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[1] During an intensive field campaign at a midlevel (1640 m above sea level) mountain in central Europe, cloud water samples were collected using a cloud water sampler and subsequently analyzed for organic and inorganic ions, total carbon (TC), and black carbon (BC). Cloud water surface tension (s) was measured using the ring method. Generally, the cloud water samples had surface tensions lower than that of pure water. The average value of s was 95.2% of the s of water, while the lowest value was 83.3%. A trend of lower s with higher concentrations of organic material (OC, obtained as TC-BC) was found at lower OC concentrations than those previously described [Charlson et al., 2001;Facchini et al., 1999a]. The effect of the lower s on cloud droplet activation was modeled using Köhler theory. For an assumed dry sulphate nucleus with 0.05 mm diameter, the critical supersaturation would be decreased by 7% (average s) and by 22% for minimum s.

Passive samplers were used to monitor ammonia concentrations at rural inner alpine and pre-alpine, as well as urban, sites in Austria and Bavaria. Elevated concentrations were measured both at farms (up to 36 microg NH3 m(-3)) and at urban locations (up to 28 microg NH3 m(-3)). At urban locations a linear relationship between the traffic density and the NH3 concentration was found, but there was no marked seasonal trend. The highest ammonia concentrations were measured in a traffic tunnel (up to 78 microg NH3 m(-3)). The presence of livestock breeding or small scale alpine pastures resulted in elevated concentrations at the rural sites (8.1-12 and 2.5-4.6 microg NH3 m(-3), respectively), compared to the surrounding areas (3.1 and 0.9 microg NH3 m(-3)). Agriculture related sources are usually limited either spatially or seasonally. As the emissions were moderate in our case, a rapid removal and dilution of ammonia was possible and therefore the NH3 burden was only local. Sources related to traffic are more evenly distributed both geographically and seasonally. The WHO guideline, annual average concentration of 8 microg m(-3) for the protection of vegetation, was only exceeded at farms, at the urban station with the heaviest traffic and in the Tauerntunnel.