ENVIRONMENTAL CHEMISTRY OF ORGANIC COMPOUNDS IN AIR, PRECIPITATION, AND WATER

Precipitation is an important mechanism for the removal of organic compounds from the atmosphere. Snow and rain samples collected at an urban and a rural site have been analyzed to identify and quantify volatile and extractable organic compounds. Hydrocarbons, polycyclic aromatic hydrocarbons, terpenes, alcohols, carboxylic acids and phenols from natural and anthropogenic sources have been found in snow and rain. Most of these compounds are associated with particulate matter that is removed from the atmosphere by precipitation. The organic constituents of urban precipitation are primarily of anthropogenic orgin, but there is a small, but significant, contribution from natural sources. At a remote mountainous site in Colorado the organic compounds isolated from precipitation samples appear to arise predominantly from natural sources.; Most hydrophobic vapor phase organic compounds are not significantly removed by precipitation and are not, in general, detected in snow and rain.; The removal of airborne particulate matter by precipitation results in the deposition of substantial quantities ((mu)g/m('2)hr) of organic compounds. The washout ratios of particulate phase organic compounds were found to be approximately the same as previously determined values for inorganic species in the atmosphere.; Volatile and semi-volatile organic compounds have been measured in the source waters and at various stages in the drinking water treatment process at the Betasso treatment plant near Boulder, CO. The source waters entering this plant contain extremely low levels of organic compounds, but chloroform and bromodichloromethane were detected in water after various stages of treatment, in the finished water and in the distribution system. Large seasonal variation in the concentrations of trihalomethanes were observed, with the highest concentration found during the spring. The results of multivariate statistical analyses and in-plant measurements show that the water quality of the source waters and the practice of raw water chlorination were the major factors in the formation of trihalomethanes.; Semi-volatile organic compounds were present at very low levels (ng/L) in the source and potable waters. Most of the semi-volatile organic compounds in the source water were from natural sources, while the treated potable water contained organic compounds from natural and anthropogenic sources.