Friday, April 24, 2009

Henry speaks: Mercury in the Onondaga Lake Remedy?

As part of the requirements of FOR496/797 Environmental Career Strategies for Women, students share responsibility for reporting on the presentations in the Women in Scientific and Environmental Professions Speaker Series.  The following was prepared by Liz Canal, Rebecca Maurer, and Shavaun Jenkins.

Dr. Betsy Henry, Senior Managing Scientist, Exponent, Schenectady, launched SUNY ESF’s 2009 Women in Scientific and Environmental Professions Speaker Series with  Mercury in the Onondaga Lake Remedy on February 24. The Department of Chemistry and the ESF Women’s Caucus jointly sponsored the seminar.
Dr. Henry discussed the background of mercury contamination including the global mercury cycle over the last 20 years, US fish consumption advisories, analysis of mercury in water, and the mercury transformation processes in aquatic systems.  Attention was then focused on the history of mercury bioaccumulation in Onondaga Lake and the remedial investigation that took place from 1992-2001, as well Exponent’s involvement with that process.  
Dr. Henry is working with Honeywell International (formerly AlliedSignal) and the DEC to clean up Allied’s mass depositing of mercury over the years. Mercury had been used as an electrode in the production of chlorine, caustic potash (KOH) and caustic soda (NaOH); briny groundwater made Syracuse uniquely suited for these industries.  Elemental mercury is of particular concern because of its potential to methylate in non-oxygen environments such as deep water and sediment.  Methylmercury is a soluable neurotoxin that bioaccumulates, becoming more concentrated as larger fish eat smaller ones. 
Henry explained that Honeywell, DEC & EPA had been working toward “a phase of a consent decree” on how the lake could be cleaned.  The data took over a decade to collect and assisted in creating a feasibility study, where all the alternatives to cleaning the lake were evaluated. January 2007 marked the beginning of the five year design schedule that would allow the cleaning of the sediment from the lake to actually begin.
The first step in remediation was to decrease external sources of mercury contamination from former Allied Signal, particularly the former LCP Bridge Street Plant, Metropolitan Syracuse Wastewater Treatment Plant (METRO), and groundwater infiltration in 2007.  Soil washing has separated more than 7 tons of elemental mercury from 85 tons of processed soil.  To stop groundwater infiltration, a barrier wall was set up from 35 to 70 feet in depth.  The groundwater that would have entered Onondaga Lake is now pumped to a treatment plant.  The next step in the Remedy will be elimination of mercury through dredging and capping.   “Natural recovery” will be monitored for the two-thirds of the lake bottom where clean lake sediment is burying the contaminated waste sediment.  Additions of oxygen and nitrate are planned to delay the production of additional methylmercury, and Onondaga County is spending $500 million to stop polluting the lake with sewage by 2012. These steps are designed to meet the remedial goal of reducing mercury concentration in sediment, water, and fish tissue to levels that are “protective of human health and environment.”   
In 2012 they will “get inside the lake to address internal processes” including resuspension of in-lake waste deposits, which are primarily made up of calcium carbonate (CaCO3); methane gas ebullition, poor water diffusion, and methyl mercury production.
Dr. Henry’s experience includes management of investigations, risk assessment, and agency negotiations at some of the most prominent mercury sites in the country. With a broad background in the transport and fate of contaminants in the environment, Dr. Henry specialty is in the transport, fate, and bioaccumulation of mercury in both terrestrial and aquatic systems. More recently, she has worked closely with engineers during remedial design to understand and address risks associated with mercury contamination.
Dr. Henry received her B.S. in agronomy from Colorado State University and her Ph.D. in Environmental Engineering from Harvard University.  In addition to her position with Exponent, she serves as president of ReTree Schenectady, a non-profit organization dedicated to the planting, care, and conservation of current and future generations of trees in the City of Schenectady. 
 For more information about the Women in Scientific and Environmental Professions Speaker Series, please visit

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