Heterogeneous reactions of isoprene and ozone on α-Al2O3: The suppression effect of relative humidity. (February 2020)

• Record Type: Journal Article
• Authors: Lian, Hong-Yang; Pang, Shu-Feng; He, Xiang; Yang, Miao; Ma, Jia-Bi; Zhang, Yun-Hong
• Is Part Of: Chemosphere. Volume 240(2020)
• Publication Date: 2020-02
• Subjects: Heterogeneous reactions -- Isoprene -- α-Al2O3 -- Relative humidity -- Micro-FTIR; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2019.124744
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: The heterogeneous reactions of α-Al2 O3 particles with a mixture of ozone (∼50 ppm) and isoprene (∼50 ppm) were studied as a function of relative humidities (RHs). The reactions were monitored in real time through the microscopic Fourier transform infrared (micro-FTIR) spectrometer. The results show that the presence of ozone leads to the rapid conversion of isoprene to carboxylate (COO − ) ions on the surfaces of α-Al2 O3 particles in the initial stage. The water significantly suppresses the formation of the carboxylate ions. For the isoprene ozonolysis reaction on the α-Al2 O3 particles, the reactive uptake coefficient is strongly suppressed by over a factor of 8 when the RH increases from 8% to 89%. The negative correlation between RH with the secondary organic aerosol (SOA) produced by isoprene ozonolysis plays a key role in the actual atmospheric environment under high humidity. Our results may provide insight into the ozonolysis process of biogenic alkenes over mineral aerosol surfaces with the influence of RHs. Highlights: The first time to research the heterogeneous reaction of C5 H8 /O3 on α-Al2 O3 particles. Carboxylate are formed on α-Al2 O3 particles obviously. Reactions of C5 H8 /O3 on α-Al2 O3 particles exhibit RH dependence. The reaction rates and uptake coefficients decrease with increasing RH.