Temperature Effects on Optical Properties and Chemical Composition of Secondary Organic Aerosol Derived from n -Dodecane

Abstract. Environmental temperature plays a vital role in controlling chemical transformations that lead to the formation of secondary organic aerosol (SOA), and ultimately impact composition and optical properties of the aerosol particles. In this study, we investigate optical properties of n-dodecane secondary organic aerosol under two temperature conditions: 5 °C and 25 °C. It is shown that low temperature can enhance the real part of refractive index (RI) of the SOA at the wavelengths of 532 nm and 375 nm. Mass spectrometry analysis reveals that molecular composition of n-dodecane SOA is significantly modified by temperature: a large amount of oligomers are formed under low temperature condition, which lead to higher RI values. These findings will help improve our understanding of the chemical composition and optical properties of SOA under different temperature conditions, and provide another possible explanation of the low visibility during winter.