Analysis of Alpha Activity Levels and Dependence on Meteorological Factors over a Complex Terrain in Northern Iberian Peninsula (2014–2018)

Abstract

Alpha ambient concentrations in ground-level air were measured weekly in Bilbao (northern Spain) by collecting aerosols in filters between 2014 and 2018. Over this period, the alpha activity concentrations in the aerosol’s samples range from 13.9 µBq/m3 to 246.5 µBq/m3, with a mean of 66.49 ± 39.33 µBq/m3. The inter-annual and intra-annual (seasonal and monthly) variations are analyzed, with the highest activity in autumn months and the lowest one in winter months. Special attention has been paid to alpha peak concentrations (weekly concentrations above the 90th percentile) and its relationship with regional meteorological scenarios by means of air mass trajectories and local meteorological parameters. The meteorological analysis of these high alpha concentrations has revealed two airflow patterns-one from the south with land origin and one from the north with maritime origin-mainly associated with these alpha peak concentrations. Surface winds during representative periods of both airflow patterns are also analyzed in combination with 222Rn concentrations, which demonstrated the different daily evolution associated with each airflow pattern. The present results are relevant in understanding trends and meteorological factors affecting alpha activity concentrations in this area, and hence, to control potential atmospheric environmental releases and ensure the environmental and public health.

Five Years (2014–2018) of Beta Activity Concentration and the Impact of Synoptic and Local Meteorological Conditions in Bilbao (Northern Spain)

“…These results agree with the components of the alpha activity concentration identified and analyzed in previous studies at the same site [16]. In this sense, a positive correlation between alpha and gross beta (0.67) was found, which can be explained by the principal source term of both the airborne alpha and gross beta concentration being the same in normal situations.…”

“…Every year, maximum values are reached during autumn (October-November-December), while the minimum ones are registered during winter (January-February-March) (Figure 7). Box-plots describing the shape of the seasonal distribution of values and its variability help to summarize and compare this seasonal variability of the beta These results agree with the components of the alpha activity concentration identified and analyzed in previous studies at the same site [16]. In this sense, a positive correlation between alpha and gross beta (0.67) was found, which can be explained by the principal source term of both the airborne alpha and gross beta concentration being the same in normal situations.…”

“…The minimum value (P5) increases from 107 µBq/m 3 to 224 µBq/m 3 , while the maximum value (P95) ranges from 803 µBq/m 3 to 1315 µBq/m 3 . The occurrence of the maximum in autumn is not in line with previous works analyzing beta activity concentrations conducted in the Iberian Peninsula [16][17][18], which showed that the maximum average values are reached in the summer and that the minimum values are obtained in the winter. On the contrary, similar behaviour has been found in other analyses, such as in Milan [27] and New York [28].…”

“…The counting time was 1000 min, and the detection limits obtained were between 9.45 µBq/m 3 and 129.30 µBq/m 3 , and the uncertainties, which had a coverage factor k = 2, were 13.50 ± 10.05 µBq/m 3 . In the same filters, the alpha and beta activity concentration could be sampled and measured, so the values could be used for a previous alpha concentration study that was taking place during the same period [16]. On the same roof where the low air sampler was located, there was also a high flow sampler.…”

Meteorological Approach in the Identification of Local and Remote Potential Sources of Radon: An Example in Northern Iberian Peninsula

“…concentrations. In this area, one pattern of sea-land breeze has been identified [42]. Briefly, the breeze presents nocturnal flows from the southwest from midnight until midday, followed by the arrival of flows from the northwest overnight.…”