg. We will discuss Hg contamination in and mobilization potential from Penobscot estuary sediments.
Timothy D. Jardine1, Tom A. Al2, Kerry T.B. MacQuarrie3, Charles D. Ritchie4, Paul A. Arp5, Antu Maprani6, and Richard A. Cunjak7
1Canadian Rivers Institute and Department of Biology, University of New Brunswick, Fredericton, NB, 506-458-7148, tim.jardine@unb.ca
2Canadian Rivers Institute and Department of Geology, University of New Brunswick, Fredericton, NB, 506-447-3189, tal@unb.ca
3Canadian Rivers Institute and Department of Civil Engineering, University of New Brunswick, Fredericton, NB, 506-453-5121, ktm@unb.ca
4Faculty of Forestry and Environmental Management, University of New Brunswick, Fredericton, NB, 506-452-6332, charles.ritchie@unb.ca
5Faculty of Forestry and Environmental Management, University of New Brunswick, Fredericton, NB, 506-453-4931, arp1@unb.ca
6Canadian Rivers Institute and Department of Geology, University of New Brunswick, Fredericton, NB, 506-447-3189, b976u@unb.ca
7Canadian Rivers Institute and Department of Biology, University of New Brunswick, Fredericton, NB, 506-452-6204, cunjak@unb.ca
Water striders (Hemiptera: Gerridae) indicate mercury levels in freshwater systems
Contaminant monitoring programs are often limited by logistics and conservation concerns, particularly with large-bodied fish species that are difficult to capture or are threatened or endangered. Alternative taxa, such as stream invertebrates, have higher reproductive capacities and hence lower concern about their conservation, but their small size and absence from many sites renders their use in contaminant analysis problematic. Ubiquitous, intermediate size organisms may therefore be useful in contaminant monitoring because they possess characteristics ideal for both conservation and analysis. We measured total mercury concentrations in the large bodied, predatory invertebrate, the water strider (Hemiptera: Gerridae) and a popular recreational fish species, brook trout (Salvelinus fontinalis), from a variety of stream sites in New Brunswick. There was a strong association between the two variables (r2 = 0.81) across sites. The relationship persisted in systems where atmospheric deposition was the likely cause of mercury contamination and in a system where a point source (an abandoned gold mine) was a likely contributor to ambient mercury levels. These results indicate that water strider mercury levels may be useful in building a predictive model for food chain entry of mercury. The use of surrogate species such as the water strider holds great potential for expanding contaminant monitoring programs.
Sarah J. Nelson (student)1, K.C. Weathers2, K.B. Johnson3, J.S. Kahl4
1Senator George J. Mitchell Center for Environmental and Watershed Research, Orono, ME, 207/581-3454, sarah.nelson@umit.maine.edu
2Institute of Ecosystem Studies, Millbrook, NY, 845/677-7600, weathersk@ecostudies.org
3Senator George J. Mitchell Center for Environmental and Watershed Research, Orono, ME, 207/581-3396, ken.johnson@umit.maine.edu
4Center for the Environment, Plymouth State University, Plymouth, NH, 603/535-3179, jskahl@plymouth.edu
Does Vegetation Matter? Mercury Deposition at Acadia National Park, Maine
Forty-five states in the U.S. - including Maine - have fish consumption advisories for mercury (Hg), the toxic form of which bioaccumulates in the food chain and causes neurological damage in humans. In-watershed transformations determine how much of the toxic form of Hg (MeHg) is found in a water body. However, the main source of Hg to Maine's watersheds is atmospheric deposition - from outside the watersheds. While much is known about spatial and temporal patterns of wet deposition, estimates of dry and fog deposition are uncommon or highly uncertain, and these forms of deposition can comprise half or more of total deposition. Throughfall - the water that falls to the forest floor during a precipitation event - has been used as a surrogate for total deposition. In paired research watersheds at Acadia National Park, we: (1) examined the relationships between wet deposition and throughfall fluxes of Hg during the 2000 and 2004 growing seasons, and (2) began a study of Hg in snow throughfall. In a network of 52 sites distributed throughout two small watersheds at Acadia, throughfall deposition at coniferous sites was 40.2 (±1.2) ng/m2/day, and at deciduous sites was 31.9 (±1.6) ng/m2/day during the leaf-on season. Deposition was, on average, 1.6 (deciduous), 2.3 (coniferous), and 2.6 (mixed) times higher at forested than open sites. Our data suggest that some combination of dry and fog deposition of Hg is at least equivalent to wet deposition and that coniferous vegetation intercepts greater amounts of Hg than deciduous vegetation.
Michael Bank (student)1, Cynthia Loftin2, Jeff Crocker3, Robert MacDonald4, and Aria Amirbahman5
1Harvard University, Harvard Forest, Petersham, MA, 978/724-3302 x244, msbank@fas.harvard.edu
2US Geological Survey, Maine Cooperative Fish and Wildlife Research Unit, University of Maine, Orono, ME, 207/581-2843, Cyndy_Loftin@umenfa.maine.edu
3Program in Ecology & Environmental Sciences, University of Maine, Orono, ME, crockerjb7@hotmail.com
4Harvard University, Harvard Forest, Petersham, MA, 978/724-3302 x282, rimcdon@fas.harvard.edu
5Department of Civil and Environmental Engineering, University of Maine, Orono, ME, 207/581-1277, Aria_Amirbahman@umit.maine.edu
Mercury, Stream Salamanders and Watershed Heterogeneity: Coping with a Risky Environment
Mercury (Hg) bioaccumulation in salamanders has received little attention despite widespread Hg contamination of aquatic ecosystems and reports of worldwide amphibian declines. Here we report the spatial distribution of Hg concentrations in two-lined salamander (Eurycea bislineata) larvae from 14 watersheds in Acadia National Park, Maine, USA, June-July 2001 and 2002. The specific objectives of this investigation were to determine the effects of watershed land cover on: a) Hg levels (ng/g wet wt.) in two-lined salamander larvae, b) larval salamander Hg bioconcentration factors (Log {total Hg in salamander larvae / total Hg in water}), and c) larval salamander biomass (g/m2). We classified land cover types into 6 categories (% open, % wet, % conifer forest, % hardwood forest, % mixed forest and % disturbed habitat) for statistical analyses and used linear regression analyses and Akaike's Information Criterion (AICc) to select the best approximating models for larval salamander total Hg concentrations, bioconcentration factors, and biomass. Our study indicates that variation in watershed land cover types among the 14 drainages was relatively high. Percent conifer forest in the watershed was the best approximating model for larval biomass (negative trend) and bioconcentration factors (positive trend) in larvae. Percent hardwood forest (negative trend) in the watershed was the best approximating model for total Hg concentrations in larvae. Overall, our results indicate that watershed land cover can exert strong controls over mercury bioaccumulation, bioconcentration and biomass in stream obligate biota such as two-lined salamander larvae.
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