America’s coal-fired power plants emit around 48 tons of mercury each year. Western Research Institute is working with the EPA, the National Institute for Standards and Technology (NIST), the power industry and instrument vendors to develop national protocols to define NIST traceability for mercury vapor pressure based calibration units.
The efforts of this broad partnership formed the basis for the preliminary draft traceability protocol issued by EPA in May 2007, the conceptual interim protocol issued in August 2007, and the finalized interim NIST traceability protocols for both elemental and oxidized mercury vapor calibrators issued on July 1, 2009.
WRI performed an extensive review of mercury continuous emission monitor (CEM) calibration technology for coal-fired power plants and generated data in support of the NIST traceability protocols. A mandatory QC check procedure to verify proper operation of an individual mercury calibrator was also developed by WRI and is included as Section 7.2.2 in the interim protocol for elemental mercury vapor calibrators.
Although continuous emission monitoring spectrometers only detect elemental mercury, the monitoring systems must also measure the mercury in oxidized mercury species, such as mercuric oxide and mercuric chloride, by converting them to elemental mercury. The WRI research team evaluated and confirmed the efficiency of the oxidized mercury generator technology to quantify the oxidation reaction.
WRI is currently evaluating output from evaporative mercuric chloride calibrators and comparing it with output from elemental mercury calibrators to resolve some outstanding technical issues before the protocols are promulgated in 2011.