Observation of strong NOx release over Qiyi Glacier, China

• Main Authors: Lin, Weili, Wang, Feng, Ye, Chunxiang, Zhu, Tong
• Format: Text
• Language: English
• Published: 2021
• Subjects: Antarctic; Arctic; Antarc*; ice core
• Online Access: https://doi.org/10.5194/tc-2021-32; https://tc.copernicus.org/preprints/tc-2021-32/

NO x 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 NO 3 − in snow/ice. Released NO x 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/m 2 and was increased by the strong reflection of snow/ice and clouds against the sun, and strengthened by the topographical effect. The concentrations of NO 3 − and NH 4 + in water from melting snow were hardly detected, but the average concentration (±1σ) of NO 3 − in snow samples was 8.7 ± 2.7 μmol/L. Strong correlations were observed between NO x (NO 2 ) mixing ratios and UVB radiation levels in the Tibetan glacier. Vertical experiments revealed a negative gradient of NO x (NO 2 ) 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 NO 3 − concentrations in snow/ice, the mixing ratios of NO x 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 NO x in the boundary layer of highland glaciers and snow surfaces.