A Primer on Mercury: From the Classroom Bench to Serious Environmental Consequences
By Bill Byers (ASL Newsletter's guest writer)
Many of us may remember interacting with liquid mercury metal in chemistry classes. It has a fascinating shimmering appearance and a surface tension that causes it to form interesting beads when placed on a flat surface. Heavy objects, such as bricks, and lead weights will float on the surface of liquid mercury.
However, as a chemical in the environment, mercury is not nearly as playful. It is one of 12 pollutants listed by the U.S. Environmental Protection Agency (EPA) as persistent, bioaccumulative, and toxic chemicals (PBTs.) EPA's challenge in reducing risks from mercury stems from the pollutants' ability to travel long distances, transfer easily among air, water, and land, and linger for generations in people and the environment (that is, bioaccumulate.) For example, biomagnification of up to 106 occurs within aquatic food chains.
Coal-burning power plants are now the largest human-caused source of mercury emissions to the air in the United States, accounting for over 40 percent of all domestic human-caused mercury emissions.
The character of mercury as a global and local pollutant, combined with its increasingly more apparent toxicity, has resulted in a host of international accords, regional compacts, national regulations and state and local regulations. Along with the regulations, a need for high-precision analyses and testing of new technologies for mercury control has developed. CH2M HILL's Applied Sciences Laboratory (ASL) is very much in the thick of these important new technologies.
For example, ASL has conducted treatability studies to support the capture of mercury from a variety of sources, including coal-fired power plants. Amended Silicates, Inc., a CH2M HILL joint venture company established to commercialize a proprietary sorbent material designed to capture mercury from the flue gas of coal-fired power plants, has used ASL capabilities to support the development and testing of the sorbent. In addition, Tom Higgins/WDC has developed several novel technologies for capturing mercury from wastewater and air discharges from flue gas desulfurization systems in coal-fired power plants, with pilot testing conducted in ASL's facilities.
Since the mid 1990s, ASL has preformed total mercury measurement in environmental samples by cold vapor atomic absorption (CVAA) spectrophotometer, the gold standard instrument for high precision mercury analysis (down to 0.001 µg/L.) In 2006 ASL added cold vapor atomic fluorescence (CVAF) to measure ultra-trace levels of Hg (down to 0.0001 µg/L.) To add to these important capabilities, ASL is now installing instrumentation to analyze for methyl mercury. Methyl mercury is the specific form of mercury that passes along the food chain into the food we eat.
In many cases, Hg (both total and methyl) must be measured at levels below ubiquitous background levels. To do this on environmental samples requires careful planning and scrupulous care. Here again, ASL can assist in developing sampling plans and providing clean sampling supplies and protocols.
For assistance in understanding the unique requirements for mercury sampling and analysis, please don't hesitate to contact Kathy McKinley/CH2M HILL ASL Customer Services at 541.768.3144.
