Effect of aluminium dust on secondary organic aerosol formation in m-xylene/NO x photo-oxidation

Abstract

As an important anthropogenic volatile organic compound (VOC), m-xylene has attracted numerous attentions due to its potential in secondary organic aerosol (SOA) formation. In this study, effects of aluminium dust seeds (boehmite and alumina) on SOA yield and aerosol size in m-xylene/NO x photo-oxidation were investigated in a 2 m 3 smog chamber at 30°C and 50% relative humidity. Compared to the seed-free system, the presence of aluminium seeds resulted in an increase in the SOA yield, and also enhanced the O 3 concentration in the chamber. The photolysis of O 3 is a major source of OH radical, which is the most important oxidant of m-xylene. The increase in O 3 concentration could result in the generation of more OH radicals, and finally contribute to the SOA formation. Seed particles influence the SOA size mainly by acting as condensation nuclei. Semi-volatile organic compounds (SVOCs) were condensed onto these nuclei, resulting in the increase in SOA size. However, when aluminium seeds with high concentrations were introduced into the system, SVOCs that had been condensed onto each particle were dispersed by these seeds, leading to the reduction in aerosol size.

SO<sub>2</sub> and NH<sub>3</sub> emissions enhance organosulfur compounds and fine particle formation from the photooxidation of a typical aromatic hydrocarbon

“…The particle-phase C-N stretch has been also characterized in m-xylene photooxidation experiments with NH 3 addition and was suggested to account for nitrogen-containing compounds (Liu et al, 2015b). A smog chamber study also found that the coexistence of SO 2 and NH 3 substantially enhanced the formation of nitrogen-containing compounds from the photooxidation of toluene (Chu et al, 2016).…”

“…In the current work, the presence of SO 2 could promote the increase in particle acidity. Elevating particle acidity could facilitate the reaction of NH 3 /NH + 4 with carbonyl-containing compounds, leading to the formation of nitrogen-containing organic compounds (Liu et al, 2015b).…”

“…Laboratory evidence suggests that NH 3 can influence SOA composition via the neutralization of organic acids (Hao et al, 2020) and via the NH 3 uptake by carbonyl-containing compounds (Flores et al, 2014). The reaction of organic compounds in particle phase with NH 3 can decrease gaseous NH 3 concentrations and can enhance the formation of nitrogen-containing organic compounds (Liu et al, 2015b), which are a class of brown carbon and could modify SOA optical properties. The neglect of NH 3 effects on SOA formation might increase the model-measurement disagreement in SOA mass and can lead to an overprediction of NH 3 concentration in the gas phase, especially in a complex urban environment.…”

Dust-Dominated Coarse Particles as a Medium for Rapid Secondary Organic and Inorganic Aerosol Formation in Highly Polluted Air

“…Extensive laboratory studies were carried out to investigate SA formation on several kinds of synthetic dust particles. − Dry dust particles can only adsorb a limited amount of trace gases because of limited reactive surface areas. However, increases in relative humidity (RH) can facilitate the uptake of SO 2 , NO 2 , NH 3 , and water-soluble volatile organic compounds (VOCs) on dust ,, and thereby leads to SA formation.…”