Study explores climatic regulation of mercury deposition in plateau lake

LANZHOU -- Chinese scientists have recently uncovered the long-term interaction between climate change and mercury (Hg) deposition in a lake on the Qinghai-Tibet Plateau, according to the Northwest Institute of Eco-Environment and Resources (NIEER) under the Chinese Academy of Sciences.

"This joint study also provides scientific support for analyzing pollutant transport pathways and protecting the regional ecological environment in the context of future climate change," said Kang Shichang, a researcher at the NIEER.

The study was led by the NIEER in collaboration with researchers from Tianjin University and Tongji University, with the findings published in the journal Global and Planetary Change.

As a global pollutant, mercury is released into the atmospheric environment through human activities or natural processes, continuously accumulating in terrestrial ecosystems after being transported via the atmospheric cycle.

The Qinghai-Tibet Plateau is one of the regions globally with the widest distribution of glaciers and permafrost in the middle and low latitudes, and it stores a large amount of accumulated mercury. Climate warming has led to the accelerated melting of glaciers and permafrost in this region, which will significantly accelerate the release and re-migration of mercury in the cryosphere, according to Kang.

"This plateau is essential for evaluating global ecological impact by tracing the source and transformation of mercury in its lake sediments. Situated at the transition zone of the Indian summer monsoon (ISM) and the westerlies, Cuona Lake on this plateau provides an ideal natural archive for understanding long-term interactions between mercury deposition and climate change," Kang said.

Researchers carried out a study on the sediment core CN12/01 from the lake. They systematically analyzed various parameters, such as total mercury concentration, mercury isotope composition, clay mineral assemblage, and selected elemental concentration in lake sediments.

The study revealed the main sources of mercury in the lake and its accumulation process over the past approximately 13,000 years. The findings indicated that the temporal variations in Hg accumulation in the sediment core have been influenced by distinct atmospheric patterns.

The study also indicated that Cuona Lake transitioned from functioning as a mercury "transporter" to a "sink" around 6,000 years ago. This shift was associated with the climatic transition of ISM-westerlies patterns and represents an important process in regulating the mercury cycle within the terrestrial ecosystems of the Qinghai-Tibet Plateau.

In the context of global warming, the Qinghai-Tibet Plateau is highly sensitive to climate change, with temperatures rising at a rate roughly two to three times the global average, according to Kang.

This study provides an important scientific basis for understanding the climate regulation effect of the Qinghai-Tibet Plateau lake system on the global mercury cycle, Kang said.

"It also sheds light on the mercury migration process and its environmental effects on the plateau, as well as the follow-up research on the global mercury cycle in the cryosphere," he added.