Toward real-time measurement of atmospheric mercury concentrations using cavity ring-down spectroscopy
Cavity ring-down spectroscopy (CRDS) is a direct absorption technique that utilizes path lengths up to multiple kilometers in a compact absorption cell and has a significantly higher sensitivity than conventional absorption spectroscopy. This tool opens new prospects for study of gaseous elemental m...
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2010-03-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/10/2879/2010/acp-10-2879-2010.pdf |
| _version_ | 1818007932924592128 |
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| author | X. Faïn H. Moosmüller D. Obrist |
| author_facet | X. Faïn H. Moosmüller D. Obrist |
| author_sort | X. Faïn |
| collection | DOAJ |
| description | Cavity ring-down spectroscopy (CRDS) is a direct absorption technique that utilizes path lengths up to multiple kilometers in a compact absorption cell and has a significantly higher sensitivity than conventional absorption spectroscopy. This tool opens new prospects for study of gaseous elemental mercury (Hg<sup>0</sup>) because of its high temporal resolution and reduced sample volume requirements (&lt;0.5 l of sample air). We developed a new sensor based on CRDS for measurement of (Hg<sup>0</sup>) mass concentration. Sensor characteristics include sub-ng m<sup>&minus;3</sup> detection limit and high temporal resolution using 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 Hg<sup>0</sup> absorption line on a pulse-to-pulse basis to facilitate differential absorption measurements. Hg<sup>0</sup> absorption measurements with this CRDS laboratory prototype are highly linearly related to Hg<sup>0</sup> concentrations determined by a Tekran 2537B analyzer over an Hg<sup>0</sup> concentration range from 0.2 ng m<sup>&minus;3</sup> to 573 ng m<sup>&minus;3</sup>, implying excellent linearity of both instruments. The current CRDS instrument has a sensitivity of 0.10 ng Hg<sup>0</sup> m<sup>&minus;3</sup> at 10-s time resolution. Ambient-air tests showed that background Hg<sup>0</sup> levels can be detected at low temporal resolution (i.e., 1 s), but also highlight a need for high-frequency (i.e., pulse-to-pulse) differential on/off-line tuning of the laser wavelength to account for instabilities of the CRDS system and variable background absorption interferences. Future applications may include ambient Hg<sup>0</sup> flux measurements with eddy covariance techniques, which require measurements of Hg<sup>0</sup> concentrations with sub-ng m<sup>&minus;3</sup> sensitivity and sub-second time resolution. |
| first_indexed | 2024-04-14T05:22:18Z |
| format | Article |
| id | doaj.art-320aa6ea7df840f988e9f73c27a338e5 |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-04-14T05:22:18Z |
| publishDate | 2010-03-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-320aa6ea7df840f988e9f73c27a338e52022-12-22T02:10:07ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242010-03-0110628792892Toward real-time measurement of atmospheric mercury concentrations using cavity ring-down spectroscopyX. FaïnH. MoosmüllerD. ObristCavity ring-down spectroscopy (CRDS) is a direct absorption technique that utilizes path lengths up to multiple kilometers in a compact absorption cell and has a significantly higher sensitivity than conventional absorption spectroscopy. This tool opens new prospects for study of gaseous elemental mercury (Hg<sup>0</sup>) because of its high temporal resolution and reduced sample volume requirements (&lt;0.5 l of sample air). We developed a new sensor based on CRDS for measurement of (Hg<sup>0</sup>) mass concentration. Sensor characteristics include sub-ng m<sup>&minus;3</sup> detection limit and high temporal resolution using 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 Hg<sup>0</sup> absorption line on a pulse-to-pulse basis to facilitate differential absorption measurements. Hg<sup>0</sup> absorption measurements with this CRDS laboratory prototype are highly linearly related to Hg<sup>0</sup> concentrations determined by a Tekran 2537B analyzer over an Hg<sup>0</sup> concentration range from 0.2 ng m<sup>&minus;3</sup> to 573 ng m<sup>&minus;3</sup>, implying excellent linearity of both instruments. The current CRDS instrument has a sensitivity of 0.10 ng Hg<sup>0</sup> m<sup>&minus;3</sup> at 10-s time resolution. Ambient-air tests showed that background Hg<sup>0</sup> levels can be detected at low temporal resolution (i.e., 1 s), but also highlight a need for high-frequency (i.e., pulse-to-pulse) differential on/off-line tuning of the laser wavelength to account for instabilities of the CRDS system and variable background absorption interferences. Future applications may include ambient Hg<sup>0</sup> flux measurements with eddy covariance techniques, which require measurements of Hg<sup>0</sup> concentrations with sub-ng m<sup>&minus;3</sup> sensitivity and sub-second time resolution.http://www.atmos-chem-phys.net/10/2879/2010/acp-10-2879-2010.pdf |
| spellingShingle | X. Faïn H. Moosmüller D. Obrist Toward real-time measurement of atmospheric mercury concentrations using cavity ring-down spectroscopy Atmospheric Chemistry and Physics |
| title | Toward real-time measurement of atmospheric mercury concentrations using cavity ring-down spectroscopy |
| title_full | Toward real-time measurement of atmospheric mercury concentrations using cavity ring-down spectroscopy |
| title_fullStr | Toward real-time measurement of atmospheric mercury concentrations using cavity ring-down spectroscopy |
| title_full_unstemmed | Toward real-time measurement of atmospheric mercury concentrations using cavity ring-down spectroscopy |
| title_short | Toward real-time measurement of atmospheric mercury concentrations using cavity ring-down spectroscopy |
| title_sort | toward real time measurement of atmospheric mercury concentrations using cavity ring down spectroscopy |
| url | http://www.atmos-chem-phys.net/10/2879/2010/acp-10-2879-2010.pdf |
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