Aerosols in Northern Morocco-2: Chemical Characterization and PMF Source Apportionment of Ambient PM2.5

Insufficient data on the chemical composition of PM 2.5 and its emission sources in the southwestern (SW) Mediterranean area has been identified. Ambient PM 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 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 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 2 = 0.97) obtained between gravimetrically measured and chemically determined PM 2.5 mass. The one-year average concentration of PM 2.5 was 17.96 µg/m 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 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 2.5 emission sources, regarding their typical tracers, were ammonium sulfate (SO 4 2− , NH 4 + , K + , NO 3 −), road traffic and biomass burning emissions (OC, BC), fresh sea salt (Cl − , K + , NO 3 −), aged sea salt (Mg 2+ , Na + , Ca 2+), and oxalate-rich (oxalate, NO 3 −) factors. Further, it is hoped that these findings help to improve the scientific understanding of SW Mediterranean aerosols