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[en] The U.S. Department of Energy (US DOE) has mobilized its National Laboratories to address the broad range of environmental effects of ocean and river energy development. The National Laboratories are using a risk-based approach to set priorities among environmental effects, and to direct research activities. Case studies will be constructed to determine the most significant environmental effects of ocean energy harvest for tidal systems in temperate estuaries, for wave energy installations in temperate coastal areas, wave installations in sub-tropical waters, and riverine energy installations in large rivers. In addition, the National Laboratories are investigating the effects of energy removal from waves, tides and river currents using numerical modeling studies. Laboratory and field research is also underway to understand the effects of electromagnetic fields (EMF), acoustic noise, toxicity from anti-biofouling coatings, effects on benthic habitats, and physical interactions with tidal and wave devices on marine and freshwater organisms and ecosystems. Outreach and interactions with stakeholders allow the National Laboratories to understand and mitigate for use conflicts and to provide useful information for marine spatial planning at the national and regional level.
[en] This report summarizes a 3-year research project undertaken to better understand the nature and magnitude of mercury (Hg) fluxes in East Fork Poplar Creek (EFPC). This project addresses the requirements of Action Plan 1 in the 2011 Oak Ridge Reservation-wide Comprehensive Environmental Response, Compensation, and Liability Act Five Year Review (FYR). The Action Plan is designed to address a twofold 2011 FYR issue: (1) new information suggests mobilization of mercury from the upper and lower EFPC streambeds and stream banks is the primary source of mercury export during high-flow conditions, and (2) the current Record of Decision did not address the entire hydrologic system and creek bank or creek bed sediments. To obtain a more robust watershed-scale understanding of mercury sources and processes in lower EFPC (LEFPC), new field and laboratory studies were coupled with existing data from multiple US Department of Energy programs to develop a dynamic watershed and bioaccumulation model. LEFPC field studies for the project focused primarily on quantification of streambank erosion and an evaluation of mercury dynamics in shallow groundwater adjacent to LEFPC and potential connection to the surface water. The approach to the stream bank study was innovative in using imagery from kayak floats' surveys from the headwaters to the mouth of EFPC to estimate erosion, coupled with detailed bank soil mercury analyses. The goal of new field assessments and modeling was to generate a more holistic and quantitative understanding of the watershed and the sources, flux, concentration, transformation, and bioaccumulation of inorganic mercury (IHg) and methylmercury (MeHg). Model development used a hybrid approach that dynamically linked a spreadsheet-based physical and chemical watershed model to a systems dynamics, mercury bioaccumulation model for key fish species. The watershed model tracks total Hg and MeHg fluxes and concentrations by examining upstream inputs, floodplain runoff, floodplain leaching, bank soil erosion, and periphyton matrix dynamics. The bioaccumulation model tracks the feeding, growth, and mercury assimilation of representative individual fish through their typical life span using key inputs of fish size, water temperature, and diet. The LEFPC watershed was divided into five modeling reaches, and fluxes and concentrations are assessed at this spatial scale. Following are the key findings of the field and laboratory studies and the watershed and bioaccumulation modeling: •The greatest flux of total mercury (HgT) in LEFPC is related to stormflow transport of Hg-contaminated solids entering the creek because of bank erosion in the upper reaches of the creek. • The second greatest flux originates from upper EFPC (Station 17 representing the exit stream sampling point near the boundary of the Y-12 Complex), and appears to control base flow fluxes. • The observed increase in MeHg concentration and flux from upstream to downstream is related primarily to instream methylation by periphyton and other biological activity. • A meaningful substantial reduction of the HgT flux in LEFPC would require addressing the flux of HgT originating from bank erosion and from Station 17. • Actions to reduce LEFPC floodplain leaching and runoff would not produce much of an impact on HgT or MeHg concentrations or fluxes unless other major sources are eliminated first. This project addresses the Action Plan goal to evaluate the role of LEFPC bank soil sources and to consider the entire EFPC hydrologic system. Model conclusions are dependent on the data available at the time of this assessment. However, a robust understanding and quantification for some mercury-related parameters and relationships is still lacking; there is a continued need for field data collection and modeling improvements. Model predictions should be viewed cautiously, with comparisons of the magnitude of predictions between scenarios being more valid than absolute predictions of concentrations or fluxes. With continued updates and refinement, the watershed-scale model can be a useful, valuable tool for future EFPC research prioritization, technology development, and remedial decision-making.
[en] The purpose of this report is to assess new data that has become available and provide an update to the evaluations and modeling presented in the Oak Ridge National Laboratory (ORNL) Technical Manuscript Evaluation of lower East Fork Poplar Creek (LEFPC) Mercury Sources (Watson et al., 2016). Primary sources of field and laboratory data for this update include multiple US Department of Energy (DOE) programs including Environmental Management (EM; e.g., Biological Monitoring and Abatement Program, Mercury Remediation Technology Development [TD], and Applied Field Research Initiative), Office of Science (Mercury Science Focus Areas [SFA] project), and the Y-12 National Security Complex (Y-12) Compliance Department.