Author: Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Gas–particle Phase Partitioning and Particle Size Distribution of Chlorinated and Brominated Polycyclic Aromatic Hydrocarbons in Haze
Author: Gas/particle Partitioning and Particle Size Distributions of Polycyclic Aromatic Hydrocarbons (PAHS) in the Atmosphere
Author: Shi-Ping LiuCharacterization of Polycyclic Aromatic Hydrocarbons (PAH) in Particulate and Gaseous Emissions from Agricultural Burning
Author: Haleh KeshtkarParticle Size Distribution of Polycyclic Aromatic Hydrocarbons in Motorcycle Exhaust Emissions
Author: Hsi-Hsien YangTheoretical Modelling and Mechanistic Study of the Formation and Atmospheric Transformations of Polycyclic Aromatic Compounds and Carbonaceous Particles
Author: Antonius IndartoPublisher: Universal-Publishers
ISBN: 1599423340
Category :
Languages : en
Pages :
Book Description
Polycyclic Aromatic Hydrocarbons (PAHs) and soot share the same origin (incomplete combustion or pyrolysis) and nature, namely structural and electronic features. The purpose of the research work discussed in this thesis is to offer a theoretical contribution to elucidate some aspects of PAH and soot particle formation. The interest in carrying out such a work lies on one hand in the ubiquitous presence of both species in the environment, on the other hand on the concern for their impact on both human health, specifically involving the respiratory system, and climate, in particular as regards global warming. Thus, a better knowledge on the formation mechanisms of PAHs and soot could then help the efforts to reduce their concentration in our atmosphere. Since the formation mechanisms still presents unclear aspects, the suggestions and indications which can be offered by a theoretical study come out to be complementary to the large amount of experimental data collected so far. In setting up models aimed to mimic what happens in real pyrolysis or combustion situations, we have exploited the fact that PAHs and soot share as a common trait the presence of condensed unsaturated cycles (whose aromatic character can be variable). Thus, though types of soot of different origin will exhibit, on a larger scale, a variety of structural traits, we have chosen an assortment of PAH-like models to study different processes, together with other smaller unsaturated closed and open shell species that are known to play a role in the synthesis course. A preliminary phase of the study was aimed to assess which computational level could be both dependable and affordable to investigate the growth of a PAH-like radical when it is adsorbed onto soot platelets (particle phase). Then the Bittner-Howard variant of the widely accepted Hydrogen Abstraction Acetylene Addition (HACA) growth mechanism has been explored by Density Functional Theory (DFT) at the level mentioned above, both in the gas and particle phases, and over a wide range of temperatures. A parallel mechanism, differing from HACA, based on polyynes and characterized by the proliferation of radical centers, has also been studied for a variety of models at a multiconfigurational theory level. To the end, we have explored several reaction pathways starting from the addition of the propargyl radical to butadiyne.
Semivolatile Polycyclic Aromatic Hydrocarbons
Author: Elisabeth GalarneauPublisher:
ISBN: 9780494278864
Category :
Languages : en
Pages : 330
Book Description
This thesis considers-aspects relating to the particle/gas partitioning of polycyclic aromatic hydrocarbons (PAHs) in the ambient atmosphere. An extensive data set collected by the Integrated Atmospheric Deposition Network (IADN) was examined for insights relating to partitioning. This data set showed features not observed in previous studies. In particular, relationships between partitioning and saturated vapour pressure were observed to be less uniform among PAH species than previously noted. Furthermore, a distinct seasonality in those relationships was observed. With the greater understanding of the atmospheric variations in PAH partitioning derived from the IADN measurements, an effort to incorporate these substances in a regional air quality model was undertaken. An emissions inventory was prepared for Canada and the United States. Estimated emissions include sources not considered by the US EPA through its National Emissions Inventory. When sources missing from the NEI are considered, the agreement between the two inventories is reduced to a factor of 2.5. Environment Canada's regional air quality model (AURAMS) was adapted to include PAHs and the sorptive partitioning process to which they are subject. A pair of test simulations demonstrated that the model was functional. Results obtained using two different partitioning expressions agreed in terms of simulated PAH concentrations and partitioning coefficients, but less so between PAH particulate fractions. Results of the test simulations demonstrate that the model is ready for a full-scale evaluation though such work is outside the scope of this thesis. Ambient measurements of semivolatile organic compounds can be subject to sampling artefacts caused by variations in atmospheric conditions over the times required to collect enough air to meet analytical requirements. One such artefact caused by temperature variations was examined with a mathematical model. Results of the model showed that twenty-four-hour sampling is best conducted with start and end times that coincide with the morning occurrence of daily average temperature.
Temporal Variation of Particle Size Distribution of Polycyclic Aromatic Hydrocarbons at Different Roadside Air Environments in Bangkok, Thailand
Author: Tomomi HoshikoPublisher:
ISBN:
Category : Science
Languages : en
Pages :
Book Description
Temporal Variation of Particle Size Distribution of Polycyclic Aromatic Hydrocarbons at Different Roadside Air Environments in Bangkok, Thailand.
Assessing the Influence of Secondary Organic Versus Primary Carbonaceous Aerosols on Long-range Atmospheric Polycyclic Aromatic Hydrocarbon Transport
Author: Carey Lee FriedmanPublisher:
ISBN:
Category :
Languages : en
Pages : 10
Book Description
We use the chemical transport model GEOSChem to evaluate the hypothesis that atmospheric polycyclic aromatic hydrocarbons (PAHs) are trapped in secondary organic aerosol (SOA) as it forms. We test the ability of three different partitioning configurations within the model to reproduce observed total concentrations in the midlatitudes and the Arctic as well as midlatitude gas-particle phase distributions. The configurations tested are (1) the GEOSChem default configuration, which uses instantaneous equilibrium partitioning to divide PAHs among the gas phase, a primary organic matter (OM) phase (absorptive), and a black carbon (BC) phase (adsorptive), (2) an SOA configuration in which PAHs are trapped in SOA when emitted and slowly evaporate from SOA thereafter, and (3) a configuration in which PAHs are trapped in primary OM/BC upon emission and subsequently slowly evaporate. We also test the influence of changing the fraction of PAHs available for particle-phase oxidation. Trapping PAHs in SOA particles upon formation and protecting against particle-phase oxidation (2) better simulates observed remote concentrations compared to our default configuration (1). However, simulating adsorptive partitioning to BC is required to reproduce the magnitude and seasonal pattern of gas-particle phase distributions. Thus, the last configuration (3) results in the best agreement between observed and simulated concentration/phase distribution data. The importance of BC rather than SOA to PAH transport is consistent with strong observational evidence that PAHs and BC are coemitted.
Pollution Abstracts
Author: Publisher:
ISBN:
Category : Pollution
Languages : en
Pages : 844
Book Description
Indexes material from conference proceedings and hard-to-find documents, in addition to journal articles. Over 1,000 journals are indexed and literature published from 1981 to the present is covered. Topics in pollution and its management are extensively covered from the standpoints of atmosphere, emissions, mathematical models, effects on people and animals, and environmental action. Major areas of coverage include: air pollution, marine pollution, freshwater pollution, sewage and wastewater treatment, waste management, land pollution, toxicology and health, noise, and radiation.
Gas and Particulate Sampling of Airborne Polycyclic Aromatic Compounds
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 12
Book Description
The denuder surfaces of the gas and particle (GAP) sampler (developed at the Atmospheric Environment Service of Environment Canada) have been modified by coating with XAD-4 resin, using techniques developed at Lawrence Berkeley National Laboratory (LBNL) for the lower capacity integrated organic vapor/particle sampler (IOVPS). The resulting high capacity integrated organic gas and particle sampler (IOGAPS) has been operated in ambient air at 16.7 L min−1 for a 24-hour period in Berkeley, California, USA. Simultaneous measurements were made at the same collection rate with a conventional sampler that used a filter followed by two sorbent beds. Gas and particle partition measurements were determined for 13 polycyclic aromatic hydrocarbons (PAH) ranging from 2-ring to 6-ring species. The IOGAPS indicated a higher particle fraction of these compounds than did the conventional sampler, suggesting that the conventional sampler suffered from 'blow-off' losses from the particles collected on the filter.