A temporally and spatially resolved validation of emission inventories by measurements of ambient volatile organic compounds in Beijing, China

摘要

Understanding the sources of volatile organic compounds (VOCs) is essentialfor ground-level ozone and secondary organic aerosol (SOA) abatementmeasures. We made VOC measurements at 27 sites and online observations atan urban site in Beijing from July 2009 to January 2012. Based on thesemeasurement data, we determined the spatial and temporal distribution ofVOCs, estimated their annual emission strengths based on their emissionratios relative to carbon monoxide (CO), and quantified the relativecontributions of various sources using the chemical mass balance (CMB)model. These results from ambient measurements were compared with existingemission inventories to evaluate the spatial distribution, species-specificemissions, and source structure of VOCs in Beijing. The measured VOCdistributions revealed a hotspot in the southern suburban area of Beijing,whereas current emission inventories suggested that VOC emissions wereconcentrated in downtown areas. Compared with results derived from ambientmeasurements, the annual inventoried emissions of oxygenated VOC (OVOC)species and C2–C4 alkanes may be underestimated, while the emissions ofstyrene and 1,3-butadiene may be overestimated by current inventories.Source apportionment using the CMB model identified vehicular exhaust as themost important VOC source, with the relative contribution of 49%, ingood agreement with the 40–51% estimated by emission inventories. Therelative contribution of paint and solvent utilization obtained from the CMBmodel was 14%, significantly lower than the value of 32% reported byone existing inventory. Meanwhile, the relative contribution of liquefiedpetroleum gas (LPG) usage calculated using the CMB model was 6%, whereasLPG usage contribution was not reported by current emission inventories.These results suggested that VOC emission strengths in southern suburbanarea of Beijing, annual emissions of C2–C4 alkanes, OVOCs and some alkenes,and the contributions of solvent and paint utilization and LPG usage incurrent inventories all require significant revisions.