<p>In this study, the weekly total water-soluble inorganic ions (TWSII) concentrations of PM_2.5 in the coastal city of Algeria, Bou-Ismail, were determined from December 29th, 2013, to June 29th, 2014, under the ChArMEx project. This study aimed to identify the seasonal sources and chemical composition of PM2.5-bound water-soluble inorganic ions (WSIIs) in a coastal city of Algeria using principal component analysis (PCA). The findings indicated that the TWSII concentration was 14.06 ± 0.22&#xa0;µg m⁻³ during the winter and 12.35 ± 0.42&#xa0;µg m⁻³ during the spring. The Na⁺, NH₄⁺, NO₃⁻, and Cl⁻ ions were the main TWSII in winter, whilst Na⁺, NH₄⁺, oxalate, and NO₃⁻ ions were the main WSII in spring. PCA identified two sources for winter: PC1 is a mix of pollutants from secondary organic traces, marine sources, and stationary emissions from burning, while PC2 encompasses operations, construction materials, and secondary gas-particle transformations. For spring, four sources were identified: PC1, marine aerosol emissions; PC2, stationary emissions, agricultural practices, marine biogenic emissions, and biomass burning; PC3, photochemical response; and PC4, soil dust. The whole sample campaign had a 1.29 cationic-to-anionic regression slope. The [NO₃⁻]/[SO₄²⁻] mass ratio was greater than (1) The findings indicated the strong influence of pollutants from mobile sources over stationary sources. Pathway 1 includes all west and northwest air masses from the sample location. Large air masses traverse the Atlantic via Spain, Portugal, southern France, and western Algeria. An air mass from the south traversed the Algerian Desert and southern Libya in Pathway (2) In pathway 3, northwest Italy and Tunisia across the Mediterranean Sea were the most polluted.</p>