CLOUDWATER CHEMISTRY FROM 10 SITES IN NORTH-AMERICA

Cloudwater and rainwater samples were collected at 2.5 m above ground during 2 years from 10 nonurban sites in North America. On the average, cloudwater collected from sites in the eastern United States was more acidic and had higher concentrations of NO3- and SO42- than that at sites in the Western United States and Puerto Rico. Of all the sites in the network, cloudwater from Maine had the highest concentrations of these ions. Concentrations of hydrogen ion, nitrate, and sulfate were significantly higher in cloudwater than in rainwater at most sites; however, on a paired-event basis, enrichment factors for cloud vs rain varied greatly. In contrast to distributions of inorganic anions, the concentrations of formate and acetate in cloudwater and rainwater were similar at sites in the western and eastern United States, suggesting that these compounds originated primarily with natural rather than anthropogenic sources.