posted on 2022-01-10, 13:03authored byBen Yu, Lin Yang, Hongwei Liu, Cailing Xiao, Duo Bu, Qiangying Zhang, Jianjie Fu, Qianggong Zhang, Zhiyuan Cong, Yong Liang, Ligang Hu, Yongguang Yin, Jianbo Shi, Guibin Jiang
Deposition
of atmospheric mercury (Hg) is the most important Hg
source on the high-altitude Himalayas and Tibetan Plateau. Herein,
total gaseous Hg (TGM) at an urban and a forest site on the Tibetan
Plateau was collected respectively from May 2017 to October 2018,
and isotopic compositions were measured to clarify the influences
of landforms and monsoons on the transboundary transport of atmospheric
Hg to the Tibetan Plateau. The transboundary transported anthropogenic
emissions mainly originated over Indo-Gangetic Plain and carried over
the Himalayas by convective storms and mid-tropospheric circulation,
contributing over 50% to the TGM at the Lhasa urban site, based on
the binary mixing model of isotopes. In contrast, during the transport
of TGM from South Asia with low altitude, the uptake by evergreen
forest in Yarlung Zangbo Grand Canyon largely decreased the TGM level
and shifted isotopic compositions in TGM at the Nyingchi forest site,
which are located at the high-altitude end of the canyon. Our results
provided direct evidence from Hg isotopes to reveal the distinct patterns
of transboundary transport to the Tibetan Plateau shaped by landforms
and climates, which is critical to fully understand the biogeochemical
cycling of Hg in the high-altitude regions.