10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Aerosol Optical Absorption Properties at a High Mountain Site in the Western Mediterranean
Jose Nicolás, Nuria Galindo, Ramón Castañer, Eduardo Yubero, Javier Crespo, Carlos Pastor, FRANCO LUCARELLI, Giulia Calzolai, Silvia Nava, Miguel Hernández University, Elche, Spain
Abstract Number: 170 Working Group: Remote/Regional Atmospheric Aerosol
Abstract Measurements of particulate matter (PM), absorption coefficient (σap) and Absorption Angstrom Exponent (AAE) have been performed during three years (2014-2016) at a remote site (1558 m a.s.l) located in the southeast of the Iberian Peninsula, close to the Mediterranean coast. Mean values ± (standard deviation) of the measured parameters were: PM10 (11.3±19.8 μg m-3), σap (2.18±1.45 Mm-1 / λ=520 nm) and AAE (1.190±0.225). PM concentrations and σap were maxima during summer, while AAE values were highest during the colder months, as expected for high altitude environments with scarce human activity. The influence that both, air masses coming from the Sahara desert loaded with mineral dust (SDE) and the height of the Planetary Boundary Layer (PBL), had on the studied parameters was also analyzed. During SDEs, σap and AAE levels increased. These increments were slightly higher when the sampling point was located within the free troposphere (FT) and correlated with the intensity of the event. In the case of SDEs with high mineral dust (MD) concentrations, AAE values increased up to 30% and σap values were more than double compared to average values for non-event days. However, the seasonal variability of the optical parameters could not be attributed to these episodes since the MD load at the sampling point did not show significant seasonal differences. For this reason, the different spectral absorption behavior observed between the warmest and the coldest months may be attributed to the seasonal differences in the percentage contribution of Brown Carbon (BrC) to PM levels. These results indicate that for short wavelengths (UV and VIS), the absorption due to non-BC absorbers during the winter was almost twice that registered during summer time.