The atmospheric oxidation of isoprene 2-methyl-13-butadiene

Question

Abstract :

The atmospheric oxidation of isoprene (2-methyl-1,3-butadiene, C5H8) leads to the formation of secondary organic aerosol (SOA). In this study, the mechanism of SOA formation by isoprene photooxidation is comprehensively investigated, by measurements of SOA yields over a range of experimental conditions, namely isoprene and NOx concentrations. Hydrogen peroxide is used as the radical precursor, substantially constraining the observed gas-phase chemistry; all oxidation is dominated by the OH radical, and organic peroxy radicals (RO2) react only with HO2 (formed in the OH+ H₂O₂ reaction) or NO concentrations, including NOx free conditions. At high NOx, yields are found to decrease substantially with increasing [NOx], indicating the importance of RO2 chemistry in SOA formation. Under low-NOx conditions, SOA mass is observed to decay rapidly, a result of chemical reactions of semi-volatile SOA components, most likely organic hydroperoxides.

 

Outlines:

• Mechanism of SOA formation from isoprene oxidation
• Laboratory measurements of aerosol growth from isoprene oxidation
• Gas-phase oxidation
• NOx level (RO2 chemistry)

Answer 1

For the chemistry problem illustrated below, respond as per requisite. The atmospheric oxidation of isoprene leads to the formation of secondary organic aerosol. In this study, the method of SOA formation via isoprene photooxidation is thoroughly investigated, by measurements of SOA outcomes over a range of experimental situations, namely isoprene and NOx concentrations. Hydrogen peroxide is employed as the radical precursor, substantially restraining the observed gas-phase chemistry; all oxidation is dominated via the OH radical and organic peroxy radicals react with only HO2 or NO concentrations, including NOx free conditions. At high NOx, outcomes are found to reduce substantially with rising [NOx], pointing out the significance of RO2 chemistry in SOA formation. In low-NOx conditions, SOA mass is noticed to decay rapidly, an outcome of chemical reactions of semi-volatile SOA components. Outlines: 1) Method of SOA formation from isoprene oxidation