Simplification of the representation of the organic component of atmospheric particulates.
We present an analysis of recent field data to investigate the variation in the organic component of atmospheric aerosol and its behaviour in the moist environment. In all locations the degree of oxygenation of the organic material increases with photochemical age, as does the particulate hygroscopicity. These changes will generally occur in spatial scales comparable to a single cell in global models at representative boundary layer wind speeds. Using ADDEM, a new model of the equilibrium state of multicomponent aerosol, we show that inorganic component changes must be responsible for the increase in particulate hygroscopicity with photochemical age. It is suggested that a common representation of nearfield and background organic aerosol composition is sufficient to describe the behaviour of organic components in a variety of field experiments; nearfield small mode organics being dominated by a combustion-derived unoxidised signature, whilst the background accumulation mode is more oxygenated and dominates in air masses with a photochemical age of more than a couple of days. This representation may be used within the sub-saturated regime to predict the behaviour of ambient particulates in the moist atmosphere. Whether a similar common representation can be used for cloud activation prediction in supersaturated environments, or for investigation of gas-to-particle partitioning, should be investigated.
McFiggans
Gordon
G
Atmospheric Science Group, University of Manchester, PO Box 88, Sackville Street, Manchester, UK, M60 1QD.
Alfarra
M Rami
MR
Allan
James
J
Bower
Keith
K
Coe
Hugh
H
Cubison
Mike
M
Topping
Dave
D
Williams
Paul
P
Decesari
Stefano
S
Facchini
Cristina
C
Fuzzi
Sandro
S
D000336:Aerosols / Q000032:analysis; D000393:Air Pollutants / Q000032:analysis*; D001272:Atmosphere / Q000032:analysis / Q000737:chemistry*; D004784:Environmental Monitoring / Q000379:methods*; D005843:Geography; D017745:Incineration; D007287:Inorganic Chemicals / Q000032:analysis; D009930:Organic Chemicals / Q000032:analysis*; D010083:Oxidants, Photochemical / Q000032:analysis; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D013816:Thermodynamics; D014919:Wind
D000336:Aerosols; D000393:Air Pollutants; D007287:Inorganic Chemicals; D009930:Organic Chemicals; D010083:Oxidants, Photochemical; D010100:Oxygen