CHEMICAL CHARACTERIZATION OF 3 SUMMER CLOUD EPISODES AT WHITEFACE MOUNTAIN

Cloudwater and aerosol samples were collected during three 1987 summer events at Whiteface Mountain, New York. Dominant inorganic components in cloudwater were SO42-, NO3-, H+, and NH4+. Maximum levels were 978, 256, 421, and 832 mu eq l(-1), respectively. pH values in cloudwater ranged from 3.1 to 4.4. Large variations in concentrations were found, which can best be explained, on the basis of back-trajectory analysis, by different origins of air masses. A concave concentration versus a time profile for the ionic concentrations was observed, possibly as a result of dilution and concentration as liquid water content changed over the life of the cloud. Dominant components of the aerosol were NH4+ and SO42. Changes in the gas-phase concentrations of SO2 O-3, and H2O2 during a cloud event indicated a considerable S(IV) oxidation potential by H2O2. Free acidity (H+) was 32 - 81% of the total acidity. Carboxylic acid concentrations were dominated by formic acid (13.9 - 39.9 mu eq l(-1)), acetic acid (5.1 - 14.7 mu eq l(-1)), oxalic acid (2.9 - 19.3 mu eq l(-1)), malonic acid (3.9 - 14.7 mu eq l(-1)), and pyruvic acid (2.4 - 8.6 mu eq l(-1)); these acids have accounted for 7 - 15% of the dissolved organic carbon and up to 22% of the free acidity. Multivariate factor analysis yielded three components that accounted for 91% of the variability of all the parameters: transported scid component, combination of fossil-fuel combustion and automobile emission, auld nontransported biogenic component. Primary pollutant concentrations and photochemical activity during long-range transport were the major factors in controlling the chemical species concentrations at the downwind site.