Polycyclic aromatic hydrocarbons (PAH) are common aquatic contaminants found at industrially contaminated sites. Alkylated PAH have been identified as a component of oil that is chronically toxic to the early life stages of fish. These compounds are important target analytes in Natural Resource Damage Assessment following oil spills, and often the focus of remedial activities. However, the mechanisms of PAH and alkyl-PAH toxicity are not well understood. The enzymatic metabolism of alkyl-PAH generates ring (OH-ring) and chain hydroxylated (OH-chain) derivatives, and has been associated with the increased prevalence of toxicity in early life stages (ELS) of fish. The role of PAH metabolism in toxicity remains unclear, and may involve the byproducts of metabolism such as reactive oxygen species (ROS), reactive intermediates, metabolites themselves, or a combination thereof. Using 1-methylphenanthrene (1MP) as a model alkyl-PAH, this research describes the relative toxicity of a suite of hydroxylated alkyl-PAH to the early life stages of fish, proposing an association between the formation of para-quinones and enhanced toxicity. The results of this thesis demonstrate: (1) hydroxylated derivatives of 1MP differ in toxicity from their non-hydroxylated counterpart; (2) ring hydroxylated 1MP derivatives are more toxic than both chain-hydroxylated derivatives and 1MP itself; (3) the location of ring-hydroxylation can affect toxicity and (4) the octanol-water partition coefficient (Kow) is a poor predictor of toxicity for hydroxylated APs derivatives. / Thesis (Master, Environmental Studies) -- Queen's University, 2011-04-24 12:15:43.323

This thesis is based on a research project aimed at the selective modification of the known cyclopenta-fused polycyclic aromatic hydrocarbon (CP-PAH) based electron acceptor cyclopenta[hi]aceanthrylene. Starting form 2,7-bis(trimethylsilyl)cyclopenta-[hi]aceanthrylene, we utilized bromination and/or C-H activation strategies that could orthogonally functionalize the cyclopenta[hi]aceanthrylene core. Depending on which reagents were utilized, aromatic substitutions could be directed to either the five-membered rings or the six-membered rings. The functionalization location had dramatic effects on the resulting material's optical band gap with the highest occupied molecular orbital being most affected. We further demonstrate how these materials are good electron acceptors through cyclic voltammetry as well as a fluorescence quenching experiments with poly(3-hexylthiophene). Lastly, we have extended the described functionalization strategy to dicyclopenta[de,mn]tetracene based CP-PAHs.

In this work we will discuss fragmentation and molecular growth processes in collisions of Polycyclic Aromatic Hydrocarbon (PAH) molecules, fullerenes, or their clusters with atoms or atomic ions. Simple collision models as well as molecular structure calculations are used to aid the interpretations of the present and other experimental results. Fragmentation features at center-of-mass collision energies around 10 keV are dominated by interactions between the fast ion/atom and the electron cloud in the molecules/clusters (electronic stopping processes). This electronic excitation energy is rapidly distributed on the vibrational degrees of freedom of the molecule or of the molecules in a cluster and may result in fragmentation. Here, the fragmentation is statistical and favors the lowest-energy dissociation channels which are losses of intact molecules from clusters, H- and C2H2-losses from isolated PAHs, and C2-loss from fullerene monomers. We will also discuss the possibility of formation of molecular H2 direct from native PAHs which reach high enough energies when interacting with ions, electrons, or photons. For the experiments at lower center of mass collision energies (~100 eV) a single atom may be knocked out in close atom-atom interaction. Such non-statistical fragmentation are due to nuclear stopping processes and gives highly reactive fragments which may form covalent bonds with other molecules in a cluster on very short time scales (picoseconds). This process may be important when considering the formation of new species. For collision between 12 keV Ar2+ and clusters of pyrene (C16H10) molecules, new molecules, e.g. C17H10+, C30H18+, C31H19+, etc are detected. We also observe molecular fusion processes for He and Ar ions colliding with clusters of C60 molecules. These and related molecular fusion processes may play a key role for understanding molecular growth processes under certain astrophysical conditions.

<p>I dag när biobränsle används i allt större utsträckning och uttagen från skog har ökat finns ett behov av att använda restprodukten från förbränning, askan, till skogsmarkerna. Askan från förbränning av trädbränsle innehåller, förutsatt att den är väl utbränd, många näringsämnen och har ett högt pH, därför kan den användas för att återföra näringsämnen till skogen och minska försurning i marker.</p><p>Vid förbränning av träpulver tillsätts svavel för att minska CO-utsläppen till luft. Syftet med denna studie var att undersöka hur svavel påverkar flygaskans kvalité. Är det någon skillnad i halten oförbränt kol och PAH-halt i askan när svavel har tillsatts i bränslet, och hur stor påverkan har syre på halten oförbränt kol och PAH-halten.</p><p>Det insamlades tolv referensprover för att se den normala variationen av halten oförbränt kol i flygaskan under en tolvdagarsperiod. Därefter samlades ytterligare 14 prover in under hög/låg syrehalt och med eller utan svavel. På tio av dessa prover analyserades 16 PAH, och på alla prover analyserades halten oförbränt kol. Halten oförbränt kol analyserades med glödgningsförlust enligt SS 18 71 87. 16 PAH analyserades genom mätning med GS-MS.</p><p>Resultaten visar att det är generellt mycket höga halter oförbränt kol i askproverna och det ger en sämre aska för återföring. Hög syrehalt i förbränningskammaren ger en signifikant lägre halt oförbränt kol i askan. PAH-halten tyder på en ökning i samband med ökad halt oförbränt i askan. Tillsatser av svavel till bränslet verkar ge som effekt att halten oförbränt i askan minskar.</p> / <p>Today with the increase in biofuel use and the removal of wood from the forest, there is an increased need for recycling the ash from combustion back to the forest. Ash from combustion of wood contains many nutrients and has a high pH and therefore can be used to restore nutrients to the forest and to reduce acidification of the ground.</p><p>Sulphur is induced to the combustion of wood-powder in order to reduce emissions of CO to the air. The purpose of this study was to examine how the induction of sulphur to the fuel affects the quality of the fly ash, if there is a difference in loss on ignition, if the PAH-content is affected of the admixture of sulphur in the fuel and how significant is the effect of the oxygen content in the combustion.</p><p>Twelve reference samples were collected during a twelve-day period to see the normal variation of the loss on ignition. Then another 14 samples were collected under high/low oxygen content and with or without sulphur. On ten of the samples 16 PAH:s were analysed, and the loss on ignition was analysed on all samples. Loss on ignition was analysed according to the SS 18 71 87. Sixteen PAH:s were analysed by measuring with GS-MS.</p><p>The results show that there is a generally high loss on ignition on all of the ash samples and that results in a lower quality ash for recycling. Oxygen content has a significant effect on the loss on ignition in the ash and high oxygen content in the combustion chamber gives a lower loss on ignition. PAH content indicate an increase in connection with an increased loss on ignition. Admixture of sulphur to the fuel indicates that the loss on ignition in the ash decreases.</p>

I dag när biobränsle används i allt större utsträckning och uttagen från skog har ökat finns ett behov av att använda restprodukten från förbränning, askan, till skogsmarkerna. Askan från förbränning av trädbränsle innehåller, förutsatt att den är väl utbränd, många näringsämnen och har ett högt pH, därför kan den användas för att återföra näringsämnen till skogen och minska försurning i marker. Vid förbränning av träpulver tillsätts svavel för att minska CO-utsläppen till luft. Syftet med denna studie var att undersöka hur svavel påverkar flygaskans kvalité. Är det någon skillnad i halten oförbränt kol och PAH-halt i askan när svavel har tillsatts i bränslet, och hur stor påverkan har syre på halten oförbränt kol och PAH-halten. Det insamlades tolv referensprover för att se den normala variationen av halten oförbränt kol i flygaskan under en tolvdagarsperiod. Därefter samlades ytterligare 14 prover in under hög/låg syrehalt och med eller utan svavel. På tio av dessa prover analyserades 16 PAH, och på alla prover analyserades halten oförbränt kol. Halten oförbränt kol analyserades med glödgningsförlust enligt SS 18 71 87. 16 PAH analyserades genom mätning med GS-MS. Resultaten visar att det är generellt mycket höga halter oförbränt kol i askproverna och det ger en sämre aska för återföring. Hög syrehalt i förbränningskammaren ger en signifikant lägre halt oförbränt kol i askan. PAH-halten tyder på en ökning i samband med ökad halt oförbränt i askan. Tillsatser av svavel till bränslet verkar ge som effekt att halten oförbränt i askan minskar. / Today with the increase in biofuel use and the removal of wood from the forest, there is an increased need for recycling the ash from combustion back to the forest. Ash from combustion of wood contains many nutrients and has a high pH and therefore can be used to restore nutrients to the forest and to reduce acidification of the ground. Sulphur is induced to the combustion of wood-powder in order to reduce emissions of CO to the air. The purpose of this study was to examine how the induction of sulphur to the fuel affects the quality of the fly ash, if there is a difference in loss on ignition, if the PAH-content is affected of the admixture of sulphur in the fuel and how significant is the effect of the oxygen content in the combustion. Twelve reference samples were collected during a twelve-day period to see the normal variation of the loss on ignition. Then another 14 samples were collected under high/low oxygen content and with or without sulphur. On ten of the samples 16 PAH:s were analysed, and the loss on ignition was analysed on all samples. Loss on ignition was analysed according to the SS 18 71 87. Sixteen PAH:s were analysed by measuring with GS-MS. The results show that there is a generally high loss on ignition on all of the ash samples and that results in a lower quality ash for recycling. Oxygen content has a significant effect on the loss on ignition in the ash and high oxygen content in the combustion chamber gives a lower loss on ignition. PAH content indicate an increase in connection with an increased loss on ignition. Admixture of sulphur to the fuel indicates that the loss on ignition in the ash decreases.

Polycyclic aromatic hydrocarbons (PAHs) are environmentally significant because of their ubiquity and the toxicity of some. Their recalcitrance and persistence makes them problematic environmental contaminants. Microbial degradation is considered to be the primary mechanism of PAH removal from the environment. Biodegradation kinetics of individual PAHs by pure and mixed cultures have been reported by several researchers. However, contaminated sites commonly have complex mixtures of PAHs whose individual biodegradability may be altered in mixtures. Biodegradation kinetics for fluorene, naphthalene, 1,5-dimethylnaphthalene and 1- methylfluorene were evaluated in sole substrate systems, binary and ternary systems using Sphingomonas paucimobilis EPA505. The Monod model was fitted to the data from the sole substrate experiments to yield biokinetic parameters, (qmax and Ks). The first order rate constants (qmax/Ks) for fluorene, naphthalene and 1,5- dimethylnaphthalene were comparable, although statistically different. However, affinity constants for the three compounds were not comparable. Binary and ternary experiments indicated that the presence of another PAH retards the biodegradation of the co-occurring PAH. Antagonistic interactions between substrates were evident in the form of competitive inhibition, demonstrated mathematically by the Monod multisubstrate model. This model appropriately predicted the biodegradation kinetics in mixtures using the sole substrate parameters, validating the hypothesis of common enzyme systems. Competitive inhibition became pronounced under conditions of: Ks1 << Ks, S1 >> Ks1 and S1 >> S. Experiments with equitable concentrations of substrates demonstrated the effect of concentration on competitive inhibition. Ternary experiments with naphthalene, 1,5-dimethylnapthalene and 1-methylfluorene revealed preferential degradation, where depletion of naphthalene and 1,5-dimethylnapthalene proceeded only after the complete removal of 1-methylfluorene. The substrate interactions observed in binary and ternary mixtures require a multisubstrate model to account for simultaneous degradation of substrates. However, developing models that account for sequential degradation may be useful in scenarios where PAHs may not be competitive substrates. These mixture results prove that substrate interactions must be considered in designing effective bioremediation strategies and that sole substrate performance is limited in predicting biodegradation kinetics of complex mixtures.

Ph.D. afhandling, Roskilde universitetscenter 2004.

No description available.

The toxicity and ubiquitousness of PAHs within different terrestrial environments has been an increasing cause for concern amongst environmental scientists in the last decades, in particular regarding their transport within the soil. In an attempt to understand the role of pure inorganic phases in PAH-mobility; experiments exposing mineral soil components with low organic matter content to a PAH-representative were carried out. The systems consisted of four different mineral phases (quartz sand, hematite, iron coated quartz sand and montmorillonite) which were individually exposed to naphthalene in electrolyte solutions prepared at increasing ionic strengths (NaNO3: 0.001 M; 0.01 M; 0.1 M) and pH (4.0 and 5.5). All experiments were conducted over at 24 reaction intervals and at ambient temperature conditions.Mineral geosorbents are traditionally known to be poor PAH-scavengers; in particular when compared to organic, high surface area materials such as activated carbons. On this basis, a preliminary validation experiment (Proof of Concept Experiment) was conducted to test the sensitivity of the selected extraction method (SPME) under complete uptake (activated carbon) and very low uptake (quartz sand) conditions. By extracting and analysing the supernatant after 24 hr of exposure of both sorbents to naphthalene under identical conditions it was concluded that SPME was a feasible extraction technique, yielding good reproducibility (n=3, inter-day RSD%= 11.18% ) even at very low PAH concentrations (0.2 µg / L). The final concentration of naphthalene in the sample supernatant after 24 hours was determined by GC-FID. All samples were extracted using the Solid Phase Microextraction method developed during the Proof of Concept which allowed the rapid extraction of naphthalene in the headspace HS-SPME (extraction time = 3 minutes) using temperature control and ultrasonication as means of agitation. Each sample set included triplicates of blanks and samples as well as calibration standards (in duplicate where possible)Out of the four minerals, only quartz sand and hematite showed a slight tendency towards naphthalene removal from solution; a finding which correlated well with increasing ionic strength. The other two minerals did not show any such trend and the results were deemed inconclusive. In regards to the results for quartz and hematite; the detected uptake was found to be below the sensitivity of the current SPME extraction method according to the error analysis carried out by comparing the sample and blank means whilst accounting for error equal to 1σ. The overlapping of both means in the majority of the samples indicated that both averages were too close to be accurately resolved (due to very low naphthalene uptake). Modifications to the SPME method could improve the reproducibility and decrease the spread of the data; however, this measure would only guarantee higher statistical confidence (95 %) and not higher naphthalene uptake by these minerals. These observations lead to the conclusion that naphthalene was being salted out of solution rather than being removed by sorption; and under these experimental conditions it would not have been possible to detect any real PAH-mineral interaction. In view of this outcome, a different approach was attempted in order to detect surface reactions between the minerals and naphthalene. A series of preliminary (qualitative) surface analysis (AFM, XPS and ATR-FTIR) on pre-loaded mineral specimens were carried out in air at ambient temperature conditions. No naphthalene was positively identified on the surfaces of the studied sorbents. Factors such as molecular size, sorbents characteristics (i.e. roughness, surface charge) and loading conditions impeded the detection of the target molecules. Innovative sample preparation protocols as well as controlled analytical conditions would need to be implemented and evaluated before this kind of analytical tool can be used. The main outcome of this research work was the successful adaptation of SPME to the rapid extraction of naphthalene in electrolyte solutions at optimal and sub-optimal concentration levels; as the proof of concept preliminary experiment showed.

The threat to the environment and human health posed by the emission of soot particles and their precursors during the combustion process has attracted widespread attention for some time. Generation of soot particles includes the precursor’s formation, particle nucleation, and the growth and oxidation of soot particles; these processes are experimentally and numerically studied in this dissertation. Fuel composition is one of the most important parameters in the study of the combustion emissions. In the first portion of this research, quantified soot precursors were detected in a jet stirred reactor and a flow reactor of several gasoline surrogates, which covered various fuel compositions and different MON numbers. A kinetic model was made to capture the polycyclic aromatic formations and help to clarify the chemistry behind them. Major reaction pathways were discussed, as well as the role of important intermediate species, such as acetylene, and resonantly stabilized radicals like allyl, propargyl, cyclopentadienyl, and benzyl in the formation of polycyclic aromatic hydrocarbons. In the second section, a Fourier-transform ion cyclotron resonance mass spectrometry was first used to probe the chemical constituents of soot particles. By examining the soot particle generated in the early stage of nucleation, some information about the nucleation process was gained. The aromatics in the infant soot particles were all peri-condensed, of a size and shape easily linked by Van der Waals forces to form aromatic dimers and bigger clusters under the specified flame conditions. Compositions in the mature soot particles indicated that soot particles grow through the carbonization process. As a hydrogen carrier, ammonia was considered a good additive for controlling soot formation. In the third portion of this work, chemical effects of ammonia on soot formation were studied. Ammonia can suppress soot formation by reducing the precursor’s formation. Chemical kinetic analysis revealed that C-N species generated in ethylene-ammonia flames removed carbon from participating in soot precursor formation, thereby reducing soot formation, however, high concentrations of toxic hydrogen cyanide may be formed, which warrants further investigation.