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Abstract: The central Himalaya can be regarded as an ideal site for developing a long-term ice core dust record to reflect the environmental signals from regional to semi-hemispheric scales. Here we present a dust record from segments of a 108.83-m ice core recovered from the East Rongbuk (ER) Glacier (27°59′N, 86°55′E; 6518 m a.s.l.) on the northeast slope of Mt. Qomolangma (Everest) in the central Himalaya, covering the period AD 600–1960. Due to rapidly layer thinning and coarse sampling, we primarily discuss the changes in the dust record since AD 1500 in this paper. Results show a significant positive relationship between the dust concentration and reconstructed air temperatures during this period, suggesting a likely cold–humid and warm–dry climatic pattern in the dust source regions, namely Central Asia. This is associated with the variability in the strength of the westerlies and its corresponding precipitation. [Copyright &y& Elsevier]

Abstract: Rare earth element (REE) concentrations in ice samples from the upper 8.4m of a Mt. Everest ice core retrieved from the col of the East Rongbuk Glacier (28.03°N, 86.96°E, 6518ma.s.l.) on the northeast ridge of Mt. Everest in September 2002 are presented. REEs display large seasonal variations, with high concentrations in the non-monsoon season and low concentrations in the summer monsoon season. This seasonality is useful for ice core dating. When normalized to a shale standard, the Mt. Everest REEs exhibit a consistent shale-like pattern with a slight enrichment of middle REEs during both seasons. However, individual monsoon REE patterns display differences, possibly resulting from diversified sources. Non-monsoon REE patterns are stable and are associated with the westerlies. Investigation of potential sources for the Everest REEs suggests an absence of anthropogenic contributions and minimal input from local provenances. REEs in Mt. Everest samples are most likely representative of a stable well-mixed REE background of the upper troposphere consisting of a mixture of aerosols transported by the atmospheric circulation from the west windward arid regions such as the Thar Desert, West Asia, the Sahara Desert and other uncertain provenances. [Copyright &y& Elsevier]

In May 2005, a total of 14 surface snow (0–10cm) samples were collected along the climbing route from the advanced base camp to the summit (6500–8844m a.s.l.) on the northern slope of Mt. Everest (Qomolangma). A 108m firn/ice core was retrieved from the col of the East Rongbuk Glacier (28.03°N, 86.96°E, 6518m a.s.l.) on the north eastern saddle of Mt. Everest in September 2002. Surface snow and the upper 3.5m firn samples from the core were analyzed for major and trace elements by inductively coupled plasma mass spectroscopy (ICP-MS). Measurements show that crustal elements dominated both surface snow and the firn core, suggesting that Everest snow chemistry is mainly influenced by crustal aerosols from local rock or prevalent spring dust storms over southern/central Asia. There are no clear trends for element variations with elevation due to local crustal aerosol inputs or redistribution of surface snow by strong winds during the spring. Seasonal variability in snow/firn elements show that high elemental concentrations occur during the non-monsoon season and low values during the monsoon season. Ca, Cr, Cs, and Sr display the most distinct seasonal variations. Elemental concentrations (especially for heavy metals) at Mt. Everest are comparable with polar sites, generally lower than in suburban areas, and far lower than in large cities. This indicates that anthropogenic activities and heavy metal pollution have little effect on the Mt. Everest atmospheric environment. Everest firn core REE concentrations are the first reported in the region and seem to be comparable with those measured in modern and Last Glacial Maximum snow/ice samples from Greenland and Antarctica, and with precipitation samples from Japan and the East China Sea. This suggests that REE concentrations measured at Everest are representative of the background atmospheric environment. [Copyright &y& Elsevier]

This case study provides a framework for future monitoring and evidence for human source pollution in the Khumbu region, Nepal. We analyzed the chemical composition (major ions, major/trace elements, black carbon, and stable water isotopes) of pre-monsoon stream water (4300-5250 m) and snow (5200-6665 m) samples collected from Mt. Everest, Mt. Lobuche, and the Imja Valley during the 2019 pre-monsoon season, in addition to a shallow ice core recovered from the Khumbu Glacier (5300 m). In agreement with previous work, pre-monsoon aerosol deposition is dominated by dust originating from western sources and less frequently by transport from southerly air mass sources as demonstrated by evidence of one of the strongest recorded pre-monsoon events emanating from the Bay of Bengal, Cyclone Fani. Elevated concentrations of human-sourced metals (e.g., Pb, Bi, As) are found in surface snow and stream chemistry collected in the Khumbu region. As the most comprehensive case study of environmental chemistry in the Khumbu region, this research offers sufficient evidence for increased monitoring in this watershed and surrounding areas., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 The Authors. Published by Elsevier B.V. All rights reserved.)