Characterization of cooking fumes in Hong Kong

Abstract

Cooking is such a common activities in commercial restaurants and residential households for food preparation. Unfortunately, cooking fume emission can be considered as a serious air pollution source in a developed, densely populated city such as Hong Kong owing to its large number of restaurants and residential dwellings located in urban area. As a result, it is important to exam the chemical compositions and characteristics of the particles emitted by cooking activities. In this study, six commercial restaurants, including two Chinese restaurants, two western restaurants and two fast food restaurants and one common residential dwelling were selected for sampling and analysis. For commercial restaurants, samples were collected through each restaurant's exhaust ducts during peak hours. Over 80 organic compounds were identified and quantified in this study. For residential dwellings, different Chinese cooking methods were applied in the kitchen to evaluate cooking emissions. On average, the mass concentrations of PM2.5 in western restaurants were much lower than that of in Chinese and Fast food restaurants. As far as the chemical compositions are concerned, the aerosol is predominately organic matter consisting of organic carbon (OC) (over 70%) in all commercial restaurants as expected. Fatty acids, alkanes, PAHs and steroids were the major organic compounds emitted from all commercial restaurants. Of the quantified organic mass, over 70% was fatty acids. The mass of PM2.5, organic species, the distribution of n-alkanes and PAHs indicated the dissimilarities between different styles of restaurants. The average emission rates of PM2.5, total gas phase PAHs, total particle phase PAHs gas and particle phase organic compounds from commercial sources in Hong Kong were calculated to be 2.30x105 kg/year, 1.21xl03 kg/year, 2.16xl02 kg/year, 1.62xl03 kg/year and 3.26xl04 kg/year, respectively. However, Chinese restaurant has the highest percentage of emission, over 80%, because of its largest number. Traffic has long been recognized as the major contributors to PM2.5 and PAHs. It is calculated that PM2.5, gas and particle phase PAHs from commercial cooking sources equate 17.9%, 9.2% and 18.3% of emissions from vehicular traffic sources. This is the first time a commercial and residential cooking emission profiles database has been collected for Hong Kong. Although the database can only provide a general idea with a high degree of uncertainty, it will become a useful tool to understand and plan strategies to improve Hong Kong's air quality.