Chemistry of Organic Sulfates and Nitrates in the Urban Atmosphere

The paper overviews the current state of knowledge regarding the origin, formation mechanisms, properties and atmospheric implications of organic sulfates (organosulfates, OS) and organic nitrates (organonitrates, ON). Based on field measurements and smog chamber experiments, these esters have been proved to be relevant components of ambient atmospheric aerosols. Despite the fact that chemical knowledge on esters of sulfuric and nitric acids with simple alcohols has been well documented since the advent of classical organic chemistry (a second part of the nineteenth century), it has been only a recent decade since the discovery of these species in the airborne particulate matter attracted attention of the atmospheric community owing to their enhanced polarity and hydrophilic properties. The advances in the field of analytical instrumentations, chiefly in mass spectrometry, made it possible to provide a detailed characterization of organo-sulfates/nitrates at the molecular level. The composition of aerosol samples collected from various field campaigns showed clearly that organo-sulfates/nitrates may serve as excellent molecular tracers for anthropogenically affected aerosol sources, as it is the case of urban atmosphere.