Impact of humidity on the ozone initiated oxidation of limonene, delta3-carene, and alpha-pinene.
The effect of water on the initial secondary organic aerosol (SOA) formation from gas-phase ozonolysis of limonene, delta3-carene, and alpha-pinene (-3 and approximately 1.5 x 10(11) molecule cm(-3) reacted) has been investigated in a flow reactor at controlled relative humidity (RH), temperature (298 +/- 0.4 K), and reaction time (270 +/- 2 s). Low amounts of terpene converted minimize the impact of secondary reactions. A comparison of the SOA formation from the three terpenes was made for initial rate of reactions being around 7.5 x 10(8) and 15 x 10(8) molecule cm(-3) s(-1). The most efficient species in producing SOA was limonene, while alpha-pinene was the least efficient. The results showed that an enhancement in water vapor concentration (<2-85% RH) caused an increase in both integrated mass (M10-300nm) and total number (N10-300nm). The effect on number and mass were a factor of 2-3 and 4-8, respectively. Physical water up-take can partly explain the increase in mass, but not the observed increase in number. Therefore it was concluded that the increase in water concentration must, by a gas-phase reaction, produce more low volatility product(s).
Jonsson
Asa M
AM
Department of Chemistry, Atmospheric Science, Göteborg University, SE-412 96 Göteborg, Sweden. asajon@chem.gu.se
Hallquist
Mattias
M
Ljungström
Evert
E
D000393:Air Pollutants / Q000737:chemistry*; D000081008:Bicyclic Monoterpenes; D053138:Cyclohexenes; D006813:Humidity; D000077222:Limonene; D039821:Monoterpenes / Q000737:chemistry*; D010084:Oxidation-Reduction; D010126:Ozone / Q000737:chemistry*; D013729:Terpenes / Q000737:chemistry*; D014867:Water / Q000737:chemistry
D000393:Air Pollutants; D000081008:Bicyclic Monoterpenes; D053138:Cyclohexenes; D039821:Monoterpenes; D013729:Terpenes; D014867:Water; D010126:Ozone; D000077222:Limonene; C030218:3-carene; C005451:alpha-pinene