Atmos. Chem. Phys. Discuss., 13, 27201-27241, 2013
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Three years of aerosol mass, black carbon and particle number concentrations at Montsec (southern~Pyrenees, 1570 m a.s.l.)
A. Ripoll1,2, J. Pey1,*, M. C. Minguillón1, N. Pérez1, M. Pandolfi1, X. Querol1, and A. Alastuey1
1Institute of Environmental Assessment and Water Research (IDAEA-CSIC), Jordi Girona 18–26, 08034, Barcelona, Spain
2Departament d'Astronomia i Meteorologia, Universitat de Barcelona, Martí i Franquès 1, 08–28, Barcelona, Spain
*now at: Aix-Marseille Université, CNRS, LCE FRE 3416, Marseille, 13331, France

Abstract. Time variation of mass particulate matter (PM1 and PM1−10), black carbon (BC) and particle number (N) concentrations at the high altitude site of Montsec (MSC) in the southern Pyrenees was interpreted for the period 2010–2012. The MSC site registered higher PM10 (12 μg m−3) and N > 7 nm (2209 # cm−3) concentrations than those measured at other high altitude sites in central Europe (PM10: 3–9 μg m−3 and N: 634–2070 # cm−3). By contrast, BC concentrations at MSC (0.2 μg m−3) were equal or even lower than those measured at these European sites (0.2–0.4 μg m−3). These differences were attributed to the lower influence of anthropogenic emissions and to the higher relevance of Saharan dust transport and new particle formation (NPF) processes at MSC. The different time variation of PM and BC concentrations compared with that of N suggests that these aerosol parameters were governed by diverse factors at MSC. Both PM and BC concentrations showed marked differences for different meteorological scenarios, with enhanced concentrations under North African outbreaks (PM1−10: 13 μg m−3, PM1: 8 μg m−3 and BC: 0.3 μg m−3) and low concentrations when Atlantic advections occurred (PM1−10: 5 μg m−3, PM1: 4 μg m−3 and BC: 0.1 μg m−3). Because of the contrasting origin of the air masses in the warmer seasons (spring and summer) and in the colder seasons (autumn and winter), PM and BC concentrations showed a marked increase in summer, with a secondary maximum in early spring, and were at their lowest during winter. The maximum in the warmer seasons was attributed to long-range transport processes which mask the breezes and regional transport breaking the daily cycles of these pollutants. By contrast, PM and BC concentrations showed clear diurnal cycles with maxima at midday in the colder seasons. A statistically significant weekly variation was also obtained for the BC concentrations, displaying a progressive increase from Tuesday to Saturday, followed by a significant decrease on Sunday and Monday. N concentrations depended more on local meteorological variables such as solar radiation than on the air mass origin. Therefore, the highest concentrations of N were associated with summer regional episodes (N > 3 nm: 4461 # cm−3 and N > 7 nm: 3021 # cm−3) and the lowest concentrations were related to winter regional scenarios (N > 3 nm: 2496 # cm−3 and N > 7 nm: 1073 # cm−3). This dependence on solar radiation also accounted for the marked diurnal cycle of N concentrations throughout the year with a peak at midday and for the absence of a weekly pattern. Measurements carried out at MSC enabled us to characterize the tropospheric background aerosols in the Western Mediterranean Basin (WMB). Our results highlight the importance of the NPF processes in southern Europe, reveal much lower anthropogenic emissions than in central Europe, and underline the contribution of natural long-range transport such as Saharan dust.

Citation: Ripoll, A., Pey, J., Minguillón, M. C., Pérez, N., Pandolfi, M., Querol, X., and Alastuey, A.: Three years of aerosol mass, black carbon and particle number concentrations at Montsec (southern~Pyrenees, 1570 m a.s.l.), Atmos. Chem. Phys. Discuss., 13, 27201-27241, doi:10.5194/acpd-13-27201-2013, 2013.
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