E.D. Vicente

Mutagenicity assessment of aerosols in emissions from domestic combustion processes

Domestic biofuel combustion is one of the major sources of regional and local air pollution, mainly regarding particulate matter and organic compounds, during winter periods. Mutagenic and carcinogenic activity potentials of the ambient particulate matter have been associated with the fraction of polycyclic aromatic hydrocarbons (PAH) and their oxygenated (OPAH) and nitrogenated (NPAH) derivatives. This study aimed at assessing the mutagenicity potential of the fraction of this polycyclic aromatic compound in particles (PM10) from domestic combustion by using the Ames assays with Salmonella typhimurium TA98 and TA100. Seven biofuels, including four types of pellets and three agro-fuels (olive pit, almond shell and shell of pine nuts), were tested in an automatic pellet stove, and two types of wood (Pinus pinaster, maritime pine, and Eucalyptus globulus, eucalypt) were burned in a traditional wood stove. For this latter appliance, two combustion phases—devolatilisation and flaming/smouldering—were characterised separately. A direct-acting mutagenic effect for the devolatilisation phase of pine combustion and for both phases of eucalypt combustion was found. Almond shell revealed a weak direct-acting mutagenic effect, while one type of pellets, made of recycled wastes, and pine (devolatilisation) presented a cytotoxic effect towards strain TA100. Compared to the manually fired appliance, the automatic pellet stove promoted lower polyaromatic mutagenic emissions. For this device, only two of the studied biofuels presented a weak mutagenic or cytotoxic potential.

Organic tracers in aerosols from the residential combustion of pellets and agro-fuels

The consumption of pellets and alternative biofuels, such as some agricultural residues, has experienced a tremendous growth in Mediterranean countries, which has changed the panorama of biomass burning emissions. To apply source apportionment models, specific chemical signatures for smoke aerosols are necessary. In this study, filter samples of fine particles (PM2.5) from the combustion of four different types of pellets and three agro-fuels (shell of pine nuts, olive pit and almond shell) in a pellet stove were collected. The PM2.5 samples were extracted with dichloromethane/methanol and the dried extracts were silylated before injection into the gas chromatograph-mass spectrometer (GC-MS). The analysis included monosaccharide anhydrides, resin acids, methoxyphenols and sterols. The amounts emitted were highly variable and dependent on both biofuel and combustion temperature. On average, the anhydrosugar particle mass fractions for the seven biofuels were 30 to 70 times lower than the values reported for manually fired systems. The highest levoglucosan emissions were observed for olive pit. Levoglucosan to mannosan ratios ranged from values around 2 for pellets and shell of pine nuts to much higher quotients, similar to those reported for hardwood combustion. Irrespective of biofuel, vanillin and vanillic acid were always present in the smoke samples. Coniferyl alcohol was only detected in samples from the combustion of olive pit and pellets with the highest softwood content. Sinapyl alcohol was exclusively emitted by olive pit. Dehydroabietic and isopimaric acids were represented in emissions whether from all type of pellets or from shell of pine nuts, whilst abietic acid was only quantifiable in PM2.5 from the combustion of pellets made of coniferous wood. Sitosterol was solely detected in smoke particles from shell of pine nuts and olive pit.

Emissions from the combustion of eucalypt and pine chips in a fluidized bed reactor.

Interest in renewable energy sources has increased in recent years due to environmental concerns about global warming and air pollution, reduced costs and improved efficiency of technologies. Under the European Union (EU) energy directive, biomass is a suitable renewable source. The aim of this study was to experimentally quantify and characterize the emission of particulate matter (PM2.5) resulting from the combustion of two biomass fuels (chipped residual biomass from pine and eucalypt), in a pilot-scale bubbling fluidized bed (BFB) combustor under distinct operating conditions. The variables evaluated were the stoichiometry and, in the case of eucalypt, the leaching of the fuel. The CO and PM2.5 emission factors were lower when the stoichiometry used in the experiments was higher (0.33±0.1 g CO/kg and 16.8±1.0 mg PM2.5/kg, dry gases). The treatment of the fuel by leaching before its combustion has shown to promote higher PM2.5 emissions (55.2±2.5 mg/kg, as burned). Organic and elemental carbon represented 3.1 to 30 wt.% of the particle mass, while carbonate (CO3(2-)) accounted for between 2.3 and 8.5 wt.%. The particulate mass was mainly composed of inorganic matter (71% to 86% of the PM2.5 mass). Compared to residential stoves, BFB combustion generated very high mass fractions of inorganic elements. Chloride was the water soluble ion in higher concentration in the PM2.5 emitted by the combustion of eucalypt, while calcium was the dominant water soluble ion in the case of pine.

Chemical profiling of PM 10 from urban road dust

Road dust resuspension is one of the main sources of particulate matter with impacts on air quality, health and climate. With the aim of characterising the thoracic fraction, a portable resuspension chamber was used to collect road dust from five main roads in Oporto and an urban tunnel in Braga, north of Portugal. The PM10 samples were analysed for: i) carbonates by acidification and quantification of the evolved CO2, ii) carbonaceous content (OC and EC) by a thermo-optical technique, iii) elemental composition by ICP-MS and ICP-AES after acid digestion, and iv) organic speciation by GC-MS. Dust loadings of 0.48±0.39mgPM10m-2 were obtained for asphalt paved roads. A much higher mean value was achieved in a cobbled pavement (50mgPM10m-2). In general, carbonates were not detected in PM10. OC and EC accounted for PM10 mass fractions up to 11% and 5%, respectively. Metal oxides accounted for 29±7.5% of the PM10 mass from the asphalt paved roads and 73% in samples from the cobbled street. Crustal and anthropogenic elements, associated with tyre and brake wear, dominated the inorganic fraction. PM10 comprised hundreds of organic constituents, including hopanoids, n-alkanes and other aliphatics, polycyclic aromatic hydrocarbons (PAH), alcohols, sterols, various types of acids, glycerol derivatives, lactones, sugars and derivatives, phenolic compounds and plasticizers. In samples from the cobbled street, these organic classes represented only 439μgg-1PM10, while for other pavements mass fractions up to 65mgg-1PM10 were obtained. Except for the cobbled street, on average, about 40% of the analysed organic fraction was composed of plasticizers. Although the risk via inhalation of PAH was found to be insignificant, the PM10 from some roads can contribute to an estimated excess of 332 to 2183 per million new cancer cases in adults exposed via ingestion and dermal contact.