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MONITORING THE RESPONSE TO CHANGING MERCURY DEPOSITION
Citation:
Mason, R. P., M. L. Abbott, D. Bodaly, O R. Bullock, C. T. Driscoll, D. Evers, S. E. Lindberg, M. Murray, AND E. Swain. MONITORING THE RESPONSE TO CHANGING MERCURY DEPOSITION. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 1:15A-22A, (2005).
Impact/Purpose:
The objective of this task is to improve EPA's ability to accurately predict the concentrations and deposition of air pollutants in the atmosphere that are known or suspected to cause cancer or other serious health effects to humans, or adverse environmental effects. It is an essential component of EPA's National Air Toxics Assessment (NATA), which seeks to identify and quantify the concentrations and sources of those hazardous air pollutants which are of greatest potential concern, in terms of contribution to population risk. It is a major contributor to NERL's Air Toxics Research Program.
"Air toxics" or "hazardous air pollutants" (HAPs) is a category that covers a large variety of chemicals, which range from relatively non reactive to extremely reactive; can exist in the gas, aqueous, and/or particle phases; display a large range of volatilities; experience varying deposition velocities, including in some cases revolatilization; and are emitted from a wide variety of sources at a large variety of different scales. In addition, concentrations of air toxics are needed by regulators for both short (days) as well as long (up to a year) time scales. These requirements challenge our current capabilities in air quality models far beyond the needs for other pollutants, such as ozone. The specific work being done under this task involves 1.) developing and testing chemical mechanisms which are appropriate for describing the chemistry of air toxics; 2.) incorporating these chemical and physical mechanisms into EPA's CMAQ modeling system and applying the model at a variety of scales; and 3.) developing the methods for using models to predict HAPs concentrations at subgrid or neighborhood scales; and 4.) using these tools to assess the magnitude and variability of concentrations to which urban populations are exposed.
Description:
There is a crucial need to document the impact and effectiveness of regulation of anthropogenic mercury (Hg) emissions on human, wildlife and ecosystem health to ascertain the need for further controls. The impact of elevated methylmercury (MeHg) levels in fish on human and wildlife populations is well documented and is the driver for current and impending controls. Scientists and policy makers need to develop a monitoring framework to accurately evaluate the effectiveness of regulation, and the monitoring strategy outlined below was the result of such an effort by a group of 32 Hg scientists from academia, industry, government and non-profit organizations. To monitor change in Hg loadings to aquatic systems and the resultant alteration in MeHg incorporation into fish and wildlife, the proposed monitoring strategy details the need for a comprehensive investigation (in air, water and the watershed) at 5-10 continentally- distributed locations (intensive sites). Additionally, it includes the collection of samples at a larger number of sites (cluster sites) that are widely distributed across freshwater and coastal ecosystems, but associated with the intensive sites. At the cluster sites, wet Hg deposition would be measured in conjunction with seasonal sediment and water collections for total Hg and MeHg. Biota sampling would consist of yearling fish, piscivorous fish and wildlife. To be successful, this program should begin without delay and last 15-20 years. Federal commitment and involvement would be required to maintain such a long-term monitoring effort. This monitoring framework would answer the question of whether change is occurring in atmospheric Hg input and how this change is reflected in a variety of aquatic ecosystems and in their organisms. In addition, this program would provide the information necessary to demonstrate the impact of Hg emission reductions from anthropogenic sources in the USA on fish MeHg concentration.
The United States Environmental Protection Agency through its Office of Research and Development partially funded and collaborated in the research descrived here. It has been subjected to Agency review and approved for publication.