Atmos. Chem. Phys. Discuss., 9, 22143-22175, 2009
www.atmos-chem-phys-discuss.net/9/22143/2009/
doi:10.5194/acpd-9-22143-2009
© Author(s) 2009. This work is distributed
under the Creative Commons Attribution 3.0 License.
Review Status
This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Toward a real-time measurement of atmospheric mercury concentrations using cavity ring-down spectroscopy
X. Faïn, H. Moosmüller, and D. Obrist
Division of Atmospheric Sciences, Desert Research Institute, 2215 Raggio Parkway, Reno, NV 89512, USA

Abstract. A new sensor based on cavity ring-down spectroscopy (CRDS) has been developed for the measurement of gaseous elemental mercury (Hg0) mass concentration with sub-ng m−3 detection limit and high temporal resolution. Cavity ring-down spectroscopy is a direct absorption technique that utilizes path lengths of up to multiple kilometers in a compact absorption cell and has a significantly higher sensitivity than conventional absorption spectroscopy. Our prototype uses a frequency-doubled, tuneable dye laser emitting pulses at ~253.65 nm with a pulse repetition frequency of 50 Hz. The dye laser incorporates a unique piezo element attached to its tuning grating allowing it to tune the laser on and off the Hg0 absorption line on a pulse to pulse basis to facilitate differential absorption measurements. Hg0 absorption measurements with this CRDS laboratory prototype are highly linearly related to Hg0 concentrations determined by a Tekran 2537B analyzer over a Hg0 concentration range of four orders of magnitude, from 0.2 ng m−3 to 573 ng m−3 implying excellent linearity of both instruments. The current CRDS instrument has a~sensitivity of 0.10 ng m−3 at 10 s time resolution. This tool opens new prospects for the study of Hg0 because of its high temporal resolution and reduced limited sample volume requirements (<0.5 l of sample air). Future applications may include ambient Hg0 flux measurements with eddy covariance techniques, which require measurements of Hg0 concentrations with sub-ng m−3 sensitivity and sub-second time resolution.

Citation: Faïn, X., Moosmüller, H., and Obrist, D.: Toward a real-time measurement of atmospheric mercury concentrations using cavity ring-down spectroscopy, Atmos. Chem. Phys. Discuss., 9, 22143-22175, doi:10.5194/acpd-9-22143-2009, 2009.
 
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