Atmospheric mercury deposition over the land surfaces and the associated uncertainties in observations and simulations: a critical review

Zhang, Lei; Zhou, Peisheng; Cao, Shuzhen; Zhao, Yu

doi:https://doi.org/10.5194/acp-19-15587-2019

Articles | Volume 19, issue 24

https://doi.org/10.5194/acp-19-15587-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/acp-19-15587-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 19, issue 24

Review article

|

20 Dec 2019

Review article |

| 20 Dec 2019

Atmospheric mercury deposition over the land surfaces and the associated uncertainties in observations and simulations: a critical review

Lei Zhang, Peisheng Zhou, Shuzhen Cao, and Yu Zhao

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Final revised paper (published on 20 Dec 2019)
Supplement to the final revised paper
Preprint (discussion started on 13 May 2019)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

- Printer-friendly version

- Supplement

RC1: 'Review of Global deposition of speciated atmospheric mercury to terrestrial surfaces: an overview', Anonymous Referee #3, 31 May 2019
- AC4: 'Reply to Comments from Reviewer #3', Lei Zhang, 19 Aug 2019
RC2: 'Interactive comment on “Global deposition of speciated atmospheric mercury to terrestrial surfaces: an overview” by Lei Zhang et al.', Anonymous Referee #2, 06 Jun 2019
- AC3: 'Reply to Comments from Reviewer #2', Lei Zhang, 19 Aug 2019
RC3: 'Review of Lei et al., “Global deposition of speciated atmospheric mercury to terrestrial surfaces: an overview”', Anonymous Referee #1, 10 Jun 2019
- AC2: 'Reply to Comments from Reviewer #1', Lei Zhang, 19 Aug 2019
AC1: 'Revised Manuscript_20190819', Lei Zhang, 19 Aug 2019
AC5: 'Supporting Information_20190819', Lei Zhang, 19 Aug 2019

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by Lei Zhang on behalf of the Authors (20 Aug 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (20 Aug 2019) by Leiming Zhang

RR by Anonymous Referee #2 (28 Aug 2019)

RR by Anonymous Referee #4 (07 Oct 2019)

Suggestions for revision or reasons for rejection

The revised version reads better than the ACPD version, but some improvements can be made before it can be accepted for final publication. Below is a list of some specific comments for the authors to consider. Line numbers used here are from the revised manuscript (not the one posted on ACPD)

Line 45: TGM (GEM+GOM) is usually monitored and commonly used in literature, but TM is seldom used.

Lines 99-101: The Asia–Pacific Mercury Monitoring Network was established under the effort of Taiwan central University. There might be a more appropriate reference for this network from their publications than the one cited here.

Line 107-108: Values in bracket are multiple year range of annual average? Better use this format “Annual average (multiple year range) of Hg wet deposition…”

Line 120-122: the second half of the sentence does not explain the first half because GEM is not soluble. You should cite references showing high RM (especially GOM) in Asia.

The paragraph starting on line 142: A substantial revision is needed here. Wet deposition flux mainly depends on precipitation amount, column air concentration, and sometimes long-range transport from in-cloud scavenging, and depends little on underlying surfaces. The logic used in this paragraph is not appropriate. Even if you generated some dependence of wet deposition on the surface type, the conclusion may be applicable at different regions. However, you can indeed compare urban, rural and remote sites (instead of land use or canopy types).

The paragraph starting at Line 159: Fogs generally form in the night and dissipate (with fog droplets evaporate) when sunshine comes out. Will the fog collected Hg stay on the surface as wet deposition flux or evaporate back to the atmosphere? Similar questions also apply to the other non-precipitation events. Since earlier literature review on Hg deposition did not include this topic, a more in-depth discussion is preferred here to make this review more valuable.

Section 2.2: Measurement and modeling approaches for quantifying dry deposition of GOM and PBM and air-surface exchange fluxes of GEM, and field studies measuring GOM and PBM dry deposition and mercury in litterfall and throughfall were reviewed in detail by Wright et al. (2016). Measurement and modeling studies of air-surface exchange of GEM were also reviewed by Zhu et al. (2016). In this section, these earlier reviews shroud be first mentioned and then point out what additional knowledge this review is intend to provide. This section is poorly written in my opinion. A synthesis of existing literature is needed, instead of listing results from certain individual publications.

Section in 2.3: the previous comment also applies to this section.

Lines 276-278: Not sure how you generated this conclusion (see the Figure provided in Wright et al, 2016) on this topic.

Line 313: Any reference to support this statement?

Section 3.1.2: see comment above about evaporation of the non-precipitating events.

Section 3.2.1: There are some confusions here: Eq. (4) is the inferential method for estimating (modeling) dry deposition while the paragraph following this equation discusses flux measurement.

Line 490: I cannot agree with the stamen, or this statement is not expressed clearly.

Line 528: a portion of wet deposition may be intercepted by the canopy and cannot reach to the throughfall, especially if precipitation amount is small.

Section 4: Are the whole section focusing on CTMS? If so, the title may specify the discussions are for CTMs

Paragraph starting on line 837: uncertainty discussion on GOM measurements should be combined into earlier sections. Here only list a brief recommendation for future research needs.

Line 849: It is pretty clear that GEM dry deposition is more important than previously considered in CTMS over vegetated surfaces. It is a dominant contributor in the dry deposition budget (dry dep of GEM>GOM+PBM) over regions with low GEM emissions.

Lien 857: Again, I feel such deposition may not necessarily stay on the ground surface.

Line 866-867: not exactly true (in some parts of Asia).

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ED: Reconsider after major revisions (07 Oct 2019) by Leiming Zhang

AR by Lei Zhang on behalf of the Authors (12 Nov 2019) Author's response Manuscript

ED: Publish as is (26 Nov 2019) by Leiming Zhang

AR by Lei Zhang on behalf of the Authors (30 Nov 2019) Manuscript

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Short summary

One of the most important processes in the global mercury biogeochemical cycling is the deposition of atmospheric mercury to the land surfaces. In this paper, results of wet, dry, and forest Hg deposition from global observation networks, individual monitoring studies, and observation-based simulations are reviewed. Uncertainties in the observation and simulation of global speciated atmospheric Hg deposition to the land surfaces are systemically estimated.