Abstract：
One of the main factors that affect urban air quality is meteorology. The objective of this study is to understand and characterise the influence that \"Galerna\" (GL) (an abrupt westerly change over the northern coast of Spain) has on the daily variability of the air quality over Bilbao city (northern Spain). A total of 46 one-day periods from 2009 to 2019 during which GL have been analysed. Radon observations at the Bilbao city radiological station were used because radon is a suitable atmospheric tracer by which to assess and characterise air quality dynamics. The cluster analysis of these periods revealed that increases in radon concentrations, mainly in the afternoon, are associated with the occurrence of GL, but that, this increase in the daily variability of radon concentrations in Bilbao is not reflected in all these GL periods. This variability in the impact of the GL scenario on radon concentrations is associated with the location of Bilbao: along the Nervion valley and 16 km from the coast. The analysis of three GL periods using 10-min surface meteorological and radon data showed an anomalous increase in radon with the arrival of maritime winds, which is associated with the process of a progressive accumulation of radon concentrations over the coastal area in the previous days, and the displacement of these air masses inland owing to the development of the GL event. Our results consequently identify the impact of GL on urban air quality in the afternoon, along with the fact that the complex layout of this coastal area, with the presence of valleys and mountains, favours the formation of reservoir layers above the coastal and valley areas, thus influencing on daily variability of air pollution concentrations. These increases in radon concentrations do not present a significant impact on human health.
摘要：
影响城市空气质量的主要因素之一是气象学。这项研究的目的是了解和描述“Galerna”（GL）（西班牙北部海岸的突然西风变化）对毕尔巴鄂市（西班牙北部）空气质量每日变化的影响。从2009年到2019年，总共有46个为期一天的时间段对GL进行了分析。之所以使用毕尔巴鄂市放射站的氡观测，是因为氡是一种合适的大气示踪剂，可用来评估和表征空气质量动态。对这些时期的聚类分析表明，氡浓度增加，主要是在下午，与GL的出现相关联，但是，毕尔巴鄂氡浓度每日变化的增加并没有反映在所有这些GL时期。GL方案对氡浓度影响的这种变化与毕尔巴鄂的位置有关：沿着Nervion山谷，距海岸16公里。利用10分钟地面气象和氡数据对三个GL周期的分析显示，随着海上风的到来，氡异常增加，这与前几天沿海地区氡浓度逐渐积累的过程有关，以及由于GL事件的发展，这些气团向内陆的位移。因此，我们的结果确定了GL对下午城市空气质量的影响，随着这个沿海地区复杂的布局，山谷和山脉的存在，有利于沿海和山谷地区以上储层的形成，从而影响空气污染浓度的日变化。氡浓度的这些增加不会对人类健康产生重大影响。
