Chemistry of dews and frosts in Indianapolis. (Reannouncement with new availability information)
Dews and frosts forming on chemically clean Teflon surfaces were sampled for pH and ion concentrations during a 13-month period in urban Indianapolis, Indiana. We predicted that dews forming in this polluted atmosphere would be acidic due to absorption of SO2 NO2 and CO2, but that frost pH would be neutral due to the lack of gas absorption. However, measured pH ranged from 6.0 to 7.2, and dew and frost pH were not significantly different. Anion and cation concentrations did not differ between dews and frosts, implying similar mechanisms and rates for scavenging of atmospheric chemicals. Sulfite and nitrite were present in many samples, indicating SO2 and NO2 absorption by both dews and frosts. The presence of ions lacking gaseous sources suggested that sedimentation of aerosols, primarily carbonates and salts, from surrounding agricultural lands occurred into dews and frosts as they formed. Carbonate deposition may have been responsible for near-neutral dew and frost pH. Dews sampled from sugar maple leaves were depleted of ammonium and enriched in other ions, but did not differ substantially in pH, compared to dews simultaneously sampled from Teflon. Temporal (overnight) sampling of dews on Teflon showed that dew chemistry changed substantially during the course of the night.
- Research Organization:
- Butler Univ., Indianapolis, IN (United States). Holcomb Research Inst.
- OSTI ID:
- 80539
- Report Number(s):
- AD-A--235397/7/XAB; CNN: Grant AFOSR-85-0225
- Country of Publication:
- United States
- Language:
- English
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