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Characteristics and Performances of a Nanostructured Material for Passive Samplers of Gaseous Hg
 
 
Article

Validating an Evaporative Calibrator for Gaseous Oxidized Mercury

1
Jožef Stefan International Postgraduate School, Jamova Cesta 39, 1000 Ljubljana, Slovenia
2
Department of Environmental Sciences, Jožef Stefan Institute, Jamova Cesta 39, 1000 Ljubljana, Slovenia
3
Laboratorio de Análisis por Activación Neutrónica, Centro Atómico Bariloche, Av. Bustillo km 9.5, Bariloche 8400, Argentina
*
Author to whom correspondence should be addressed.
Academic Editor: Eduard Llobet
Sensors 2021, 21(7), 2501; https://doi.org/10.3390/s21072501
Received: 23 February 2021 / Revised: 30 March 2021 / Accepted: 1 April 2021 / Published: 3 April 2021
(This article belongs to the Special Issue Global Mercury Assessment Sensing Strategies)
Understanding atmospheric mercury chemistry is the key for explaining the biogeochemical cycle of mercury and for improving the predictive capability of computational models. Increased efforts are being made to ensure comparable Hg speciation measurements in the air through establishing metrological traceability. While traceability for elemental mercury has been recently set, this is by no means the case for gaseous oxidized mercury (GOM). Since a calibration unit suitable for traceable GOM calibrations based on evaporation of HgCl2 solution was recently developed, the purpose of our work was to extensively evaluate its performance. A highly specific and sensitive 197Hg radiotracer was used for validation over a wide range of concentrations. By comparing experimental and calculated values, we obtained recoveries for the calibration unit. The average recoveries ranged from 88.5% for 1178 ng m−3 HgCl2 gas concentration to 39.4% for 5.90 ng m−3 HgCl2 gas concentration. The losses were due to the adsorption of oxidized Hg on the inner walls of the calibrator and tubing. An adsorption isotherm was applied to estimate adsorption enthalpy (ΔHads); a ΔHads value of −12.33 kJ mol−1 was obtained, suggesting exothermal adsorption. The results of the calibrator performance evaluation suggest that a newly developed calibration unit is only suitable for concentrations of HgCl2 higher than 1 µg m−3. The concentration dependence of recoveries prevents the system from being used for calibration of instruments for ambient GOM measurements. Moreover, the previously assessed uncertainty of this unit at µg m−3 level (2.0%, k = 2) was re-evaluated by including uncertainty related to recovery and was found to be 4.1%, k = 2. Calibrator performance was also evaluated for HgBr2 gas calibration; the recoveries were much lower for HgBr2 gas than for HgCl2 gas even at a high HgBr2 gas concentration (>1 µg m−3). As HgBr2 is often used as a proxy for various atmospheric HgBr species, the suitability of the unit for such calibration must be further developed. View Full-Text
Keywords: gaseous oxidized mercury; traceability; calibration; 197Hg radiotracer gaseous oxidized mercury; traceability; calibration; 197Hg radiotracer
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MDPI and ACS Style

Gačnik, J.; Živković, I.; Ribeiro Guevara, S.; Jaćimović, R.; Kotnik, J.; Horvat, M. Validating an Evaporative Calibrator for Gaseous Oxidized Mercury. Sensors 2021, 21, 2501. https://doi.org/10.3390/s21072501

AMA Style

Gačnik J, Živković I, Ribeiro Guevara S, Jaćimović R, Kotnik J, Horvat M. Validating an Evaporative Calibrator for Gaseous Oxidized Mercury. Sensors. 2021; 21(7):2501. https://doi.org/10.3390/s21072501

Chicago/Turabian Style

Gačnik, Jan, Igor Živković, Sergio Ribeiro Guevara, Radojko Jaćimović, Jože Kotnik, and Milena Horvat. 2021. "Validating an Evaporative Calibrator for Gaseous Oxidized Mercury" Sensors 21, no. 7: 2501. https://doi.org/10.3390/s21072501

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