Articles | Volume 22, issue 23
© Author(s) 2022. This work is distributed underthe Creative Commons Attribution 4.0 License.
Different physicochemical behaviors of nitrate and ammonium during transport: a case study on Mt. Hua, China
- Final revised paper (published on 13 Dec 2022)
- Supplement to the final revised paper
- Preprint (discussion started on 16 Jun 2022)
- Supplement to the preprint
Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor |
: Report abuse
RC1: 'RC on acp-2022-342', Anonymous Referee #2, 27 Jul 2022
- AC1: 'Reply on RC1', Gehui Wang, 30 Sep 2022
RC2: 'Comment on acp-2022-342', Anonymous Referee #1, 05 Aug 2022
- AC2: 'Reply on RC2', Gehui Wang, 30 Sep 2022
RC3: 'Comment on acp-2022-342', Anonymous Referee #3, 20 Aug 2022
- AC3: 'Reply on RC3', Gehui Wang, 30 Sep 2022
- AC4: 'Reply on RC3', Gehui Wang, 30 Sep 2022
- AC1: 'Reply on RC1', Gehui Wang, 30 Sep 2022
Peer review completion
AR: Author's response | RR: Referee report | ED: Editor decision
AR by Gehui Wang on behalf of the Authors (30 Sep 2022)  Author's response Author's tracked changes Manuscript
ED: Referee Nomination & Report Request started (10 Oct 2022) by Xavier Querol
RR by Anonymous Referee #1 (28 Oct 2022)
ED: Publish subject to minor revisions (review by editor) (07 Nov 2022) by Xavier Querol
AR by Gehui Wang on behalf of the Authors (11 Nov 2022)  Author's response Author's tracked changes Manuscript
ED: Publish as is (14 Nov 2022) by Xavier Querol
The manuscript is a case study on the behaviour of nitrate and ammonium aerosols during transport. Based on the comparison between the chemical composition of MPs sampled simultaneously (with 4h resolution) in a mountain site and a nearby site located at low altitude, the authors describe the processes that soluble inorganic compounds undergo. During transport, the NH4NO3 volatilizes, the formed HNO3 reacts with the dust, forming coarse nitrate, and the available NH3 reacts with the NH4HSO4 forming (NH4)2SO4. The isotopic study points to unidirectional reactions and additional ammonia partition into the particulate phases reducing aerosol acidity during transport.
A weakness of the article is that some references of interest are missing. A very recent paper on variation of 15N in total particulate N by Wiedenhaus et al., 2021, presents results related to the enrichment of 15N different from those presented in this article, probably because Wiedenhaus et al have determined 15N for N total. Given the close relationship with the present manuscript, this document should be referenced and similarities/differences should be discussed.
The volatilization of NH4NO3 and the formation of coarse nitrate is a well-known process by interaction on HNO3 with coarse sodium and calcium aerosols. Authors did not mention any previous reference to these processes. Authors shall include classical references such as Harrison and Pio 1983, Pakkanen 1996, and others (line 351 and others),
The increase in NO3 at the mountain site during September 12 and 13 is partially attributed to an external input. This may affect the interpretations of the origin of the nitrate based on the comparison between the averaged concentrations obtained in the studied sites. Therefore, this episode must be excluded for the calculation of the averages used for the interpretation of the modifications of the ions suffered during the transport from the lower levels to the mountain site.
Ammonia concentrations are not shown. However, some conclusions are based on the differences between the concentrations measured in MF and MS (Lines 407-408). These values, of key interest for the interpretation of data, must be presented or a reference must be included.
Throughout the text, the authors used the term "surface" (surface pollutants…) to refer to the low-elevation site, located in the valley. This is not appropriate. The measurements made at both sites are made at surface level, although at different heights with respect to sea level. I would distinguish between mountain and valley sites, or between high and low elevation sites.
Line 92: WHO: add year: WHO, 2021, and add the refence in the reference list:”
Lines 155 and 159: add altitude to the coordinates: e.g. (34º 32’N. 110º5’E, 400 m a.s.l.)
Line 309: delete parenthesis
Line 326: with latitude? Or with altitude?
Figure S2: please, better describe the reason of including Xi’an and Dazhou in Figure S2
Line 407: add reference for observational NH3 data
Line 453-455: any explanation for these differences?
Line 460-462 and figure 9: were the samples collected 12-13 September discarded? Origin of pollutant at the two sites may differs during this period.
Harrison R. M. and Pio C. A. (1983) Size-differentiated composition of inorganic atmospheric aerosols of both marine and polluted continental origin. Atmospheric Environment 22, 1733-1783.
Pakkanen, T. A. 1996. Study of formation of coarse particle nitrate aerosol. Atmos. Environ. 30 (14):2475–82.
Hanna Wiedenhaus, Laura Ehrnsperger, Otto Klemm & Harald Strauss (2021) Stable 15N isotopes in fine and coarse urban particulate matter, Aerosol Science and Technology, 55:7, 859-870 DOI: 10.1080/02786826.2021.1905150
WHO 2021. WHO global air quality guidelines. Particulate matter (PM2.5 and PM10), ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide. Geneva: World Health Organization; 2021.