Coupled Partitioning, Dilution, and Chemical Aging of Semivolatile Organics

• Published in: Environmental science & technology 2006-04, Vol.40 (8), p.2635-2643
• Main Authors: Donahue, N. M, Robinson, A. L, Stanier, C. O, Pandis, S. N
• Format: Article
• Language: English
• Subjects: Aerosols; Air Pollutants; Applied sciences; Atmospheric pollution; Emissions; Exact sciences and technology; Models, Chemical; Organic Chemicals - chemistry; Oxidation; Oxidation-Reduction; Pollutants physicochemistry study: properties, effects, reactions, transport and distribution; Pollution; Temperature; VOCs; Volatile organic compounds; Volatility; Volatilization
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es052297c

A unified framework of semi-volatile partitioning permits models to efficiently treat both semi-volatile primary emissions and secondary organic aerosol production (SOA), and then to treat the chemical evolution (aging) of the aggregate distribution of semi-volatile material. This framework also reveals critical deficiencies in current emissions and SOA formation measurements. The key feature of this treatment is a uniform basis set of saturation vapor pressures spanning the range of ambient organic saturation concentrations, from effectively nonvolatile material at 0.01 μg m-3 to vapor-phase effluents at 100 mg m-3. Chemical evolution can be treated by a transformation matrix coupling the various basis vectors. Using this framework, we show that semi-volatile partitioning can be described in a self-consistent way, with realistic behavior with respect to temperature and varying organic aerosol loading. The time evolution strongly suggests that neglected oxidation of numerous “intermediate volatility” vapors (IVOCs, with saturation concentrations above ∼1 mg m-3) may contribute significantly to ambient SOA formation.