Emission of volatile organic compounds and production of secondary organic aerosol from stir-frying spices

Tengyu Liu; Qianyun Liu; Zijun Li; Lei Huo; ManNin Chan; Xue Li; Zhen Zhou; Chak K Chan

doi:10.1016/j.scitotenv.2017.05.147

Emission of volatile organic compounds and production of secondary organic aerosol from stir-frying spices

Sci Total Environ. 2017 Dec 1:599-600:1614-1621. doi: 10.1016/j.scitotenv.2017.05.147. Epub 2017 May 19.

Authors

Tengyu Liu¹, Qianyun Liu², Zijun Li³, Lei Huo⁴, ManNin Chan⁵, Xue Li⁶, Zhen Zhou⁶, Chak K Chan⁷

Affiliations

¹ School of Energy and Environment, City University of Hong Kong, Hong Kong, China.
² Division of Environment, Hong Kong University of Science and Technology, Hong Kong, China.
³ Earth System Science Programme, The Chinese University of Hong Kong, Hong Kong, China.
⁴ Institute of Atmospheric Environment Safety and Pollution Control, Jinan University, Guangzhou, China.
⁵ Earth System Science Programme, The Chinese University of Hong Kong, Hong Kong, China; The Institute of Environment, Energy and Sustainability, The Chinese University of Hong Kong, Hong Kong, China.
⁶ Institute of Atmospheric Environment Safety and Pollution Control, Jinan University, Guangzhou, China; Guangdong Provincial Engineering Research Center for On-line Source Apportionment System of Air Pollution, Guangzhou, China.
⁷ School of Energy and Environment, City University of Hong Kong, Hong Kong, China. Electronic address: [email protected].

PMID: 28535590
DOI: 10.1016/j.scitotenv.2017.05.147

Abstract

Cooking is an important source of volatile organic compounds (VOCs) and a potential source of secondary organic aerosol (SOA) both indoors and outdoors. In this study, VOC emissions from heating corn oil and stir-frying spices (i.e. garlic, ginger, myrcia and zanthoxylum piperitum (Sichuan pepper)) were characterized using an on-line membrane inlet vacuum ultraviolet single-photon ionization time-of-flight mass spectrometer (VUV-SPI-TOFMS). VOC emissions from heating corn oil were dominated by aldehydes, which were enhanced by factors of one order of magnitude when stir-frying spices. Stir-frying any of the spices studied generated large amounts of methylpyrrole (m/z 81). In addition, stir-frying garlic produced abundant dihydrohydroxymaltol (m/z 144) and diallyldisulfide (DADS) (m/z 146), while stir-frying ginger, myrcia and zanthoxylum piperitum produced abundant monoterpenes (m/z 136) and terpenoids (m/z 152, 154). SOA formed from emissions of stir-frying spices through reactions with excess ozone in a flow reactor as well as primary organic aerosol (POA) emissions were characterized using a scanning mobility particle sizer (SMPS) and a high-resolution time-of-flight aerosol mass spectrometer (HR-TOF-AMS). Stir-frying garlic and ginger generated similar POA concentrations to those from heating corn oil while stir-frying myrcia and zanthoxylum piperitum generated double the amount of emissions. No SOA was observed from stir-frying garlic and ginger. The rates of SOA production from stir-frying myrcia and zanthoxylum piperitum were 1.8μgmin^-1g_spice^-1 and 8.7μgmin^-1g_spice^-1, equivalent to 13.4% and 53.1% of their own POA emission rates, respectively. Therefore, the contribution of stir-frying spices to ambient organic aerosol levels is likely dominated by POA. The rates of total terpene emission from stir-frying myrcia and zanthoxylum piperitum were estimated to be 5.1μgmin^-1g_spice^-1 and 24.9μgmin^-1g_spice^-1, respectively. Our results suggest that stir-frying spices could be an important source of terpenes in indoor environments in Hong Kong, at least during cooking.

Keywords: Cooking emissions; Secondary organic aerosol; Spices; Terpenes; Volatile organic compounds.