Concentration of ionic compounds in the wintertime deposition: results and trends from the Austrian Alps over 11 years (1983–1993)

Abstract

Chemical analyses performed on samples taken annually from snow pits on a glacier in the Austrian Central Alps allowed for an assessment of the wintertime deposition loads of acidifying components into very remote areas for European standards. An analysis of ion-to-ion regression revealed that there were two different clusters of samples. One cluster exhibited a Cl - to Na + ratio close to one, the other, much smaller group of samples had a distinctly higher ratio. Those samples which belonged to the group of equimolar Cl - and Na + also tended to exhibit a higher NH + 4 to SO 2- 4 ratio. While the discrepancy was attributed to two different source regions affecting the receptor area, no source identification was possible at this stage. The total deposition (in the glacier samples, both wet and dry deposition were incorporated) was compared to the figures given in the official emission inventories of the possible source area in Central Europe. High interannual variability of sulfate deposition prevented a statistically meaningful trend to be found. Neither nitrate deposition nor nitrogen oxide emissions indicated an increasing or decreasing trend, while ammonia emission figures were decreasing, but the deposition increasing. In contrast to literature data on trends in precipitation in Central Europe, no increase in pH was observed at this remote site. With respect to the average emission density in the source area, the per-area deposition in the remote area accounted for at least 12% for sulfur oxides and 22% for nitrogen oxides and reduced nitrogen. In absolute terms, the total influx of S- and N-compounds during a winter period was found to be in the order of 3 kg ha -1 each (as a minimum estimate). It may be assumed that this is the lower limit of deposition to be expected in Central Europe.