Assessing Biogenic and Biomass Burning Sources in Winter PM2.5 through Saccharide Characterization in Changzhou, YRD region, China

Organic aerosols constitute a major fraction of atmospheric particulate matter, and their accurate quantification holds significant scientific and environmental relevance. Saccharide compounds have been widely employed as molecular tracers owing to their distinct source-specific signatures. In this study, high-volume samplers were deployed to collect paired winter daytime and nighttime PM _2.5 samples in Changzhou, Eastern China. Target analytes—including anhydrosaccharides (levoglucosan, mannosan, and galactosan), sugar alcohols (erythritol, arabitol, and mannitol), and the monosaccharide glucose—were quantified to apportion organic carbon (OC) sources based on saccharide biomarkers. The total saccharide concentrations in winter PM _2.5 averaged 262.8 ± 174.3 ng m ^‒ ³ during the day and 301.5 ± 259.8 ng m ^‒ ³ at night, with consistently higher nocturnal levels observed across all saccharide species. Levoglucosan was the dominant compound, accounting for 69.7% of the total saccharides. Diagnostic ratios of levoglucosan/mannosan and mannosan/galactosan pointed to crop residue burning as the predominant source of anhydrosaccharides, with a minor contribution from hardwood combustion. Backward trajectory analysis indicated that air masses originated predominantly from the southwest (37.50%), followed by the northeast (28.13%), east (14.06%), and north (20.31%); trajectories from the northeast were generally slower-moving, whereas those from the north exhibited higher transport speeds. Elevated concentrations of levoglucosan, arabitol, WSOC, HULIS-C, OC, and EC were associated with air masses arriving from the southwest, while peak glucose levels coincided with northeastern trajectories. Potential source contribution function (PSCF) analysis identified southwestern Anhui Province as the primary source region for levoglucosan, northern Jiangxi and southwestern Anhui for arabitol, and northeastern Jiangsu for glucose. Molecular tracer-based source apportionment revealed that biomass burning was the leading contributor to OC (17 ~ 24%), exhibiting consistently higher contributions during nighttime under both relatively clean and high OC conditions. Fungal spore emissions represented the second-largest biogenic source, whereas plant-derived OC was negligible—indicating minimal input from plant debris in the Changzhou area. These findings enhance the understanding of OC sources in winter PM _2.5 and provide a scientific foundation for targeted air pollution mitigation strategies in the economically developed Yangtze River Delta region of China.