Different roles of water in secondary organic aerosol formation from toluene and isoprene

Abstract

Abstract. Roles of water in the formation of secondary organic aerosol (SOA) from the irradiations of toluene-NO2 and isoprene-NO2 were investigated in a smog chamber. Experimental results show that the yield of SOA from toluene almost 10 doubled as relative humidity increased from 5% to 85%, whereas the yield of SOA from isoprene under humid conditions decreased by 2.6 times as compared to that under dry conditions. The distinct difference of RH effects on SOA formation from toluene and isoprene is well explained with our experiments and model simulations. The increased SOA from humid toluene-NO2 irradiations is mainly contributed by O−H-containing products such as polyalcohols formed from aqueous reactions. The major chemical components of SOA in isoprene-NO2 irradiations are oligomers formed from the gas phase. SOA formation 15 from isoprene-NO2 irradiations is controlled by stable Criegee intermediate (SCI) that is greatly influenced by water. As a result, high RH can obstruct the oligomerization reaction of SCI to form SOA.

Anthropogenic–Biogenic Interactions at Night: Enhanced Formation of Secondary Aerosols and Particulate Nitrogen- and Sulfur-Containing Organics from β-Pinene Oxidation

“…When there were no inorganic gas pollutants present during βpinene ozonolysis (βO), the main absorption band peaks were observed at approximately 1710 cm −1 ,r e p r e s e n t i n gt h e stretching vibration of CO in carbonyl compounds. 103,104 The 105 When NO 2 was added into β-pinene ozonolysis (βON and βONS), the formation of organic nitrates can be evidenced by the strong absorption bands at 1634 (NO 2 asymmetric stretching), 1281 (NO 2 symmetric stretching), and 856 cm −1 (NO symmetric stretching). 76,108 The weak peak at 752 cm −1 also corresponds to organic nitrates.…”

Effect of relative humidity on the composition of secondary organic aerosol from the oxidation of toluene

“…In previous studies on the effect of RH on SOA yield from toluene in the presence of hygroscopic seed Kamens et al, 2011;Faust et al, 2017;Liu et al, 2017;Jia and Xu, 2017), an opposite effect was observed in which the SOA yield increased at high RH. This was attributed to the aqueous partitioning and subsequent reactions in ALW of smaller photooxidation products, such as glyoxal (Faust et al, 2017).…”

“…The comparison between different experiments is complicated by the fact that some experiments are done in the presence of hygroscopic seed particles, where ALW may be playing a role; others are done with seed particles containing strong acids, which favor acid-catalyzed chemistry, and others use no seed particles. For toluene SOA produced in presence of hygroscopic seed particles, the yield is generally found to be larger under high-RH conditions Kamens et al, 2011;Faust et al, 2017;Liu et al, 2017;Jia and Xu, 2017) because additional organic compounds are produced by the aqueous photochemistry of small highly soluble compounds, such as glyoxal, partitioned in ALW. However, Cao and Jang (2010) observed a negative correlation between RH and SOA yield for low-NO x experiments; i.e., lower RH resulted in higher SOA yields.…”

“…Most of these studies focused on the effect of RH on SOA yield (Edney et al, 2000;Zhou et al, 2011;Cocker III et al, 2001;Kamens et al, 2011;Cao and Jang, 2010;Faust et al, 2017;Liu et al, 2017;Jia and Xu, 2017) and not the chemical composition of SOA particles. The comparison between different experiments is complicated by the fact that some experiments are done in the presence of hygroscopic seed particles, where ALW may be playing a role; others are done with seed particles containing strong acids, which favor acid-catalyzed chemistry, and others use no seed particles.…”

Secondary organic aerosol formation from photooxidation of furan: effects of NO<sub>x</sub> level and humidity

“…The results were compared with the mass concentrations detected in humid mode, in which the humid air in the chamber was introduced into the SMPS with the sheath air set at 10 L min -1 . The ALW was calculated as the difference between the particle mass concentrations determined at dry and humid modes (Jia and Xu, 2017). On the basis of the recorded particle volume concentration and assumed particle density, a total suspended particulate (TSP in μg m -3 ) could be translated.…”