Three years of aerosol mass, black carbon and particle number concentrations at Montsec (southern Pyrenees, 1570 m a.s.l.) 1Institute of Environmental Assessment and Water Research (IDAEA-CSIC), Barcelona, 08034, Spain
30 Apr 2014
*now at: Aix-Marseille Université, CNRS, LCE FRE 3416, Marseille, 13331, France
Received: 30 Jul 2013 – Published in Atmos. Chem. Phys. Discuss.: 21 Oct 2013 Abstract. Time variation of mass particulate matter (PM1 and PM1&minus10), black
carbon (BC) and number of particles (N3: number of particles with an
aerodynamic diameter higher than 3 nm, and N10: higher than 10 nm)
concentrations at the high-altitude site of Montsec (MSC) in the southern
Pyrenees was interpreted for the period 2010–2012.
Revised: 11 Mar 2014 – Accepted: 13 Mar 2014 – Published: 30 Apr 2014
At MSC, PM10 (12 μg m−3) and N7
(2140 # cm−3) three-year arithmetic average concentrations were
higher than those measured at other high-altitude sites in central Europe
during the same period (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 to or even lower than those measured
at these European sites (0.2–0.4 μg m−3). These differences
were attributed to the higher relevance of Saharan dust transport and to the
higher importance of the biogenic precursor emissions and new particle
formation (NPF) processes, and to the lower influence of anthropogenic
emissions 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 air outbreaks (PM1&minus10: 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). PM and BC concentrations increased in summer,
with a secondary maximum in early spring, and were at their lowest in winter,
due to the contrasting origin of the air masses in the warmer seasons (spring
and summer) and in the colder seasons (autumn and winter). The maximum in the
warmer seasons was attributed to long-range transport processes that 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
temperature and solar radiation intensity than on the origin of the air mass.
Therefore, arithmetic averages as a function of meteorological episodes
showed the highest concentrations of N during summer regional episodes
(N3: 4461 # cm−3 and N7: 3021 # cm−3) and the
lowest concentrations during winter regional scenarios (N3:
2496 # cm−3 and N7: 1073 # cm−3). This dependence on
temperature and 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, underline
the high contribution of long-range dust transport with respect to central
Europe and its prevalence in elevated layers, and reveal that MSC is much
less affected by anthropogenic emissions than other high-altitude sites in
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., 14, 4279-4295, doi:10.5194/acp-14-4279-2014, 2014.