scholarly journals The effects of meteorological parameters and diffusive barrier reuse on the sampling rate of a passive air sampler for gaseous mercury

2017 ◽  
Vol 10 (10) ◽  
pp. 3651-3660 ◽  
Author(s):  
David S. McLagan ◽  
Carl P. J. Mitchell ◽  
Haiyong Huang ◽  
Batual Abdul Hussain ◽  
Ying Duan Lei ◽  
...  
Keyword(s):  
Wind Speed ◽  
Meteorological Parameters ◽  
Sampling Rate ◽  
Effect Of Temperature ◽  
Wind Speeds ◽  
Passive Air Sampler ◽  
Molecular Diffusivity ◽  
Air Sampler ◽  
Gaseous Mercury ◽  
High Level

Abstract. Passive air sampling of gaseous mercury (Hg) requires a high level of accuracy to discriminate small differences in atmospheric concentrations. Meteorological parameters have the potential to decrease this accuracy by impacting the sampling rate (SR), i.e., the volume of air that is effectively stripped of gaseous mercury per unit of time. We measured the SR of a recently calibrated passive air sampler for gaseous Hg in the laboratory under varying wind speeds (wind still to 6 m s−1), temperatures (−15 to +35 °C), and relative humidities (44 to 80 %). While relative humidity has no impact on SR, SR increases slightly with both wind speed (0.003 m3 day−1 increase in SR or 2.5 % of the previously calibrated SR for every m s−1 increase for wind speeds  > 1 m s−1, typical of outdoor deployments) and temperature (0.001 m3 day−1 increase in SR or 0.7 % for every 1 °C increase). The temperature dependence can be fully explained by the effect of temperature on the molecular diffusivity of gaseous mercury in air. Although these effects are relatively small, accuracy can be improved by adjusting SRs using measured or estimated temperature and wind speed data at or near sampling sites. We also assessed the possibility of reusing Radiello® diffusive barriers previously used in the passive air samplers. The mean rate of gaseous Hg uptake was not significantly different between new and previously used diffusive barriers in both lab and outdoor deployments, irrespective of the applied cleaning procedure. No memory effect from Radiellos® previously deployed in a high Hg atmosphere was observed. However, a loss in replicate precision for the dirtiest Radiellos® in the indoor experiment suggests that cleaning is advisable prior to reuse.

scholarly journals The effects of meteorological parameters and diffusive barrier reuse on the sampling rate of a passive air sampler for gaseous mercury

2017 ◽  
Author(s):  
David S. McLagan ◽  
Carl P. J. Mitchell ◽  
Haiyong Huang ◽  
Batual Abdul Hussain ◽  
Ying Duan Lei ◽  
...  
Keyword(s):  
Wind Speed ◽  
Meteorological Parameters ◽  
Sampling Rate ◽  
Effect Of Temperature ◽  
Wind Speeds ◽  
Passive Air Sampler ◽  
Molecular Diffusivity ◽  
Air Sampler ◽  
Gaseous Mercury ◽  
High Level

Abstract. Passive air sampling of gaseous mercury (Hg) requires a high level of accuracy to discriminate small differences in atmospheric concentrations. Meteorological parameters have the potential to decrease this accuracy by impacting the sampling rate (SR), i.e., the volume of air that is effectively stripped of gaseous mercury per unit of time. We measured the SR of a recently calibrated passive air sampler for gaseous Hg in the laboratory under varying wind speeds (wind-still – 6 m s−1), temperatures (−15–35 °C), and relative humidities (44–80 %). While relative humidity has no impact on SR, SR increases slightly with both wind speed (0.003 m3 day−1 increase in SR or 2.5 % of the previously calibrated SR for every m s−1 increase for wind speeds > 1 m s−1, typical of outdoor deployments) and temperature (0.001 m3 day−1 increase in SR or 0.7 % for every 1 °C increase). The temperature dependence can be fully explained by the effect of temperature on the molecular diffusivity of gaseous mercury in air. Although these effects are relatively small, accuracy can be improved by adjusting SRs using measured or estimated temperature and wind speed data at or near sampling sites. We also assessed the possibility of reusing Radiello® diffusive barriers previously used in the passive air samplers. The mean rate of gaseous Hg uptake was not significantly different between new and previously used diffusive barriers in both lab and outdoor deployments, irrespective of the applied cleaning procedure. No memory effect from Radiellos® previously deployed in a high Hg atmosphere was observed. However, a loss in replicate precision for the dirtiest Radiellos® in the indoor experiment suggests that cleaning is advisable prior to reuse.

scholarly journals A High-Precision Passive Air Sampler for Gaseous Mercury

2015 ◽  
Vol 3 (1) ◽  
pp. 24-29 ◽  
Author(s):  
David S. McLagan ◽  
Carl P. J. Mitchell ◽  
Haiyong Huang ◽  
Ying Duan Lei ◽  
Amanda S. Cole ◽  
...  
Keyword(s):  
High Precision ◽  
Passive Air Sampler ◽  
Air Sampler ◽  
Gaseous Mercury

scholarly journals Experimental Evaluations of Sampling Rate for Passive Air Sampler

2016 ◽  
Vol 26 (4) ◽  
pp. 203-210 ◽  
Author(s):  
Takahiro ISHIZAKA ◽  
Ayato KAWASHIMA
Keyword(s):  
Sampling Rate ◽  
Passive Air Sampler ◽  
Air Sampler

scholarly journals Supplementary material to "Global evaluation and calibration of a passive air sampler for gaseous mercury"

2018 ◽  
Author(s):  
David S. McLagan ◽  
Carl P. J. Mitchell ◽  
Alexandra Steffen ◽  
Hayley Hung ◽  
Cecilia Shin ◽  
...  
Keyword(s):  
Global Evaluation ◽  
Passive Air Sampler ◽  
Air Sampler ◽  
Gaseous Mercury ◽  
Supplementary Material

scholarly journals Global evaluation and calibration of a passive air sampler for gaseous mercury

2018 ◽  
Vol 18 (8) ◽  
pp. 5905-5919 ◽  
Author(s):  
David S. McLagan ◽  
Carl P. J. Mitchell ◽  
Alexandra Steffen ◽  
Hayley Hung ◽  
Cecilia Shin ◽  
...  
Keyword(s):  
Sampling Rate ◽  
Ease Of Use ◽  
Global Evaluation ◽  
Data Set ◽  
Wind Speeds ◽  
Industry Standard ◽  
Gaseous Mercury ◽  
Wide Range ◽  
The Difference ◽  
Very High

Abstract. Passive air samplers (PASs) for gaseous mercury (Hg) were deployed for time periods between 1 month and 1 year at 20 sites across the globe with continuous atmospheric Hg monitoring using active Tekran instruments. The purpose was to evaluate the accuracy of the PAS vis-à-vis the industry standard active instruments and to determine a sampling rate (SR; the volume of air stripped of gaseous Hg per unit of time) that is applicable across a wide range of conditions. The sites spanned a wide range of latitudes, altitudes, meteorological conditions, and gaseous Hg concentrations. Precision, based on 378 replicated deployments performed by numerous personnel at multiple sites, is 3.6 ± 3.0 %1, confirming the PAS's excellent reproducibility and ease of use. Using a SR previously determined at a single site, gaseous Hg concentrations derived from the globally distributed PASs deviate from Tekran-based concentrations by 14.2 ± 10 %. A recalibration using the entire new data set yields a slightly higher SR of 0.1354 ± 0.016 m3 day−1. When concentrations are derived from the PAS using this revised SR the difference between concentrations from active and passive sampling is reduced to 8.8 ± 7.5 %. At the mean gaseous Hg concentration across the study sites of 1.54 ng m−3, this represents an ability to resolve concentrations to within 0.13 ng m−3. Adjusting the sampling rate to deployment specific temperatures and wind speeds does not decrease the difference in active–passive concentration further (8.7 ± 5.7 %), but reduces its variability by leading to better agreement in Hg concentrations measured at sites with very high and very low temperatures and very high wind speeds. This value (8.7 ± 5.7 %) represents a conservative assessment of the overall uncertainty of the PAS due to inherent uncertainties of the Tekran instruments. Going forward, the recalibrated SR adjusted for temperature and wind speed should be used, especially if conditions are highly variable or deviate considerably from the average of the deployments in this study (9.89 ∘C, 3.41 m s−1). Overall, the study demonstrates that the sampler is capable of recording background gaseous Hg concentrations across a wide range of environmental conditions with accuracy similar to that of industry standard active sampling instruments. Results at sites with active speciation units were inconclusive on whether the PASs take up total gaseous Hg or solely gaseous elemental Hg primarily because gaseous oxidized Hg concentrations were in a similar range as the uncertainty of the PAS.

scholarly journals Global evaluation and calibration of a passive air sampler for gaseous mercury

2018 ◽  
Author(s):  
David S. McLagan ◽  
Carl P. J. Mitchell ◽  
Alexandra Steffen ◽  
Hayley Hung ◽  
Cecilia Shin ◽  
...  
Keyword(s):  
Sampling Rate ◽  
Ease Of Use ◽  
Global Evaluation ◽  
Data Set ◽  
Wind Speeds ◽  
Industry Standard ◽  
Gaseous Mercury ◽  
Wide Range ◽  
The Difference ◽  
Very High

Abstract. Passive air samplers (PASs) for gaseous mercury (Hg) were deployed for time periods between 1 month and 1 year at 20 sites across the globe with continuous atmospheric Hg monitoring using active Tekran instruments. The purpose was to evaluate the accuracy of the PAS vis-à-vis the industry standard active instruments and to determine a sampling rate (SR; the volume of air stripped of gaseous Hg per unit of time) that is applicable across a broad variety of conditions. The sites spanned a wide range of latitudes, altitudes, meteorological conditions, and gaseous Hg concentrations. Precision, based on 378 replicated deployments performed by numerous personnel at multiple sites, is 3.6 ± 3.0 %*, confirming the PAS's excellent reproducibility and ease-of-use. Using a SR previously determined at a single site, gaseous Hg concentrations derived from the globally distributed PASs deviate from Tekran-based concentrations by 14.2 ± 10 %. A recalibration using the entire new data set yields a slightly higher SR of 0.1354 ± 0.016 m3 day−1. When concentrations are derived from the PAS using this revised SR the difference is reduced to 8.8 ± 7.5 %. At the mean gaseous Hg concentration across the study sites of 1.54 ng m−3, this represents an ability to resolve concentrations to within 0.13 ng m−3. Adjusting the sampling rate to deployment specific temperatures and wind speeds does not decrease the difference in active–passive concentration further (8.7 ± 5.7 %), but reduces its variability by leading to better agreement in Hg concentrations measured at sites with very high and very low temperatures and very high wind speeds. This value (8.7 ± 5.7 %) represents a conservative assessment of the overall uncertainty of the PAS due to inherent uncertainties of the Tekran instruments. Going forward, the recalibrated SR adjusted for temperature and wind speed should be used, especially if conditions are highly variable or deviate considerably from the average of the deployments in this study (9.89 °C, 3.41 m s−1). Overall, the study demonstrates that the sampler is capable of recording background gaseous Hg concentrations across a wide range of environmental conditions with accuracy similar to that of industry standard active sampling instruments. Results at sites with active speciation units were inconclusive on whether the PASs take up total gaseous Hg or solely gaseous elemental Hg primarily because gaseous oxidized Hg concentrations were in a similar range as the uncertainty of the PAS.

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