A comprehensive assessment of emissions from prescribed fires in two Mediterranean shrublands: chemical and morphological analysis

Prescribed burning is widely used to reduce fuel loads and mitigate wildfire risk in Mediterranean shrublands, yet field-based emission factors (EFs) for these ecosystems remain scarce, limiting the accuracy of emission inventories and atmospheric models. This study investigates gaseous and particulate emissions from prescribed fires in Calluna vulgaris and Genista hispanica shrublands in northwestern Spain to characterize emission profiles and evaluate how vegetation-specific fire behaviour influences atmospheric emissions. A field-based approach combined gravimetric analysis, thermal–optical transmittance, ion chromatography, Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Calluna burns were more intense and flaming (modified combustion efficiency, MCE = 90.6 %), whereas Genista burns were dominated by smouldering combustion (MCE = 70.8 %). Gas-phase concentrations of CO2, CO, CH4, C2H6, and total organic carbon were higher in Calluna fires, although EFs for incomplete-combustion products (CO, CH4, TOC, and elemental carbon) were generally higher for Genista. PM2.5 EFs reached 53.5 g kg−1 for Calluna and 44.7 g kg−1 for Genista. Organic and elemental carbon accounted for 28.1 % and 32.9 % of PM2.5 mass, respectively, while water-soluble inorganic ions contributed 6.9 % and 4.5 %. Morphological analysis revealed abundant tar-ball-like submicrometric organic particles and aggregates with thick organic coatings, suggesting effects on aerosol optical properties, hygroscopicity, and cloud condensation nuclei activity. These field-derived EFs improve the representation of Mediterranean shrubland fires in emission inventories and atmospheric chemistry–transport models, contributing to a better understanding of their impacts on air quality and the carbon cycle.