The role of mesoscale meteorology in modulating the 222 Rn concentrations in Huelva (Spain) e impact of phosphogypsum piles M.A. Hern  andez-Ceballos a , A. Vargas b, * , D. Arnold c , J.P. Bolívar d a European Commission, Joint Research Centre (JRC), Institute for Transuranium Elements (ITU), Ispra, VA, Italy b Institute of Energy Technologies (INTE), Technical University of Catalonia, Barcelona, Spain c Central Institute for Meteorology and Geodynamics (ZAMG), Vienna, Austria d Department of Applied Physics, University of Huelva, Campus de Excelencia Internacional del Mar (CEIMAR), Huelva, Spain article info Article history: Received 9 January 2015 Received in revised form 26 February 2015 Accepted 7 March 2015 Available online Keywords: Outdoor radon Phosphogypsum piles Sea-land breezes Iberian Peninsula abstract The combined analysis of 222 Rn activity concentrations and mesoscale meteorological conditions at Huelva city (Spain) was addressed in this study to understand the potential impact of phosphogypsum piles on the 222 Rn activity concentrations registered at this area. Hourly mean data from April 2012 to February 2013 registered at two sampling sites (Huelva city and in the background station of El Are- nosillo, located 27 km to the south-east) have been used in the study. The results of the present study showed a large difference in mean radon concentrations between the two stations during the sampling period, 6.3 ± 0.4 Bq m 3 at Huelva and 3.0 ± 0.2 Bq m 3 at El Arenosillo. The analysis has demonstrated that hourly 222 Rn concentrations at Huelva city above 22 Bq m 3 , with nocturnal peaks up to 50 Bq/m 3 , mainly coincided with the occurrence of a pure sea-land breeze cycle. Mesoscale circulations in this region are mainly characterized by two patterns of sea-land breeze, pure and non-pure, with the phosphosypsum piles directly upstream (south) of the city during the afternoon on pure sea-breeze days. The difference between mean 222 Rn activity concentrations at Huelva city were 9.9 ± 1.5 Bq m 3 for the pure pattern and 3.3 ± 0.5 Bq m 3 for the non-pure pattern, while in the background station concentrations were 3.9 ± 0.4 Bq m 3 and 2.8 ± 0.4 Bq m 3 respectively. Considering these large differences, a detailed analysis of composites and case studies of represen- tative sea-land breeze cycles of both types and their impact on 222 Rn activity concentration was per- formed. The results suggested that the presence of the phosphogypsum piles was necessary in order to justify the high 222 Rn activity concentrations observed at Huelva compared with the background station in the afternoons on pure sea breeze days (1.5e2.0 Bq m 3 ). On the other hand, large night time dif- ferences between the two sites on these days were likely to be associated with a combination of shallow density currents travelling down the Guadalquivir valley and, again, the presence of phosphogypsum piles. The results have demonstrated a significant impact of the phosphogypsum piles on 222 Rn activity concentrations in Huelva city during the occurrence of pure sea breeze days. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction Phosphogypsum (PG), a by-product coming from the production of phosphoric acid, which is mainly used for manufacturing phos- phate fertilizers, has been stored in a broad open-air area (about 1200 ha) for the last 40 years close to the city of Huelva (Southwest Spain). PG, which is largely made of calcium sulphate, is mainly obtained through the so called ‘‘wet chemical treatment’’ of phos- phate rock, a procedure well known to have associated high activities of natural radioactivity (Bolívar et al., 2009; Lawrence et al., 2004). Storing PG as open piles (PGP) exposed to various weathering conditions may lead to radioactive contamination of the sur- rounding environment system as PG contains enhanced concen- trations of naturally occurring radioactive materials (i.e. 226 Ra, 238 U, 232 Th, 210 Pb). Therefore, extensive studies have been carried out worldwide to evaluate the impact of PG on air quality, for example, Al Attar et al. (2011) in Syria, and Saueia and Mazzilli (2006) in Brazil. * Corresponding author. E-mail addresses: miguelhceballos@gmail.com, miguelwrf@gmail.com (M.A. Hern andez-Ceballos), arturo.vargas@upc.edu (A. Vargas). Contents lists available at ScienceDirect Journal of Environmental Radioactivity journal homepage: www.elsevier.com/locate/jenvrad http://dx.doi.org/10.1016/j.jenvrad.2015.03.023 0265-931X/© 2015 Elsevier Ltd. All rights reserved. Journal of Environmental Radioactivity 145 (2015) 1e9