VOC reactivity and its effect on ozone production during the HaChi summer campaign

Abstract

Abstract. Measurements of ozone and its precursors conducted within the HaChi (Haze in China) project in summer 2009 were analyzed to characterize volatile organic compounds (VOCs) and their effects on ozone photochemical production at a suburban site in the North China Plain (NCP). Ozone episodes, during which running 8-h average ozone concentrations exceeding 80 ppbv lasted for more than 4 h, occurred on about two thirds of the observational days during the 5-week field campaign. This suggests continuous ozone exposure risks in this region in the summer. Average concentrations of nitrogen oxides (NO x ) and VOCs are about 20 ppbv and 650 ppbC, respectively. On average, total VOC reactivity is dominated by anthropogenic VOCs. The contribution of biogenic VOCs to total ozone-forming potential, however, is also considerable in the daytime. Key species associated with ozone photochemical production are 2-butenes (18 %), isoprene (15 %), trimethylbenzenes (11 %), xylenes (8.5 %), 3-methylhexane (6 %), n-hexane (5 %) and toluene (4.5 %). Formation of ozone is found to be NO xlimited as indicated by measured VOCs/NO x ratios and further confirmed by a sensitivity study using a photochemical box model NCAR MM. The Model simulation suggests that ozone production is also sensitive to changes in VOC reactivity under the NO x -limited regime, although this sensitivity depends strongly on how much NO x is present.

Impact of biogenic volatile organic compounds on ozone production at the Taehwa Research Forest near Seoul, South Korea

“…This shows the nonlinear nature of tropospheric photochemistry. In agreement with recent East Asian megacity studies in China and Japan (Wang et al, 2008;Bao et al, 2010;Ran et al, 2011;Geng et al, 2011), observations and model simulations at the TRF site in South Korea demonstrate the importance of natural VOC emissions in regional photochemistry near megacities. The presented observational and modeling results also show that the TRF site near the edge of the Seoul Metropolitan Area is suitable for investigating anthropogenic and biogenic interactions including VOCs and reactive nitrogen compounds (e.g.…”

“…Bao et al (2010) presented a 3-D photochemical modeling study of regional ozone production, in the Kinki region of Japan, with and without BVOC photochemistry and concluded that BVOC emissions from the suburban area can significantly contribute to ozone enhancement in the urban region. Ran et al (2011) showed VOC measurement results from a suburban site near Beijing and Tianjin, China in the summer of 2010. Although their site is downwind of two megacities, their analysis indicates that biogenic isoprene (C 5 H 8 ) was the second most dominant OH sink among all of the VOC species measured in the afternoon when photochemistry is very active.…”

Observation of atmospheric peroxides during Wangdu Campaign 2014 at a rural site in the North China Plain

“…This is comparable to the literature results with the inclusion of heterogeneous reaction (Liang et al, 2013b;Wu et al, 2015), but notably shorter than the recent studies conducted by Khan et al (2015) and Nguyen et al (2015) without the coupling of the heterogeneous process. Although dry deposition is thought to dominate the atmospheric lifetime of peroxides in previous studies (Reeves and Penkett, 2003), its role in the lifetime of atmospheric peroxides is insignificant during Wangdu Campaign 2014. The sensitivity of modeled relative loss of dry deposition to the uncertainties in the planetary boundary layer height was low as the contribution of dry deposition to the loss of H 2 O 2 in Phase I decreased no more than 10 % with the PBL height doubled.…”

“…In the NCP, it has been revealed that the vehicular exhaust is the predominant source responsible for the VOC species such as propene, trans/cis-2-butene and trimethylbenzene in the surrounding areas of the observation site (Yuan et al, 2009;Ran et al, 2011;Wu et al, 2016), while the vegetation governs the release of isoprene. It is recommended to take measures for vehicle emission control and land use management (e.g., modifying the amount and types of vegetation) in order to mitigate the pollution of atmospheric peroxides in the NCP Figure 5.…”

“…They serve as temporary reservoirs for HO x radicals, contributing to the atmospheric oxidation capacity (Reeves and Penkett, 2003). Peroxides also participate in the conversion of S(IV) to S(VI) in the aqueous phase, leading to the acid precipitation and the formation of secondary sulfate (SO 2− 4 ) aerosols in the troposphere (Calvert et al, 1985;Stein and Saylor, 2012).…”