Seasonal variability of aerosol absorption parameters at a remote site with high mineral dust loads

作者：Nicolas J F^*; Castaner R; Crespo J; Yubero E; Galindo N; Pastor C

来源：Atmospheric Research, 2018, 210: 100-109.

DOI：10.1016/j.atmosres.2018.04.008

• Absorption coefficient
• Absorption angstrom exponent
• Particulate matter
• Mountain site
• Saharan dust events
• Planetary boundary layer

Measurements of particulate matter (PM), absorption coefficient ((tap) 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 mu g.m(-3)), PM1 (3.0 +/- 1.9 mu g.m(-3)), sigma(ap) (2.18 +/- 1.45 Mm(-1)/ lambda = 520 nm) and AAE (1.190 +/- 0.225). PM concentrations and sigma(ap) 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, sigma(ap) 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 sigma(ap) 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.

• 出版日期2018-9-15