Investigation of spatial trends and neurochemical impacts of mercury in herring gulls across the Laurentian Great Lakes

Herring gulls (Larus argentatus) bioaccumulate mercury (Hg) but it is unknown whether they are exposed at levels of neurological concern. Here we studied brain tissues from gulls at five Great Lakes colonies and one non-Great Lakes colony during spring of 2001 and 2003. Total brain Hg concentrations ranged from 0.14 to 2.0 μg/g (dry weight) with a mean of 0.54 μg/g. Gulls from Scotch Bonnet Island, on the easternmost edge of the Great Lakes, had significantly higher brain Hg than other colonies. No association was found between brain Hg concentration and [3H]-ligand binding to neurochemical receptors (N-methyl-d-aspartate, muscarinic cholinergic, nicotinic cholinergic) or nicotinic receptor α-7 relative mRNA expression as previously documented in other wildlife. In conclusion, spatial trends in Hg contamination exist in herring gulls across the Great Lakes basin, and herring gulls accumulate brain Hg but not at levels associated with sub-clinical neurochemical alterations.     

Monitoring and assessment of wetlands using Earth Observation: the GlobWetland project

The overall objective of the Ramsar Convention, signed in 1971, is the conservation and wise use of wetlands by national action and international cooperation as a means to achieving sustainable development. This complex and challenging task requires national, local and international bodies involved in the implementation of the convention to rely on suitable geo-information to better understand wetland areas, complete national inventories, perform monitoring activities, carry out assessments and put in practice suitable management plans based on updated and reliable information. In the last years, Earth Observation (EO) technology has been revealed as a key tool and unique information source to support the environmental community in different application domains, including wetlands' conservation and management. In this context, the European Space Agency (ESA) in collaboration with the Ramsar Secretariat launched in 2003 the "GlobWetland" project in order to demonstrate the current capabilities of Earth Observation technology to support inventorying, monitoring, and assessment of wetland ecosystems. This paper collects the main results and findings of the "GlobWetland" project, providing an overview of the current capabilities and limits of EO technology as a tool to support the implementation of the Ramsar Convention. The project was carried out in collaboration with several regional, national and local conservation authorities and wetland managers, involving 50 different wetlands across 21 countries on four continents. This large range of users provided an excellent test bed to assess the potential of this technology to be applied in different technical, economic and social conditions.     

Mason Valley Groundwater Model: Linking Surface Water and Groundwater in the Walker River Basin,Nevada1

Carroll, Rosemary W.H., Greg Pohll, David McGraw, Chris Garner, Anna Knust, Doug Boyle, Tim Minor, Scott Bassett, and Karl Pohlmann, 2010. Mason Valley Groundwater Model: Linking Surface Water and Groundwater in the Walker River Basin, Nevada. Journal of the American Water Resources Association (JAWRA) 46(3):554-573. DOI: 10.1111/j.1752-1688.2010.00434.x Abstract: An integrated surface water and groundwater model of Mason Valley, Nevada is constructed to replicate the movement of water throughout the different components of the demand side of water resources in the Walker River system. The Mason Valley groundwater surface water model (MVGSM) couples the river/drain network with agricultural demand areas and the groundwater system using MODFLOW, MODFLOW’s streamflow routing package, as well as a surface water linking algorithm developed for the project. The MVGSM is capable of simulating complex feedback mechanisms between the groundwater and surface water system that is not dependent on linearity among the related variables. The spatial scale captures important hydrologic components while the monthly stress periods allow for seasonal evaluation. A simulation spanning an 11-year record shows the methodology is robust under diverse climatic conditions. The basin-wide modeling approach predicts a river system generally gaining during the summer irrigation period but losing during winter months and extended periods of drought. River losses to the groundwater system approach 25% of the river’s annual budget. Reducing diversions to hydrologic response units will increase river flows exiting the model domain, but also has the potential to increase losses from the river to groundwater storage.     

A Comparative Assessment of Runoff Nitrogen from Turf,Forest, Meadow,and Mixed Landuse Watersheds

Landscaping paradigms that encourage high‐input, intensively managed and mono‐culture turf/lawn landscapes have raised concerns about water quality. We conducted a watershed‐scale assessment of landscaping practices that included turf, urban, forest, native meadow, and mixed landuse watersheds with a professional golf course and a parking lot. The turf site was moderately managed and had lower fertilizer inputs than those typically used by homeowners and golf courses. Stream water sampling was performed during base flow and storm events. Highest nitrate and total nitrogen concentrations in runoff were observed for the mixed watershed draining the golf course. In contrast, concentrations in base flow from the turf watershed were lower than expected and were comparable to those measured in the surrounding meadow and forest sites. Total nitrogen concentrations from the turf site increased sharply during the first storms following fertilization, suggesting that despite optimal management there exists a risk for nutrient runoff following fertilization. Overall, this study suggests that turf or lawns, when managed properly, pose minimal water quality risk to surface waters. Rate, timing of application, and the type of fertilizer appear to be the key factors affecting water quality. Better education of homeowners and landscaping professionals with regard to these factors may be a cost‐effective strategy to reduce nonpoint source pollution.     

Observations on the methane oxidation capacity of landfill soils

The objective of this study was to determine the role of CH₄ loading to a landfill cover in the control of CH₄ oxidation rate (g CH₄ m⁻² d⁻¹) and CH₄ oxidation efficiency (% CH₄ oxidation) in a field setting. Specifically, we wanted to assess how much CH₄ a cover soil could handle. To achieve this objective we conducted synoptic measurements of landfill CH₄ emission and CH₄ oxidation in a single season at two Southeastern USA landfills. We hypothesized that percent oxidation would be greatest at sites of low CH₄ emission and would decrease as CH₄ emission rates increased. The trends in the experimental results were then compared to the predictions of two differing numerical models designed to simulate gas transport in landfill covers, one by modeling transport by diffusion only and the second allowing both advection and diffusion. In both field measurements and in modeling, we found that percent oxidation is a decreasing exponential function of the total CH₄ flux rate (CH₄ loading) into the cover. When CH₄ is supplied, a cover’s rate of CH₄ uptake (g CH₄ m⁻² d⁻²) is linear to a point, after which the system becomes saturated. Both field data and modeling results indicate that percent oxidation should not be considered as a constant value. Percent oxidation is a changing quantity and is a function of cover type, climatic conditions and CH₄ loading to the bottom of the cover. The data indicate that an effective way to increase the % oxidation of a landfill cover is to limit the amount of CH₄ delivered to it.     

Anionic surfactant remediation of soil columns contaminated by nonaqueous phase liquids

A variety of column experiments have been completed for the purpose of selecting and evaluating suitable surfactants for remediation of nonaqueous phase liquids (NAPLs). The various NAPLs tested in the laboratory experiments were tetrachloroethylene (PCE), trichloroethylene (TCE), jet fuel (JP4) and a dense nonaqueous phase liquid from a site at Hill Air Force Base, UT. Both Ottawa sand and Hill field soil were used in these experiments. Surfactant candidates were first screened using phase behavior experiments and only the best ones were selected for the subsequent column experiments. Surfactants which showed high contaminant solubilization, fast coalescence times, and the absence of liquid crystal phases and gels during the phase behavior experiments were tested in soil column experiments. The primary objective of the soil column experiments was to identify surfactants that recovered at least 99% of the contaminant. The secondary objective was to identify surfactants that show low adsorption and little or no loss of hydraulic conductivity during the column experiments. Results demonstrated that up to 99.9% of the contaminants were removed as a result of surfactant flooding of the soil columns. The addition of xanthan gum polymer to the surfactant solution was shown to increase remediation efficiency as a lower volume of surfactant was required for recovering a given volume of NAPL. Based on these experimental results, guidelines for designing highly efficient and robust surfactant floods have been developed and applied to a field demonstration.