A biogenic volatile organic compounds emission inventory for Beijing

The present study presents us the first detailed inventory for volatile organic compounds (VOC) emissions from vegetation over Beijing, China. The spatially and temporally resolved inventory was developed based on a Geographic Information system (GIS), Remote sensing (RS) data and field measurement data, such as digitized land-use data, normalized difference vegetation index (NDVI) and temperature and photosynthetic active radiation (PAR) data from direct real-time measurement. The inventory has a spatial resolution of 1×1 km2 and a time resolution of 1 h. Urban, agriculture, and natural land-use distributions in Beijing were combined with biomass factors for each land-use category to produce a spatially resolved biomass inventory. A biogenic emission inventory was developed by combining the biomass inventory with hourly emission rates for tree, shrub, and ground cover species of the study area. Twenty-three kinds of the emission rate data of the 39 vegetation types in Beijing were identified using a bag-enclosure sampling method followed by GC-FID analysis in our field measurement. Other emission rate data were quoted from previous study or assigned with the taxonomic method. Correcting for environmental factors, including light intensity and temperature, we arrive a value of 1.6×1010 gC for total annual biogenic VOC emissions from Beijing, including 7.9×109 gC for isoprene, 3.5×109 gC for monoterpenes, and 4.8×109 gC for OVOC. Some uncertainties are also discussed in this study.