Synergistic impacts of anthropogenic and biogenic emissions on summer surface O3 in East Asia

A factor separation technique and an improved regional air quality model (RAQM) were applied to calculate synergistic contributions of anthropogenic volatile organic compounds (AVOCs), biogenic volatile organic compounds (BVOCs) and nitrogen oxides (NOx) to daily maximum surface O₃ (O_3DM) concentrations in East Asia in summer (June to August 2000). The summer averaged synergistic impacts of AVOCs and NOx are dominant in most areas of North China, with a maximum of 60 ppbv, while those of BVOCs and NOx are notable only in some limited areas with high BVOC emissions in South China, with a maximum of 25 ppbv. This result implies that BVOCs contribute much less to summer averaged O_3DM concentrations than AVOCs in most areas of East Asia at a coarse spatial resolution (1°× 1°) although global emissions of BVOCs are much greater than those of AVOCs. Daily maximum total contributions of BVOCs can approach 20 ppbv in North China, but they can reach 40 ppbv in South China, approaching or exceeding those in some developed countries in Europe and North America. BVOC emissions in such special areas should be considered when O₃ control measures are taken. Synergistic contributions among AVOCs, BVOCs and NOx significantly enhance O₃ concentrations in the Beijing-Tianjin-Tangshan region and decrease them in some areas in South China. Thus, the total contributions of BVOCs to O_3DM vary significantly from day to day and from location to location. This result suggests that O₃ control measures obtained from episodic studies could be limited for long-term applications.