Daily evolution of VOCs in Beijing: chemistry, emissions, transport, and policy implications
- 1Department of Chemistry, University of Leicester, Leicester, UK
- 2Department of Physics and Astronomy, Earth Observation Science Group, University of Leicester, Leicester, UK
- 3School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, UK
- 4Centre for Climate and Resilience Research (CR2), Department of Geophysics, University of Chile, Santiago, Chile
- 5Department of Geography, University College London, London, UK
- 6National Centre for Atmospheric Science, University of York, UK
- 7Wolfson Atmospheric Chemistry Laboratories, University of York, UK
- 8Ministry of Education Key Laboratory for Earth System Modeling, Department of Earth System Science, Tsinghua University, Beijing, China
- 9National Centre for Atmospheric Science, School of Chemistry, University of Leeds, Leeds, UK
- 10School of Chemistry, University of Leeds, Leeds, UK
- 11Beijing Innovation Centre for Engineering Science and Advanced Technology, State Key Joint Laboratory for Environmental Simulation and Pollution Control, Centre for Environment and Health, College of Environmental Sciences and Engineering, Peking University, Beijing, China
- 12Centre for Environmental Health and Sustainability, University of Leicester, Leicester LE1 7RH, UK
- anow at: British Antarctic Survey, Natural Environment Research Council, Cambridge CB3 0ET, UK
Abstract. Volatile organic compounds (VOCs) are important precursors to the formation of ozone (O3) and secondary organic aero-sols (SOA) and can also have direct human health impacts. Generally, given the range and number of VOC species, their emissions are poorly characterised. The VOC levels in Beijing during two campaigns (APHH) were investigated using a dispersion model (NAME), and a chemical box model (AtChem2) in order to understand how chemistry and transport affect the VOC concentrations in Beijing. Emissions of VOCs in Beijing and contributions from outside Beijing were modelled using the NAME dispersion model combined with the emission inventories and were used to initialize the AtChem2 box model. The modelled concentrations of VOCs from the NAME-AtChem2 combination were then compared to the output of a chemical transport model (GEOS-Chem). The results from the emission inventories and the NAME air mass pathways suggest that industrial sources to the south of Beijing and within Beijing both in summer and winter are very important in con-trolling the VOC levels in Beijing. A number of scenarios with different nitrogen oxides to ozone ratios (NOx / O3) and hydroxyl (OH) levels were simulated to determine the changes in VOC levels. In Beijing over 80 % of VOC are emitted locally during winter, while during summer about 35 % of VOC concentrations (greater for some individual species) are transported into Beijing from the surrounding regions. Most winter scenarios are in good agreement with daily GEOS-Chem simulations, with the best agreements seen for the modelled concentrations of ethanol, benzene and propane with correlation coefficients of 0.67, 0.63 and 0.64 respectively. Furthermore, the production of formaldehyde within 24 hours air travel from Beijing was investigated, and it was determined that 90 % of formaldehyde in the winter and 83 % in the summer in Beijing is secondary, produced from oxidation of non-methane volatile organic compounds (NMVOCs). The benzene / CO and toluene / CO ratios during the campaign is very similar to the ratio derived from literature for 2014 in Beijing, however more data are needed to enable investigation of more species over longer timeframes to determine whether this ratio can be applied to predicting VOCs in Beijing. The results suggest that VOC concentrations in Beijing are driven predominantly by sources within Beijing and by local atmospheric chemistry during the winter, and by a combination of transport and chemistry during the summer. Moreover, the relationship of the NOx / VOC and O3 during winter and summer shows the need for season-specific policy measures.
Marios Panagi et al.
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Marios Panagi et al.
Marios Panagi et al.
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