A5050205837- Mercury impact and mitigation studies
- Toxic Organic Pollutants Impact
- Advanced Aircraft Design and Technologies
- Rocket and propulsion systems research
- Heavy Metal Exposure and Toxicity
- Marine animal studies overview
- Heavy metals in environment
- Marine and coastal ecosystems
- Peatlands and Wetlands Ecology
- Environmental Toxicology and Ecotoxicology
- Water Treatment and Disinfection
- Coral and Marine Ecosystems Studies
- Coastal wetland ecosystem dynamics
- Selenium in Biological Systems
- Computational Fluid Dynamics and Aerodynamics
- Pharmaceutical and Antibiotic Environmental Impacts
- Methane Hydrates and Related Phenomena
- Isotope Analysis in Ecology
- Marine Biology and Ecology Research
- Water Quality Monitoring and Analysis
- Analytical Chemistry and Sensors
- Atmospheric and Environmental Gas Dynamics
- Marine and fisheries research
- Marine and coastal plant biology
- Analytical chemistry methods development
University of Maryland Center for Environmental Science
2013-2022
Imperial College London
2004-2018
University System of Maryland
2004-2010
University of Toronto
2010
Fisheries and Oceans Canada
1997-2004
University of Alberta
2004
Tetra Tech (Canada)
2002
Trent University
2002
McGill University
1992-1998
University of Waterloo
1997
A chemical equilibrium model for Hg complexation in sediments with sulfidic pore waters is presented. The purpose of the was to explain observed relationships between water sulfide, dissolved inorganic (HgD), and bulk methylmercury (MeHg) surficial two biogeochemically different ecosystems, Florida Everglades Patuxent River, MD. constructed test hypothesis that availability methylation a function concentration neutral complexes rather than Hg2+ or total HgD. included interaction mercury...
Methylmercury contamination of fisheries from centuries industrial atmospheric emissions negatively impacts humans and wildlife worldwide. The response fish methylmercury concentrations to changes in mercury deposition has been difficult establish because sediments/soils contain large pools historical contamination, many factors addition affect mercury. To test directly the changing deposition, we conducted a whole-ecosystem experiment, increasing load lake its watershed by enriched stable...
Experimental flooding of a boreal forest wetland caused the to change from being small, natural carbon sink, with respect atmosphere, −6.6 g C m-2 yr-1 large source +130 yr-1. This was by death vegetation, which eliminated photosynthetic CO2 sink and stimulated microbial production CH4 decomposition plant tissues peat. Another type activity that increased methylation inorganic mercury much more toxic methyl (MeHg) form. The MeHg prior became an even larger (39 fold) after flooding....
The METAALICUS (Mercury Experiment To Assess Atmospheric Loading In Canada and the US) project is a whole ecosystem experiment designed to study activity, mobility, availability of atmospherically deposited mercury. investigate dynamics mercury newly onto terrestrial ecosystem, an enriched stable isotope (202Hg) was sprayed Boreal forest subcatchment in that allowed us, for first time, monitor fate "new" deposition distinguish it from native historically stored ecosystem. Newly more reactive...
For the past 9 years, we experimentally flooded a wetland complex (peatland surrounding an open water pond) at Experimental Lakes Area (ELA), northwestern Ontario, Canada, to examine biogeochemical cycling of methyl mercury (MeHg) in reservoirs. Using input−output budgets, found that prior flooding, was net source approximately 1.7 mg MeHg ha-1 yr-1 downstream ecosystems. In first year yields from reservoir increased 40-fold 70 yr-1. Subsequently, annual declined (10−50 yr-1) but have...
Anthropogenic releases of mercury (Hg)1-3 are a human health issue4 because the potent toxicant methylmercury (MeHg), formed primarily by microbial methylation inorganic Hg in aquatic ecosystems, bioaccumulates to high concentrations fish consumed humans5,6. Predicting efficacy pollution controls on MeHg is complex many factors influence production and bioaccumulation MeHg7-9. Here we conducted 15-year whole-ecosystem, single-factor experiment determine magnitude timing reductions following...
A hydrobiogeochemical investigation of a small headwater peatland located in the Experimental Lakes Area, northwestern Ontario, Canada, examined surface and subsurface hydrologic pathways their relation to movement spatial variability methylmercury (CH 3 Hg + ). The hydrology controls mass flux CH downstream pond from terrestrial ecosystems, influences production and/or accumulation peatland. Distinct zones groundwater recharge discharge were observed within peatland, these corresponded, low...
Methane emissions were measured by a static chamber technique at 39 sites along transect from the James Bay coast southeastern tip of Hudson to Kinosheo Lake, northwest Moosonee, Ontario, Canada. These represented five major wetland ecosystems successional gradient inland. Measurements made ≈ 10‐day intervals early June mid‐August, and once in mid‐September mid‐October 1990. Seasonal CH 4 fluxes small (<2 g m −2 ) recently emerged coastal marsh, fen, tamarack interior fen ecosystems,...
Fluxes of CO 2 and CH 4 were determined by a static chamber technique at eight drained swamp peatland sites, with crop forest covers. Over 6‐ month period (May ‐ October, 1991), fluxes ranged from −5 to 7 mg m −2 d −1 not correlated either soil temperature or water table position. Integrated seasonal emissions −0.40 0.04 g over 147 days; the sites grass cover small sink whereas horticultural crops showed no significant flux. Laboratory incubations that highest consumption rates (3 9 μg )...
Abstract The complexation of Hg under sulfidic conditions influences its bioavailability for microbial methylation. Neutral dissolved Hg‐sulfide complexes are readily available to Hg‐methylating bacteria in culture, and thermodynamic models predict that inorganic dominate speciation natural conditions. However, these have not been validated the field. To examine waters, octanol/water partitioning methods were modified use environmentally relevant conditions, a centrifuge ultrafiltration...
An extensively diverse array of brominated disinfection byproducts (DBPs) were generated following electrochemical natural coastal/estuarine water, which is one the main treatment methods currently under consideration for ballast water treatment. Ultra-high-resolution mass spectrometry revealed 462 distinct DBPs at a relative abundance in spectra more than 1%. A DBP with almost 22% was identified as 2,2,4-tribromo-5-hydroxy-4-cyclopentene-1,3-dione, an analogue to several previously...
Methylmercury (MeHg) bioaccumulation in marine food webs poses risks to fish-consuming populations and wildlife. Here we develop test an estuarine mercury cycling model for a coastal embayment of the Bay Fundy, Canada. Mass budget calculations reveal that MeHg fluxes into sediments from settling solids exceed losses sediment-to-water diffusion resuspension. Although measured methylation rates benthic are high, rapid demethylation results negligible net situ production MeHg. These suggest...
Coral reefs are impacted by a variety of anthropogenic stressors including inputs chemical contaminants. Although data is currently limited, sunscreens containing ultraviolet (UV) filters have recently been suggested as an emerging class To provide further on the toxicity UV filter oxybenzone (benzophenone-3 or BP-3) to corals, we conducted three independent acute tests exposing colonial stony coral Galaxea fascicularis BP-3 (0.31 10 mg/L nominal concentrations). Assessments included daily...
Landfill leachate organic matter was molecularly characterized by FT-ICR-MS, revealing a significant and previously unidentified organochlorine signature.
Abstract A review of Hg concentrations cited in the literature reveals values general sequence: grassland herbs < trees and shrubs aquatic macrophytes Sphagnum mosses lichens fungi, excluding those samples collected near point sources environmental Hg. Samples vegetation from wetland upland catchments Experimental Lakes Area contained 4 to 160 μg total (THg) kg −1 0.1 139 methyl (MeHg) . The lowest both THg MeHg were found leaves needles shrubs, highest occurred bryophytes, feather...
The fate of mercury (Hg) deposited on forested upland soils depends a wide array biogeochemical and hydrological processes occurring in the soil landscape. In this study, Hg soil, soilwater, streamwater were measured across subcatchment METAALICUS watershed northwestern Ontario, Canada, where stable isotope (spike Hg) was applied to distinguish newly from already resident (ambient Hg). total, we able account for 45% total mass spike during entire loading phase experiment, with approximately...