the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 31 Mar 2025
Measurement report: Year-long chemical composition, optical properties, and sources of atmospheric aerosols in the northeastern Tibetan Plateau
Abstract. Due to significant climatic effects, brown carbon (BrC) aerosol has received much attention in recent years. In this study, a year-long fine particular-matter (PM2.5) samples were collected at Waliguan Baseline Observatory in the northeast of the Tibet Plateau to investigate the optical properties of water-soluble BrC and its source. The average concentration of PM2.5 throughout the year was 10.3 ± 7.4 μg m–3, with maximum in spring (14.0 ± 1.6 μg m−3) and winter (12.5 ± 1.6 μg m–3) and minimum in fall (7.95 ± 0.9 μg m–3) and summer (7.14 ± 0.9 μg m−3). Organic aerosol (OA) was the major component accounting for 37.7 % on average, followed by sulfate (21.3 %), nitrate (12.1 %), and other species. OA and nitrate peaked during winter, while sulfate increased significantly during summer. Backward trajectory analysis on air mass reveals that the sources of the polluted air mass were mainly transported from the northeast and east of the sampling site. The seasonally average carbon-based mass absorption efficiency (MAE) of WS-BrC at 365nm were 0.92 ± 0.54 m2g−1 in spring, 0.40 ± 0.24 m2g–1 in summer, 0.81 ± 0.46 m2g−1 in fall, 0.97 ± 0.49 m2g−1 in winter, respectively. Comparison with other results, BrC in this study is weakly absorbed throughout the year, with that during the summer being the most photobleaching BrC. The chemical compositions of BrC are further investigated by parallel factorization analysis on the three-dimensional excitation-emission matrix and positive matrix factorization analysis on OA.
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Notice on discussion status
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Preprint
(2663 KB)
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(2663 KB) - Metadata XML
- BibTeX
- EndNote
- Final revised paper
Journal article(s) based on this preprint
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2025-41', Anonymous Referee #1, 01 May 2025
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AC1: 'Reply on RC2', J. Z. Xu, 27 Jun 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-41/egusphere-2025-41-AC1-supplement.pdf
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AC1: 'Reply on RC2', J. Z. Xu, 27 Jun 2025
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RC2: 'Comment on egusphere-2025-41', Anonymous Referee #2, 05 May 2025
This study reports aerosol characteristics from a remote site in the Tibetan Plateau. The authors find seasonal variation in the aerosol composition and absorption properties. The analysis is strengthened by the use of multiple complimentary analysis techniques, providing results of interest to the community.
General comments:
- Throughout the manuscript, the authors note that many of the seasonal differences in the absorption properties are due to photobleaching (i.e. line 330, line 447). However, it is also possible that the aerosol sources are different between the seasons. For example, you mention coal burning as an aerosol source in the winter, which is highly absorbing. Can you comment on if you do expect different sources across seasons at this site? Additionally, do you expect a role of non-absorbing SOA (such as biogenic SOA) to decrease the MAE in the summer.
- It would be useful to add additional information on how to interpret the HIX and BIX results in section 3.3. It is clear that there are seasonal differences, however, further information on the importance of the differences would be useful.
Minor Comments:
- Sections 2.3.3 and 2.3.4: These sections should be renamed to something more informative
- Line 206: should this be nondispersive infrared gas detector?
- Line 226: This sentence is vague, was PMF run using PET2?
- Section 2.3.7: How often were trajectories initiated?
- Line 270: What are the percentage values for precipitation? Percent of days with precipitation?
- Line 283: It doesn’t seem that Ca2+ is that much higher in spring than fall, and it is not negligible even in summer and winter. Is there other data to support increased mineral dust in spring, or is mineral dust present year round.
- Consider expanding the discussion in the paragraph starting at line 449. The combination of the EEM and PMF data is intriguing, however, I’m having trouble understanding this paragraph. Can you provide details on what is meant by “correlation analysis”? Why is there no correlation seen with C4?
- Figure 2: It is difficult to see the time trends in the minor components due to the scale. Consider revising the figure to better show all the species, for example splitting the middle panel into two axes.
Typographical
There are several grammatical errors throughout the manuscript. I recommend the authors carefully proofread the manuscript. A few specific cases are listed below
Line 41: “…and strongly interacted with ambient conditions during transport” meaning of this sentence is unclear
Line 65: “Precipitation in the mountain areas, through aerosol-cloud interaction, is the major origination (Qi et al., 2022)” meaning is unclear
Line 278; NH4+ should be NH4+
Citation: https://doi.org/10.5194/egusphere-2025-41-RC2 -
AC1: 'Reply on RC2', J. Z. Xu, 27 Jun 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-41/egusphere-2025-41-AC1-supplement.pdf
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2025-41', Anonymous Referee #1, 01 May 2025
-
AC1: 'Reply on RC2', J. Z. Xu, 27 Jun 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-41/egusphere-2025-41-AC1-supplement.pdf
-
AC1: 'Reply on RC2', J. Z. Xu, 27 Jun 2025
-
RC2: 'Comment on egusphere-2025-41', Anonymous Referee #2, 05 May 2025
This study reports aerosol characteristics from a remote site in the Tibetan Plateau. The authors find seasonal variation in the aerosol composition and absorption properties. The analysis is strengthened by the use of multiple complimentary analysis techniques, providing results of interest to the community.
General comments:
- Throughout the manuscript, the authors note that many of the seasonal differences in the absorption properties are due to photobleaching (i.e. line 330, line 447). However, it is also possible that the aerosol sources are different between the seasons. For example, you mention coal burning as an aerosol source in the winter, which is highly absorbing. Can you comment on if you do expect different sources across seasons at this site? Additionally, do you expect a role of non-absorbing SOA (such as biogenic SOA) to decrease the MAE in the summer.
- It would be useful to add additional information on how to interpret the HIX and BIX results in section 3.3. It is clear that there are seasonal differences, however, further information on the importance of the differences would be useful.
Minor Comments:
- Sections 2.3.3 and 2.3.4: These sections should be renamed to something more informative
- Line 206: should this be nondispersive infrared gas detector?
- Line 226: This sentence is vague, was PMF run using PET2?
- Section 2.3.7: How often were trajectories initiated?
- Line 270: What are the percentage values for precipitation? Percent of days with precipitation?
- Line 283: It doesn’t seem that Ca2+ is that much higher in spring than fall, and it is not negligible even in summer and winter. Is there other data to support increased mineral dust in spring, or is mineral dust present year round.
- Consider expanding the discussion in the paragraph starting at line 449. The combination of the EEM and PMF data is intriguing, however, I’m having trouble understanding this paragraph. Can you provide details on what is meant by “correlation analysis”? Why is there no correlation seen with C4?
- Figure 2: It is difficult to see the time trends in the minor components due to the scale. Consider revising the figure to better show all the species, for example splitting the middle panel into two axes.
Typographical
There are several grammatical errors throughout the manuscript. I recommend the authors carefully proofread the manuscript. A few specific cases are listed below
Line 41: “…and strongly interacted with ambient conditions during transport” meaning of this sentence is unclear
Line 65: “Precipitation in the mountain areas, through aerosol-cloud interaction, is the major origination (Qi et al., 2022)” meaning is unclear
Line 278; NH4+ should be NH4+
Citation: https://doi.org/10.5194/egusphere-2025-41-RC2 -
AC1: 'Reply on RC2', J. Z. Xu, 27 Jun 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-41/egusphere-2025-41-AC1-supplement.pdf
Peer review completion
Post-review adjustments
Journal article(s) based on this preprint
Data sets
Comprehensive dataset of atmospheric aerosols (PM2.5) at Waliguan Station (2019-2020) Jianzhong Xu and Kemei Li https://www.doi.org/10.12072/ncdc.nieer.db6809.2025
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Kemei Li
Yanqing An
Jianzhong Xu
Miao Zhong
Wenhui Zhao
Xiang Qin
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(2663 KB) - Metadata XML
See attached file.