Global warming accelerates uptake of atmospheric mercury in regions experiencing glacier retreat

Abstract

As global climate continues to warm, melting of glaciers releases a large quantity of mercury (Hg) originally locked in ice into the atmosphere and downstream ecosystems. Here, we show an opposite process that captures atmospheric Hg through glacier-to-vegetation succession. Our study using stable isotope techniques at 3 succession sites on the Tibetan Plateau reveals that evolving vegetation serves as an active “pump” to take up gaseous elemental mercury (Hg0) from the atmosphere. The accelerated uptake enriches the Hg pool size in glacier-retreated areas by a factor of ∼10 compared with the original pool size in the glacier. Through an assessment of Hg source–sink relationship observed in documented glacier-retreated areas in the world (7 sites of tundra/steppe succession and 5 sites of forest succession), we estimate that 400 to 600 Mg of Hg has been accumulated in glacier-retreated areas (5‰ of the global land surface) since the Little Ice Age (∼1850). By 2100, an additional ∼300 Mg of Hg will be sequestered from the atmosphere in glacier-retreated regions globally, which is ∼3 times the total Hg mass loss by meltwater efflux (∼95 Mg) in alpine and subpolar glacier regions. The recapturing of atmospheric Hg by vegetation in glacier-retreated areas is not accounted for in current global Hg models. Similar processes are likely to occur in other regions that experience increased vegetation due to climate or land use changes, which need to be considered in the assessment of global Hg cycling.

Underestimated Sink of Atmospheric Mercury in a Deglaciated Forest Chronosequence

“…Hg isotopic signatures in (a and b) precipitation, woody biomass, deep soil and rocks, lichen, moss on trees and on ground, throughfall of deciduous forest ("Throughfall_D", at the 1990, 1980, 1970, and 1958 retreat sites), and throughfall of coniferous forests ("Throughfall_C", at the 1930, 1890, and 1830 retreat sites). The Hg isotopic signatures of precipitation, deep soil, and rocks have been documented in our earlier study 38.…”

“…The higher Hg 0 fractions in the above ground woody biomass than in the underground woody The atmospheric Hg 0 accumulation rate in organic soils is derived from our earlier study. 38 The uncertainties in Hg source fractions in woody biomass are as following: 25% for atmospheric Hg 0 , 9% for atmospheric Hg 2+ , and 14% for geological Hg. biomass suggests a foliage-to-root transport after atmospheric uptake.…”

“…Our earlier studies suggest that the recession of glaciers is followed by rapid establishment of vegetative ecosystems that capture 2−3 times more atmospheric Hg than the Hg released from glacier melting. 25,38 Combining the input of Hg to forest soil in our earlier research, 38 this study presents new data of Hg isotopic signatures in the samples of moss and lichen covers grown on ground and vegetation, in woody biomass, and in throughfall to infer their Hg sources and accumulation processes in the whole forest chronosequence ecosystems. Implications of this atmospheric Hg 0 deposition term on the global Hg cycling are also discussed.…”

“…(d) Variations of atmospheric Hg 0 deposition fluxes in throughfall and in litterfall, and atmospheric Hg 0 accumulation rate in organic soils. (e) Variations of atmospheric Hg 0 pool size in total moss covers and in woody biomass.The atmospheric Hg 0 accumulation rate in organic soils is derived from our earlier study 38. The uncertainties in Hg source fractions in woody biomass are as following: 25% for atmospheric Hg 0 , 9% for atmospheric Hg 2+ , and 14% for geological Hg.…”

A Systematic Study of the Novel Materials used in Solar Cell Technologies, Opportunities and Challenges

“…On an average a rise of 10-20 cm in the sea level has been observed on an annual scale as the temperature of the oceans have increased (Weldekidan et al, 2018). The melting of the glaciers have been responsible for the release of a large amount of mercury trapped in the ice into the atmosphere and the other downstream ecosystems (Wang et al, 2020).…”