USGS Washington Water Science Center
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9722-D6M - Potential Sources of Mercury in Sinclair Inlet (Operable Unit B, Marine, Bremerton Naval Complex)
Problem - Operable Unit B (OU B) Terrestrial and OU B Marine are two of six operable units at the Bremerton Naval Complex (BNC). Elevated levels of various inorganic and organic chemicals have been found in OU B Terrestrial and the sediments of Sinclair Inlet, in which OU B Marine is located. One of the primary issues remaining at the site is that there is insufficient information to determine whether remedial action taken at OU B Marine with respect to mercury in sediment is protective of ingestion of mercury through rockfish consumption by subsistence fishers.
Objectives - Objectives -- The overall objective of this study is to estimate the magnitudes of the different predominant sources of mercury to OU B Marine (Sinclair Inlet) at the BNC, the transformation of Hg to a bioavailable form (methyl-mercury) in OU B, and the impact of the sources and transformation processes on the mercury burden in marine organisms. The individual primary objectives are:
Objective 1 - Describe the sources of mercury to Sinclair Inlet and their relationship with mercury concentrations in fish tissue using mainly existing data, and new or slightly refined applications of existing models.
Objective 2 - Describe the occurrence of methyl-mercury in fresh-water sources of mercury in the marine-water column and in the pore water of Sinclair Inlet sediments.
Objective 3 - Evaluate the submarine discharge of mercury from the ground-water system represented by monitoring well LTMP-3.
Objective 4 - Collect six stormwater samples and prepare a report on Objectives 1-3.
Objective 5 - Describe and quantify the biogeochemical processes that lead to methylation of mercury in sediments, the release of methylmercury and ionic mercury from sediments, and the bioaccumulation of methylmercury into the base of the pelagic food web.
Objective 6 - Prepare Report on methylation processes in Sinclair Inlet (Objective 5)
Objective 7 - Define if there is a source of mercury for well LTMP-5, similar to what has been defined for LTMP-3 under objective 3. (combined with Objective 8 to form objective 12)
Objective 8 - Estimate the loading of dissolved and particulate mercury from the largest storm drain on the BNC in a manner that includes the release of mercury to Sinclair Inlet by tidal pumping of seawater through the storm drain. (combined with objective 7 to form objective 12)
Objective 9 - Measure the loadings of mercury from the storm drain PSNS015 during two ebbing tides from a tidal height of greater than 12 ft mean lower low water (MLLW) during a dry period.
Objective 10 - Revise Report on Sources and Sink of Total Mercury in Sinclair Inlet in the absence of total suspended loadings data by quantifying sources and sinks of filtered total mercury and qualitatively comparing concentration of total mercury of solids from sources, in sediment and in solids suspended in the water column
Objective 11 - Update loadings due to changes in operations of the steam plant and reduce the uncertainty of loadings of dry dock discharges and streams.
Objective 12 - Examine the facilitation of total mercury release to Sinclair Inlet by tidally influenced stormdrains.
Task A (previous objective 7). Examine the releases of total mercury by flushing of seawater landward through storm drains into groundwater from two filled areas of the Bremerton naval complex that have elevated concentrations of total mercury in soil, and have not been previously investigated.
Task B (previous objective 8). Identify the geographical location, the temporal variability and the geochemical mechanism that leads to release of total mercury to freshwater transported by the most extensive stormwater drainage basin on the Bremerton naval complex
Relevance and Benefits - Through Objectives 1 to 4, this study will address the first long-term goal of the USGS 2007-2017 Strategic Science Directions, to monitor and report on the state of the Nation’s terrestrial, freshwater, and coastal ecosystems, and to study the causes and consequences of ecological change. Conducting a basin-wide assessment of the source and transport of a contaminant is one the major goals of the USGS Washington Water Science Center. The study serves a local need to develop a better understanding of the relation between sources, processes, and concentrations of mercury in Sinclair Inlet. Through Objective 5, this study will address the first long-term goal of the USGS 2007-2017 Strategic Science Directions, to monitor and report on the state of the Nation’s terrestrial, freshwater, and coastal ecosystems, and to study the causes and consequences of ecological change. Conducting a basinwide assessment of the source and transport of contaminants is a major direction of the USGS Washington Water Science Center’s Strategic Plan. The study will serve a local need to develop a better understanding of the relation between sources, processes, and concentrations of mercury in Sinclair Inlet.
Approach - Objectives 1 to 4 of this proposed study will be met through three general approaches over three fiscal years. First, available data on concentrations of mercury in the tissue of various marine organisms from Sinclair Inlet and other waters of Puget Sound will be used to assess whether mercury concentrations in Sinclair Inlet biota, especially fin fish, are elevated relative to biota in other areas of Puget Sound. Second, a survey of methyl-mercury within the marine environment of Sinclair Inlet and known sources of mercury to Sinclair Inlet that also could contribute methyl-mercury will be conducted. Finally, ground-water discharges to Sinclair Inlet from an area in OU B Terrestrial particularly high in mercury will be defined, along with mercury flux and the degree to which mercury-methylation is occurring in the shallow nearshore ground-water system. For Objective 5, seasonal surveys of the potential of sediments to methylate mercury will be conducted at 20 sites in Sinclair Inlet in the winter, spring, and summer of 2009. The measure of methylation potential combined with the analysis of reactive mercury will be used to assess the overall production of mercury in the inlet. At six of the twenty sites, the production estimates of the methylation potential measurements will be assessed by multiple measurements of the flux of total mercury and methylmercury from the sediments using core incubation experiments. Finally, the production and flux of methylmercury in the sediments will be related to living marine resources by monthly surveys of the concentrations of filtered and particulate total mercury and methylmercury in the water column and the concentrations of biologically available methylmercury in zooplankton and, as feasible, in phytoplankton. This project will also take advantage of the scheduled sampling effort in August 2008 as part of the current ongoing Sinclair Inlet study, and will gather preliminary data on concentrations of methylmercury in biota, the methylation potential of sediments, and the flux of methylmercury from sediments in order to refine the sampling and experimental parameters that will be used in 2009 for this proposed study.