Ambient formaldehyde and its contributing factor to ozone and OH radical in a rural area |
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| Authors: | Wang Xiaoyan Wang Huixiang Wang Shaoli |
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| Institution: | 1. School of Environmental Science and Optoeclectronic Technology, University of Science and Technology of China, Hefei 230026, China;2. Key laboratory of Environmental Optical and Technology, Anhui Institute of Optics and Fine Mechanies, Chinese Academy of Science, Hefei 230031, China;3. CAS Center for Excellence in Urban Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China;4. Max Planck Institute for Chemistry, Mainz 55128, Germany;2. School of Resource and Environment, Yunnan University, Yunnan 650000, China;3. School of Information Science, Yunnan University of Finance and Economics, Yunnan 650000, China;4. Shanghai Institute of Measurement Testing Technology, Shanghai 200233, China;5. Xishuangbanna Tropical Botanical Garden of Chinese Academy of Sciences, Yunnan 666100, China;6. Fudan Tyndall Centre, Fudan University, Shanghai 200433, China |
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| Abstract: | Formaldehyde (HCHO), as well as correlative pollutants was measured from 1 to 31 July in 2007 at Mazhuang, a rural site located in the east of China. Gaseous HCHO was scrubbed from the air with an acidic 2,4-dinitrophenylhydrazine (DNPH) solution, which leaded to the reaction of HCHO with DNPH and produced a stable product, 2,4-dinitrophenylhydrazone, followed by online analysis by high-performance liquid chromatography (HPLC) coupled with Ultraviolet detector. During the observation period, mixing ratios of HCHO ranged from 0.2 ppbv to 6.2 ppbv, with an average of 1.5 ± 0.67 ppbv. HCHO shows an evident diurnal variation, the maximum appeared during 12:00–14:00. The average concentration diurnal variations of measured HCHO, ozone (O3), Methylhydroperoxides (MHP, CH3OOH), hydrogen peroxide (H2O2), nitrogen oxides (NOx) and meteorological parameters were compared. The similar variations of HCHO, O3 and radiation imply that photo-oxidation of hydrocarbons might be the major source for HCHO. Based on the maximum incremental reactivity (MIR) coefficient of HCHO, the calculation shows that HCHO contributes about 20% to total observed O3 during the study period. In order to compare the contributions of O3, HCHO and HONO to OH radical, photolysis rate parameters (J-values) of the three compounds were calculated by the Tropospheric Ultraviolet and Visible (TUV) Radiation Model (4.4 version). Based on the comparison, this study reaches the conclusion that O3 is the dominant source of OH radical at Mazhuang. This study also uses P(HCHO)/P(O3) which represents the ratio of contrbutions of HCHO and O3 to OH radical, to discuss the action of HCHO in OH radical soucers. The result shows that P(HCHO)/P(O3) is 12.5% on average, with the maximum of 21.0% at 13:00P.M. and minimum of 7.5% before 9:00A.M. and after 17:00P.M..Therefore HCHO is also an important source of OH radical and cannot be ignored. |
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