AUTHOR=Pio Casimiro A. , Cardoso João G. , Cerqueira Mário A. , Calvo Ana , Nunes Teresa V. , Alves Célia A. , Custódio Danilo , Almeida Susana M. , Almeida-Silva Marina 

TITLE=Seasonal variability of aerosol concentration and size distribution in Cape Verde using a continuous aerosol optical spectrometer

JOURNAL=Frontiers in Environmental Science

VOLUME=Volume 2 - 2014

YEAR=2014

URL=https://www.frontiersin.org/journals/environmental-science/articles/10.3389/fenvs.2014.00015

DOI=10.3389/fenvs.2014.00015

ISSN=2296-665X

ABSTRACT=One year of, almost continuous, measurements of aerosol optical properties and chemical composition were performed at the outskirts of Praia, Santiago Island, Cape Verde, within the framework of CV-DUST (Atmospheric aerosol in Cape Verde region: seasonal evaluation of composition, sources and transport) research project, during  2011. This article reports the aerosol number and mass concentration measurements using a GRIMM Optical Aerosol Spectrometer that provides number size discrimination into 31 size ranges from 0.25 to 32 µm. Time series of 5 min average PM10 concentrations revealed peak values higher than 1000 µg.m-3 during winter dust storm events originating over Northern Africa. The 24 hours average concentrations exceeded the World Health Organization (WHO) guidelines for PM2.5 and PM10 in 20% and 30% of the 2001 days, respectively. Annual average mass concentrations (±standard deviation) for PM1, PM2.5 and PM10 were 5±5, 19±21 and 48±64 µg.m-3, respectively. The annual PM2.5 and PM10 values were also above the limits prescribed by the WHO (10 and 20 µg.m-3, respectively). The aerosol mass size distribution revealed two main modes for particles smaller than 10 µm: a fine mode (0.7-0.8 µm), which possibly results of gas to particle conversion processes; and a coarse mode with maxima at 3-4 µm, which is associated with desert dust and sea salt sources. Within the coarse mode two sub-modes with maxima at 5-6 µm and 10-12 µm were frequently present.