Accumulation of Atmospheric Mercury in Glacier Cryoconite over Western China

Cryoconite is a granular aggregate, comprised of both mineral and biological material, and known to accumulate atmospheric contaminants. In this study, cryoconite was sampled from seven high-elevation glaciers in Western China to investigate the spatial and altitudinal patterns of atmospheric mercury (Hg) accumulation in the cryoconite. The results show that total Hg (Hg T ) concentrations in cryoconite were significant with relatively higher Hg accumulation in the southern glaciers (66.0 ± 29.3 ng g –1 ), monsoon-influenced regions, than those in the northern glaciers (42.5 ± 20.7 ng g –1 ), westerlies-influenced regions. The altitudinal profile indicates that Hg T concentrations in the northern glaciers decrease significantly with altitude, while those in the southern glaciers generally increase toward higher elevations. Unexpectedly high accumulation of methyl–Hg (MeHg) with an average of 1.0 ± 0.4 ng g –1 was also detected in the cryoconite samples, revealing the surface of cryoconite could act as a potential site for Hg methylation in alpine environments. Our preliminary estimate suggests a storage of ∼34.3 ± 17.4 and 0.65 ± 0.28 kg of Hg T and MeHg from a single year of formation process in the glacier cryoconite. Therefore, glacier cryoconite could play an important role in Hg storage and transformation, which may result in downstream effects on glacier-fed ecosystems under climate warming scenario.