Variability of mineral dust deposition in the western Mediterranean basin and south-east of France

Abstract

Abstract. Previous studies have provided some insight into the Saharan dust deposition at a few specific locations from observations over long time periods or intensive field campaigns. However, no assessment of the dust deposition temporal variability in connection with its regional spatial distribution has been achieved so far from network observations over more than 1 year. To investigate dust deposition dynamics at the regional scale, five automatic deposition collectors named CARAGA (Collecteur Automatique de Retombées Atmosphériques insolubles à Grande Autonomie in French) have been deployed in the western Mediterranean region during 1 to 3 years depending on the station. The sites include, from south to north, Lampedusa, Majorca, Corsica, by satellites, more than 80 % of the major dust deposition events are recorded at only one station, suggesting that the dust provenance, transport and deposition processes (i.e. wet vs. dry) of dust are different and specific for the different deposition sites in the Mediterranean studied area. The results tend to indicate that wet deposition is the main form of deposition for mineral dust in the western Mediterranean basin, but the contribution of dry deposition (in the sense that no precipitation was detected at the surface) is far from being negligible, and contributes 10 to 46 % to the major dust deposition events, depending on the sampling site.

Estimating chemical composition of atmospheric deposition fluxes from mineral insoluble particles deposition collected in the western Mediterranean region

“…Rinse water and rainwater pass through an AA Millipore ® cellulose ester filter with a 0.8 µm porosity in order to collect the insoluble fraction of the deposition. A complete description of the CARAGA collector and sampling network can be found in Laurent et al (2015) and Vincent et al (2016). After being brought back to the laboratory, collected filters were ashed following a progressive increase in temperature up to 550 • C in order to destroy and vaporize the filter and organic matters.…”

“…From 2011 to 2013, 108 samples corresponding to the most intense weekly dust deposition samples were studied by Vincent et al (2016), and a Saharan origin was identified for 107 selected samples by using satellite data and air mass trajectories. The selected samples account for 84, 78 and 73 % in mass of the total deposition in Lampedusa (37 samples), Mallorca (21 samples) and Corsica (11 samples), and it contributes for around 50 % in Frioul (21 samples) and Le Casset (17 samples).…”

“…Measured total mass fluxes of atmospheric deposition and the weighing and ignition protocols used to quantify the mineral deposition are presented in Laurent et al (2015) and Vincent et al (2016). In the present study, we investigate the possibility of using the CARAGA ashed samples to estimate the elemental mass deposition flux of nutrients and trace metals.…”

“…To do that, a long-term and large-scale deposition sampling network is required (Schulz et al, 2012). In order to obtain a long timeseries of deposition mass fluxes at several sampling sites, a CARAGA (Collecteur Automatique de Retombées Atmosphériques insolubles à Grande Autonomie) collector has been developed (Laurent et al, 2015) and implemented at five sites in the western Mediterranean region (Vincent et al, 2016). This collector has up to 6 months autonomy without human intervention.…”

In situ measurements of desert dust particles above the western Mediterranean Sea with the balloon-borne Light Optical Aerosol Counter/sizer (LOAC) during the ChArMEx campaign of summer 2013

“…Buat-Ménard and Chesselet, 1979;Martin et al, 1991;Swap et al, 1992;Duce, 1995;Alpert et al, 1998;Mahowald et al, 2009Mahowald et al, , 2011Maher et al, 2010;Liu et al, 2011;Choobari et al, 2014;Li et al, 2016). Desert dust aerosol is of particular interest in the Mediterranean region where it is (i) frequently observed in high concentrations in the troposphere; (ii) is a major component of surface PM 10 Rea et al, 2015), aerosol optical depth (Moulin et al, 1998;Gkikkas et al, 2013;Nabat et al, 2013), atmospheric deposition (Pye, 1992;Vincent et al, 2016); and (iii) affecting the regional air quality (Querol et al, 2009); atmospheric thermodynamics (e.g. Alpert et al, 1998;Chaboureau et al, 2011); radiative budget and climate (e.g.…”