Characteristics and Formation Mechanism of Surface Ozone in a Coastal Island of Southeast China: Influence of Sea-land Breezes and Regional Transport

Baoye Hu,Hong Wang,Youwei Hong,Yuxiang Yang,Lingling Xu,Mengren Li,Naihua Chen,Xin Wu,Jinsheng Chen,Taotao Liu

doi:10.4209/aaqr.2019.04.0193

Abstract

ABSTRACT The ozone (O3) concentrations in island cities are low due to the relatively low concentrations of O3 precursors. However, Pingtan, a typical island city along the southeast coast of China, suffers from frequent O3 pollution. In this study, one year of hourly O3 concentration data collected from three sites (rural, suburban, and urban) on Pingtan were used to investigate the characteristics and formation mechanism of O3 pollution. The results showed that the minimum O3 concentrations measured at the three sites were larger than 55.53 µg m–3, which was likely caused by low NO titration over Pingtan. The O3 concentrations in summer were low because of the East Asian monsoon. The daily maximum O3 concentrations with sea and land breezes (SLBs) were higher than those without SLBs at all three sites (8.52, 9.84, and 14.30 µg m–3 at the rural, suburban, and urban sites, respectively). In addition, SLBs amplified the diurnal variation in O3 concentrations. Cluster analysis and the analysis of an episode of high O3 concentration indicated that the developed Yangtze River Delta is the main source of O3 in Pingtan. This study helps reveal the characteristics and formation mechanism of O3 pollution in island cities.

Highlights

Surface ozone (O3) is a key component of photochemical smog and is harmful to public health, vegetation (NRC, 1991), and crop yield (Lal et al, 2017)
The results showed that the minimum O3 concentrations measured at the three sites were larger than 55.53 μg m–3, which was likely caused by low NO titration over Pingtan
Based on the O3 data available for January to December 2015, the following three air quality monitoring stations in different areas of Pingtan were selected for this study: (1) 36-Degree Reservoir (36DR), a rural site, is situated in the center of Pingtan and is surrounded by forests and lakes; (2) Jinjing Bay (JJB), a suburban site, is located in the southwestern region of Pingtan and is a developing area with considerable ongoing construction; and (3) Government of County (GC), an urban site, is located in downtown Pingtan and is surrounded by the main road, which has a high volume of motor vehicles

Summary

Introduction

Surface ozone (O3) is a key component of photochemical smog and is harmful to public health, vegetation (NRC, 1991), and crop yield (Lal et al, 2017). The number of photochemical studies focused on the mainland of China has increased substantially since 2005, especially in the Beijing-Tianjin-Hebei (BTH) region, the Pearl River Delta (PRD) region, and the Yangtze River Delta (YRD) region (Wang et al, 2017). The number of photochemical studies focused on island cities are limited. The meteorological conditions of island cities are complex and are affected by sea and land breezes (SLBs). Using the WRF-CHEM model, Bei et al (2018) found that land breeze transports pollutants from the inland to coastal areas, causing O3 episodes over the gulf, while sea breeze recirculates the pollutants, aggravating air pollution over the gulf. To the best of our knowledge, few studies have investigated the effects of SLBs on islands of southeast China

Methods

Results

Conclusion