A traceable and continuous flow calibration method for gaseous elemental mercury at low ambient concentrations

Andron, Teodor D.; Corns, Warren T.; Živković, Igor; Ali, Saeed Waqar; Vijayakumaran Nair, Sreekanth; Horvat, Milena

doi:https://doi.org/10.5194/amt-17-1217-2024

Articles | Volume 17, issue 4

https://doi.org/10.5194/amt-17-1217-2024

© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/amt-17-1217-2024

© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 17, issue 4

Research article

|

20 Feb 2024

Research article |

| 20 Feb 2024

A traceable and continuous flow calibration method for gaseous elemental mercury at low ambient concentrations

Teodor D. Andron, Warren T. Corns, Igor Živković, Saeed Waqar Ali, Sreekanth Vijayakumaran Nair, and Milena Horvat

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Final revised paper (published on 20 Feb 2024)
Supplement to the final revised paper
Preprint (discussion started on 21 Sep 2023)
Supplement to the preprint

Interactive discussion

Status: closed

RC1:
'Comment on amt-2023-169', Anonymous Referee #2, 11 Oct 2023

The sentence "The Hg-free air was assured by the pump of the Zeeman AAS system, being the difference between the flow of N2 coming from the impinger, and the flow of the pump." (line 148) is unclear for me. It is obvious, that the Hg free air was produced by the pump of the Zeeman AAS system. What difference and what pump is meant in the second part of the sentence? Would it be posible to re-formulate this sentence?
What is the precision of setting/stability of the air flow arising from the entrance pump of Lumex?

Citation: https://doi.org/10.5194/amt-2023-169-RC1
- AC1: 'Reply on RC1', Teodor Andron, 18 Oct 2023
  
  Indeed it was not the best choice of words. We changed the phrase with :˝As the N2 flow is lower than the flow of the pump inside the Zeeman AAS, a T-piece was placed between the impinger and the device. This allows for the air from outside to enter the system in order to compensate for difference in flows and pressure. The air passes through a Hg filter in order to assure that it does not interfere with the analysis.˝
  The flow was measured during each experiment and the variation of the flow is <1% which was taken into account when calculating the combined uncertainty of measurement results.
  
  Citation: https://doi.org/10.5194/amt-2023-169-AC1
RC2:
'Comment on amt-2023-169', Anonymous Referee #2, 11 Oct 2023

The precise reading of the Lumex unit is pressure dependent. Let's consider an atmosphere with a constant air Hg concentration. At a higher pressure, a higher absolute amount of Hg enters the Lumex measuring cell and the instrument records a higher absorbance.
Was this problem considered in any way in the calibration method discussed? Has the pressure of the gaseous mixture entering the Lumex been monitored or measured in any way?

Citation: https://doi.org/10.5194/amt-2023-169-RC2
- AC2: 'Reply on RC2', Teodor Andron, 18 Oct 2023
  
  Indeed the pressure plays a vital role in the actual amount of the analyte entering the system. The pressure was checked in order to be sure that it does not change compared to when it is sampling atmospheric air. This is also one of the reasons why we placed another T-split before the device, in order to compensate for the differences between the flows and pressure that might me between the flow/pressure of the pump and the outflow coming from the impinger.
  
  Citation: https://doi.org/10.5194/amt-2023-169-AC2
RC3:
'Comment on amt-2023-169', Anonymous Referee #1, 12 Oct 2023

Please, see the attached.

Citation: https://doi.org/10.5194/amt-2023-169-RC3
- AC3: 'Reply on RC3', Teodor Andron, 23 Oct 2023
  
  Thank you for your comments. Please see the attached.
  
  Citation: https://doi.org/10.5194/amt-2023-169-AC3

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload

AR by Teodor Andron on behalf of the Authors (20 Nov 2023) Author's response Author's tracked changes Manuscript

ED: Publish as is (22 Nov 2023) by Pierre Herckes

AR by Teodor Andron on behalf of the Authors (12 Dec 2023)

Short summary

Atmospheric mercury monitoring is an important activity in order to model the global trajectory of this toxic element and to assess if certain areas are polluted or not in accordance to global guidelines. One of the analysers tested in this work is globally used in this regard due to its practicality compared with other devices. Because it is only calibrated by the manufacturer at very high concentrations, we wanted to see how it performs at ambient mercury concentrations.