Identifying Sources of Organic and Inorganic Components in PM2.5 from Algeria: Insights from Diagnostic Ratios and PMF Analysis

Abstract The present study investigates the spatial variation, chemical composition and sources of PM 2.5 at five different sites in Bouira Province, Algeria. This work provides the first integrated multi-site molecular tracer and Positive matrix factorization (PMF) based source apportionment of PM 2.5 in Bouira Province, contributing new insights into aerosol sources in North African Mediterranean environments. Mean PM 2.5 concentrations ranged from 7.9 to 597 µg m −3 , indicating strong spatial variability driven by traffic, industrial, and natural sources, and underscoring the need for air quality control strategies aligned with World Health Organization guidelines. A comprehensive chemical characterization was performed, including water-soluble ions, trace metals, carbonaceous fractions, and organic compounds (n-alkanes, PAHs, hopanes, sugars, and dicarboxylic acids). Total PAHs ranged from 1.39 to 56.8 ng m −3 , with highest levels at traffic and industrial sites. Oxygenated PAHs exceeded methyl-PAHs at all locations, reaching 7.46 ng m −3 , reflecting secondary formation processes. Hopanes ratios (C 29 αβ/C 30 αβ = 1.07–2.93) indicated mixed gasoline-diesel combustion sources. PMF applied to 74 PM 2.5 samples and 80 species resolved seven factor with strong model performance (r 2 = 0.98). PM 2.5 was dominated by soil/dust (34%) and a mixed marine-saline factor (24%), followed by petrochemical activities (12%), diesel vehicles (11%), nitrate (11%), metallurgical processes (6%), and gasoline vehicles (2%). Source profiles were well distinguished using specific tracers (e.g., PAHs, EC, Pb for traffic; V and Mo for petrochemical sources; crustal elements for dust and sea spray by marine ions). These findings provide robust source attribution and highlight the importance of integrated chemical approaches to support air quality management in data-scarce regions. Graphical Abstract