Temperature effects on optical properties and chemical composition of secondary organic aerosol derived from &amp;lt;i&amp;gt;n&amp;lt;/i&amp;gt;-dodecane

Junling Li,Wenyu Zhang,Bo Shi,Hong Li,Weigang Wang,Mingyuan Liu,Yan Chen,Kun Li,Li Zhou,Chao Peng,Maofa Ge

doi:10.5194/acp-20-8123-2020

Abstract

Abstract. Environmental temperature plays a vital role in controlling chemical transformations that lead to the formation of secondary organic aerosol (SOA) and ultimately impact the composition and optical properties of the aerosol particles. In this study, we investigated optical properties of n-dodecane SOA under two temperature conditions: 5 and 25 ∘C. It was shown that low-temperature conditions could enhance the real part of the refractive index (RI) of the SOA at wavelengths of 532 and 375 nm. Mass spectrometry analysis revealed that the molecular composition of n-dodecane SOA was significantly modified by temperature: a large amount of oligomers were formed under low-temperature conditions, which led 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 will provide one possible explanation for the low visibility in suburban areas during winter.

Highlights

Organic aerosol, especially secondary organic aerosol (SOA), plays a vital role in air quality, climate change and human health (Kanakidou et al, 2005; Poschl, 2005; Mellouki et al, 2015; Poschl and Shiraiwa, 2015; von Schneidemesser et al, 2015; Shrivastava et al, 2017)
As similar amounts of n-dodecane and oxidant were added to the smog chamber and the reaction rate was lower under low temperature, the reaction time under lowtemperature conditions was significantly longer than that at room temperature: 4–5 h for room temperature and 8–9 h for low-temperature conditions
The total surface concentration and mass reached a maximum after 3 h, whereas it reached a maximum after 6 h under low-temperature conditions

Summary

Introduction

Especially secondary organic aerosol (SOA), plays a vital role in air quality, climate change and human health (Kanakidou et al, 2005; Poschl, 2005; Mellouki et al, 2015; Poschl and Shiraiwa, 2015; von Schneidemesser et al, 2015; Shrivastava et al, 2017). Due to the variety of precursors and oxidation pathways, the composition of SOA is very complicated and variable (Lu, 2018; von Schneidemesser et al, 2015; Poschl and Shiraiwa, 2015; Hallquist et al, 2009; George et al, 2015), and the optical properties of SOA exhibit different characteristics (Shrivastava et al, 2017; Zhang et al, 2015; Moise et al, 2015; Laskin et al, 2015). J. Li et al.: Temperature effects on optical properties and chemical composition of SOA cal characteristics (e.g., morphology and shape) of a particle (Moise et al, 2015). Quantifying the RI of aerosol particles is highly important to evaluate their optical properties and to further estimate their impacts on atmospheric visibility and the Earth’s radiative balance

Methods

Results

Conclusion