The Editor,
Journal of Glaciology
Sir,
Despite their value in understanding the chemistry of the atmosphere, few snow-chemistry studies have been conducted in remote areas, particularly in Asia. Studies to date have been limited to Nepal and India (Reference Ikegami, Ikegami, Inoue, Higuchi and OnoIkegami and others, 1978; Reference Mayewski, Mayewski, Lyons and AhmadMayewski and others, 1981, 1983, 1984; Reference Lyons, Lyons, Mayewski and SpencerLyons and Mayewski, 1983). To add to these studies, we present chemical analyses of samples collected at an elevation of 6300 m on Xixabangma glacier, a north-north-easterly flowing glacier that descends from Xixabangma Peak (8012 m a.s.l.; lat. 28°21’N., long. 85°47’ E.) in the Mount Everest area. A total of three fresh snowfalls were analyzed for chloride, nitrate, sulfate, and sodium.
Samples were collected (J.L.C.) in adherence with clean-sampling techniques (i.e. non-particulating masks and garments, and polyethylene gloves). Wide-mouth LPE bottles with polyethylene tops were used both as sample scoops and sample containers. Anion analyses were performed using a Dionex 2010 ion chromatograph with an AS-4 column, a 0.5 ml sample loop and a 0.0021 M NaHCO3/0.0017 M Na2CO3, eluent. Sodium was analyzed via flame atomic absorption spectrometry using a Perkin-Elmer 2280 system. The average precision for chloride, nitrate, sulfate, and sodium was 3%, 5%, 3%, and 10%, respectively. Extra sample bottles were filled with Milli-Q water taken into the field and analyzed to serve as container and methodology blanks. Blank values were ≈ 1 µg kg-1 for chloride and nitrate, ≈ 2 µg kg-1 for sulfate, and ≈ 3 µg kg-1 for sodium. Although relatively few samples were collected as part of this study and no air-mass back trajectories are available, a general discussion of the chemical species concentrations for these samples is presented because of the uniqueness of this data set and the potential implications for future work in the area.
Few Asian snow-chemistry data are available for comparison with the Xixabangma glacier data (Table I). Most of the chloride values measured in this study are close to the only other chloride values of 14–174 µg kg-1 for fresh snow from Nun Kun in Ladakh, India (Reference Mayewski, Mayewski, Lyons and AhmadMayewski and others, 1983). However, even the range of values for nitrite plus nitrate of 0-81 µg kg-1 from Nun Kun snow (Reference Mayewski, Mayewski, Lyons and AhmadMayewski and others, 1983) and the mean (< 100 µg kg-1) of snow in remote areas in general (Reference Lyons and MayewskiLyons and others, 1985) is notably less than the range of nitrate in this study.
Table I Chemical Species Concentrations in Fresh Snow (µg kg-1)
The range in chemical concentrations (Table I) for the three fresh snow events combined is relatively diverse with values differing by factors of ≈ 8, ≈ 3, ≈ 6, and ≈ 5 for chloride, nitrate, sulfate, and sodium, respectively, despite the fact that all of the events occurred within 8 days of each other. The samples all appear similar physically, exhibiting stellar crystal form and densities of approximately 0.2 Mg m-3, with the only difference being the slightly higher temperature (Table I) for the 8 May 1984 event. Ratios of chloride to sodium and nitrate to sulfate are similar for 1 May and 9 May compared to 8 May. While the range of chloride and sodium values for the 8 May storm event is high, this storm event, relative to the 1 May and 9 May events, is still characterized by higher chloride to sodium ratios which are, in general, close to the value in sea-water (≌ 1.8). In addition, the 8 May event has lower nitrate and sulfate values than the 1 and 9 May events.
Although the cause of the differences in chemistry of the Xixabangma glacier fresh snow events cannot be adequately inferred from the limited number of samples available for this study, the existence of such different chemical signatures is encouraging for future studies in the region.
