Lake Whatcom Completed

9722-9HM - Elevated Levels of Mercury in Lake Whatcom Fish -- Identification of Potential Sources and Contributing Factors with Recommendations for Additional Sampling Needed to Determine Sources - Completed FY2004

Problem - Elevated levels of mercury have been detected in fish and sediment collected from Lake Whatcom, a large, natural lake located in Whatcom County, Washington. The lake is a source of drinking water for about 86,000 people, and it is used extensively for sport fishing, swimming, and other types of recreation. Possible sources of mercury in Lake Whatcom are atmospheric deposition, tributary discharges, landfills, dumpsites, and local mining operations. Local interest has focused on a nearby chloralkali plant that discharged mercury to the atmosphere from early 1960s until the late 1900s.

Objectives

The objectives of this study are to:

1. Estimate the relative importance of potential sources of mercury in the Lake Whatcom watershed and in the basin draining to the middle fork of the Nooksack River by examining the relation between concentrations of mercury in surface sediments of the lake and the proximity of the potential sources or locations where runoff from the potential source areas enters the lake.
2. Determine if accumulation rates of mercury in Lake Whatcom and other nearby lakes are different than what can be attributed to global sources and use rate differences along with other data to infer the effects of known local and regional sources of airborne mercury.
3. Utilize available data on concentrations of mercury in the tissue of fish from Lake Whatcom and other local lakes to help identify sources of mercury.
4. Investigate the possibility that geochemical, biological, and physical processes occurring in Lake Whatcom or in connected wetlands affect the distribution of mercury in fish tissue and sediment.
5. Recommend additional sampling or other information needed to confirm sources and refine the understanding of processes identified by completing the first three objectives.

Relevance and Benefits - This study will address the second long-term goal of the USGS 2000-2005 Strategic Plan to maintain, provide and improve long-term environmental and natural resources information, systematic analyses and investigations, and predictive tools for scenario building and decision making about natural systems. Conducting a basin-wide assessment of the source and transport of a contaminant is one of the major goals of the USGS Washington Water Science Center Science Plan. The study serves a local need to develop a better understanding of the relation between sources, processes, and concentrations of mercury in Lake Whatcom.

Approach - The study will assess the importance of potential sources of mercury in Lake Whatcom by comparing spatial variations in concentrations in sediment and fish with the proximity of sources (or zone of influence in the case of local airborne sources) and by comparing the rates of accumulation of mercury in sediments of Lake Whatcom and other local lakes with global rates and with each other. Concentrations of methylmercury in sediments from Lake Whatcom and available data on concentrations of mercury in Lake Whatcom fish will be compared to assess the effects of mercury speciation on concentrations. The study relies to a great extent on available data, including potential sources of mercury and concentrations of mercury in sediment and fish of Lake Whatcom and other local lakes. Mercury accumulation rates and levels of methylmercury in sediments of Lake Whatcom will be determined by a study to be conducted by the Washington State Department of Ecology. This study will work closely with that study and fund the sampling and analysis of core samples from five other local lakes.