MRI: Development of a LASER Sensor for the Measurement of Elemental and Reactive Gaseous Mercury

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The Principal Investigators (PIs) will develop a novel laser based sensor for the detection of gas phase elemental mercury, Hg(0),and reactive gaseous mercury (RGM). The instrument will be based on a single 50 Hz, Nd-Yag laser that will be used to pump two compact dye lasers. Preliminary efforts by the PIs have shown this technology to be feasible. Upon completion, the instrument will be capable of measuring gaseous elemental mercury with a temporal resolution and precision that will allow for Hg(0) flux measurements to be made using the eddy correlation technique. The instrument, when configured for in-situ sampling for measurement of Hg(0) will achieve detection limits which match those of current instrumentation but in a significantly shorter time period. This improvement in temporal resolution and the detection approach offer significant advantages over current approaches for measurement of Hg(0) on aircraft platforms. The same instrument can be reconfigured to operate with presampling on denuders for the sampling of RGM. It will be possible to significantly reduce sampling time compared with current approaches and offer the possibility of temporal resolution necessary to obtain well resolved diurnal profiles of RGM. It also shows promise for the speciation of RGM using programmable thermal decomposition/desorption from denuders. This instrumentation will be used primarily for research and research training but it will be integrated into educational activities and it will improve exposure to, and increase access and use of, state-of-the-art laser systems by scientists, graduate and undergraduate students at the University of Miami. The ability to accurately measure the chemical speciation and deposition rates of elemental and reactive gaseous mercury has major implications for regulatory policy and the implementation of the U.S. Clean Air Mercury Rule.