Impact of sea-land breezes on 210Pb in southern Iberian Peninsula – Feasibility study on using submicron-sized aerosol particles to analyze 210Pb hourly patterns

This work addresses the impact of mesoscale circulations on 210Pb concentrations in southwestern Iberian Peninsula by analysing the 210Pb database at El Arenosillo station during 2004–2011 (128 periods with a time scale of 48 h).The analysis of surface winds during each one of these periods has revealed the positive impact of the two sea-land breeze patterns (pure and non-pure), previously identified in this region, on 210Pb activity concentrations. An average value of 0.80 ± 0.09 mBq m−3 was obtained for the pure pattern (34 periods), 0.54 ± 0.09 mBq m−3 for the non-pure pattern (23 periods) and 0.46 ± 0.04 mBq m−3 for the rest (71 periods).The analysis of one representative period of each sea-land breeze patterns is also presented. To perform this analysis we have used: hourly surface wind observations, surface wind fields simulated by the WRF mesoscale model and the hourly database of sub-micron-particle size range in the accumulation mode (NACC). The use of this type of particles to investigate the hourly temporal variability of 210Pb is based on the high correlation, obtained in the present work, between 210Pb activity and particles in the accumulation mode (R = 0.90).The analysis reveals that the highest concentrations of NACC, and hence, 210Pb, are obtained when the sampling area is under the influence of the pure breeze, due to it favours the accumulation of particles previously transported by Mediterranean flows along the Guadalquivir valley. In the case of the non-pure pattern, the increase in the concentration of particles is related to the arrival of background synoptic winds from the continental areas of western Iberian Peninsula. In the latest, the increment of NACC is faster and around 400 particles cm−3, while in the case of the pure pattern, it is progressive up to 1400 particles cm−3.