In-cloud scavenging of gases and aerosols at a mountain site in Central Switzerland

✍ Scribed by B. Oberholzer; J. L. Collett; J. Staehelin; A. Waldvogel

• Book ID: 104626138
• Publisher: Springer Netherlands
• Year: 1992
• Tongue: English
• Weight: 587 KB
• Volume: 14
• Category: Article
• ISSN: 0167-7764
• DOI: 10.1007/bf00115223

✦ Synopsis

An in-cloud scavenging case study of the major ions (NH4+, 5042-and NO3-) determining the cloudwater composition at a mountain site (1620 m.a.s.i.) is presented. A comparison between in-cloud measurements of the cloudwater composition, liquid water content, gas concentrations and aerosol concentrations and pre-cloud gas and aerosol concentrations yields the following results. Cloudwater concentrations resulted from scavenging of about half of the available NH3, aerosol NH4+, aerosol NO3-, and aerosol SO42-. Approximately a third of the SO 2 was scavenged by the cloudwater and oxidized to SO42-. Cloud acidity during the first two hours of cloud interception (pH 3.24) was determined mostly by the scavenged gases (NH 3, SO 2, and HNO3); aerosol contributions to the acidity were found to be small. Observations of gas and aerosol concentrations at three elevations prior to several winter precipitation events indicated that NH 3 concentrations are typically half (12 -80 %) of the total (gas and aerosol) N (-III) concentrations. HNO 3 typically is present at much lower concentrations (1 -55 %) than aerosol NO3-. Concentrations of SO 2 are a substantial component of total sulfur, with concentrations averaging 60 % (14 -76 %) of the total S (IV and VI).