A New Modelling Strategy for Secondary Organic Aerosols

摘要

In recent years, air quality issues related to airborne particulate matter (PM), or aerosols, have received increasing attention of regulatory agencies, scientific community, and industry due to the adverse health and environmental effects caused by aerosols. In general, atmospheric aerosols are liquid and/or solid mixtures of nitrate, sulphate, ammonia, elemental carbon, organics, and mineral materials. While some of the aerosol components are directly emitted by various sources (primary aerosols), the components that are secondarily formed in the atmosphere (secondary aerosols) are also important contributors to the total atmospheric aerosol loading and to the adverse effects caused by aerosols. The formation of secondary aerosols, especially secondary organic aerosols (SOA), involves extremely complicated chemical and physical processes in the atmosphere. The composition of SOAs is complex and varies widely. Typical SOAs contain hundreds of organic species. The organic species are formed through gas phase reactions of emitted volatile organic compounds (VOC) with various oxidants and are transferred to existing particles through condensation, and possible nucleation, processes. Major components of SOAs include mostly high molecular weight, low vapour pressure organic species. The species normally contain oxygen — or nitrogen - containing functional groups. Because of their low vapour pressure, bi — or multi — functional compounds are some key species found in SOAs (Seinfeld and Pandis 1998; National Research Council 1977; Knoighs et al., 1975; Schuetzle et al., 1975; 1973; Schuetzle, 1972). VOCs that are most probable SOA precursors incldue olefins, especially cyclic olefins and diolefins (Hoffmann et al., 1997; Hatakeyama et al., 1987; Hatakeyama et al., 1985; Kamens et al., 1982. ), and high molecular weight olefins (Forstner et al., 1997a); aromatics, especially substituted aromatics (Forstner et al., 1997b; Odum et al., 1997; Izumi and Fukuyama, 1990); long chain alkanes; and other long chain and high molecular weight VOCs, such as high molecular weight carbonyls or carboxylic acids.