Biomass burning emissions and influence of combustion variables in the cone-calorimeter

Emissions from biomass burning are highly variable and depend on combustion conditions as well as fuel properties. Simultaneous emissions from pyrolysis, smouldering, and combustion of the biomass material(s) burning leads to uncertainties in how these processes contribute to emissions of individual or groups of compounds as well as to total particle emissions. These uncertainties are difficult to constrain when analysing real-world emissions but also when performing laboratory studies of e.g., cook-stove emissions in more controlled environments. This study was designed to reduce some of this variability by enabling highly reproducible conditions by controlling combustion via adjustment of a few key factors. The aim of this study was to identify how these factors influenced emissions, and how different pyrolysis and burn conditions in turn contributed to the particle emissions.In this study, we used a controlled atmosphere cone calorimeter according to ISO 5660‐5. We controlled fuel moisture content, the air flow to the combustion and O2 available for combustion, and the total heat flux (HF) to the fuel to study the independent effect of combustion variables on the aerosol emissions. In each experiment a small 10x10x1 cm piece of Birch-wood was put in a sample holder and combusted under controlled conditions. We conducted over 40 experiments, varying HF and flow conditions while monitoring fuel mass loss to quantify emission yields. An Aerosol Mass Spectrometer (AMS, Aerodyne Billerica, USA), a multi‐wavelength aethalometer (AE33, Magee Sci., USA) and a particle size spectrometer (DMS5000, Cambustion, UK) measured time‐resolved evolution in particle properties during burns. Our results showed that pyrolysis conditions in the absence of O2 resulted in organic aerosol (OA) emissions with mass yields (g/g fuel) from a few percent at the lowest HF and up to ten percent at the highest HF. During combustion in air, equivalent black carbon (eBC) emissions were found to moderately increase with increasing HF. eBC was also found to increase when the O2 availability or combustion was reduced (O2 deficient combustion). Polycyclic aromatic hydrocarbon (PAH) was here defined separately from OA in the AMS analysis. PAH emissions were low for pyrolysis and combustion at high air flows (excessive O2 availability). In contrast, O2 deficient combustion conditions resulted in dramatically increased PAH emissions, with yields as high as to 0.5% (g/g fuel). The relationship between PAH emissions and availability of air and O2 during combustion is illustrated in Figure 1. Future analyses include a more detailed PAH analysis including off-line GC-MS, thermal-optical carbon analysis, UV-VIS absorption of MeOH soluble OA. We will parameterize emissions based on the initial conditions such as HF, moisture content, air flow rate (cooling) and O2 availability. A mechanistic understanding of relationships between combustion variables and emissions can aid the development of cleaner biomass combustion technologies and will improve fire emission models

Acute Cardiovascular Effects of Controlled Exposure to Dilute Petrodiesel and Biodiesel Exhaust in Healthy Volunteers: A Crossover Study

Abstract Background Air pollution derived from combustion is associated with considerable cardiorespiratory morbidity and mortality in addition to environmental effects. Replacing petrodiesel with biodiesel may have ecological benefits, but impacts on human health remain unquantified. The objective was to compare acute cardiovascular effects of blended and pure biodiesel exhaust exposure against known adverse effects of petrodiesel exhaust (PDE) exposure in human subjects. In two randomized controlled double-blind crossover studies, healthy volunteers were exposed to PDE or biodiesel exhaust for one hour. In study one, 16 subjects were exposed, on separate occasions, to PDE and 30% rapeseed methyl ester biodiesel blend (RME30) exhaust, aiming at PM10 300 μg/m3. In study two, 19 male subjects were separately exposed to PDE and exhaust from a 100% RME fuel (RME100) using similar engine load and exhaust dilution. Generated exhaust was analyzed for physicochemical composition and oxidative potential. Following exposure, vascular endothelial function was assessed using forearm venous occlusion plethysmography and ex vivo thrombus formation was assessed using a Badimon chamber model of acute arterial injury. Biomarkers of inflammation, platelet activation and fibrinolysis were measured in the blood. Results In study 1, PDE and RME30 exposures were at comparable PM levels (314 ± 27 μg/m3; (PM10 ± SD) and 309 ± 30 μg/m3 respectively), whereas in study 2, the PDE exposure concentrations remained similar (310 ± 34 μg/m3), but RME100 levels were lower in PM (165 ± 16 μg/m3) and PAHs, but higher in particle number concentration. Compared to PDE, PM from RME had less oxidative potential. Forearm infusion of the vasodilators acetylcholine, bradykinin, sodium nitroprusside and verapamil resulted in dose-dependent increases in blood flow after all exposures. Vasodilatation and ex vivo thrombus formation were similar following exposure to exhaust from petrodiesel and the two biodiesel formulations (RME30 and RME100). There were no significant differences in blood biomarkers or exhaled nitric oxide levels between exposures. Conclusions Despite differences in PM composition and particle reactivity, controlled exposure to biodiesel exhaust was associated with similar cardiovascular effects to PDE. We suggest that the potential adverse health effects of biodiesel fuel emissions should be taken into account when evaluating future fuel policies. Trial registration ClinicalTrials.gov, NCT01337882 /NCT01883466. Date of first enrollment March 11, 2011, registered April 19, 2011, i.e. retrospectively registered

Effect of wood smoke exposure on vascular function and thrombus formation in healthy fire fighters

Background: Myocardial infarction is the leading cause of death in fire fighters and has been linked with exposure to air pollution and fire suppression duties. We therefore investigated the effects of wood smoke exposure on vascular vasomotor and fibrinolytic function, and thrombus formation in healthy fire fighters. Methods: In a double-blind randomized cross-over study, 16 healthy male fire fighters were exposed to wood smoke (~1 mg/m3 particulate matter concentration) or filtered air for one hour during intermittent exercise. Arterial pressure and stiffness were measured before and immediately after exposure, and forearm blood flow was measured during intra-brachial infusion of endothelium-dependent and -independent vasodilators 4–6 hours after exposure. Thrombus formation was assessed using the ex vivo Badimon chamber at 2 hours, and platelet activation was measured using flow cytometry for up to 24 hours after the exposure. Results: Compared to filtered air, exposure to wood smoke increased blood carboxyhaemoglobin concentrations (1.3% versus 0.8%; P &lt; 0.001), but had no effect on arterial pressure, augmentation index or pulse wave velocity (P &gt; 0.05 for all). Whilst there was a dose-dependent increase in forearm blood flow with each vasodilator (P &lt; 0.01 for all), there were no differences in blood flow responses to acetylcholine, sodium nitroprusside or verapamil between exposures (P &gt; 0.05 for all). Following exposure to wood smoke, vasodilatation to bradykinin increased (P = 0.003), but there was no effect on bradykinin-induced tissue-plasminogen activator release, thrombus area or markers of platelet activation (P &gt; 0.05 for all). Conclusions: Wood smoke exposure does not impair vascular vasomotor or fibrinolytic function, or increase thrombus formation in fire fighters. Acute cardiovascular events following fire suppression may be precipitated by exposure to other air pollutants or through other mechanisms, such as strenuous physical exertion and dehydration.Originally included in thesis in manuscript form.</p

Traffic related air pollution with emphasis on particle associated polycyclic aromatic hydrocarbons : Tire wear and biodiesel exhaust emissions

Particulate matter (PM) is regarded as one of the more important components of air pollution causing adverse health effects. A large group of compounds associated with PM are polycyclic aromatic compounds (PACs) which comprises polycyclic aromatic hydrocarbons (PAHs). Several PACs are known for their mutagenic and carcinogenic properties as well as have the ability to induce oxidative stress. With the growing importance of non-exhaust particles relative to vehicular tail-pipe emissions in urban air, it is necessary to investigate the possible contribution of PAHs from the different non-exhaust sources, as these inputs are far less characterized than tail-pipe emissions and their impact on human health is largely unknown. In this thesis automobile tires, an important non-exhaust traffic related source to particles, have been investigated for its content of highly carcinogenic dibenzopyrene isomers. In a separate study benzothiazoles, a class of compounds used as vulcanization accelerators in tire manufacture, were determined to evaluate their use as potential markers for tire wear particles in ambient air. Analysis of the tires showed a substantial variation in the PAH content between different makes of tires, likewise did the benzothiazoles content vary. By determining benzothiazole in air particles collected at a busy street in Stockholm the tire rubber contribution to airborne particles was estimated to 0.7 and 5.5 % for PM10 and all airborne particles, respectively. Together with the determined content of dibenzopyrenes and the relatively low mass contribution of tire wear to airborne particles in the urban air, estimated in this thesis as well as suggested by the literature, tire wear appears to be a minor traffic related contributor of these PAH compounds in the urban air. Nevertheless, tire wear may be an important source to 2-mercaptobenzothiazole in the urban air. Biodiesel, a biofuel produced from plant and animal fats, has been suggested as a suitable replacement for conventional petroleum based diesel fuels. While the majority of studies have focused on health outcomes from petroleum diesel exhaust exposure, human health effects related to biodiesel exhaust exposure is much less investigated. Biodiesel exhaust particles have been compared with conventional petroleum diesel by determining &gt;40 PAHs in two separate studies on two different diesel engines, running on neat rapeseed methyl ester (RME), petroleum diesel and a fuel blend of 3:7 RME : petroleum diesel. One of the biodiesel studies also included determination of four oxygenated PAHs (Oxy-PAHs). The exhaust from biodiesel combustion differed from petroleum diesel combustion with regards to particle size, number of emitted particles, relative amount of volatile material adsorbed on the particles and emission of particle-associated PAHs and Oxy-PAHs. A portion of these volatile compounds originated from unburned or partially combusted biodiesel fuel, which interfered with the analysis. A sample cleanup method was therefore developed for determination of PAH in lipid rich matrices. Biodiesel combustion produced lower emission of PAHs and Oxy-PAH with the exception of a few PAHs with higher molecular weights. In comparison with petroleum diesel, the biodiesel particles had a higher relative composition of PAHs with more than four rings. At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 5: Manuscript.</p

Screening av hälsofarliga ämnen och toxicitet förknippade med partiklar (PM10)

Syftet med denna studie är att kartlägga variationen i oxidativ potential, PAH, oxy-PAH och nitro-PAH förknippade med partiklar (PM10). En viktig fråga är om det finns någon relation mellan toxicitet och halterna av de ämnen som analyseras (PAH, oxy-PAH, nitro-PAH och metaller). Bakgrunden är den bristande kunskapen om vilka kemiska komponenter i partiklarna som har störst inverkan på toxiciteten och hälsoeffekterna. Partiklar insamlades på 3 platser: regional och urban bakgrund och vid en trafiknära plats intill en motorväg. De toxiska analyserna innefattade oxidativ potential med både acellulära och intracellulära metoder.Resultaten visade generellt en högre oxidativ potential för prover insamlade under vinterperioden. Kemisk analys av insamlade partiklar visade att de högsta halterna av PAH (45 föreningar) och oxy-PAH (10 föreningar) uppmättes under vintermånaderna november och december. Högst halter under samtliga månader av total PAH uppmättes i trafikmiljö följt av urban och regional bakgrund. Periodvis kunde koncentrationerna av oxy-PAH i urban bakgrund överstiga koncentrationerna i trafikmiljö, men de var lägst i regional bakgrund under samtliga mättillfällen. Generellt observerades en positiv korrelation mellan totala PAH-halter (summan av PAH, oxy-PAH och nitro-PAH) och oxidativ potential, dvs. att de prover under provtagningsperioden som hade högre totala PAH-halter hade också högre cellulär oxidativ potential. Proverna från urban bakgrund och trafiknära plats visade också en högre oxidativ potential än regional bakgrund. Större mängd partiklar per prov skulle behövts för att kunna göra mer detaljerade analyser av kemisksammansättning och för att kunna dra mer säkra slutsatser om de toxiska effekterna av partiklarna och vilka ämnen som är mest betydelsefulla för de toxiska effektern

Time-resolved analysis of particle emissions from residential biomass combustion : Emissions of refractory black carbon, PAHs and organic tracers

Time-resolved particle emissions from a conventional wood stove were investigated with aerosol mass spectrometry to provide links between combustion conditions, emission factors, mixing state of refractory black carbon and implications for organic tracer methods. The addition of a new batch of fuel results in low temperature pyrolysis as the fuel heats up, resulting in strong, short-lived, variable emission peaks of organic aerosol-containing markers of anhydrous sugars, such as levoglucosan (fragment at m/z 60). Flaming combustion results in emissions dominated by refractory black carbon co-emitted with minor fractions of organic aerosol and markers of anhydrous sugars. Full cycle emissions are an external mixture of larger organic aerosol-dominated and smaller thinly coated refractory black carbon particles. A very high burn rate results in increased full cycle mass emission factors of 66, 2.7, 2.8 and 1.3 for particulate polycyclic aromatic hydrocarbons, refractory black carbon, total organic aerosol and m/z 60, respectively, compared to nominal burn rate. Polycyclic aromatic hydrocarbons are primarily associated with refractory black carbon-containing particles. We hypothesize that at very high burn rates, the central parts of the combustion zone become air starved, leading to a locally reduced combustion temperature that reduces the conversion rates from polycyclic aromatic hydrocarbons to refractory black carbon. This facilitates a strong increase of polycyclic aromatic hydrocarbons emissions. At nominal burn rates, full cycle emissions based on m/z 60 correlate well with organic aerosol, refractory black carbon and particulate matter. However, at higher burn rates, m/z 60 does not correlate with increased emissions of polycyclic aromatic hydrocarbons, refractory black carbon and organic aerosol in the flaming phase. The new knowledge can be used to advance source apportionment studies, reduce emissions of genotoxic compounds and model the climate impacts of refractory black carbon, such as absorption enhancement by lensing. Bio4Energ