Multi-class organic marker profiling of urban PM10 in Strasbourg, northeastern France: Seasonal distribution of exhaust, non-exhaust, and biomass burning tracers

Atmospheric particulate matter (PM) is strongly influenced by both combustion and non-exhaust traffic emissions, yet their simultaneous molecular characterization over seasonal cycles remains rare in the French monitoring literature. This study addresses this question through the first year-round application of a suite of organic tire-related markers (TRMs) applied alongside polycyclic aromatic hydrocarbons (PAHs), monosaccharide anhydrides (MAs), and methoxyphenols (MPhs) in 36 weekly PM 10 samples collected at a semi-urban, traffic-adjacent site in Cronenbourg (northeastern France) over four seasons (winter 2023-autumn 2024), using a validated multi-residue method targeting 48 compounds. Combustion-derived PAHs (median Σ 13 PAHs 16.6 ng m -3 ) and organic TRM (median Σ 12 TRMs 4.5 ng m -3 ) showed a weak, non-significant positive association (r = 0.26 , p = 0.132), indicating that a monotonic co-variation between the two tracer groups was not detected under the present sampling conditions. PAH concentrations were dominated by high-molecular-weight, traffic and heating-associated compounds in winter (BghiP 5.8 ng m -3 , BaP 5.6 ng m -3 ), consistent with pyrogenic combustion amplified by residential heating demand. Complementary MA and MPh diagnostic ratios (L/M = 0.57-6.35) identified a biomass-burning signature consistent with predominantly softwood-related combustion. Biomass-burning markers showed a directional 1.5-3.2-fold enrichment in autumn-winter relative to spring-summer, though this difference did not reach statistical significance for any individual marker (Kruskal-Wallis, p > 0.12), consistent with a moderate rather than dominant local biomass-burning source. Compared with previous studies from French and Mediterranean sites, the molecular marker patterns suggest relatively less evidence of hardwood or agricultural-residue burning. This study also represents the first simultaneous four-season MA-MPh profiling investigation conducted in northeastern France. Together, these results suggest that exhaust combustion, non-exhaust emission, and biomass burning represent chemically distinguishable contributors to urban PM 10 , supporting consideration of source-specific rather than aggregated approaches to traffic-related air quality management.