Aerosols in Northern Morocco-2: Chemical Characterization and PMF Source Apportionment of Ambient PM[sub.2.5]

Insufficient data on the chemical composition of PM[sub.2.5] and its emission sources in the southwestern (SW) Mediterranean area has been identified. Ambient PM[sub.2.5] samples were collected in an urban area of Tetouan city, northern Morocco. Chemical mass closure calculations and positive matrix factorization were performed for the comprehensive dataset of PM[sub.2.5] chemical analyses. Mass closure improved when multipliers (1.2 and 0.23, respectively) were used for the conversion of organic carbon (OC) and calcium ion (Ca[sup.2+] ) into particulate organic matter (POM) and mineral dust masses, respectively. The mass closure model performed well in this SW Mediterranean region, with a significant correlation (r[sup.2] = 0.97) obtained between gravimetrically measured and chemically determined PM[sub.2.5] mass. The one-year average concentration of PM[sub.2.5] was 17.96 μg/m[sup.3] , and the major chemical components were POM (34%), secondary inorganic aerosol (SIA) (28%), and black carbon (18%), while unidentified mass was 4%. The mass concentration and most of the chemical components of PM[sub.2.5] showed clear seasonal variations, with a summer-high and winter-low pattern for SIA, dust, and BC. In the winter months, POM was the dominant component. Source apportionment analysis revealed that PM[sub.2.5] emission sources, regarding their typical tracers, were ammonium sulfate (SO[sub.4] [sup.2−] , NH[sub.4] [sup.+] , K[sup.+] , NO[sub.3] [sup.−] ), road traffic and biomass burning emissions (OC, BC), fresh sea salt (Cl[sup.−] , K[sup.+] , NO[sub.3] [sup.−] ), aged sea salt (Mg[sup.2+] , Na[sup.+] , Ca[sup.2+] ), and oxalate-rich (oxalate, NO[sub.3] [sup.−] ) factors. Further, it is hoped that these findings help to improve the scientific understanding of SW Mediterranean aerosols.