Spatial-temporal characteristics of ambient isoprene and monoterpene and their ozone and secondary organic aerosol formation potentials in China

Biogenic volatile organic compounds (BVOCs) are important precursors of forming ozone (O3) and secondary organic aerosols (SOA), which have important impacts on air quality and climate change. Using a literature search, this review analyzed the concentration levels and spatial-temporal distributions of isoprene and monoterpene in the atmosphere in China, mainly from biogenic emissions, and estimated their impact on O3 and SOA generation. The existing observations were mainly in the Beijing-Tianjin-Hebei region, the Pearl River Delta region, central China, and in remote mountainous areas. The results showed that isoprene is the dominant component of BVOCs in the atmosphere, and its ambient concentration is much higher than monoterpene. The site-average concentrations of isoprene and monoterpene were 0.004–3.80 and 0.0003–6.31 ppb, respectively. At vegetation sites, the concentrations of isoprene and monoterpene were 0.006–3.80 and 0.007–6.31 ppb, respectively, whereas they were 0.004–2.70 and 0.0003–1.10 ppb at urban sites. For urban sites, the higher concentrations of annual isoprene occurred mainly in several central megacities, in the Sichuan-Chongqing region, and in southern regions. For vegetation sites, higher concentrations mainly occurred in southern regions. Ambient concentrations of BVOCs in the western region were the lowest for both urban and vegetation sites. Both isoprene and monoterpene showed higher concentrations in summer. The potential of isoprene and monoterpene to form O3 were 0.05–57.21 and 0.003–72.35 ppb, while those that form SOA were 0.0002–0.21 and 0.0006–10.46 μg/m3, respectively. For urban sites, the average annual O3 formation potential (OFP) by isoprene and monoterpene were 8.70 and 2.58 ppb, and their SOA formation potential (SOAP) were 0.03 and 0.37 μg/m3. For vegetation sites, they were 7.95 and 5.31 ppb and 0.03 and 0.75 μg/m3, respectively. The annual average contributions of isoprene and monoterpene to O3 and SOA formation were higher in the Beijing-Tianjin-Hebei region, Pearl River Delta region, and central China, where experience severe air pollution in China.