the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Unexpectedly high concentrations of atmospheric mercury species in Lhasa, the largest city on the Tibetan Plateau
- 1MOE Laboratory of Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China
- 2School of Science, Tibet University, Lhasa 850000, China
- 3School of Environmental Science and Engineering, Tianjin University, Tianjin, 300072, China
- 4School of Geographic Sciences, East China Normal University, Shanghai 200241, China
- 5Key Laboratory of Microbial Technology for Industrial Pollution Control of Zhejiang Province, College of Environment, Zhejiang University of Technology, Hangzhou 310014, China
- 6State Key Laboratory of Cryospheric Science, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China
- 7Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, 100101, China
- 8CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing, 100085, China
- 9Department of Civil and Environmental Engineering, University of Wisconsin-Madison, Madison, WI, USA
- 10Wisconsin State Laboratory of Hygiene, University of Wisconsin-Madison, WI, USA
- 11Department of Earth and Atmospheric Sciences, Saint Louis University, St. Louis, MO, 63108, USA
- 1MOE Laboratory of Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China
- 2School of Science, Tibet University, Lhasa 850000, China
- 3School of Environmental Science and Engineering, Tianjin University, Tianjin, 300072, China
- 4School of Geographic Sciences, East China Normal University, Shanghai 200241, China
- 5Key Laboratory of Microbial Technology for Industrial Pollution Control of Zhejiang Province, College of Environment, Zhejiang University of Technology, Hangzhou 310014, China
- 6State Key Laboratory of Cryospheric Science, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China
- 7Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, 100101, China
- 8CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing, 100085, China
- 9Department of Civil and Environmental Engineering, University of Wisconsin-Madison, Madison, WI, USA
- 10Wisconsin State Laboratory of Hygiene, University of Wisconsin-Madison, WI, USA
- 11Department of Earth and Atmospheric Sciences, Saint Louis University, St. Louis, MO, 63108, USA
Abstract. Lhasa City is located in the central Tibetan Plateau and is the most densely populated area. As the first continuous monitoring of atmospheric mercury (Hg) species in a city on the Tibetan Plateau, our monitoring in Lhasa showed that the concentrations of gaseous elemental Hg (GEM), gaseous oxidized Hg (GOM), and particle-bound Hg (PBM) during subsequent of the Indian Summer Monsoon (S-ISM) period were 2.73 ± 1.48 ng m-3, 38.4 ± 62.7 pg m-3, and 59.1 ± 181.0 pg m-3, respectively. During the Westerly Circulation (WEC) period, the GEM, GOM and PBM concentrations were 2.11 ± 2.09 ng m-3, 35.8 ± 43.3 pg m-3, and 52.9 ± 90.1 pg m-3, respectively. The atmospheric Hg species concentrations were higher than those of previous monitoring on the Tibetan Plateau and other provincial capitals in China. Typical high-value occurrence processes were studied to investigate random events with high atmospheric Hg concentrations in Lhasa. Combustion event nearby or further away may be the main contributor of the high-concentration events. The lowest GEM concentrations occurred in the afternoon and persistently high concentrations were observed at night. The changes in GEM concentrations were consistent with the trends of other pollutant concentrations and contradictory to those of the wind speed. The high GEM concentrations at night can be attributed to the lower boundary layer height and lower wind speed. For both GOM and PBM, higher GOM concentrations occurred during the day and PBM during the night. The results of the principal component analysis indicated that local sources and wind speed are important factors influencing atmospheric Hg concentrations in Lhasa. The trajectory simulation showed that the source of the GEM in Lhasa gradually shifted from the south to the west of Lhasa from the S-ISM to the WEC periods, while both the southern and western sources were important in the late WEC period. The concentrations and change patterns of Hg species in Lhasa were significantly different than those at other monitoring sites on the Tibetan Plateau. Monitoring Hg species in Lhasa shows the possible maximum anthropogenic influences on the Tibetan Plateau and demonstrates the dramatic effect of wind on changes in urban atmospheric Hg concentrations.
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Huiming Lin et al.
Status: final response (author comments only)
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RC1: 'Comment on acp-2022-750', Yanxu Zhang, 28 Dec 2022
General comments:
This paper presents continuous observations of different atmospheric mercury species in Lhasa, the largest city on the Tibetan plateau. Atmospheric mercury was analyzed for different periods (Indian Summer Monsoon and Westerly Circulation) and further studied the daily variation of atmospheric mercury concentration as well as some typical high-value cases. The results indicate that the atmospheric mercury concentration in Lhasa is significantly higher than that in the adjacent region, reflecting the influence of local anthropogenic emissions and wind fields on the atmospheric mercury concentration in remote areas. Overall, this manuscript is clear written and makes up for the lack of observations of atmospheric mercury at high altitudes. The paper can be accepted after addressing the following comments.
Specific comments:
- Lines 91-92, “whether the Tibetan Plateau can be treated as a background area for studying atmospheric Hg”. It’s an interesting question, and what do you think about it after you've made several observations of atmospheric Hg (such as Lhasa, QNNP, SET, and Namco) on the Tibetan Plateau?
- Line 100, please add a reference for the average GEM concentrations in the Northern Hemisphere.
- Lines 110-111, “the wet deposition of total Hg and particulate Hgwas higher during the non-monsoon period than during the monsoon period”. The wet deposition is correlated with the precipitation, but why is Hg wet deposition lower during the monsoon than during the non-monsoon?
- L116, “continuous”
- L195, “categorized”
- 1, please add mark (°N, °E) to the latitude and longitude of the coordinate axis. Same for Fig. 5.
- Lines 217-219, GEM concentrations are nearly twice as high in September as in February, contrary to previous studies (e.g., Horowitz et al. 2017; Jiskra et al., 2018) that atmospheric mercury in the Northern Hemisphere is low in summer and higher in winter. Please try to explain the reason.
- Line 237, please give the definition of WEC1 and WEC2 in the paper.
- Lines 242-243, “the GEM concentration in Lhasa is low among the provincial capitals in China.” is inconsistent with “The atmospheric Hg species concentrations were higher than ... other provincial capitals in China.” in Lines 33-34.
- 2, what is the reason for the sparse observations in 2016/12?
- 3, please add the meaning of the dotted lines and the units of different observations.
- Section 3.2, it will be more intuitive to add a correlation analysis between Hg and other pollutant species? In addition, ozone, aerosols, and NO2 are thought to be related to Hg chemistry, and their relationship in plateau would be meaningful to the study of Hg.
- 4a, please add units of the pollutants.
- Line 413, what are the “four components”?
- Table 4 note, please correct “> 0:5” & “<0:1”.
- Lines 465-466, “The GEM concentration WEC2 in Lhasa is 0.16 ng m-3, higher than 1.31 in QNNP?” And the “1:31 ± 0:42 ng m-3”. Please correct.
References
Horowitz, H. M., Jacob, D. J., Zhang, Y., Dibble, T. S., Slemr, F., Amos, H. M., Schmidt, J. A., Corbitt, E. S., Marais, E. A., and Sunderland, E. M.: A new mechanism for atmospheric mercury redox chemistry: implications for the global mercury budget, Atmos. Chem. Phys., 17, 6353-6371, 10.5194/acp-17-6353-2017, 2017.
Jiskra, M., Sonke, J. E., Obrist, D., Bieser, J., Ebinghaus, R., Myhre, C. L., Pfaffhuber, K. A., Wängberg, I., Kyllönen, K., Worthy, D., Martin, L. G., Labuschagne, C., Mkololo, T., Ramonet, M., Magand, O., and Dommergue, A.: A vegetation control on seasonal variations in global atmospheric mercury concentrations, Nat. Geosci., 11, 244-250, 10.1038/s41561-018-0078-8, 2018.
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RC2: 'Comment on acp-2022-750', Anonymous Referee #1, 04 Jan 2023
This article entitled ‘Unexpectedly high concentrations of atmospheric mercury species in Lhasa, the largest city on the Tibetan Plateau’ by Lin et al. analyzes the monitoring concentrations and source analysis of atmospheric mercury in important cities on the Tibetan Plateau. According to the local meteorological conditions, the author divided the monitoring period into two periods. Indian Summer Monsoon and Westerly Circulation. The authors analyzed the unusual phases of high atmospheric mercury concentration events and attempted to analyze the causes, and also analyzing the diurnal variation of atmospheric mercury in Lhasa. This article reveals the changes of urban atmospheric mercury in clean background areas, indicating the impact of urban anthropogenic activities and wind speed on regional atmospheric mercury concentrations. The result makes sense, and the output of the study will be useful for future studies on global mercury cycling and modeling. The manuscript is generally well organized and written. After revising the questions listed below, the study is accepted for publication.
Specific commentsï¼
In line 175, the author only calculated the backward trajectory of GEM in the article, why did the author not consider analyzing the trajectory of GOM and PBM.
Line 226, the author should show the timing of ISM and WEC in Figure 2.
Line 240, Table 1, what is the purpose of dividing WEC into WEC1 and WEC2?
Line 229-231, is it possible that the change in the relationship between the concentration of GOM and PBM is related to the change in the gas-solid distribution ratio of atmospheric mercury?
Line 268& 440, the author claims that strong winds may reduce the concentration of atmospheric mercury in the city. I wonder how the atmospheric mercury concentration in Lhasa compares with the background area (such as Nam Co) under the condition of strong winds?
Line 297, how did the authors confirm that the high mercury concentration events occurred randomly?
Line 323 Table 3, Please note that colored values in tables are not allowed in ACP, please consider replacing them with italic or bold lettering.
Line 396, does the author think that the changes in atmospheric mercury in Lhasa can be extended to more cities?
Huiming Lin et al.
Huiming Lin et al.
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