Top-down estimates of benzene and toluene emissions in the Pearl River Delta and Hong Kong, China

Xuekun Fang,Ronald G Prinn,Andreas Stohl,Ming Wang,Qiang Zhang,Hai Guo,Jiamin Ou,Min Shao,Rona L Thompson,Junyu Zheng,Chen Wang

doi:10.5194/acp-16-3369-2016

Abstract

Abstract. Benzene (C6H6) and toluene (C7H8) are toxic to humans and the environment. They are also important precursors of ground-level ozone and secondary organic aerosols and contribute substantially to severe air pollution in urban areas in China. Discrepancies exist between different bottom-up inventories for benzene and toluene emissions in the Pearl River Delta (PRD) and Hong Kong (HK), which are emission hot spots in China. This study provides top-down estimates of benzene and toluene emissions in the PRD and HK using atmospheric measurement data from a rural site in the area, Heshan, an atmospheric transport model, and an inverse modeling method. The model simulations captured the measured mixing ratios during most pollution episodes. For the PRD and HK, the benzene emissions estimated in this study for 2010 were 44 (12–75) and 5 (2–7) Gg yr−1 for the PRD and HK, respectively, and the toluene emissions were 131 (44–218) and 6 (2–9) Gg yr−1, respectively. Temporal and spatial differences between the inversion estimate and four different bottom-up emission estimates are discussed, and it is proposed that more observations at different sites are urgently needed to better constrain benzene and toluene (and other air pollutant) emissions in the PRD and HK in the future.

Highlights

Benzene and toluene, two volatile organic compounds (VOCs), are toxic to humans and the environment
Fang et al (2014) showed that FLEXPART simulations driven with European Centre for Medium-Range Weather Forecasts (ECMWF) data performed slightly better than the Climate Forecast System Reanalysis (CFSR)-driven simulations for SF6 in East Asia for Hateruma, Gosan and Cape Ochiishi stations, we found that CFSR-driven FLEXPART simulations performed slightly better than the ECMWF-driven simulations for the benzene www.atmos-chem-phys.net/16/3369/2016/
Using atmospheric measurements at the Heshan site, a transport model, and an inversion algorithm, this study provides the first top-down estimate of benzene and toluene emissions in the Pearl River Delta (PRD) and Hong Kong (HK) regions, which are emission hot spots in China

Summary

Introduction

Two volatile organic compounds (VOCs), are toxic to humans and the environment. A sufficiently high exposure of toluene will lead to health issues like intra-uterine growth retardation, premature delivery, congenital malformations, and postnatal developmental retardation (Donald et al, 1991). VOCs, including benzene and toluene, are important precursors of ground-level ozone, which is produced from the reaction between VOCs and NOx in the presence of sunlight (Xue et al, 2014), and contribute to the formation of secondary organic aerosols (Henze et al, 2008). Information about the spatial and temporal distribution of benzene and toluene emissions is crucial for air quality. X. Fang et al.: Top-down estimates of benzene and toluene emissions in the Pearl River Delta simulations and predictions, health risk assessments, and emission control policy

Methods

Results

Conclusion