Abstract:

As the level of ozone (O₃) pollution has intensified in recent years, severe large-scale O₃ pollution events in the Pearl River Delta region have also occurred in spring. However, there are still few studies that focus on O₃ pollution in spring. In-depth analysis of the meteorological conditions, causes and sources of O₃ pollution in spring is of great practical significance for the prevention and control of O₃ pollution. In April of 2017, the southwestern part of the Pearl River Delta experienced multiple moderate and severe O₃ pollution events. This study first analyzed the correlation between meteorological factors and mass O₃ concentrations during this period, then used the HYSPLIT trajectory model to analyze the source of O₃ pollution in the southwestern region, and finally employed the WRF/CAMx model to quantitatively analyze source and formation sensitivity of O₃ in spring in the southwestern Pearl River Delta. The results show that the O₃ concentration in spring increases with the increase in sunshine duration and daily temperature difference, and decreases with the increase in relative humidity. When the local wind direction is easterly, O₃ pollution is the most serious in the southwest of the Pearl River Delta. The air mass transportation along the northeast and east routes has an important contribution to high level O₃ concentrations. For the daytime in spring, the contributions of natural sources, industrial sources, and traffic sources are 12%-13%, 15%-18% and about 10%, respectively. After removing the impact of background O₃, the central Pearl River Delta cities including Guangzhou and Foshan have contributed about 30%, 27% and 20% to the O₃ concentrations in Jiangmen, Zhongshan and Zhuhai, respectively. The eastern Pearl River Delta cities including Dongguan, Huizhou, and Shenzhen have contributed 27% to the O₃ concentrations in eastern sites of Zhuhai, but contributed only 10% to those at the western sites of Zhuhai. The emission of precursors in northern Guangdong also contributes more than 10% to the O₃ in Jiangmen and Zhongshan, and the local contribution is relatively small. These results indicate that the regional transport characteristics of O₃ are obvious, and the pollutants emitted by each city mainly affect its downwind cities. The results of O₃ formation sensitivity analysis demonstrate that O₃ in the southwestern Pearl River Delta in spring is mainly generated in the VOCs sensitive area. In summary, the mitigation of O₃ pollution in spring should be achieved from the perspective of joint prevention and control of regional VOCs.

Key words: Pearl River Delta, spring, ozone, source, sensitivity

摘要：

随着近年臭氧污染程度的加剧,珠三角春季也出现了较严重的大范围臭氧污染事件。然而,目前对于春季臭氧污染的研究仍较少,深入分析研究春季臭氧污染的气象条件、污染成因及其来源对于臭氧污染防治具有重大的现实意义。2017年4月珠三角西南部出现了多次臭氧中度以上污染,该研究以此为例分析了该时段气象条件与臭氧质量浓度的相关关系,利用HYSPLIT轨迹模型分析西南部地区臭氧污染的气团来源,使用WRF/CAMx模型定量分析了珠三角西南部春季臭氧来源与臭氧生成敏感性。结果表明,春季臭氧质量浓度随日照时长和气温日较差的增加而增加,随相对湿度的增加而减少。当局地风向为偏东时,珠三角西南部臭氧污染最严重。东北和偏东路径的气团输送对高质量浓度臭氧有重要贡献,春季白天天然源的贡献为12%—13%,工业源的贡献为15%—18%,交通源的贡献约为10%。除去背景臭氧后,广州和佛山等珠三角中部城市对江门、中山和珠海的臭氧贡献分别为30%、27%和20%,东莞、惠州和深圳等珠三角东部城市对珠海东面站点的臭氧贡献约为27%,但对珠海西部站点的臭氧贡献仅约为10%。粤北地区的前体物排放对江门和中山的臭氧也有超过10%的贡献,珠三角西南部本地的贡献相对较少,这说明臭氧的区域输送特征明显,每个城市排放的污染物主要影响其下风向的城市。臭氧生成敏感性分析结果表明,春季珠三角西南部臭氧主要在VOCs敏感区中生成。综上,春季臭氧污染治理宜从区域VOCs联防联控的角度进行治理。

关键词: 珠三角, 春季, 臭氧, 来源, 敏感性