Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Atmos. Chem. Phys. Discuss., 14, 18849–18877, 2014 www.atmos-chem-phys-discuss.net/14/18849/2014/ doi:10.5194/acpd-14-18849-2014 ACPD © Author(s) 2014. CC Attribution 3.0 License. 14, 18849–18877, 2014 This discussion paper is/has been under review for the journal Atmospheric Chemistry An analysis of the and Physics (ACP). Please refer to the corresponding final paper in ACP if available. impacts of VOCs and NOx An analysis of the impacts of VOCs and Y. Zou et al. NOx on the ozone formation in Guangzhou Title Page Y. Zou1, X. J. Deng1,2, B. G. Wang2, F. Li1, H. B. Tan1, T. Deng1, B. R. Mai1, and Abstract Introduction X. T. Liu1 Conclusions References 1Institute of Tropical and Marine Meteorology/Guangdong Provincial Key Laboratory of Regional Numerical Weather Prediction, CMA, Guangzhou, China Tables Figures 2Institute of Atmospheric Environmental Safety and Pollution Control, Jinan University, Guangzhou, China J I Received: 3 June 2014 – Accepted: 21 June 2014 – Published: 17 July 2014 J I Correspondence to: X. J. Deng ([email protected]) and B. G. Wang ([email protected]) Back Close Published by Copernicus Publications on behalf of the European Geosciences Union. Full Screen / Esc Printer-friendly Version Interactive Discussion 18849 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Abstract ACPD In this study, online monitoring instruments were used to monitor ozone, NOx and VOCs at the Guangzhou Panyu Atmospheric Composition Station (GPACS) of the China Me- 14, 18849–18877, 2014 teorological Administration from June 2011 to May 2012, so as to obtain their char- 5 acteristic seasonal and diurnal variations, as well as the impacts of NOx and VOCs An analysis of the on local ozone formation and Guangzhou ozone control strategies. The results show impacts of VOCs and that during the observation period the seasonal variation of ozone concentration was NOx lower in the spring and winter and higher in the summer and autumn, which is contrary Y. Zou et al. that of NOx and VOCs. At around 09:00 LT in the summer, autumn and winter, both 10 the ozone concentration and NO2/NO ratio begin to increase, and the NO2/NO ratio reached its maximum after a peak of ozone concentration, but this variation was not particularly evident in the spring. Aromatics and alkenes are the largest components Title Page for ozone formation potential, among which aromatic toluene, m-xylene, p-xylene and Abstract Introduction 1,3,5-trimethylbenzene are the most important components, with a total contribution of Conclusions References 15 about 31.6 % to ozone formation potential. Through the analysis on local ozone con- trol by the VOC/NOX ratio, it was found that when the ozone concentration reached Tables Figures a peak in the summer and autumn in which high concentrations of ozone were prone to occur, ozone generation was NOx limited, thus NOx emissions must be controlled J I to regulate the occurrence of high-concentration ozone events. In the spring and win- 20 ter, ozone generation was always VOCs controlled. Due to the relatively low ozone J I concentration, although NOx emissions could be controlled to increase ozone concen- Back Close tration, high-concentration ozone events would not occur. Therefore, for the control of ozone in Guangzhou, in addition to the control of VOCs emissions, more attention Full Screen / Esc must be paid to reducing NOx emissions, so as to achieve the purpose of controlling Printer-friendly Version 25 high-concentration ozone. Interactive Discussion 18850 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 1 Introduction ACPD Along with its rapid economic development and urbanization, the Pearl River Delta has become one of the most serious pollution areas in China (Chan et al., 2008). Differ- 14, 18849–18877, 2014 ent from the air pollution situations of Beijing, Tianjin, Hebei and the Yangtze River 5 Delta region, which involve particulate matters as the main pollutants (Wang et al., An analysis of the 2012; Zhao et al., 2011), due to the unique geographical location and climate as well impacts of VOCs and as the rapid increase in the emissions of VOCs and NOx (NO + NO2) as ozone pre- NOx cursors caused by industrial activities and the growing number of motor vehicles, in the Pearl River Delta high-concentration ozone events occur frequently and are a very Y. Zou et al. 10 prominent air pollution problem (Wang et al., 2009). Tropospheric ozone is the sec- ondary pollutant generated by photochemical reactions of VOCs and NOx under light Title Page conditions (Sillman, 1995). However, VOCs and NOx have no linear relationship with ozone formation, and their impacts on ozone formation can be described by VOC and Abstract Introduction NOx control areas (Zhang et al., 2004; Tie et al., 2007; Geng et al., 2008). In 1977, Conclusions References 15 Dodge used the model OZIPP (ozone isopleth plotting package) and drew an conclu- sion that although the specific actual situations differ, it is generally considered that Tables Figures when the VOC/NOx ratio is more than 8 : 1, ozone is formed in the NOx control area, / while when the VOC NOx ratio is less than 8 : 1, ozone is formed in the VOCs control J I area (Dodge, 1977). And later this view had been adopted and applied by many re- 20 searchers during their researches throughout the world (Sillman, 1999; Committee on J I Tropospheric Ozone Formation and Measurement, 1991; Ran et al., 2009). Therefore, Back Close the understanding of the ozone photochemical process can provide a scientific basis for the effective control of local ozone. Full Screen / Esc Currently, a greater amount of systematic long-term observation data have been Printer-friendly Version 25 available on atmospheric ozone and NOx in the Pearl River Delta region, while VOCs data which mostly involve short-term intensive observations or non-continuous long- Interactive Discussion term observations is not included in the scope of daily observations (Wang et al., 2004; Shao et al., 2009). Therefore, the relationship between VOCs, NOx and ozone cannot 18851 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | be fully revealed to discern the impacts of VOCs and NOx on ozone formation in the Pearl River Delta region. In order to more effectively solve the problem of ozone pol- ACPD lution in the Pearl River Delta, VOCs, NO and ozone were observed throughout the x 14, 18849–18877, 2014 period of one year at GPACS, focusing on analyzing the impacts of NO/NO2 ratio and 5 VOCs components on ozone formation. In addition, a large amount of research has been conducted on ozone formation in the Pearl River Delta (Wang et al., 2005; Cheng An analysis of the et al., 2010; Guo et al., 2009). Previous studies have shown that ozone was gener- impacts of VOCs and ated in the VOCs control area of the Pearl River Delta region, but only a small number NOx of scholars (Li et al., 2008) have analyzed the control areas of ozone formation with Y. Zou et al. 10 diurnal variation in the Pearl River Delta region. In order to control the occurrence of high-concentration ozone events in Guangzhou, the control areas of ozone formation with diurnal variation are explored in four scenarios herein, i.e. spring, summer, autumn Title Page and winter, thus providing a scientific basis for the control of ozone in Guangzhou. This study is organized as follows. The second section describes the methodology Abstract Introduction 15 in this study, mainly including the sampling point and observation instruments. The Conclusions References third section mainly analyzes the observed results, including characteristic analyses of ozone, NOx and VOCs, the relationship between NO2/NO ratio and ozone forma- Tables Figures tion, and an analysis of the contribution of VOCs components to ozone formation by using MIR and an equivalent propylene concentration method. In the final section, the J I 20 VOC/NOx ratio analysis method is adopted to analyze the control areas with ozone for- mation in the seasonal diurnal variation process, in order to explore the ozone control J I strategies in Guangzhou. Back Close Full Screen / Esc 2 Methodology Printer-friendly Version 2.1 Measurements Interactive Discussion 25 From June 2011 to May 2012, automatic sampling and on-line monitoring were car- ried out on ozone, NOx and VOCs. The sampling site was located at the moun- 18852 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | tain top of Dazhengang, Nancun Town, Panyu District, Guangzhou City, Guangdong Province, with an elevation of 141 m, at the latitude of 23◦00.2360 N and longitude of ACPD 113◦21.2920 E (Fig. 1). The prevailing wind, wind speed and temperature at the sam- 14, 18849–18877, 2014 pling point during the different seasons are shown in Fig. 2 and Table 1. At the sampling 5 point, northeasterly and southwesterly are the prevailing winds in spring (April, May and June), along with southwesterly in summer (June, July and August), southwesterly An analysis of the in autumn (September, October and November), and northeasterly in winter (Decem- impacts of VOCs and ber, January and February). In the different seasons, the average wind speed varies NOx around1.4 m s−1, while the average temperature undergoes more significant changes ◦ ◦ Y. Zou et al. 10 from 14.2 C in winter to 29.4 C in summer. This sampling station is a comprehensive site which is able to monitor the typical air pollution processes of the Pearl River Delta in different seasons and under different weather conditions (Deng et al., 2010). Title Page 2.2 Instrument description Abstract Introduction Conclusions References The data used in this study include the hourly concentration of ozone, NOx and VOCs 15 during the observation period (June 2011–May 2012).