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| Titel |
Deployment of a sequential two-photon laser-induced fluorescence sensor for the detection of gaseous elemental mercury at ambient levels: fast, specific, ultrasensitive detection with parts-per-quadrillion sensitivity |
| VerfasserIn |
D. Bauer, S. Everhart, J. Remeika, C. Tatum Ernest, A. J. Hynes |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 7, no. 12 ; Nr. 7, no. 12 (2014-12-08), S.4251-4265 |
| Datensatznummer |
250115983
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| Publikation (Nr.) |
 copernicus.org/amt-7-4251-2014.pdf |
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| Zusammenfassung |
| The operation of a laser-based sensor for gas-phase elemental mercury,
Hg(0), is described. It utilizes sequential two-photon laser excitation with
detection of blue-shifted laser-induced fluorescence (LIF) to provide a
highly specific detection scheme that precludes detection of anything other
than atomic mercury. It has high sensitivity, fast temporal resolution, and
can be deployed for in situ measurements in the open atmosphere with
essentially no perturbation of the environment. An ambient sample can also
be pulled through a fluorescence cell, allowing for standard addition
calibrations of the concentration. No type of preconcentration is required
and there appears to be no significant interferences from other atmospheric
constituents, including gas-phase oxidized mercury species. As a consequence,
it is not necessary to remove oxidized mercury, commonly referred to as
reactive gaseous mercury (RGM), from the air sample. The instrument has been
deployed as part of an instrument intercomparison and compares well with
conventional instrumentation that utilizes preconcentration on gold followed
by analysis using cold-vapor atomic fluorescence spectroscopy (CVAFS).
Currently, the achievable detection sensitivity is ~ 15 pg m−3
(~ 5 × 104 atoms cm−3, ~ 2 ppq)
at a sampling rate of 0.1 Hz, i.e., averaging 100 shots with a 10 Hz
laser system. Preliminary results are described for a 50 Hz instrument that
utilizes a modified excitation sequence and has monitored ambient elemental
mercury with an effective sampling rate of 10 Hz. Additional work is required
to produce the precision necessary to perform eddy correlation measurements.
Addition of a pyrolysis channel should allow for the measurement of total
gaseous mercury (TGM) and hence RGM (by difference) with good sensitivity
and time resolution. |
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