Célia Alves

This study investigates particle number concentrations (PNCs), particle number size distributions (PNSDs), and equivalent black carbon (eBC) concentrations during ironing with a typical steam iron and a steam iron with a portable boiler under different ventilation conditions. Measurements were conducted in a residential environment under low- and higher-ventilation conditions. Ironing caused a rapid and substantial increase in PNC, with concentrations increasing by up to approximately two orders of magnitude during the activity, particularly for particles between 20 and 80 nm. The maximum PNC reached 7.12 × 10⁵ particles cm⁻³ for the typical steam iron under low-ventilation conditions. Particle concentrations decreased after ironing, although the decay was slower for particles larger than approximately 80 nm. Estimated particle number emission rates ranged from 8.1 × 10¹¹ to 1.5 × 10¹² particles min⁻¹, with the highest emission rate obtained for the steam iron with a portable boiler under low-ventilation conditions. PNSDs were fitted using one or two lognormal distributions, depending on the shape of the measured distributions. Ironing produced a shift in the modal particle diameters towards larger sizes, particularly during the post-ironing period. Higher ventilation reduced particle concentrations and accelerated particle removal from the indoor environment. eBC concentrations showed only modest changes during ironing, with a slight increase under low-ventilation conditions. These results demonstrate that ironing can be an important indoor source of ultrafine and fine particles and that ventilation plays an important role in controlling their indoor concentration and persistence.

In rapidly expanding African cities, the ecotoxicological relevance of PM₁₀ remains largely unresolved, especially where particle mass, chemical composition and emission sources are rarely assessed together. Here, 116 daily PM₁₀ samples collected in Luanda between 27 June and 5 November 2023 were tested using the Microtox^® Aliivibrio fischeri assay on aqueous extracts. Chemical speciation was combined with centred log-ratio (CLR) compositional clustering to identify recurring chemical regimes, while Positive Matrix Factorisation (PMF) was used to resolve the corresponding emission sources. Toxicity was moderate but highly variable: Toxic units after 15 min (TU₁₅) ranged from 0.84 to 8.54, with changes in toxicity units between 5 and 15 min (ΔTU) varying from −1.51 to +4.84. Only 3 of the 116 samples showed TU₁₅ < 1, and none reached TU₁₅ ≥ 10. The strongest responses occurred under a metal-enriched chemical regime (C2), characterised by elevated Zn, Pb and Cd concentrations, which showed the highest mean TU₁₅ (4.22) and ΔTU (1.52). This regime coincided with PMF evidence identifying non-ferrous metallurgy plus galvanised/metal scrap handling and burning as the factor most strongly associated with toxicity (ρTU₁₅ = 0.63; ρΔTU = 0.78), followed by a Ni-rich metallurgical factor with possible aviation influence (ρTU₁₅ = 0.51). Conversely, a marine/ionic chemical regime (C3) showed lower, stable toxicity, consistent with negative marine aerosol associations. These findings show that integrating chemical regimes with PMF-resolved sources identifies metal-related emissions as the main drivers of PM₁₀ ecotoxicity.

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 CO ₂ , CO, CH ₄ , C ₂ H ₆ , and total organic carbon were higher in Calluna fires, although EFs for incomplete-combustion products (CO, CH ₄ , TOC, and elemental carbon) were generally higher for Genista . PM _2.5 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 PM _2.5 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.

Prescribed fires were conducted in two shrubland communities dominated by Genista hispanica subsp. occidentalis and Calluna vulgaris in La Cueta, León, Spain, to characterise particulate and gaseous emissions during combustion. Distinct fire dynamics were observed: Calluna exhibited a Modified Combustion Efficiency (MCE) of 90.6, indicative of flaming combustion, while Genista showed an MCE of 70.8, characteristic of smouldering conditions. Gas-phase analysis revealed notably higher concentrations of CO₂, CO, CH₄, C₂H₆, and total organic carbon (TOC) in Calluna compared to Genista, with CO₂ showing the greatest difference. Conversely, Genista exhibited slightly elevated NO and NO₂ levels. Most gas concentrations were higher for Calluna, except for hydrogen fluoride (HF), which was more abundant in Genista. Elemental carbon (EC) and organic carbon (OC) accounted for 28.1 % and 32.9 % of PM_2.5 mass in Calluna and Genista, respectively. Water-soluble inorganic ions contributed 6.9 % and 4.5 % to PM_2.5 mass, with most ions more abundant in Calluna, except chloride (Cl⁻), which was higher in Genista. In both cases, Cl^-, SO₄^2-, Na⁺, Mg²⁺, and Ca²⁺ dominated the ionic composition. Morphological analysis revealed a population dominated by tar balls (submicrometer spherical particles) and aggregates with thick organic coatings. Derived emission factors are expected to provide valuable input for numerical models evaluating the impacts of prescribed and unplanned forest fires in the Mediterranean region.