Impacts of seasonal and regional variability in biogenic VOC emissions on surface ozone in the Pearl River delta region, China

X Wang,S Situ,Z Wu,A Turnipseed,J Bai,X Jiang,A Guenther

doi:10.5194/acp-13-11803-2013

Abstract

Abstract. This study investigated the impacts of seasonal and regional variability in biogenic volatile organic compounds (BVOCs) on surface ozone over the Pearl River delta (PRD) region in southern China in 2010 with the WRF–Chem/MEGAN (Weather Research and Forecasting coupled with Chemistry/Model of Emissions of Gases and Aerosols from Nature) modeling system. Compared to observations in the literature and this study, MEGAN tends to predict reasonable BVOC emissions in summer, but may overestimate isoprene emissions in autumn, even when the local high-resolution land-cover data and observed emission factors of BVOCs from local plant species are combined to constrain the MEGAN BVOC emissions model. With the standard MEGAN output, it is shown that the impact of BVOC emissions on the surface ozone peak is ~3 ppb on average with a maximum of 24.8 ppb over the PRD region in autumn, while the impact is ~10 ppb on average, with a maximum value of 34.0 ppb in summer. The areas where surface ozone is sensitive to BVOC emissions are different in autumn and in summer, which is primarily due to the change of prevailing wind over the PRD; nevertheless, in both autumn and summer, the surface ozone is most sensitive to the BVOC emissions in the urban area because the area is usually VOC-limited. Three additional experiments concerning the sensitivity of surface ozone to MEGAN input variables were also performed to assess the sensitivity of surface ozone to MEGAN drivers, and the results reveal that land cover and emission factors of BVOCs are the most important drivers and have large impacts on the predicted surface ozone.

Highlights

Formed by photochemical reactions involving volatile organic compounds (VOCs) and the oxides of nitrogen (NOx = NO + NO2) (Chameides et al, 1992), surface ozone is the most abundant atmospheric photochemical oxidant and can adversely affect vegetation as well as human health and welfare (Aneja et al, 1992)
biogenic volatile organic compounds (BVOCs) emissions must be considered when examining anthropogenicemission-control strategies in the Pearl River delta (PRD), especially since the local government now is taking measures to reduce the anthropogenic emissions of ozone precursors from industry and mobile sources, which will increase the importance of BVOC emissions in the future
This study indicates that BVOC emissions can significantly affect surface ozone in the PRD region, and that the impacts are complex

Summary

Introduction

Measurement and modeling of BVOC emissions are essential for understanding regional and global atmospheric chemistry, carbon cycle, and climate change. BVOC emissions are considered to be responsible for the background level of surface ozone. By excluding all anthropogenic emissions, the background level of surface ozone due to BVOC emissions over the PRD region was estimated. The higher the background level is, the more difficult it is to solve the ozone problem. BVOC emissions must be considered when examining anthropogenicemission-control strategies in the PRD, especially since the local government now is taking measures to reduce the anthropogenic emissions of ozone precursors from industry and mobile sources, which will increase the importance of BVOC emissions in the future

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Results

Discussion

Conclusion