Characteristics, source apportionment and reactivity of ambient volatile organic compounds at Dinghu Mountain in Guangdong Province, China.

Volatile organic compounds (VOCs) play a very important role in the formation of ozone and secondary organic aerosols. The concentrations, compositions, and variability of VOCs were measured from 2005 to 2008 at Dinghu Mountain Forest Ecosystem Research Station, a remote station in Southeast China. Weekly samples were collected in the Dinghu Mountain area and were analysed via gas chromatography-mass spectrometry. The results revealed that the total VOC concentrations decreased continuously and that the dominant VOC components were alkanes (43%) and aromatics (33%), followed by halo-hydrocarbons (12%) and alkenes (12%). The general trend of seasonal variation indicated higher concentrations in spring and lower concentrations in summer. The positive matrix factorization model was used to identify the sources of the VOCs. Seven sources were resolved by the PMF model: (1) vehicular emissions, which contributed 25% of the total VOC concentration; (2) industrial sources and regional transportation, contributing 17%; (3) paint solvent use, contributing 17%; (4) fuel evaporation, contributing 13%; (5) stationary combustion sources, contributing 12%; (6) biogenic emissions, contributing 10%; and aged VOCs, contributing only 6%. The HYSPLIT model was used to analyse the effect of pollutant transport, and the results indicated that the transport of pollutants from cities cannot be ignored. Finally, the OH radical loss rates and ozone formation potentials (OFPs) were calculated, and the results indicated isoprene to have the highest OH radical loss rate and toluene to be the largest contributor to the OFP at the Dinghu Mountain site.