Mapping the drivers of formaldehyde (HCHO) variability from 2015–2019 over eastern China: insights from FTIR observation and GEOS-Chem model simulation
- 1Key Laboratory of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics, HFIPS, Chinese Academy of Sciences, Hefei 230031, China
- 2Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, 361021, China
- 3Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei, 230026, China
- 4Laboratory for Climate and Ocean–Atmosphere Studies, Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing 100871, China
- 5State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin 150090, China
- 6Institute of Environmental Physics, University of Bremen, P. O. Box 330440, 28334 Bremen, Germany
- 7School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
- 8Key Laboratory of Precision Scientific Instrumentation of Anhui Higher Education Institutes, University of Science and Technology of China, Hefei, 230026, China
- 9Anhui Province Key Laboratory of Polar Environment and Global Change, University of Science and Technology of China, Hefei, 230026, China
- 10Royal Belgian Institute for Space Aeronomy (BIRA-IASB), Brussels, Belgium
- 11Laboratoire des Sciences du Climat et de l'Environnement, CEA-CNRS-UVSQ, UMR8212, Gif-sur-Yvette, France
- 12School of Chemistry, University of Wollongong, Northfields Ave, Wollongong, NSW, 2522, Australia
- 13Anhui University Institutes of Physical Science and Information Technology, Hefei 230601, China
Abstract. The major air pollutant emissions have decreased and the overall air quality has substantially improved across China in recent years as a consequence of active clean air policies for mitigating severe air pollution problems. As key precursors of formaldehyde (HCHO) and ozone (O3), the volatile organic compounds (VOCs) in China are still increasing because current clean air policies lack mitigation measures for VOCs. In this study, we mapped the drivers of HCHO variability over eastern China using ground-based high-resolution Fourier transform infrared (FTIR) spectrometry and GEOS-Chem model simulation. Diurnal, seasonal, and interannual variability of HCHO over eastern China was investigated and hydroxyl (OH) radical production from HCHO was evaluated. The relative contributions of emitted and photochemical sources to the observed HCHO were analysed by using ground level carbon monoxide (CO) and Ox (O3 + nitrogen oxide (NO2)) as tracers for emitted and photochemical HCHO, respectively. Contributions of various emission sectors and geographical transport to the observed HCHO summertime enhancements were determined by using a GEOS-Chem tagged-tracer simulation. The tropospheric HCHO volume mixing ratio (VMR) reached a maximum monthly mean value of (1.1 ± 0.27) ppbv in July and a minimum monthly mean value of (0.4 ± 0.11) ppbv in January. The tropospheric HCHO VMR time series from 2015–2019 shows a positive trend of (1.43 ± 0.14) % per yr. The photochemical HCHO is the dominant source of atmospheric HCHO over eastern China for most of the year (68.1 %). In the studied years, the HCHO photolysis was an important source of OH radical over eastern China during all sunlight hours of both summer and winter days. The anthropogenic emissions (fossil fuel + biofuel emissions) accounted for 31.96 % and the natural emissions (biomass burning + biogenic) accounted for 48.75 % of HCHO summertime enhancements. The observed HCHO summertime enhancements were largely attributed to the emissions within China (76.92 %), where eastern China dominated the contribution (46.24 %). The increased trend in HCHO in recent years was largely attributed to the increase in the HCHO precursors such as CH4 and nonmethane VOCs (NMVOCs). This study can provide an evaluation of recent VOC emissions and regional photochemical capacity in China. In addition, this study is also important for regulatory and control purposes and will help to improve urban air quality and contribute to the formation of new Chinese clean air policies in the future.
Youwen Sun et al.
Youwen Sun et al.
Youwen Sun et al.
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