Monitoring of volatile organic compounds (VOCs) from an oil and gas station in northwest China for 1 year

Huang Zheng,Yang Ding,Tianpeng Hu,Gang Li,Xinli Xing,Yao Mao,Shaofei Kong,Shuanglin Li,Dantong Liu,Shihua Qi

doi:10.5194/acp-18-4567-2018

Abstract

Abstract. Oil and natural gas are important for energy supply around the world. The exploring, drilling, transportation and processing in oil and gas regions can release a lot of volatile organic compounds (VOCs). To understand the VOC levels, compositions and sources in such regions, an oil and gas station in northwest China was chosen as the research site and 57 VOCs designated as the photochemical precursors were continuously measured for an entire year (September 2014–August 2015) using an online monitoring system. The average concentration of total VOCs was 297 ± 372 ppbv and the main contributor was alkanes, accounting for 87.5 % of the total VOCs. According to the propylene-equivalent concentration and maximum incremental reactivity methods, alkanes were identified as the most important VOC groups for the ozone formation potential. Positive matrix factorization (PMF) analysis showed that the annual average contributions from natural gas, fuel evaporation, combustion sources, oil refining processes and asphalt (anthropogenic and natural sources) to the total VOCs were 62.6 ± 3.04, 21.5 ± .99, 10.9 ± 1.57, 3.8 ± 0.50 and 1.3 ± 0.69 %, respectively. The five identified VOC sources exhibited various diurnal patterns due to their different emission patterns and the impact of meteorological parameters. Potential source contribution function (PSCF) and concentration-weighted trajectory (CWT) models based on backward trajectory analysis indicated that the five identified sources had similar geographic origins. Raster analysis based on CWT analysis indicated that the local emissions contributed 48.4–74.6 % to the total VOCs. Based on the high-resolution observation data, this study clearly described and analyzed the temporal variation in VOC emission characteristics at a typical oil and gas field, which exhibited different VOC levels, compositions and origins compared with those in urban and industrial areas.

Highlights

Volatile organic compounds (VOCs) are ubiquitous in ambient air and originate from both natural processes and anthropogenic activities such as the fossil fuel combustion, industrial processes and solvent usage (Cai et al, 2010; Leuchner and Rappenglück, 2010; Baudic et al, 2016)
96.7 % were composed by benzene, toluene, and m- and p-xylene, with corresponding average concentrations of 1.13 ± 1.62, 1.06 ± 1.91 and 0.72 ± 1.94 ppbv, respectively
Ethane and propane in ambient air were reported in other oil and natural gas operation and industrial areas in the US (Pétron et al, 2012; Helmig et al, 2014; Warneke et al, 2014)

Summary

Introduction

Volatile organic compounds (VOCs) are ubiquitous in ambient air and originate from both natural processes (i.e., vegetation emissions, volcanic eruption and forest fire) and anthropogenic activities such as the fossil fuel combustion, industrial processes and solvent usage (Cai et al, 2010; Leuchner and Rappenglück, 2010; Baudic et al, 2016). As the key precursors of O3 formation (Fujita, 2001; Geng et al, 2008; Ran et al, 2009; Lyu et al, 2016), different VOC categories exhibited different ozone formation potential (OFP; Carter, 1994; Atkinson and Arey, 2003; Zou et al, 2015). Some VOC species (i.e., benzene) exhibit detrimental effects on human health (Colman Lerner et al, 2012; He et al, 2015) and they have negative impacts on air quality (Vega et al, 2011). Zheng et al.: Monitoring of volatile organic compounds for 1 year

Methods

Results

Conclusion