Fluorene Research Articles

Fe3O4@ionic liquid@methyl orange nanoparticles as a novel nano-adsorbent for magnetic solid-phase extraction of polycyclic aromatic hydrocarbons in environmental water samples

A novel nano-adsorbent, Fe3O4@ionic liquid@methyl orange nanoparticles (Fe3O4@IL@MO NPs), was prepared for magnetic solid-phase extraction (MSPE) of polycyclic aromatic hydrocarbons (PAHs) in environmental water samples. The Fe3O4@IL@MO NPs were synthesized by self-assembly of the ionic liquid 1-octadecyl-3-methylimidazolium bromide (C18mimBr) and methyl orange (MO) onto the surface of Fe3O4 silica magnetic nanoparticles, as confirmed by infrared spectroscopy, ultraviolet-visible spectroscopy and superconducting quantum interface device magnetometer. The extraction performance of Fe3O4@IL@MO NPs as a nano-adsorbent was evaluated by using five PAHs, fluorene (FLu), anthracene (AnT), pyrene (Pyr), benzo(a)anthracene (BaA) and benzo(a)pyrene (BaP) as model analytes. Under the optimum conditions, detection limits in the range of 0.1-2 ng/L were obtained by high performance liquid chromatography-fluorescence detection (HPLC-FLD). This method has been successfully applied for the determination of PAHs in environmental water samples by using the MSPE-HPLC-FLD. The recoveries for the five PAHs tested in spiked real water samples were in the range of 80.4-104.0% with relative standard deviations ranging from 2.3 to 4.9%.

Source Apportionment of Polycyclic Aromatic Hydrocarbons in Agricultural Soils of Yanqing County in Beijing, China

Guanting Reservoir in Yanqing County is a strategic drinking-water resource for Beijing, China. The agricultural soil samples (0 cm to 20 cm) were collected to determine the concentration, compositional profiles, and sources of polycyclic aromatic hydrocarbons (PAHs) surrounding the reservoir. The average measured PAH concentration was 140 ± 85.7 μg kg−1 (CV = 0.45) (dry weight or dw; n = 48; shown as arithmetic mean and standard deviation), which is lower than most of the results reported in literature. The PAH compositional profiles were dominated by 3- and 4-ring compounds, particularly phenanthrene (PHE), fluoranthene (FLA), fluorene (FLO), and pyrene (PYR). The PAH sources were estimated by analyzing the corrected ratios of isomeric PAH species derived using the multimedia fugacity model and principal component analysis/multiple linear regression (PCA/MLR). The corrected isomeric ratios of FLA/(FLA+PYR) and anthracene (ANT)/(ANT+PHE) indicate that combustion processes are the major sources of PAHs in the soil. Three principal components were identified as main sources, representing coal burning and traffic exhaust, biomass combustion and coking, and a source labeled “other,” which contribute 54%, 40%, and 6% of the total PAH, respectively (α = 0.05). Moreover, except those from local biomass burning, other PAHs were primarily deposited in the soil from distant sources via atmospheric transportation.

Laser-Induced Carbene–Carbene Rearrangement in Solution: The Diphenylcarbene–Fluorene Rearrangement

Diphenylcarbene (DPC) generated by high-intensity laser photolysis of diphenyldiazomethane rearranges to fluorene (FL) by two distinct mechanisms as revealed by methyl-group labeling. Thus, excimer laser irradiation of p,p'-dimethyldiphenyldiazomethane generates 3,6-dimethylfluorene (3,6-DMF) and 2,7-dimethylfluorene (2,7-DMF), which were identified by fluorescence measurements as well as GC-MS and comparison with authentic materials. 3,6-DMF corresponds to direct bond formation between ortho positions in DPC, referred to as ortho,ortho' coupling. 2,7-DMF corresponds to a carbene-carbene rearrangement, whereby DPC undergoes ring expansion to phenylcycloheptatetraene (PhCHT) followed by ring contraction to o-biphenylylcarbene (o-BPC), which then cyclizes to FL. The carbene-carbene rearrangement dominates over the ortho,ortho' coupling under all conditions employed. The ortho,ortho' coupling must take place in a higher excited state (most likely S2 or T1) of DPC, because it is not observed at all under thermolysis conditions, where only S1 and T0 are populated. The carbene-carbene rearrangement may take place either in a hot S1 state or more likely in a higher excited state (S2 or T1).

Ternary Diagram of Fluorenes, Dibenzothiophenes and Dibenzofurans: Indicating Depositional Environment of Crude Oil Source Rocks

Fluorene (FL), dibenzothiophene (DBT) and dibenzofuran (DBF) and their alkylated homologues are important polycyclic aromatic compounds in crude oils and source rock extracts. They share the similar chemical structure and may have genetic relationships. The parent compounds (unsubstituted), methyl-, dimethyl- and ethyl-substituted isomers are identified by comparison with retention indices reported in literatures and correlation with co-injection of internal standards in gas chromatography-mass spectrometry (GC-MS) analysis. Therefore, their relative concentrations can be determined. Based on the large data sets, this paper preliminarily establishes a ternary diagram to interpret the depositional environment/lithology for oils and related source rocks. Five typical depositional environments/lithologies are distinguished on this ternary diagram. Data points from typical marine carbonate, fluvial/deltaic/fresh lacustrine shale and swamp fall into the DBTs, FLs and DBFs end-members, respectively. Oils from marine shale have subequal contents of FLs and DBFs and lie between the zones of fluvial/deltaic/fresh lacustrine shale and swamp, but have a little higher abundance of DBTs. The oils from brackish/saline lacustrine have intermediate contents of DBTs with a wide variety and some degree overlap with that of marine shale. On the basis of the ternary diagrams, two petroleum systems in the cratonic region of the Tarim basis are defined. The majority of discovered oils were derived from the Middle-Upper Ordovician carbonate source rocks. Whereas, some oils from wells TD2, T904, LK1 and TZ62 originated from the Cambrian and Lower Ordovician source rocks. Therefore, the ternary diagram of FLs, DBTs and DBFs is a useful method to interpret depositional environment/lithology for oils and related source rocks and to definite petroleum systems as well.

Determination of Polyaromatic Hydrocarbons in Domestic, Commercial and Industrial soot samples

Abstract Polycyclic aromatic hydrocarbons (PAHs) were determined in domestic, commercial and industrial soot samples via HPLC. The study showed that benzo[a]pyrene (bap) was not present in most of the samples. The highest quantity of BaP was found in Pakistan Particle Board where its concentration was 259.12 mg/kg. The high quantity of other PAHs such as chrysene (CHR), anthracene (ANT), fluorene (FL), naphthalene (NAP), phenanthrene (PHE), acenaphthylene (ACP) and flouranthene (FTH) were found in tandoor, kabab karayi, tabakhee, brick kiln and motor car soot samples. The low concentration of most of the PAH compounds in most of the samples might be due to their photooxidative, biological and microbial degradation.

Impact of Mycelia on the Accessibility of Fluorene to PAH-Degrading Bacteria

Mycelia have been recently shown to actively transport polycyclic aromatic hydrocarbons (PAH) in water-unsaturated soil over the range of centimeters, thereby efficiently mobilizing hydrophobic PAH beyond their purely diffusive transport in air and water. However, the question if mycelia-based PAH transport has an effect on PAH biodegradation was so far unsolved. To address this, we developed a laboratory model microcosm mimicking air-water interfaces in soil. Chemical analyses demonstrated transport of the PAH fluorene (FLU) by the mycelial oomycete Pythium ultimum that was grown along the air-water interfaces. Furthermore, degradation of mycelia-transported FLU by the bacterium Burkholderia sartisoli RP037-mChe was indicated. Since this organism expresses eGFP in response to a FLU flux to the cell, it was also as a bacterial reporter of FLU bioavailability in the vicinity of mycelia. Confocal laser scanning microscopy (CLSM) and image analyses revealed a significant increase of eGFP expression in the presence of P. ultimum compared to controls without mycelia or FLU. Hence, we could show that physically separated FLU becomes bioavailable to bacteria after transport by mycelia. Experiments with silicon coated glass fibers capturing mycelia-transported FLU guided us to propose a three-step mechanism of passive uptake, active transport and diffusion-driven release. These experiments were also used to evaluate the contributions of these individual steps to the overall mycelial FLU transport rate.

Generation and distribution of PAHs in the process of medical waste incineration

After the deadly earthquake on May 12, 2008 in Wenchuan county of China, several different incineration approaches were used for medical waste disposal. This paper investigates the generation properties of polycyclic aromatic hydrocarbons (PAHs) during the incineration. Samples were collected from the bottom ash in an open burning slash site, surface soil at the open burning site, bottom ash from a simple incinerator, bottom ash generated from the municipal solid waste (MSW) incinerator used for medical waste disposal, and bottom ash and fly ash from an incinerator exclusively used for medical waste. The species of PAHs were analyzed, and the toxicity equivalency quantities (TEQs) of samples calculated. Analysis results indicate that the content of total PAHs in fly ash was 1.8×103 times higher than that in bottom ash, and that the strongly carcinogenic PAHs with four or more rings accumulated sensitively in fly ash. The test results of samples gathered from open burning site demonstrate that Acenaphthylene (ACY), Acenaphthene (ACE), Fluorene (FLU), Phenanthrene (PHE), Anthracene (ANT) and other PAHs were inclined to migrate into surrounding environment along air and surface watershed corridors, while 4- to 6-ring PAHs accumulated more likely in soil. Being consistent with other studies, it has also been confirmed that increases in both free oxygen molecules and combustion temperatures could promote the decomposition of polycyclic PAHs. In addition, without the influence of combustion conditions, there is a positive correlation between total PCDD/Fs and total PAHs, although no such relationship has been found for TEQ.

Characteristics of Atmospheric Polycyclic Aromatic Hydrocarbons (PAHs) in Gas and Particle Phase in April and July 2011 in Beijing, China

Presence of atmospheric PAHs in urban and suburban region (Beijing, China) was studied in April and July 2011. Forty-four pairs of gas and particle (TSP) phase samples were collected every six day by high volume (Hi-Vol) air samplers at four sampling sites, and determined separately by GC/MS based on USEPA Method TO-13A. Average total concentration (gas + particles) of PAHs (T-PAHs) was 135.1±49.0 ng/m3 and 181.2±40.9 ng/m3 in April and July, respectively. Gas phase PAHs (G-PAHs) was the major fraction, comprising 63–92% of T-PAHs. Lighter (2-, 3-, 4-ring) and heavier (5-,6-ring) PAHs were found predominantly in gas and particle phase, respectively. 2- to 6- ring PAHs contributed 10%, 53%, 26%, 7% and 4% of T-PAHs, respectively. Five major PAHs, naphthalene (NAP), fluorene (FLU), PHE, fluoranthene (FLA), and pyrene (PYR) contributed 70 – 90% of T-PAHs. G-PAHs increased significantly while PAHs in particle phase (P-PAHs) decreased from April to July. Volatilization from soil and more emission from power generation increase might explain the increase of G-PAHs, and the washout of P-PAHs along with particles might explain the decrease of P-PAHs. Given particulate organic carbon (OC) and elemental carbon (EC) being well correlated, P-PAHs was moderately correlated with OC and EC, suggesting that there were other mechanisms contributing to P-PAHs different from those of OC/EC. Significant correlation between P-PAHs with SO2 and NO2 suggested coal combustion and automobile exhaust to be contamination contributors.

White Light Emitting Films from Eu(III) Complexed Copolymers of Alternating Fluorene and Bis(pyrazolyl)pyridine Derivatives

4-Ethynyl-2,6-bis(pyrazolyl)pyridine (BPP) end-capped fluorene (FO) homo (P1) and FO-BPP main chain copolymers (P2 and P3) with Mn around 10 kDa were successfully prepared. The optical band gap of P1–P3 copolymers were 2.69, 2.88, and 2.90 eV, respectively. Spin-coated P2 and P3 thin films displayed blue and green dual emissions giving a mixed cyan color light under UV irradiation. By exploiting the metal coordinating ability of main chain tridentate BPP units, a red emitting Eu(III) ion coordinated conjugated polymer [FO-(BPP(Eu(tta)3))]n layer was formed on top of the P2 and P3 thin films via the dip-coating technique to achieve white color radiant films displaying triple emission with maxima at 425, 543, 614 nm and 428, 543, 611 nm for P2 and P3, respectively. The CIE (Commission internationale de l’Eclairage) coordinates were found to be (0.31, 0.35) and (0.31, 0.32) for white emitting films made from P2 and P3, respectively. These values are very close to the designated coordinates for a perfect white light emission (x = 0.33; y = 0.33).

Experimental Study of Surface and Solution Properties of Gemini -conventional Surfactant Mixtures on Solubilization of Polycyclic Aromatic Hydrocarbon

Experimental data are presented on the enhanced solubilities of fluorene (FLR) resulting from solubilization in aqueous solutions of two conventional surfactants: cationic cetyltrimethylammonium bromide (CTAB) , anionic sodium dodecyl sulfate (SDS), nonioinic polyethylene glycol dodecyl ether (Brij35) and a cationic gemini bis (hexadecyldimethylammonium) pentane dibromide (G5). The critical micellar concentration of surfactants was determined by surface tension measurements and aqueous solubilities of fluorene compound in surfactant solutions were measured spectrophotometrically. Solubilization of PAH compound commenced at the surfactant critical micelle concentration and was proportional to the concentration of surfactant in micelle. The results of the mixed systems were analyzed with the help of regular solution theory, in which the deviation of CMCexp values for mixed surfactant systems from CMCideal was measured by evaluating the interaction parameter, βm. Negative values of βm were observed in all equimolar binary systems which show synergism in the mixed micelle. Attraction force between two oppositely charged head groups lead the strongest synergism effect between cationic gemini and anionic conventional surfactant. In addition to molar solubilization ratio (MSR) solubilization efficiency is also quantified in terms of micelle-water partition coefficient (Km).

Cloning of dfdA genes from Terrabacter sp. strain DBF63 encoding dibenzofuran 4,4a-dioxygenase and heterologous expression in Streptomyces lividans

A dibenzofuran (DF)-degrader Terrabacter sp. strain DBF63 harbors the dbfA and dbfBC genes for DF degradation and the fln-dbfA, pht, and pca gene clusters for the utilization of fluorene (FN) as a sole carbon source. From this strain, dfdA1, the gene encoding the second DF dioxygenase was detected using degenerate polymerase chain reaction (PCR) and the dfdA1A2A3A4 genes were cloned from a cosmid library of the DBF63 genome. Nucleotide sequencing revealed that the dfdA genes showed considerably high identities with those of other actinobacteria, such as Terrabacter sp. strain YK3 and Rhodococcus sp. strain HA01. In the neighboring region of the dfdA genes, as many as 11 homologs for transposase and integrase genes and the putative extradiol dioxygenase gene disrupted by an insertion sequence (dfdB::ISTesp2) were found, suggesting that repeated gene rearrangement had occurred. Quantitative reverse transcription-PCR analysis revealed that dfdA1 was expressed primarily in the DF-fed strain, whereas dbfA1 was expressed in the FN-cultured strain, apparently indicating that the dfdA genes are induced by DF for the initial hydroxylation of DF in strain DBF63. Furthermore, two polycistronic gene cassettes consisting of either dfdA or dbfA together with the dbfBC gene were constructed and expressed heterologously in Streptomyces lividans, degrading DF to salicylate. Furthermore, the expressed DfdA dioxygenase degraded dibenzo-p-dioxin, carbazole, dibenzothiophene, anthracene, phenanthrene, and biphenyl, thereby exhibiting a broader substrate range than that of the DbfA dioxygenase.

Correlation between atmospheric polycyclic aromatic hydrocarbons exposure and urinary hydroxyl metabolites of polycyclic aromatic hydrocarbons in elderly population in Tianjin, China

To identify suitable hydroxyl polycyclic aromatic hydrocarbons (OH-PAHs) for co-evaluation of internal exposure level of PAHs by simultaneous determination of a variety of OH-PAHs in urine. The 24-h individual particulate matter and morning urine samples of 112 subjects were collected during June 2011. PAHs carried by individual particulate matter samples and OH-PAHs in urine samples were detected by gas chromatography-mass spectrometry. Seven OH-PAHs were detected in urine samples, among which 1-hydroxy-naphthalene (1-OHNap) concentration was the highest [(20.54 ± 28.94) µmol/mol Cr], while 1-hydroxy-pyrene (1-OHP) concentration was the lowest [(0.73 ± 0.63) µmol/mol Cr]. The concentrations of these seven OH-PAHs decreased in the following order: 1-hydroxy-naphthalene (1-OHNap) > 9-hydroxy-fluorene (9-OHFlu) > 2-hydroxy-naphthalene (2-OHNap) > 3-hydroxy-fluorene (3-OHFlu) > 2-hydroxy-fluorene (2-OHFlu) > 6-hydroxy-chrysene (6-OHChr) > 1-hydroxy-pyrene (1-OHP). The effects of gender and smoking upon the contents of OH-PAHs in urine samples were not significant. There was a good correlation between total hydroxy-naphthalene (ΣOHNap) and 1-OHNap (r = 0.948), and a good correlation was also showed between total hydroxy-fluorene (ΣOHFlu) and 9-OHFlu (r = 0.975). Naphthalene carried by atmospheric particulate matters demonstrated better correlation with 1-OHNap than 2-OHNap, while fluorene carried by atmospheric particulate matters showed better correlation with 9-OHFlu than 3-OHFlu and 2-OHFlu. The correlation coefficients of ΣOHNap, ΣOHFlu and 6-OHChr with 1-OHP were 0.427, 0.543 and 0.655, respectively, and the correlations were not strong. It cannot reflect internal exposure level of PAHs to use 1-OHP as the only biomarker, while 1-OHNap and 9-OHFlu can be well predictive of the exposure levels of corresponding total OH-PAHs, suggesting that simultaneous determination of 1-OHNap, 9-OHFlu and 1-OHP can be more accurate and comprehensive in evaluating the internal exposure level of PAHs.

A Gold-Catalyzed Route to Benzo[b]fluorenes

A Gold-Catalyzed Route to Benzo[b]fluorenes

A novel high-quality electrochromic material from 3,4-ethylenedioxythiophene bis-substituted fluorene

Poly(2,7-bis (2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-9H-fluorene) (P(EDOT-FE)), a novel electrochromic material obtained from 3,4-ethylenedioxythiophene (EDOT) bis-substituted fluorene (FE) in CH2Cl2 solution, and its applications in electrochromic devices (ECD) are discussed. The external EDOT units will not only function as donor groups but also lower the oxidation potential. Fluorescent spectral studies indicate that P(EDOT-FE) with high fluorescence quantum yields and photochemical stability is a novel green-light-emitter. P(EDOT-FE) is switched between brown in the reduced state and blue in the oxidized state. ECD based on P(EDOT-FE) and poly(3,4-ethylenedioxythiophene) (PEDOT) was also fabricated and showed a good electrochromic performance. The ECD constructed by P(EDOT-FE) and PEDOT has good optical contrast (36% at 625nm), high coloration efficiency (784cm2C−1), fast response time (0.5s at 625nm), better optical memory and long-term stability. Clear change from dark red (neutral) to dark blue color (oxidized) of ECD is demonstrated with robust cycle life. These results provide an avenue for applications of PEDOT family in electrochromic devices.

Effects of three different PAHs on nitrogen-fixing bacterial diversity in mangrove sediment

Polycyclic aromatic hydrocarbons (PAHs) are of great environmental and human health concerns due to their widespread occurrence, persistence and carcinogenic properties. There is now compelling evidence that the mangrove sediment microbial structure is susceptible to PAHs contamination. The study aimed to assess the effects of PAHs on the nitrogen-fixing bacterial community of mangrove sediment. Three types of PAHs, naphthalene (NAP), a two-ring PAH; fluorene (FLU), a three-ring PAH; and pyrene (PYR), a four-ring PAH; were applied at three doses. After 7 and 24 days of incubation, the nitrogen-fixing bacterial population and diversity were evidenced in the nifH gene polymerase chain reaction denaturing gradient gel electrophoresis profile. DGGE pattern shows that the nitrogen-fixing bacterial community changed significantly with the types and doses of PAHs, and the incubation time. As far as single PAH is concerned, high concentration of PAH has larger impact on the nitrogen-fixing bacteria than low concentration of PAH. Besides, among the three types of PAHs, NAP has the greatest short term toxicity; PYR has the strongest long-term impact, whereas FLU has relatively higher long-time effect. Multidimensional scaling analysis and correspondence analysis are two reliable multivariate analysis methods for investigating the relationship between the nitrogen-fixing bacterial community and PAHs contamination. Investigating the effect of PAHs on the nitrogen-fixing bacterial diversity could yield useful information for understanding the process of biogeochemical cycling of nitrogen in mangrove sediment. The present study reveals that nitrogen-fixing bacterial community can be used as an important parameter indicating the impact of PAHs on mangrove sediment ecosystem.

Toward design of high-performance optoelectronic materials: comparative theoretical studies on the photophysical and charge transport properties of fluorene-based compounds

As an important building block for optoelectronic applications, various chemical modifications at C9-position of fluorene have been proposed to enhance its performance by suppressing the well-known keto effect. In order to identify different substitution effects on the photophysical and charge transport properties of fluorene, we systematically study the electronic structures and photophysical behaviors of fluorene (FR) and its three dimerized counterparts, namely, 9,9′-spirobifluorene (SBF), 9,9′-bifluorenylidene (BFD), and bis(biphenyl-2-2-diyl)allene (BDA), by employing density functional theory calculations. The changes in bond length alternation indicate that the geometrical relaxations of the fluorene unit in its dimerized derivatives are smaller than FR compound. This fact was further proved by the nonradiative decay rate estimated of the first excited singlet state for each compound. Meanwhile, the vibration relaxation analyses suggest that the bridge between two fluorene fragments plays an important role in the nonradiative decay process. In addition, the injection abilities were evaluated in terms of the ionization potentials and electron affinities, and the carrier transport properties were discussed in the framework of Marcus theory. We find BFD could be a better ambipolar transport material, and BDA can be used as a high-efficient luminescent building unit with excellent hole transport property.

Synthesis and Properties of 9,9'-Diarylspriofluorene with Substituted Group at 2,7-Position of Fluorene

Synthesis and Properties of 9,9'-Diarylspriofluorene with Substituted Group at 2,7-Position of Fluorene

Effects of sludge retention time and biosurfactant on the treatment of polyaromatic hydrocarbon (PAH) in a petrochemical industry wastewater

A laboratory-scale aerobic activated sludge reactor (AASR) system was employed to investigate the effects of sludge retention time (SRT) on the removal of three polyaromatic hydrocarbons (PAHs) with low benzene rings [(acenaphthene (ACT), fluorene (FLN) and phenanthrene (PHE)] and six PAHs with high benzene rings [(benzo[b]fluoranthene (BbF), benzo[k]fluoranthene (BkF), benzo[a]pyrene (BaP), indeno[1,2,3-cd]pyrene, dibenz[a,h]anthracene (DahA), benzo[g,h,i]perylene (BghiP)] in the presence of rhamnolipid (RD), emulsan (EM) and surfactine (SR) biosurfactants. This study showed that biosurfactants enhance the PAH biodegradation by increasing the biomass growth. RD exhibits a better performance than the other biosurfactants in the removal of the chemical oxygen demand (COD) and PAHs. At a RD concentration of 15 mg/L aerobic treatment for 25 days, SRT was enough to remove over 95% of total PAHs, and COD(dis). Under the same conditions 75% of COD originating from the inert organics (COD(inert)) and 96% of COD originating from the inert soluble microbial products (COD(imp)) were removed. At 25 days SRT and 15 mg/L RD concentration, about 88% of PAHs were biodegraded by the AASR system, 4% were accumulated in the system, 3% were released in the effluent, and 5% remained in the waste sludge.

Atmospheric Concentrations and Phase Partitioning of Polycyclic Aromatic Hydrocarbons in Izmir, Turkey

Ambient air polycyclic aromatic hydrocarbon (PAH) samples were collected at a suburban (n = 63) and at an urban site (n = 14) in Izmir, Turkey. Average gas-phase total PAH (∑14PAH) concentrations were 23.5 ng m−3 for suburban and 109.7 ng m−3 for urban sites while average particle-phase total PAH concentrations were 12.3 and 34.5 ng m−3 for suburban and urban sites, respectively. Higher ambient PAH concentrations were measured in the gas-phase and ∑14PAH concentrations were dominated by lower molecular weight PAHs. Multiple linear regression analysis indicated that the meteorological parameters were effective on ambient PAH concentrations. Emission sources of particle-phase PAHs were investigated using a diagnostic plot of fluorene (FLN)/(fluorine + pyrene; PY) versus indeno[1,2,3-cd]PY/(indeno[1,2,3-cd]PY + benzo[g,h,i]perylene) and several diagnostic ratios. These approaches have indicated that traffic emissions (petroleum combustion) were the dominant PAH sources at both sites for summer and winter seasons. Experimental gas–particle partition coefficients (KP) were compared to the predictions of octanol–air (KOA) and soot–air (KSA) partition coefficient models. The correlations between experimental and modeled KP values were significant (r2 = 0.79 and 0.94 for suburban and urban sites, respectively, p < 0.01). Octanol-based absorptive partitioning model predicted lower partition coefficients especially for relatively volatile PAHs. However, overall there was a relatively good agreement between the measured KP and soot-based model predictions.

Sizes and polycyclic aromatic hydrocarbon composition distributions of nano, ultrafine, fine, and coarse particulates emitted from a four-stroke motorcycle

Thus, this study was undertaken to determine the size distribution, concentration, species, and carcinogenic potency of particulate matter and particle-bound polycyclic aromatic hydrocarbons (PAHs) emitted from 4-st/mc at various speeds (idle, 15 km/h, 30 km/h). Approximately 80% of the particles emitted from the that is, they are primary inhalable particulates. The particle total number concentrations (TNCs) emitted while idling and at 15 and 30 km/h were 2.07 × 104, 2.35 × 104, and 2.60 × 104 #/cm3, respectively; i.e., they increased at elevated speeds. Notably, most of the particles emitted at 30 km/h had diameters of less than 0.65 μm and contained higher percentages of total PAHs. Excluding incomplete combustion, we suspected that some of the lower-molecular-weight PAHs [phenanthrene (PA), anthracene (Ant), pyrene (Pyr)] obtained in the fine particles at idle originated from unburned 95-octane unleaded fuel. When operated at 15 km/h, pyrolysis of the PAHs dominated, resulting in increased amounts of medium-molecular-weight PAHs {fluorene (FL), Pyr, benz[a]anthracene (BaA), chrysene (CHR)} in the ultrafine particles. Furthermore, at 30 km/h, more pyrosynthesis products {benzo[a]pyrene (BaP), indeno[1,2,3,-cd]pyrene (IND), dibenz[a,h]anthracene (DBA)}, induced through combustion at the correspondingly higher temperature, were exhausted with the nanoparticles. Although the total concentrations of BaP-equivalent emissions were inconsistent with the total PAHs, the nanoscale-sized particulates emitted from the 4-st/mc at higher speeds had the strongest PAH-related carcinogenic potencies, which should be a great concern.