Carbon isotopic characterization of formaldehyde emitted by vehicles in Guangzhou, China

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• 作者：Ping Hu ; Sheng Wen ; Yonglin Liu ; Xinhui Bi ; Lo Yin Chan ; Jialiang Feng ; Xinming Wang ; Guoying Sheng ; Jiamo Fu
• 关键词：Formaldehyde ; Vehicle emission ; Carbon isotope ; Emission factor
• 刊名：Atmospheric Environment
• 出版年：April, 2014
• 年：2014
• 卷：86
• 期：Complete
• 页码：148-154
• 全文大小：708 K

文摘

Formaldehyde (HCHO) is the most abundant carbonyl compound in the atmosphere, and vehicle exhaust emission is one of its important anthropogenic sources. However, there is still uncertainty regarding HCHO flux from vehicle emission as well as from other sources. Herein, automobile source was characterized using HCHO carbon isotopic ratio to assess its contributions to atmospheric flux and demonstrate the complex production/consumption processes during combustion in engine cylinder and subsequent catalytic treatment of exhaust. Vehicle exhausts were sampled under different idling states and HCHO carbon isotopic ratios were measured by gas chromatograph-combustion-isotopic ratio mass spectrometry (GC-C-IRMS). The HCHO directly emitted from stand-alone engines (gasoline and diesel) running at different load was also sampled and measured. The HCHO carbon isotopic ratios were from聽鈭?0.8 to聽鈭?5.7鈥?for gasoline engine, and from聽鈭?6.2 to聽鈭?0.7鈥?for diesel engine, respectively. For diesel vehicle without catalytic converter, the HCHO carbon isotopic ratios were聽鈭?2.1聽卤聽2.1鈥? and for gasoline vehicle with catalytic converter, the ratios were聽鈭?1.4聽卤聽0.7鈥? Most of the HCHO carbon isotopic ratios were heavier than the fuel isotopic ratios (from聽鈭?9 to聽鈭?7鈥?. For gasoline vehicle, the isotopic fractionation (螖¹³C) between HCHO and fuel isotopic ratios was 7.4聽卤聽0.7鈥? which was higher than that of HCHO from stand-alone gasoline engine (螖¹³C_max聽=聽2.7鈥?, suggesting additional consumption by the catalytic converter. For diesel vehicle without catalytic converter, 螖¹³C was 5.7聽卤聽2.0鈥? similar to that of stand-alone diesel engine. In general, the carbon isotopic signatures of HCHO emitted from automobiles were not sensitive to idling states or to other vehicle parameters in our study condition. On comparing these HCHO carbon isotopic data with those of past studies, the atmospheric HCHO in a bus station in Guangzhou might mainly come from vehicle emission for the accordance of carbon isotopic data.