Cooperator: Toxic Substances Hydrology Program, U.S. Geological Survey, Reston, VA
Project Chief: David P. Krabbenhoft
Location: Nationwide
Project Number: AK710
Period of Project: July 2001–June 2010
Problem
Concerns about environmental mercury pollution and contamination of aquatic food webs stem largely from the human and wildlife health risks of dietary exposure to methylmercury, the dominant form of mercury in the edible flesh of fish and aquatic mammals. The widespread nature and adverse consequences of mercury pollution continue to prompt considerable scientific investigation, and the environmental sources, biogeochemistry, transformations, transport, fate, and effects of mercury in the environment are subjects of frequent symposia, workshops, and a large steadily expanding body of scientific literature.
Objective
The Mercury in Aquatic Ecosystems project, coordinated by the Wisconsin District Mercury Research Laboratory (WDMRL) has several overall objectives that seek to provide critical information to aid in the definition of the mercury problem and seek possible solutions or mitigation strategies. These goals are: (1) to clarify the broader mercury problem from a scientific perspective, (2) conduct research that will provide critical (but previously unavailable) information for resource managers and decision makers on what should be done to improve environmental mercury conditions, (3) continue to provide scientific leadership (within the USGS and nationally and internationally) for the planning and execution of investigations of mercury biogeochemistry, transformations, transport, and fate in the environment, and (4) serve as an intra-agency and inter-agency communication and coordination point for mercury research.
Approach
To achieve these goals, the Wisconsin District Mercury Research Team is conducting a variety of field-oriented studies. First, in the summer of 2002 we are continuing our collaboration with the NAWQA program to collect fish, water, and sediment samples from across the United States in a variety of watershed types. This synoptic type sampling will be followed by more intense sampling efforts in a few of the watersheds where the goal will be to provide a detailed understanding of the processes that control mercury bioaccumulation in food webs. In addition, the Mercury Research Team is involved in two “mercury-loading” studies in the Everglades of Florida and the Experimental Lakes Area (ELA) of Ontario, Canada, whereby the overall goal is to establish what the mercury dose to bioaccumulation response is for natural systems using traceable amounts of mercury stable isotopes. Previously, research of this kind has been conducted in laboratories or controlled environments where the natural response was not adequately represented. For the study site in Canada, we are dosing an entire watershed with three different stable isotopes of mercury (198Hg, 200Hg, and 202Hg), which are being added to the wetland, upland forests, and lake, respectively. By applying different stable isotopes to the three major components of the watershed, we will be able to track where the mercury comes from, and at what time scales, that accumulates in fish.
Progress (July 2003–June 2004)
During this time period, the Mercury Cycling in Aquatic Ecosystems project was active in a wide variety of settings across North America, evaluating the factors controlling mercury cycling and toxicity. These activities include studies at the following locations:
• The Yukon River Baseline project (Alaska)
• The Marcell Experimental Forest Sulfate Addition study (Minnesota)
• The New England Coastal Basins project (New England)
• Yellowstone National Park Mercury Emissions project (Wyoming)
• Lostwood National Wild Life Refuge Mercury Assessment project (North Dakota)
• Four Corners Source-Receptor Project (Colorado)
In addition, this project continues to focus a great deal of effort on the The Mercury Experiment to Assess Atmospheric Loadings in Canada and the U.S. (METAALICUS) project. The METAALICUS project is an internationally recognized whole-ecosystem loading experiment to assess environmental responses to changes in atmospheric loading of mercury. The USGS Mercury Research Lab is one of the principal participating investigators involved with the project, and serves as the lead group for conducting studies in the terrestrial and wetland sub-ecosystems, as well as watershed mass balances. This project is in the fourth of a five-year loading effort, in which three different stable isotopes of mercury are applied annually to the three major sub-ecosystems of the watershed (202Hg on the lake, 200Hg on the forest, and 198Hg on the wetland). Each year, the isotopic mercury additions are about 3–5 times the current ambient loading. The overall goal of the study is to assess the major processes regulating the fate and transport of newly deposited mercury to a watershed, and to determine the net effect on the food web. At the conclusion of the 5-year addition effort, the METAALICUS project will become a whole-ecosystem “mercury-reduction” study, which will probably have even more relevance to proposed mercury reduction regulations that are being considered throughout the U.S. and worldwide. As such, the METAALICUS project will serve a sentinel study for expected benefits to such regulations.
Plans (July 2004–June 2005)
Plans for this time period call for continued widespread efforts across a wide variety of ecosystem settings that will allow for a robust scientific assessment of the controlling factors of mercury cycling in aquatic ecosystems. In addition to the studies mentioned above, this project will include new study sites during this time period including a synoptic sampling effort of about 200 sensitive, high-elevation lakes in the eastern U.S. (from northern Maine to Pennsylvania), controls of mercury methylation in the Lake Pontchartrain Basin (Louisiana) and an assessment of the “mercury-halo effect” around known mercury emitters in the Milwaukee metropolitan area. |
