Geochemical fingerprints and North-African dust sources: results from a multisite network of aerosol deposition in the south-western Europe
Authors: Pey Jorge , Larrasoaña Juan Cruz , Reyes Jesús , Pérez Noemí , Cerro José Carlos , Castillo Sonia , Mata María Pilar , Orellana-Macías José María , Causapé Jesús , Valero-Garcés Blas L. , Oliva-Urcia Belén , Santos-González Javier , González-Gutiérrez Rosa Blanca 
Published: March 2021

&lt;p&gt;&lt;strong&gt;Abstract&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;The DONAIRE network (Pey et al. 2020) monitors the phenomenology of geochemical, magnetic and mineralogical variations of bulk atmospheric deposition in the Iberian Peninsula- Balearic Island. In this work we focus on recent North African dust deposition with a double objective: 1) to characterize the main geochemical fingerprints with respect to other sources of pollution; 2) to perform a source apportionment study to identify different desert-dust source areas. We used one year of data (June 2016-July 2017) from 15 monitoring sites (regional and remote, urban, industrial, or agricultural). We focus here on the impact caused by the main 4 North African dust deposition events globally affected this network.&lt;/p&gt;&lt;p&gt;Our results evidence that dust deposition patterns are controlled by: i) the meteorological scenario behind dust transport, ii) the occurrence/absence of wet deposition, and iii) the local-to-regional nearby topography. In general, the largest dust-deposition events occur nearby mountain barriers during low-pressure systems approaching Iberia and NW Africa.&lt;/p&gt;&lt;p&gt;Moderate to intense dust deposition events are well characterized by their chemical composition. The Fe/Ti, Na/Al, K/Al or (Ca+Mg)/Fe ratios reveal a number of patterns across the network. For example, Fe/Ti ratio varies from around 10-13 during warm-season events to 22-35 during cold season episodes, potentially indicating different North-African dust sources.&lt;/p&gt;&lt;p&gt;The best source apportionment solution extracts 10 factor/sources, from which three are mineral in composition. Two of them are interpreted as different North African dust mixture-of-sources, whereas the third mineral factor corresponds to regional dust particles. The overall contribution of such desert-dust sources may explain up to 90% of total episodic deposition during the most intense events.&lt;/p&gt;&lt;p&gt;These results indicate that chemical fingerprinting could be used to infer the recent North African dust deposition history. Studies on lake and peatland sequences following a similar approach are in progress and preliminary data show they be used to trace Saharan dust during the Holocene and reconstruct its relationship with climate phases.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Reference&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;Pey J., Larrasoa&amp;#241;a J.C., P&amp;#233;rez N., Cerro J.C., Castillo S. &lt;em&gt;et al.&lt;/em&gt; (2020). Phenomenology and geographical gradients of atmospheric deposition in southwestern Europe: results from a multi-site monitoring network. &lt;em&gt;Sci. Tot. Environ.&lt;/em&gt;, 140745. https://doi.org/10.1016/j.scitotenv.2020.140745.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Acknowledgements&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;POSAHPI (PID2019-108101RB-I00) and DONAIRE (CGL2015-68993-R) projects funded by Spanish Agencia Estatal de Investigaci&amp;#243;n and FEDER Funds.&lt;/p&gt;