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The Gharb rural background station located on the northernmost island in the Maltese archipelago has been used to gather PMio data since 2008. 224 samples from a monitoring campaign carried out from March 2012 to May 2013, were characterized for various metals and ions by inductively coupled plasma mass spectrometry (ICP-MS) and ion chromatography. This speciation data was used in conjunction with the positive matrix factorization (PMF) model in order to determine the contribution of Saharan dust and marine aerosol to PMio levels at the receptor. PMF managed to isolate two different crustal source contributions: a local crustal component and a trans-boundary component of North African origin. Marine aerosol, secondary nitrate/aged aerosol, and ammonium sulphate were other source contributions, which were isolated by the model. The trans-boundary crustal component (Saharan aerosol) and the marine aerosol are considered to be of natural origin and their joint contribution to PM10 levels at the site was estimated to be 39%. This value is in the upper part of the range derived from previous studies, for natural contributions to PM10 in Europe (0.5%-58%). (C) 2016 Elsevier Ltd. All rights reserved.