Abstract

NOx is released from sunlit snowpack surfaces, and this significantly influences the oxidizing capacity of the clean boundary layer atmosphere and the potential interpretation on the historical atmospheric composition recorded in the ice core. The Tibetan Plateau is an important snow-covered region in the northern midlatitudes, with strong solar radiation and relatively high NO3− in snow/ice. Released NOx on the glacier surface of the Tibetan Plateau should have a higher concentration than in Antarctic and Arctic regions. To verify this hypothesis, field observations were carried out at 4600 m asl in Qiyi Glacier in late August 2004. In late August, the surface ultraviolet-B (UVB) radiation level at 4600 m asl in Qiyi Glacier reached >4.5 W/m2 and was increased by the strong reflection of snow/ice and clouds against the sun, and strengthened by the topographical effect. The concentrations of NO3− and NH4+ in water from melting snow were hardly detected, but the average concentration (±1σ) of NO3− in snow samples was 8.7 ± 2.7 μmol/L. Strong correlations were observed between NOx (NO2) mixing ratios and UVB radiation levels in the Tibetan glacier. Vertical experiments revealed a negative gradient of NOx (NO2) mixing ratios from the glacier snow surface to a height of 30 cm. As a result of the high levels of UV radiation and high NO3− concentrations in snow/ice, the mixing ratios of NOx released by fresh snow in Qiyi Glacier in late August reached to several parts per billion (ppbv) and were approximately 1 order of magnitude higher than those observed in polar regions. This observation provides direct evidence to support the research hypothesis and confirms that the release of high concentrations of NOx in the boundary layer of highland glaciers and snow surfaces.

Highlights

  • As a result of the high levels of UV radiation and high NO3− concentrations in snow/ice, the mixing ratios of NOx released by fresh snow in Qiyi Glacier in late August reached to several parts per billion and were approximately 1 order of magnitude higher than those observed in polar regions

  • NOx and other gases may be released from sunlit snowpack in Antarctic and Arctic regions, significantly influencing the oxidizing capacity of the polar boundary layer atmosphere and the potential interpretation of the historical atmospheric 25 composition recorded in the ice core (Honrath et al, 1999; Summer and Shepson, 1999; Davis et al, 2001; Mauldin et al, 2001; Zhou et al, 2001; Dominéand Shepson, 2002; Honrath et al, 2002; Jone and Wollf, 2003; Mauldin et al, 2004; Wang et al, 2011)

  • 180 Strong correlations were observed between the NOx (NO2) mixing ratios and UVB radiation levels obtained from Qiyi Glacier, Tibetan Plateau

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Summary

Introduction

NOx and other gases may be released from sunlit snowpack in Antarctic and Arctic regions, significantly influencing the oxidizing capacity of the polar boundary layer atmosphere and the potential interpretation of the historical atmospheric 25 composition recorded in the ice core (Honrath et al, 1999; Summer and Shepson, 1999; Davis et al, 2001; Mauldin et al, 2001; Zhou et al, 2001; Dominéand Shepson, 2002; Honrath et al, 2002; Jone and Wollf, 2003; Mauldin et al, 2004; Wang et al, 2011). The characteristics of clean air, high altitude (>4000 m on average), and high surface albedo (including snow/ice reflection) subject this region to high levels of solar radiation (Chen et al, 2015). Photochemical reactions in the snow surface must be stronger and the NOx concentration must be higher in the 45 Tibetan Plateau than in Arctic and Antarctic regions. To verify this hypothesis, this paper reports observations of NOx concentration and ultraviolet-B (UVB) radiation levels in late August 2004 on the surface of Qiyi Glacier (July 1 Glacier), Tibetan Plateau. Treatments similar to the TUV model were applied in the UVB simulation for the north valley of Qomolangma (Lin et al, 2008)

Result
Measurement and simulation of UVB radiation
Inorganic ion concentrations in snow and water samples
Variations in vertical NOx distribution at different sample heights On 27
Findings
Discussion
Conclusions
Full Text
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