Unexpectedly high concentrations of atmospheric mercury species in Lhasa, the largest city in the Tibetan Plateau
<p>The city of Lhasa 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 in the Tibetan Plateau, our monitoring in Lhasa showed that the concentrations of gaseous elemental Hg (GEM),...
| Main Authors: | , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2023-04-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/23/3937/2023/acp-23-3937-2023.pdf |
| Summary: | <p>The city of Lhasa 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 in 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 the subsequent Indian summer monsoon (S-ISM) period were 2.73 <span class="inline-formula">±</span> 1.48 ng m<span class="inline-formula"><sup>−3</sup></span>,
38.4 <span class="inline-formula">±</span> 62.7 pg m<span class="inline-formula"><sup>−3</sup></span>, and 59.1 <span class="inline-formula">±</span> 181.0 pg m<span class="inline-formula"><sup>−3</sup></span>,
respectively. During the westerly circulation (WEC) period, the GEM, GOM, and
PBM concentrations were 2.11 <span class="inline-formula">±</span> 2.09 ng m<span class="inline-formula"><sup>−3</sup></span>, 35.8 <span class="inline-formula">±</span> 43.3 pg m<span class="inline-formula"><sup>−3</sup></span>, and 52.9 <span class="inline-formula">±</span> 90.1 pg m<span class="inline-formula"><sup>−3</sup></span>, respectively. The GOM and PBM
concentrations were higher than those of previous monitoring in 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 events 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<span id="page3938"/> 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 in the Tibetan Plateau.
Monitoring Hg species in Lhasa shows the possible maximum anthropogenic
influences in the Tibetan Plateau and demonstrates the dramatic effect of
wind on changes in urban atmospheric Hg concentrations.</p> |
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| ISSN: | 1680-7316 1680-7324 |