A traceable and continuous flow calibration method for gaseous elemental mercury at low ambient concentrations
<p>The monitoring of low gaseous elemental mercury (GEM) concentrations in the atmosphere requires continuous high-resolution measurements and corresponding calibration capabilities. Currently, continuous calibration for GEM is still an issue at ambient concentrations (1–2 <span class="...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2024-02-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://amt.copernicus.org/articles/17/1217/2024/amt-17-1217-2024.pdf |
| Summary: | <p>The monitoring of low gaseous elemental mercury (GEM) concentrations in the atmosphere requires continuous high-resolution measurements and corresponding calibration capabilities. Currently, continuous calibration for GEM is still an issue at ambient concentrations (1–2 <span class="inline-formula">ng m<sup>−3</sup></span>). This paper presents a continuous flow calibration for GEM, traceable to NIST 3133 Standard Reference Material (SRM). This calibration approach was tested using a direct mercury analyser based on atomic absorption spectrometry with Zeeman background correction (Zeeman AAS). The produced continuous flow of GEM standard was obtained via the reduction of <span class="inline-formula">Hg<sup>2+</sup></span> from liquid NIST 3133 SRM and used for the traceable calibration of the Zeeman AAS device. Measurements of atmospheric GEM using the calibrated Zeeman AAS were compared with two methods: (1) manual gold amalgamation atomic fluorescence spectrometry (AFS) calibrated with the chemical reduction of NIST 3133 and (2) automated gold amalgamation AFS calibrated using the mercury bell-jar syringe technique. The comparisons showed that a factory-calibrated Zeeman AAS device underestimates concentrations under 10 <span class="inline-formula">ng m<sup>−3</sup></span> by up to 35 % relative to the two other methods of determination. However, when a calibration based on NIST 3133 SRM was used to perform a traceable calibration of the Zeeman AAS, the results were more comparable with other methods. The expanded relative combined uncertainty for the Zeeman AAS ranged from 8 % for measurements at the 40 <span class="inline-formula">ng m<sup>−3</sup></span> level to 91.6 % for concentrations under 5 <span class="inline-formula">ng m<sup>−3</sup></span> using the newly developed calibration system. High uncertainty for measurements performed under 5 <span class="inline-formula">ng m<sup>−3</sup></span> was mainly due to instrument noise and concentration variation in the samples.</p> |
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| ISSN: | 1867-1381 1867-8548 |