Long-term assessment of the wet precipitation chemistry in Austria (1984-1999).

The aim of the present study was to determine the long-time trends in concentrations and depositions of major ions in wet precipitation samples collected at 11 sampling sites from the Austrian precipitation chemistry network in the period 1984-1999. The analytical results were treated by the use of least square linear regression method. It is shown that a serious decrease of sulfate (between 30% and 60% for the period) and hydrogen ion (between 60% and 102% for the period) concentrations and depositions is achieved at almost all sampling sites and in most of these cases the linear trend proves to be statistically significant. Nitrogen containing ions and base cations do not reveal a distinct trend of changing and in the majority of the sites the linear models are not adequate. In principle, an overall slight concentration and deposition decrease for these major ions is observed (up to 30% for the period of observation) but some substantial exceptions are also found (site Haunsberg or site Lobau). The changes in chloride concentration and deposition, too, do not indicate significant linear trend and, in general, are decreasing for the period of monitoring. In order to give some explanation of the exceptional behaviour of some of the major ions in several sites, an additional comparison with Austrian emission data (sulfur dioxide, nitrogen oxides, ammonium) and with data from five EMEP sites from neighbouring countries is performed. A significant West-East trend of acidity increase is found as well as a good correlation with the emission trends. Therefore, both transboundary and specific local factors could be substantial factors in the wet precipitation chemistry in the region.

Trend, seasonal and multivariate modelling study of wet precipitation data from the Austrian Monitoring Network (1990-1997).

The aim of the present study was to analyse the data structure of a large data set from rainwater samples collected during a long-term interval (1990-1997) by the Austrian Precipitation Monitoring Network. Eleven sampling sites from the network were chosen as data sources (chemical concentrations of major ions only) covering various location characteristics (height above sea level, rural and urban sampling positions, Alpine rim and Alpine valley disposition, etc.). The analytical results were treated by the application of already classical environmetric approaches, such as linear regression analysis, time-series analysis and principal components analysis (PCA). For most of the sampling sites, a distinct trend of acidity decrease of the wet precipitation was observed. An overall decrease in sulfate concentration for the whole period and all sites of 3.9% year(-1) (2.0 muequiv. L(-1) year(-1)) was found. The free acidity decrease for most of the sites was between 3.5 and 10.9% year(-1). No significant linear trends were found for nitrate. Base cations either decreased (mean percentage decrease for calcium was 5.4% year(-1) and for magnesium 4.4% year(-1)) or did not show any significant change (sodium, potassium). The overall decrease in ammonium concentration was 2.3% year(-1). Further, some typical "rural" (summer minima and winter maxima) and "urban" (winter minima and spring maxima) seasonal behaviour for the majority of the sites in consideration could be defined, indicating the influence of local emission sources. Several latent factors, named "anthropogenic", "crustal" and "mixed salt", were revealed by the multivariate modelling procedure (PCA) possessing a similar structure for most of the sites. The unavoidable exceptions observed were indications of the influence of sporadic local events (construction and agricultural activities, secondary emission sources, etc.), and an effort was made to explain these exceptions.