Measurement of emissions from air pollution sources. 3. C1-C29 organic compounds from fireplace combustion of wood

Organic compound emission rates for volatile organic compounds (VOC), gas-phase semivolatile organic compounds, and particle-phase organic compounds are measured from residential fireplace combustion of wood. Firewood from a conifer tree (pine) and from two deciduous trees (oak and eucalyptus) is burned to determine organic compound emissions profiles for each wood type including the distribution of the alkanes, alkenes, aromatics, polycyclic aromatic hydrocarbons (PAH), phenol and substituted phenols, guaiacol and substituted guaiacol, syringol and substituted syringols, carbonyls, alkanoic acids, resin acids, and levoglucosan. Levoglucosan is the major constituent in the fine particulate emissions from all three wood types, contributing 18-30% of the fine particulate organic compound emissions. Guaiacol (2-methoxyphenol), and guaiacols with additional substituents at position 4 on the molecule, and resin acids are emitted in significant quantities from pine wood combustion. Syringol (2,6-dimethoxyphenol) and syringols with additional substituents at position 4 on the molecule are emitted in large amounts from oak and eucalyptus firewood combustion, but these compounds are not detected in the emissions from pine wood combustion. Syringol and most of the substituted syringols are found to be semivolatile compounds that are present in both the gas and particle phases, but two substituted syringols that have not been previously quantified in wood smoke emissions, propionylsyringol and butyrylsyringol, are found exclusively in the particle phase and can be used to help trace hardwood smoke particles in the atmosphere. Benzene, ethene, and acetylene are often used as tracers for motor vehicle exhaust in the urban atmosphere. The contribution of wood smoke to the ambient concentrations of benzene, ethene, and acetylene could lead to an overestimate of the contribution of motor vehicle tailpipe exhaust to atmospheric VOC concentrations.     

PCDD/F,PCB, HxCBz,PAH, and PM emission factors for fireplace and woodstove combustion in the San Francisco Bay region

Emissions from residential fireplace and woodstove appliances burning fuels available from the San Francisco Bay area were sampled for polychlorinated dibenzodioxins and dibenzofurans (PCDDs/Fs), polychlorinated biphenyls (PCBs), hexachlorobenzene (HxCBz), particulate matter (PM), polycyclic aromatic hydrocarbons (PAHs), oxygenated PAHs, and the monosaccharide levoglucosan. Emission factors for these pollutants were determined, the first known characterization of this extent. Common California natural firewoods and manufactured artificial logs were tested under operating conditions intended to reflect domestic use patterns in the Bay area, which are primarily episodic burning for aesthetic reasons. Emission factors were determined by fuel type, fuel weight, mass emission rates, and energy output, highlighting differences between fuel and combustion facility type. Average PCDD/F emissions factors ranged from 0.25 to 1.4 ng toxic equivalency (TEQ)/kg of wood burned for natural wood fuels and 2.4 ng TEQ/kg for artificial logs. The natural wood emission factors are slightly lower than those which had been estimated for the U.S. inventory. Background-corrected PCBs emitted from woodstove/oak combustion (8370 ng/kg) are 3 orders of magnitude higher in mass than total PCDDs/Fs; however, their toxicity (0.014 ng TEQ/kg) is significantly lower. HxCBz emission factors varied from 13 to 990 ng/kg and were likely fuel- and appliance-specific. Relative PAH concentrations of particle-phase compounds and emission factors were consistent with others' findings. A total of 32 PAH compounds, ranging in concentration from 0.06 to 7 mg/kg, amounted to between 0.12 and 0.38% of the PM mass, depending on the wood and facility type. Preliminary analyses suggest relationships between wood combustion markers and PCDD/F levels.     

Emission of nonchlorinated and chlorinated aromatics in the flue gas of incineration plants during and after transient disturbances of combustion conditions: delayed emission effects

The profiles of different products of incomplete combustion (PIC) in the flue gas of a 1 MW pilot combustion facility were investigated under normal steady-state and disturbed combustion conditions. The behavior of emission profiles after disturbed combustion conditions was investigated in order to obtain a better understanding of emission memory effects. Highly time-resolved, quantitative on-line measurements of several aromatic species down to low ppbv or higher pptv concentrations were performed by a mobile resonance-enhanced multiphoton ionization time-of-flight mass spectrometer. Conventional analytical methods (gas chromatography-mass spectrometry and high-performance liquid chromatography) were also applied for measurement of polycyclic aromatic hydrocarbons (PAH) and polychlorinated dibenzo-p-dioxins and -furans (PCDD/F). The sampling point was located in the high-temperature region of the plant at the outlet of the post-combustion chamber at temperatures between 650 and 880 degrees C, prior to any emission reduction devices. The investigation pointed out that after a short phase of disturbed combustion conditions, e.g., due to process changes, transient puffs, or malfunctions, the composition of combustion byproducts in the flue gas can be changed drastically for a very long time ("memory emission" effect). It is suggested that carbonaceous layers, deposited on the inner walls in the high-temperature zone of the plant, might be responsible for the observed memory emission of some PAH species. Drastic changes in the profiles of the PCDD/F homologues were also observed during memory emission conditions. The PAH memory most likely is due to pyrolytic degradation of the carbonaceous layers, while the altered PCDD/F homologue pattern may be mediated by the high catalytic activity of the freshly formed deposit layers. Finally, it should be emphasized that a rich pattern of aromatic species, including PCDD/F, was found in a temperature regime well above the typical temperature window (approximately 300 degrees C) for de novo PCDD/F formation.     

Emissions of parent, nitro, and oxygenated polycyclic aromatic hydrocarbons from residential wood combustion in rural china

Residential wood combustion is one of the important sources of air pollution in developing countries. Among the pollutants emitted, parent polycyclic aromatic hydrocarbons (pPAHs) and their derivatives, including nitrated and oxygenated PAHs (nPAHs and oPAHs), are of concern because of their mutagenic and carcinogenic effects. In order to evaluate their impacts on regional air quality and human health, emission inventories, based on realistic emission factors (EFs), are needed. In this study, the EFs of 28 pPAHs (EF(PAH28)), 9 nPAHs (EF(PAHn9)), and 4 oPAHs (EF(PAHo4)) were measured for residential combustion of 27 wood fuels in rural China. The measured EF(PAH28), EF(PAHn9), and EF(PAHo4) for brushwood were 86.7 ± 67.6, 3.22 ± 1.95 × 10(-2), and 5.56 ± 4.32 mg/kg, which were significantly higher than 12.7 ± 7.0, 8.27 ± 5.51 × 10(-3), and 1.19 ± 1.87 mg/kg for fuel wood combustion (p < 0.05). Sixteen U.S. EPA priority pPAHs contributed approximately 95% of the total of the 28 pPAHs measured. EFs of pPAHs, nPAHs, and oPAHs were positively correlated with one another. Measured EFs varied obviously depending on fuel properties and combustion conditions. The EFs of pPAHs, nPAHs, and oPAHs were significantly correlated with modified combustion efficiency and fuel moisture. Nitro-naphthalene and 9-fluorenone were the most abundant nPAHs and oPAHs identified. Both nPAHs and oPAHs showed relatively high tendencies to be present in the particulate phase than pPAHs due to their lower vapor pressures. The gas-particle partitioning of freshly emitted pPAHs, nPAHs, and oPAHs was primarily controlled by organic carbon absorption.     

On-line analysis of the size distribution of fine and ultrafine aerosol particles in flue and stack gas of a municipal waste incineration plant: effects of dynamic process control measures and emission reduction devices

The size distribution of particles in the waste gas of a municipal waste incineration plant (23 MW) was measured on-line at two sampling points in the flue-gas duct (700 and 300 degrees C) as well as in the stack gas (80 degrees C). The measurements were performed during both stable combustion conditions and transient operating conditions. The particle measurements were carried out by a mobile system consisting of a home-designed sampling system with dilution device and a scanning mobility particle sizer (SMPS) for the particle size range 17-600 nm as well as an aerodynamic particle sizer (APS) for the size range 500 nm-30 microm. The APS and SMPS data were combined using a special method and a home written software tool. The maximum of the particle-size distribution in the flue gas of the incinerator shifts from about 90 nm at the 700 degrees C sampling point to about 140 nm at the 300 degrees C point, showing the particle growth by coagulation processes and condensation of inorganic and organic gaseous species with decreasing temperature. This finding is consistent with the measured concentration profiles of gaseous organic chemical species in the flue gas. While at flue-gas temperatures of 600-800 degrees C a rich pattern of polycyclic aromatic hydrocarbon species (PAH) is observable, the PAH concentrations are considerably reduced further downstream of the flue-gas channel, where the temperature drops below 500 degrees C. Condensation and reactive bonding of gaseous chemicals onto particulate matter is, among other reasons, responsible for the depletion of gas-phase species. Process control measures, such as firing the backup burners or cleaning of the grate with pressurized air, can cause dynamic changes of the particle-size distribution. Furthermore the flue-gas cleaning measures have great impact onto both the particle concentration and the size distribution. For this reason the impact of one particular emission reduction device, the wet electrostatic dust precipitator (wet-ESP), is evaluated. The wet-ESP reduces considerably the particle concentration over the whole size range. Behind the flue-gas processing units a broad maximum in the particle-size distribution occurs at about 70 nm, but no pronounced particle-size distribution could be observed. The particle concentration level atthis maximum is about 3 magnitudes lower than in the raw flue gas. However, intermittent periods lasting for several minutes of high emissions of ultrafine particles with d < 40 nm were observed. These particles are most likely formed by nucleation processes behind the wet-ESP from gas-phase constituents of the stack gas.     

Speciation of gas-phase and fine particle emissions from burning of foliar fuels

Fine particle matter with aerodynamic diameter <2.5 microm (PM2.5) and gas-phase emissions from open burning of six fine (foliar) fuels common to fire-prone U.S. ecosystems are investigated. PM2.5 distribution is unimodal within the 10-450 nm range, indicative of an accumulation mode. Smoldering relative to flaming combustion shows smaller particle number density per unit time and median size. Over 100 individual organic compounds in the primarily carbonaceous (>70% by mass) PM2.5 are chemically speciated by gas chromatography/mass spectrometry. Expressed as a percent of PM2.5 mass, emission ranges by organic compound class are as follows: n-alkane (0.1-2%), polycyclic aromatic hydrocarbon (PAH) (0.02-0.2%), n-alkanoic acid (1-3%), n-alkanedioic acid (0.06-0.3%), n-alkenoic acid (0.3-3%), resin acid (0.5-6%), triterpenoid (0.2-0.5%), methoxyphenol (0.5-3%), and phytosterol (0.2-0.6%). A molecular tracer of biomass combustion, the sugar levoglucosan is abundant and constitutes a remarkably narrow PM2.5 mass range (2.8-3.6%). Organic chemical signatures in PM2.5 from open combustion of fine fuels differ with those of residential wood combustion and other related sources, making them functional for source-receptor modeling of PM. Inorganic matter [PM2.5 - (organic compounds + elemental carbon)] on average is estimated to make up 8% of the PM2.5. Wavelength dispersive X-ray fluorescence spectroscopy and ion chromatography identify 3% of PM2.5 as elements and water-soluble ions, respectively. Compared with residential wood burning, the PM2.5 of fine fuel combustion is nitrate enriched but shows lower potassium levels. Gas-phase C2-C13 hydrocarbon and C2-C9 carbonyl emissions are speciated by respective EPA Methods T0-15 and T0-11A. They comprise mainly low molecular weight C2-C3 compounds and hazardous air pollutants (48 wt % of total quantified volatile organic carbon).     

不同单料烟叶主流烟气气溶胶粒度分布差异

为考察不同产地单料烟叶主流烟气气溶胶粒度分布差异以及16种多环芳烃的粒径分布规律, 制备了20种不同产地单料烟叶的卷烟和3种不同膨胀梗丝掺配比例的卷烟, 利用单孔道吸烟机和测量范围在0.007～9.970 μm的电子低压撞击器对样品主流烟气气溶胶粒子质量和数量进行了测量。结果表明: 1不仅不同国家单料烟叶主流烟气气溶胶粒度分布有差异, 而且国内不同产地单料烟叶主流烟气气溶胶粒度分布也存在显著差异; 国内烟叶的粒子质量和数量总体比国外的偏大; 烟叶的化学成分和物理结构等因素导致其燃烧特性不一致可能产生了气溶胶粒度分布差异; 2同一产地不同品种烟叶主流烟气气溶胶粒度分布是有差异的。在选取的三个品种中红大品种的粒子质量和数量均最大, 云85/87品种的粒子质量和数量均最小; 3不同部位烟叶主流烟气气溶胶粒度分布是有差异的, 不同产地烟叶部位的气溶胶粒度分布规律并不完全一致; 4烟丝中掺配膨胀梗丝的比例对主流烟气气溶胶粒度分布产生一定的影响。当膨胀梗丝的比例增加时, 气溶胶粒子的质量降低; 粒子数量呈先增加后降低的趋势; 5不同产地的单料烟叶主流烟气中PAHs质量的粒径分布规律相似, 粒径分布呈现单峰分布, 在0.4829μm粒径段含量最高; 分子量较低的3～4环化合物占PAHs总量比例超过80%。      

传统熏烤木材中木质素结构表征及其热解特性

为探究传统熏烤肉制品熏烤时所采用不同化学组成及结构的木材类型对产生有害物质多环芳烃的种类和生成量的影响,以传统熏烤肉制品生产时常用的松木、杨木、榉木、枣木、苹果木5种木材为研究对象,通过红外光谱、拉曼光谱、热重及热重-红外联用分析,考察5种木材中木质素的结构特征及其热解特性。结果表明：5种木材中木质素含量,以及木质素中愈创木基结构单元（G）、紫丁香基结构单元（S）含量均存在差异;热解过程基本可分为3个阶段,主要发生在200～500℃范围内,但是5种木质素的质量损失速率、质量损失温度、热解速率、热解温度均不同,说明不同木质素的热稳定性存在显著差异。熏烤木材中木质素含量,S/G结构含量及侧链结构上差异可导致其热稳定性的不同,而热解特性的不同则进一步影响多环芳烃等有害物的生成。     

Compound class specific 14C analysis of polycyclic aromatic hydrocarbons associated with PM10 and PM1.1 aerosols from residential areas of suburban Tokyo

Compound class specific radiocarbon analysis (CCSRA) was performed for polycyclic aromatic hydrocarbons (PAHs) associated with airborne particulate matter (APM) with diameter <10 microm (PM10) and <1.1 microm (PM1.1) collected from a residential area of suburban Tokyo, Japan, and seasonal and particle-size radiocarbon variations were investigated. Source diagnostic isomer pair ratios indicated mixed contributions from petroleum combustion and from biomass and coal combustion to the PAHs in APM. The delta14C- PAHs in APM, ranging from -787 to -514 per thousand, indicated dominance of fossil fuel combustion. The delta14C of 5-6 rings (HMW) PAHs were higher than the 3-4 rings (LMW) species in both PM10 and PM1.1 samples. The delta14C of HMW-PAHs indicated greater biomass-burning contributions in summer than in winter and no apparent particle-size variation. Conversely, the delta14C of LMW species showed a greater contribution from fossil sources in summer and in larger particles (PM10). This finding could be tentatively attributed to the recondensation of fossil-PAHs vaporized from petroleum sources. A 14C isotopic mass balance approach estimated that biomass burning contributes 17-45% of the PAH burden in suburban Tokyo, and that the increase in the biomass-PAH accounts for approximately 27% and 22% of winter-time elevation of LMW- and HMW-PAHs, respectively. These are far exceeding what is expected from the emission statistics for CO2 and combusted materials in Japan and emphasizing the importance of biomass-burning as a source of PAHs; which, in turn, demonstrates the utility and the significance of field-based source assessment by using CCSRA for an effective regulation of atmospheric pollution by PAHs.     

传统肉制品中多环芳烃来源和检测方法研究进展

详细阐述了目前传统肉制品中多环芳烃的产生途径主要是肉制品烟熏工艺、脂肪的焦化和裂解、蛋白质高温分解和糖的不完全燃烧造成的,指出多环芳烃检测中前处理过程的重要性和困难性,讨论了各种前处理过程和检测方式的优缺点,并将我国食品中多环芳烃限量标准与欧盟限量标准相比较,指出我国在多环芳烃限量保准方面与欧盟的差距,并对多环芳烃的检测和控制技术进行展望.     

POLYCYCLIC AROMATIC HYDROCARBONS IN BARBECUE BRIQUETS

Nine different brands of barbecue briquets currently available in the Canadian consumer market were examined for the presence of polycyclic aromatic hydrocarbons (PAH). The total concentrations of PAH ranged between 2.5 to 13.0 μg per gram of briquet sample. Some 30 to 55 individual PAH components were identified by gas chromatography - mass spectrometry. Coal briquets and wood charcoal briquets contained polycyclic aromatic hydrocarbons, while lava stones and pressed saw-dust briquets did not show their presence.     

Emission factors and importance of PCDD/Fs, PCBs, PCNs, PAHs and PM10 from the domestic burning of coal and wood in the U.K

This paper presents emission factors (EFs) derived for a range of persistent organic pollutants (POPs) when coal and wood were subject to controlled burning experiments, designed to simulate domestic burning for space heating. A wide range of POPs were emitted, with emissions from coal being higher than those from wood. Highest EFs were obtained for particulate matter, PM10, (approximately 10 g/kg fuel) and polycyclic aromatic hydrocarbons (approximately 100 mg/ kg fuel for sigmaPAHs). For chlorinated compounds, EFs were highest for polychlorinated biphenyls (PCBs), with polychlorinated naphthalenes (PCNs), dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) being less abundant. EFs were on the order of 1000 ng/kg fuel for sigmaPCBs, 100s ng/ kg fuel for sigmaPCNs and 100 ng/kg fuel for sigmaPCDD/Fs. The study confirmed that mono- to trichlorinated dibenzofurans, Cl1,2,3DFs, were strong indicators of low temperature combustion processes, such as the domestic burning of coal and wood. It is concluded that numerous PCB and PCN congeners are routinely formed during the combustion of solid fuels. However, their combined emissions from the domestic burning of coal and wood would contribute only a few percent to annual U.K. emission estimates. Emissions of PAHs and PM10 were major contributors to U.K. national emission inventories. Major emissions were found from the domestic burning for Cl1,2,3DFs, while the contribution of PCDD/F-sigmaTEQ to total U.K. emissions was minor.     

Aerosol-bound emissions of polycyclic aromatic hydrocarbons and sterols from aeration tanks of a municipal waste water treatment plant

Aeration tanks of wastewater treatment plants (WWTP) are a potential source of atmospheric aerosol particles. Several groups of organic compounds (sterols, polycyclic aromatic hydrocarbons, estrogens) were analyzed in aerosol particles sampled at a municipal WWTP, and the particle size distribution was measured directly with optical particle counters. Aerosol emissions from an activated treatment tank equipped with fine bubble diffusers were low; however, at the preaeration tank equipped with coarse bubble diffusers, sterol concentrations up to 14 ng m(-3) were measured. Directly next to the tank, sterols were associated mainly to particles with aerodynamic diameter >1.35 microm. The results suggest that coprostanol could be a useful tracer for monitoring the emission of aerosol particles from WWTPs. Moreover, wastewater treatment could contribute substantially to the atmospheric concentrations of cholesterol and 24-ethylcholesterol. Aeration tanks with fine bubble diffusers are no major source of atmospheric aerosol particles, whereas coarse bubbling devices seem to emit considerable amounts of aerosol particles.     

Reactions of hydroxyl radicals and ozone with acenaphthene and acenaphthylene

Acenaphthene and acenaphthylene are polycyclic aromatic hydrocarbons (PAHs) emitted into the atmosphere from a variety of incomplete combustion sources such as diesel exhaust. Both PAHs are present in the gas phase under typical atmospheric conditions and therefore can undergo atmospheric gas-phase reactions with the hydroxyl (OH) radical and for acenaphthylene with ozone. Using a relative rate method, rate constants have been measured at 296 +/- 2 K for the OH radical reactions with acenaphthene and acenaphthylene of (in units of 10(-11) cm3 molecule(-1) s(-1)) 8.0 +/- 0.4 and 12.4 +/- 0.7, respectively, and for the O3 reaction with acenaphthylene of (1.6 +/- 0.1) x 10(-16) cm3 molecule(-1) s(-1). The products of the gas-phase reactions of acenaphthene and acenaphthylene and their fully deuterated analogues have been investigated using in situ atmospheric pressure ionization tandem mass spectrometry (API-MS) and gas chromatography-mass spectrometry (GC-MS). The major products identified from the OH radical-initiated reaction of acenaphthene and acenaphthylene were a 10 carbon ring-opened product and a dialdehyde, respectively. The major product observed from the API-MS analysis of the O3 reaction with acenaphthylene was a secondary ozonide, which was not observed by GC-MS.     

Modeling the role of alkanes, polycyclic aromatic hydrocarbons, and their oligomers in secondary organic aerosol formation

A computationally efficient method to treat secondary organic aerosol (SOA) from various length and structure alkanes as well as SOA from polycyclic aromatic hydrocarbons (PAHs) is implemented in the Community Multiscale Air Quality (CMAQ) model to predict aerosol concentrations over the United States. Oxidation of alkanes is predicted to produce more aerosol than oxidation of PAHs driven by relatively higher alkane emissions. SOA from alkanes and PAHs, although small in magnitude, can be a substantial fraction of the SOA from anthropogenic hydrocarbons, particularly in winter, and could contribute more if emission inventories lack intermediate volatility alkanes (>C(13)) or if the vehicle fleet shifts toward diesel-powered vehicles. The SOA produced from oxidation of alkanes correlates well with ozone and odd oxygen in many locations, but the lower correlation of anthropogenic oligomers with odd oxygen indicates that models may need additional photochemically dependent pathways to low-volatility SOA.     

Emission factors of carbon monoxide and size-resolved aerosols from biofuel combustion

This study reports emission factors of carbon monoxide and size-resolved aerosols from combustion of wood, dung cake, and biofuel briquette in traditional and improved stoves in India. Wood was the cleanest burning fuel, with higher emissions of CO from dung cake and particulate matter from both dung cake and briquette fuels. Combustion of dung cake, especially in an improved metal stove, resulted in extremely high pollutant emissions. Instead, biogas from anaerobic dung digestion should be promoted as a cooking fuel for public health protection. Pollutant emissions increased with increasing stove thermal efficiency, implying that thermal efficiency enhancement in the improved stoves was mainly from design features leading to increased heat transfer but not combustion efficiency. Compared to the traditional stove, the improved stoves resulted in the lower pollutant emissions on a kW h-1 basis from wood combustion but in similar emissions from briquette and dung cake. Stove designs are needed with good emissions performance across multiple fuels. Unimodal aerosol size distributions were measured from biofuel combustion with mass median aerodynamic diameters of 0.5-0.8 micron, about a factor of 10 larger than those from fossil fuel combustion (e.g. diesel), with potential implications for lung deposition and health risk.     

Reductions in emissions of carbonaceous particulate matter and polycyclic aromatic hydrocarbons from combustion of biomass pellets in comparison with raw fuel burning

Biomass pellets are emerging as a cleaner alternative to traditional biomass fuels. The potential benefits of using biomass pellets include improving energy utilization efficiency and reducing emissions of air pollutants. To assess the environmental, climate, and health significance of replacing traditional fuels with biomass pellets, it is critical to measure the emission factors (EFs) of various pollutants from pellet burning. However, only a few field measurements have been conducted on the emissions of carbon monoxide (CO), particulate matter (PM), and polycyclic aromatic hydrocarbons (PAHs) from the combustion of pellets. In this study, pine wood and corn straw pellets were burned in a pellet burner (2.6 kW), and the EFs of CO, organic carbon, elemental carbon, PM, and PAHs (EF(CO), EF(OC), EF(EC), EF(PM), and EF(PAH)) were determined. The average EF(CO), EF(OC), EF(EC), and EF(PM) were 1520 ± 1170, 8.68 ± 11.4, 11.2 ± 8.7, and 188 ± 87 mg/MJ for corn straw pellets and 266 ± 137, 5.74 ± 7.17, 2.02 ± 1.57, and 71.0 ± 54.0 mg/MJ for pine wood pellets, respectively. Total carbonaceous carbon constituted 8 to 14% of the PM mass emitted. The measured values of EF(PAH) for the two pellets were 1.02 ± 0.64 and 0.506 ± 0.360 mg/MJ, respectively. The secondary side air supply in the pellet burner did not change the EFs of most pollutants significantly (p > 0.05). The only exceptions were EF(OC) and EF(PM) for pine wood pellets because of reduced combustion temperatures with the increased air supply. In comparison with EFs for the raw pine wood and corn straw, EF(CO), EF(OC), EF(EC), and EF(PM) for pellets were significantly lower than those for raw fuels (p < 0.05). However, the differences in EF(PAH) were not significant (p > 0.05). Based on the measured EFs and thermal efficiencies, it was estimated that 95, 98, 98, 88, and 71% reductions in the total emissions of CO, OC, EC, PM, and PAHs could be achieved by replacing the raw biomass fuels combusted in traditional cooking stoves with pellets burned in modern pellet burners.     

Secondary organic aerosol formation from aromatic precursors. 1. Mechanisms for individual hydrocarbons

Quantitative kinetic and physical phase partitioning models of secondary organic aerosol (SOA) formation resulting from the reactions of aromatic species were integrated into a mechanism for gas-phase reactions. Using the resulting model, analyses of the sensitivity of SOA formation to several parameters (e.g., VOC/NOx ratio, rate parameters) were performed. Results indicated that aerosol yield (SOA formed per amount of hydrocarbons reacted) depends on the extent of conversion of parent hydrocarbons, partitioning coefficient, initial aerosol mass concentration, and rate parameters. On the basis of the sensitivity studies, models for SOA yield were developed for 11 aromatic compounds. Comparison of the results from current SOA models to the results from this study suggests that mechanisms describing SOA formation from aromatic species must incorporate the reactions of reactive intermediates.     

Modeling semivolatile organic aerosol mass emissions from combustion systems

Experimental measurements of gas-particle partitioning and organic aerosol mass in diluted diesel and wood combustion exhaust are interpreted using a two-component absorptive-partitioning model. The model parameters are determined by fitting the experimental data. The changes in partitioning with dilution of both wood smoke and diesel exhaust can be described by two lumped compounds in roughly equal abundance with effective saturation concentrations of approximately 1600 microg m(-3) and approximately 20 microg m(-3). The model is used to investigate gas-particle partitioning of emissions across a wide range of atmospheric conditions. Under the highly dilute conditions found in the atmosphere, the partitioning of the emissions is strongly influenced by the ambient temperature and the background organic aerosol concentration. The model predicts large changes in primary organic aerosol mass with varying atmospheric conditions, indicating that it is not possible to specify a single value for the organic aerosol emissions. Since atmospheric conditions vary in both space and time, air quality models need to treat primary organic aerosol emissions as semivolatile. Dilution samplers provide useful information about organic aerosol emissions; however, the measurements can be biased relative to atmospheric conditions and constraining predictions of absorptive-partitioning models requires emissions data across the entire range of atmospherically relevant concentrations.     

Polycyclic aromatic hydrocarbon emissions from the combustion of alternative fuels in a gas turbine engine

We report on the particulate-bound polycyclic aromatic hydrocarbons (PAH) in the exhaust of a test-bed gas turbine engine when powered by Jet A-1 aviation fuel and a number of alternative fuels: Sasol fully synthetic jet fuel (FSJF), Shell gas-to-liquid (GTL) kerosene, and Jet A-1/GTL 50:50 blended kerosene. The concentration of PAH compounds in the exhaust emissions vary greatly between fuels. Combustion of FSJF produces the greatest total concentration of PAH compounds while combustion of GTL produces the least. However, when PAHs in the exhaust sample are measured in terms of the regulatory marker compound benzo[a]pyrene, then all of the alternative fuels emit a lower concentration of PAH in comparison to Jet A-1. Emissions from the combustion of Jet A-1/GTL blended kerosene were found to have a disproportionately low concentration of PAHs and appear to inherit a greater proportion of the GTL emission characteristics than would be expected from volume fraction alone. The data imply the presence of a nonlinear relation between fuel blend composition and the emission of PAH compounds. For each of the fuels, the speciation of PAH compounds present in the exhaust emissions were found to be remarkably similar (R(2) = 0.94-0.62), and the results do provide evidence to support the premise that PAH speciation is to some extent indicative of the emission source. In contrast, no correlation was found between the PAH species present in the fuel with those subsequently emitted in the exhaust. The results strongly suggests that local air quality measured in terms of the particulate-bound PAH burden could be significantly improved by the use of GTL kerosene either blended with or in place of Jet A-1 kerosene.