Trends of non-methane hydrocarbons (NMHC) emissions in Beijing during 2002–2013

M Wang,C.-C Chang,Y Yang,M Hu,W Chen,S Lu,B Wang,B Yuan,M Shao,Y Li,L Zeng,Q Zhang,Y Liu

doi:10.5194/acp-15-1489-2015

Abstract

Abstract. Non-methane hydrocarbons (NMHCs) play a critical role in the photochemical production of ozone (O3) and organic aerosols. Obtaining an accurate understanding on temporal trends of NMHC emissions is essential for predicting air quality changes and evaluating the effectiveness of current control measures. In this study, we evaluated temporal trends of anthropogenic NMHC emissions during August in Beijing based on ambient measurements during selected summer periods at an urban site in Beijing from 2002 to 2013. In the contrast to the results from the most recent inventory (Multi-resolution Emission Inventory for China, MEIC), which reported that anthropogenic NMHC emissions during August increased by 28% from 2004 to 2012, whereas mixing ratios of NMHCs measured at this urban site decreased by 37% during the same time period. A positive matrix factorization (PMF) model was applied to these NMHC measurements for source apportionment. The results showed that the relative contributions of vehicular exhaust and gasoline evaporation to measured NMHC concentrations decreased by 66% during August from 2004 to 2012, comparable to the relative decline of 67% for transportation-related NMHC emissions reported by the MEIC inventory. This finding indicates that the implementation of stricter emissions standards for new vehicles and specific control measures for in-use vehicles has been effective for reducing transportation-related NMHC emissions. In addition, the PMF results suggested that there were no significant temporal changes in NMHC concentrations from solvent use and industry during August from 2004 to 2012, in contrast with the rapid rate of increase (8.8% yr−1) reported by the MEIC inventory. To re-evaluate the NMHC emissions trends for solvent use and industry, annual variations in NMHC / NOx ratios were compared between ambient measurements at the PKU site and the MEIC inventory. In contrast to the significant rise in NMHC / NOx ratios from the MEIC inventory, the measured NMHC / NOx ratios declined by 14% during August from 2005 to 2012. The inferred NMHC / NOx ratios based on PMF results exhibited a comparable decline of 11% to measured ratios. These results indicate that the increase rate for NMHC emissions from solvent use and industry in Beijing might be overestimated in the current inventory; therefore, additional research is necessary to verify the NMHC emission trends for this source.

Highlights

The temporal trends in tropospheric ozone (O3) levels has been of great concern during recent years
3.1 Anthropogenic Non-methane hydrocarbons (NMHCs) emissions during August in Beijing reported by the multi-resolution emission inventory for China (MEIC) inventory
The MEIC inventory indicated that total anthropogenic NMHC emissions during August in Beijing significantly increased by 35 % from 2002 to 2012

Summary

Introduction

The temporal trends in tropospheric ozone (O3) levels has been of great concern during recent years. Over the past three decades, significant declines in O3 levels have been observed in urban areas of the United States (US; Lefohn et al, 2010; Warneke et al, 2012). M. Wang et al.: Trends of NMHC emissions in Beijing during 2002–2013 have suggested that O3 levels in China have been increasing (Wang et al, 2009; Zhang et al, 2014). Non-methane hydrocarbons (NMHCs) and nitrogen oxides (NOx) are precursors of photochemically produced O3; obtaining accurate knowledge on temporal trends in NMHC emissions is helpful for understanding O3 trends in urban regions (von Schneidemesser et al, 2014; Zhang et al, 2014)

Methods

Results

Conclusion