期刊
SCIENCE OF THE TOTAL ENVIRONMENT
卷 814, 期 -, 页码 -出版社
ELSEVIER
DOI: 10.1016/j.scitotenv.2021.152575
关键词
Aromatic hydrocarbon; Photochemical oxidation; Carbonyl interconversion; Secondary organic aerosols; Atmospheric fate
资金
- National Key R&D Program of China [2019YFC0214402]
- National Natural Science Foundation of China [42177354, 21777032]
- Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program [2017BT01Z032]
- Key-Area Research and Development Program of Guangdong Province [2019B110206002]
This study investigates the interconversion between monocarbonyls and dicarbonyls and their role in the production of secondary organic aerosols (SOA) during the photochemical oxidation of aromatic hydrocarbons. The results show that the formation of monocarbonyls leads to a decrease in SOA production, while the presence of OH radicals affects the balance of photolysis and influences SOA formation. These interconversion reactions play a significant role in reducing SOA production.
Photochemical oxidation (including photolysis and OH-initiated reactions) of aromatic hydrocarbon produces carbonyls, which are involved in the formation of secondary organic aerosols (SOA). However, the mechanism of this process remains incompletely understood. Herein, the monocarbonyl-dicarbonyl interconversion and its role in SOA production were investigated via a series of photochemical oxidation experiments for m-xylene and representative carbonyls. The results showed that SOA mass concentration peaked at 113.5 +/- 3.5 mu g m-3 after m-xylene oxidation for 60 min and then decreased. Change in the main oxidation products from dicarbonyl (e.g., glyoxal, methylglyoxal) to monocarbonyl (e.g., formaldehyde) was responsible for this decrease. The photolysis of methylglyoxal or glyoxal produced formaldehyde, favoring SOA formation, while photopolymerization of formaldehyde to glyoxal decreased SOA production. The presence of center dot OH altered the balance of photolysis interconversion, resulting in greater production of formaldehyde and SOA from glyoxal than methylglyoxal. Both photolysis and OH-initiated transformations of glyoxal to formaldehyde were suppressed by methylglyoxal, while glyoxal accelerated the reaction of center dot OH with methylglyoxal to generate products which reversibly converted to glyoxal and methylglyoxal. These interconversion reactions reduced SOA production. The present study provides a new research perspective for the contribution mechanism of carbonyls in SOA formation and the findings are also helpful to efficiently evaluate the atmospheric fate of aromatic hydrocarbons.
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