Naphthalene Research Articles

Shape-Selective Isopropylation of Aromatic Hydrocarbons over H-Mordenite in Supercritical Carbon Dioxide Medium

Abstract The isopropylation of aromatic hydrocarbons isobutylbenzene (IBB), naphthalene (NP), and biphenyl (BP) was examined over H-mordenite (MOR), H-β (BEA), and H-Y (FAU) zeolites in supercritical carbon dioxide (sc-CO2) medium. MOR was only selective for the formation of the least bulky 4-isobutylcumene (4-IBC) in the isopropylation of IBB. In particular, the catalytic activity and selectivity for 4-IBC were enhanced by the dealumination of MOR; MOR with 110 of SiO2/Al2O3 ratio rendered the highest performance; however, the catalytic activity was decreased by further dealumination. Thermogravimetric analyses confirmed the reduction of coke formation on the catalysts in sc-CO2 medium, preventing the deactivation of MOR. Shape-selective formation of the least bulky isomers, 2,6-diisopropylnaphthalene (2,6-DIPN) and 4,4′-diisopropylbiphenyl (4,4′-DIPB), was also observed in the isopropylation of NP and BP over MOR in sc-CO2. sc-CO2 works as an efficient medium to access and/or replace substrates and their products to/from acidic sites in the MOR channels. In particular, the removal of coke precursors from acidic sites on the zeolite is enhanced by the sc-CO2 medium, resulting in decreased coke formation.

Use of mycelia as paths for the isolation of contaminant‐degrading bacteria from soil

SummaryMycelia of fungi and soil oomycetes have recently been found to act as effective paths boosting bacterial mobility and bioaccessibility of contaminants in vadose environments. In this study, we demonstrate that mycelia can be used for targeted separation and isolation of contaminant‐degrading bacteria from soil. In a ‘proof of concept’ study we developed a novel approach to isolate bacteria from contaminated soil using mycelia of the soil oomycete Pythium ultimum as translocation networks for bacteria and the polycyclic aromatic hydrocarbon naphthalene (NAPH) as selective carbon source. NAPH‐degrading bacterial isolates were affiliated with the genera Xanthomonas, Rhodococcus and Pseudomonas. Except for Rhodococcus the NAPH‐degrading isolates exhibited significant motility as observed in standard swarming and swimming motility assays. All steps of the isolation procedures were followed by cultivation‐independent terminal 16S rRNA gene terminal fragment length polymorphism (T‐RFLP) analysis. Interestingly, a high similarity (63%) between both the cultivable NAPH‐degrading migrant and the cultivable parent soil bacterial community profiles was observed. This suggests that mycelial networks generally confer mobility to native, contaminant‐degrading soil bacteria. Targeted, mycelia‐based dispersal hence may have high potential for the isolation of bacteria with biotechnologically useful properties.

Sex differences in the development of airway epithelial tolerance to naphthalene

Exposure to air pollution has been linked to pulmonary diseases. Naphthalene (NA), an abundant polycyclic aromatic hydrocarbon in tobacco smoke and urban air, is a model toxicant for air pollution effects in the lung. Repeated exposures to NA in male mice result in tolerance, defined as the emergence of a resistant cell phenotype after prior exposure. Tolerance has not been studied in females. Females have sex differences in airway epithelial responses and in the prevalence of certain airway diseases. Male and female mice were exposed to a tolerance-inducing regimen of NA, and lungs were examined by airway level to characterize the cellular changes associated with repeated NA exposure and to assess the expression of genes and proteins involved in NA bioactivation and detoxification. The airway epithelium in treated males resembled that of controls. Females in the tolerant state were characterized by dense populations of ciliated cells in midlevel, distal, and bifurcating airways and a lower abundance of Clara cells at all airway levels. Cytotoxicity following a secondary challenge dose was also greater in females than males. Furthermore, females had decreased gene/protein expression of CYP2F2, a P-450 that metabolizes NA to a toxic epoxide, and glutamate-cysteine ligase, the rate-limiting enzyme in glutathione synthesis, than NA-tolerant males at all airway levels examined. We conclude that, while females develop tolerance, sex differences exist in the tolerant state by airway level, and females remain more susceptible than males to repeated exposures to NA.

Walking the tightrope of bioavailability: growth dynamics of PAH degraders on vapour‐phase PAH

SummaryMicrobial contaminant degradation may either result in the utilization of the compound for growth or act as a protective mechanism against its toxicity. Bioavailability of contaminants for nutrition and toxicity has opposite consequences which may have resulted in quite different bacterial adaptation mechanisms; these may particularly interfere when a growth substrate causes toxicity at high bioavailability. Recently, it has been demonstrated that a high bioavailability of vapour‐phase naphthalene (NAPH) leads to chemotactic movement of NAPH‐degrading Pseudomonas putida (NAH7) G7 away from the NAPH source. To investigate the balance of toxic defence and substrate utilization, we tested the influence of the cell density on surface‐associated growth of strain PpG7 at different positions in vapour‐phase NAPH gradients. Controlled microcosm experiments revealed that high cell densities increased growth rates close (< 2 cm) to the NAPH source, whereas competition for NAPH decreased the growth rates at larger distances despite the high gas phase diffusivity of NAPH. At larger distance, less microbial biomass was likewise sustained by the vapour‐phase NAPH. Such varying growth kinetics is explained by a combination of bioavailability restrictions and NAPH‐based inhibition. To account for this balance, a novel, integrated ‘Best Equation’ describing microbial growth influenced by substrate availability and inhibition is presented.

Transient absorption spectroscopy detection of sensitized delayed fluorescence in chiral benzophenone/naphthalene systems

Transient absorption spectroscopy has proven to be a powerful tool to investigate the formation and decay of excited singlet states upon triplet–triplet annihilation, following T–T energy transfer from a selectively excited sensitizer. Thus, upon selective excitation of benzophenone (BZP) by laser flash photolysis (LFP) at λ = 355 nm in the presence of naphthalene (NPT), a negative band centered at 340 nm has been detected, with growth and decay in the microsecond timescale. It has been assigned to the P-type NPT delayed-fluorescence. In the case of chiral BZP/NPT systems, stereodifferentiation has been observed in the kinetics of the involved photophysical processes.

Generation and Characterization of aCyp2f2-Null Mouse and Studies on the Role of CYP2F2 in Naphthalene-Induced Toxicity in the Lung and Nasal Olfactory Mucosa

The CYP2F enzymes, abundantly expressed in the respiratory tract, are active toward many xenobiotic compounds, including naphthalene (NA). However, the precise roles of these enzymes in tissue-selective chemical toxicity have been difficult to resolve. A Cyp2f2-null mouse was generated in this study by disrupting the Cyp2f2 fourth exon. Homozygous Cyp2f2-null mice, which had no CYP2F2 expression and showed no changes in the expression of other P450 genes examined, were viable and fertile and had no in utero lethality or developmental deficits. The loss of CYP2F2 expression led to substantial decreases in the in vitro catalytic efficiency of microsomal NA epoxygenases in lung (up to ~160-fold), liver (~3-fold), and nasal olfactory mucosa (OM; up to ~16-fold), and significant decreases in rates of systemic NA (300 mg/kg i.p.) clearance. The Cyp2f2-null mice were largely resistant to NA-induced cytotoxicity, when examined at 24 h after NA dosing (at 300 mg/kg i.p.), and to NA-induced depletion of total nonprotein sulfhydryl (NPSH), examined at 2 h after dosing, in the lungs. In contrast, the loss of CYP2F2 expression did not alleviate NA-induced NPSH depletion or tissue toxicity in the OM. Mouse CYP2F2 clearly plays an essential role in the bioactivation and toxicity of NA in the lung but not in the OM. The Cyp2f2-null mouse should be valuable for studies on the role of CYP2F2 in the metabolism and toxicity of numerous other xenobiotic compounds and for future production of a CYP2F1-humanized mouse.

Biological Monitoring of Blood Naphthalene Levels as a Marker of Occupational Exposure to PAHs among Auto-Mechanics and Spray Painters in Rawalpindi

BackgroundRoutine exposure to chemical contaminants in workplace is a cause for concern over potential health risks to workers. In Pakistan, reports on occupational exposure and related health risks are almost non-existent, which reflects the scarce availability of survey data and criteria for determining whether an unsafe exposure has occurred. The current study was designed to evaluate blood naphthalene (NAPH) levels as an indicator of exposure to polycyclic aromatic hydrocarbons (PAHs) among automobile workshop mechanics (MCs) and car-spray painters (PNs). We further determined the relationship between blood NAPH levels and personal behavioural, job related parameters and various environmental factors that may further be associated with elevated risks of occupational exposures to PAHs.MethodsSixty blood samples (n = 20 for each group i.e. MC, PN and control group) were collected to compare their blood NAPH levels among exposed (MCs and PNs) and un-exposed (control) groups. Samples were analyzed using high pressure liquid chromatography (HPLC). Data regarding demographic aspects of the subjects and their socioeconomic features were collected using a questionnaire. Subjects were also asked to report environmental hygiene conditions of their occupational environment.ResultsWe identified automobile work areas as potential sites for PAHs exposure, which was reflected by higher blood NAPH levels among MCs. Blood NAPH levels ranged from 53.7 to 1980.6 μgL-1 and 54.1 to 892.9 μgL-1 among MCs and PNs respectively. Comparison within each group showed that smoking enhanced exposure risks several fold and both active and passive smoking were among personal parameters that were significantly correlated with log-transformed blood NAPH levels. For exposed groups, work hours and work experience were job related parameters that showed strong associations with the increase in blood NAPH levels. Poor workplace hygiene and ventilation were recognized as most significant predictors related to differences among workplaces that may enhance the extent of exposure to chemical contaminants.ConclusionsIt appeared that chemical exposure at the workplace may be influenced by multiple environmental factors, but poor workplace hygiene and duration of exposure (long work hours) were the most important factors. Smoking and negligence of workers regarding self protection were among some of the important personal behaviours than can be addressed with better training. There is also a need to improve workplaces hygiene and to rationalize work hours to minimize health risks. Since smoking was an important confounding factor that supplemented most of the actual occupational exposure, a study based on non-smoker subjects is needed to separate out the effects of smoking and other confounding factors that may obscure measurements of actual extent of occupational exposure.

ChemInform Abstract: Shape‐Selective Alkylation of Naphthalene over Zeolites: Steric Interaction of Reagents with Zeolites

AbstractReview: 53 refs.

Crystallization of Syndiotactic Polystyrene Monitored by Angular Distributions of Polarized Fluorescence

The method to measure polarized fluorescence by rotating a sample around the excitation light (PFR) was applied to observe the initial stage of crystallization of syndiotactic polystyrene (SPS) induced by the exposure of naphthalene (NP) vapors. At room temperature, no crystallization of SPS appeared when the stretched films were exposed by NP vapors. PFR clearly evidenced that the NP molecules were not distributed uniformly but rather with a sort of orientation in the oriented amorphous SPS. NP molecules were clathrated in SPS films in the case of the exposure at 80°C. However, the exposure of NP vapors at 60°C was found to produce SPS/NP clathrate cocrystalline structure with only a small amount but rather mainly produce a trans-planar mesomorphic phase. In this initial stage, the wide angle X-ray diffraction revealed diffuse and unclear, whereas PFR was effective to determine orientation and distribution of the NP molecules. The NP molecules staying in the amorphous region were shown to be oriented due to the formation of a trans-planar mesomorphic phase, and their main arrangements were first determined by PFR.

Naphthalene Triplet Excited State as a Probe for the Assessment of Drug Distribution in Binary Protein Systems

Three drugs containing the naphthalene (NP) chromophore, namely, naproxen (NPX), propranolol (PPN), and cinacalcet (CIN), but with different affinities toward serum albumins (SAs) and α-1-acid glycoproteins (AAGs) have been employed for the assessment of drug distribution in binary SA/AAG systems. These three drugs represent an appropriate choice for checking whether a methodology based on transient absorption spectroscopy of a given reporter can be employed for discrimination between different distribution patterns in multicompartmental biological media. Thus, upon laser flash photolysis (LFP) of NPX, PPN, and CIN in the presence or absence of proteins, the NP triplet excited state ((3)NP*) at ∼420 nm was always detected, although the kinetics of the decay traces was structure- and medium-dependent. In aerated PBS, only a very short triplet lifetime (τ(T)) was found (1-2 μs). By contrast, in the presence of SAs, two longer triplet lifetimes (5-76 μs) were observed, ascribed to (3)NP* within site I and site II. Upon binding to AAGs, only a long τ(T) (15-47 μs) was found. When the two proteins were present simultaneously in the same media, fitting of the decay traces was clearly consistent with a distribution of the drug between the different biological compartments and the bulk solution, which correlates well with the known protein affinities of every drug. Experiments were performed in both human (HSA/HAAG) and bovine protein media (BSA/BAAG). The results showed that SAs are the major carriers for NPX; by contrast, PPN binds preferentially to AAGs. An intermediate situation was found for CIN, which presents comparable affinity for both proteins. The results obtained for the two enantiomers of each drug were very similar, although a small stereodifferentiation was observed between the triplet lifetimes in the protein binding sites.

SSZ-60: Synthetic investigation and catalytic application to the alkylation of biphenyl and naphthalene

An aluminosilicate [Al]-SSZ-60 zeolite was prepared through borosilicate [B]-SSZ-60, which was synthesized using cis- and trans- N-ethyl- N-(3,3,5-trimethylcyclohexyl)pyrrolidinium hydroxide ([ETMCHP] +OH −). [B]-SSZ-60 was obtained by using an equimolar mixture of cis-/trans-[ETMCHP] +OH −. Only small amounts of [B]-SSZ-60 were formed in the presence of [ETMCHP] +OH − ( cis/trans ratio = 96/4, 76/24, and 21/79), and a SSZ-60 phase was not observed in the presence of [ETMCHP] +OH − ( cis/ trans = 4/96). [B]-SSZ-60 was aluminated to form [Al]-SSZ-60 with a SiO 2/Al 2O 3 ratio of 163, a surface area of 62.2 m 2/g, and a pore volume of 0.10 mL/g. The zeolite was used in the alkylation of biphenyl (BP) and naphthalene (NP). The selectivity for 4,4′-diisopropylbiphenyl (4,4′-DIPB) was less than 30% at temperatures of 200–300 °C in the isopropylation of BP, and the predominant isomers were 2,x′-DIPB. However, the selectivity for 4,4′-di- sec-butylbiphenyl (4,4′-DSBB) and 4,4′-di- tert-butylbiphenyl (4,4′-DTBB) was 50–60% and 70–80%, respectively in the sec- and tert-butylations. The selectivity for β,β-diisoprpylnaphthalene (β,β-DIPN) was less than 30% in the isopropylation of NP, and predominant isomers were α,β-DIPN and α,α-DIPN. The selectivities for β,β-di- sec-butylnaphthalene (β,β-DSBN) and β,β-di- tert-butylnaphthalene (β,β-DTBN) were enhanced using bulky agents. SSZ-60 channels are too large for shape-selective formation of the least bulky isomers in the isopropylation of BP and NP. The isopropylation occurs under operation of kinetic and/or thermodynamic controls. However, bulky agents enhance the exclusion of bulky product isomers by increasing steric interactions within the channels in the sec- and tert-butylations. These results indicate that the selectivity for the least bulky isomers is determined by the exclusion of bulky transition states by zeolite channels. Thus, the fit of the transition state in zeolite channels is essential for high selectivities.

P53 codon 271 CGT to CAT mutant fraction does not increase in nasal respiratory and olfactory epithelia of rats exposed to inhaled naphthalene

A 2-year rat tumor bioassay testing whole body exposure to naphthalene (NA) vapor found a significant increase in nasal respiratory epithelial adenomas in male rats and in olfactory epithelial neuroblastomas in female rats. To obtain mechanistic insight into NA-induced nasal carcinogenesis, NA dose–response was characterized in nasal epithelium using a tumor-relevant endpoint. Specifically, levels of p53 codon 271 CGT to CAT mutation were measured in nasal respiratory and olfactory epithelium of NA-exposed male and female rats by allele-specific competitive blocker-PCR (ACB-PCR). Male and female, 8–9 week-old F344 rats (5 rats/group) were exposed to 0, 0.1, 1.0, 10, and 30 ppm NA vapor for 13 weeks (6 h/day, 5 days/week). The geometric mean p53 mutant fraction (MF) levels in nasal epithelium of control treatment groups ranged between 2.05 × 10 −5 and 3.05 × 10 −5. No significant dose-related changes in p53 mutant fraction (MF) were observed in the olfactory or respiratory epithelia of female rats. However, statistically significant treatment-related differences were observed in male respiratory and olfactory epithelium, with the p53 MF in the respiratory epithelium of male rats exposed to 30 ppm NA significantly lower than that in controls. Further, a significant trend of decreasing p53 MF with increasing dose was observed in the male respiratory epithelium. Of the tissue types analyzed, respiratory epithelium is the most sensitive to the cytotoxic effects of NA, suggesting cytotoxicity may be responsible for the loss of p53 mutation. Because ACB-PCR has been used successfully to detect the effects of known mutagenic carcinogens, the absence of any significant increases in p53 MF associated with NA exposure adds to the weight of evidence that NA does not operate through a directly mutagenic mode of action.

Microbial growth with vapor-phase substrate

Limited information exists on influences of the diffusive transport of volatile organic contaminants (VOC) on bacterial activity in the unsaturated zone of the terrestrial subsurface. Diffusion of VOC in the vapor-phase is much more efficient than in water and results in effective VOC transport and high bioavailability despite restricted mobility of bacteria in the vadose zone. Since many bacteria tend to accumulate at solid-water, solid-air and air–water interfaces, such phase boundaries are of a special interest for VOC-biodegradation. In an attempt to evaluate microbial activity toward air-borne substrates, this study investigated the spatio-temporal interplay between growth of Pseudomonas putida (NAH7) on vapor-phase naphthalene (NAPH) and its repercussion on vapor-phase NAPH concentrations. Our data demonstrate that growth rates of strain PpG7 were inversely correlated to the distance from the source of vapor-phase NAPH. Despite the high gas phase diffusivity of NAPH, microbial growth was absent at distances above 5 cm from the source when sufficient biomass was located in between. This indicates a high efficiency of suspended bacteria to acquire vapor-phase compounds and influence headspace concentration gradients at the centimeter-scale. It further suggests a crucial role of microorganisms as biofilters for gas-phase VOC emanating from contaminated groundwater or soil.

Isopropylation of naphthalene over H-mordenite, H-Y, and H-beta zeolites: Roles of isopropylnaphthalene isomers

Isopropylation of naphthalene (NP) was examined over H-mordenite (MOR), H-Y zeolite (FAU), and HBeta zeolite (BEA) in order to elucidate roles of isopropylnaphthalene (IPN) isomers during the catalysis. 2-IPN was the predominant isomer over MOR and works as a precursor for the selective formation of β,β-DIPN, particularly, 2,6-DIPN. In contrast, 1-IPN was predominant (with 2-IPN as a minor isomer) over FAU and BEA at low temperatures; dialkylation accompanied by the consumption of 1- and 2-IPN led to predominant formation of α,α- and α,β-DIPN. The formation of β,β-DIPN from 2-IPN was enhanced at higher temperatures. Bulky transition states of 1-IPN in IPN isomers and α,α- and α,β-DIPN among DIPN isomers were hindered by the interaction with MOR channels, resulting in the selective formation of β,β-DIPN, particularly 2,6-DIPN through the less bulky 2-IPN. FAU and BEA allow the formation of α,α- and α,β-DIPN from both of 1- and 2-IPN isomers because their channels are too large to exclude bulky transition states. The catalysis over FAU and BEA occurred under kinetic control at lower temperatures, and thermodynamic control also participates at higher temperatures.

弯曲型向列相液晶研究进展

The bent-core nematic liquid crystals discovered in recent years is a new kind of liquid crystals with special electro-optical property.The molecules have the unique bent shape,performing great characteristics which are different from rod-like liquid crystals.However,these molecules with bent-core nematic commonly have high melting point and wide temperature range of smetic phases.This paper overviews the current state of research in the field of bent-core nematic liquid crystals of molecular structures,properties and the research situation of bent-core molecules with nematic phases based on the substituted resorcinol,naphthalene,oxadiazole etc as the central units and ester group,C=N(N=N) etc as the bridge bonds,and the influence of lateral substitution on the liquid crystal behavior was given.

Characterization of polycyclic aromatic hydrocarbons in fog–rain events

Atmospheric polycyclic aromatic hydrocarbons (PAHs) mainly originate from incomplete combustion or pyrolysis of materials containing carbon and hydrogen. They exist in gas and particle phases, as well as dissolved or suspended in precipitation (fog or rain). Current studies in atmospheric PAHs are predominantly focused on fog and rainwater samples. Some sampling difficulties are associated with fog samples. This study presented the first observation of the characteristics of PAHs in fog samples using a solid phase microextraction (SPME) technique. Eighteen fog samples were collected during ten fog events from March to December 2009 in the Shanghai area. PAHs were extracted by SPME and analyzed by gas chromatography-mass spectrometry (GC-MS). As the compounds were partially soluble in water, with solubility decreasing with increasing molecular weight, low molecular weight (LMW) PAH compounds were universally found in the fog water samples. Naphthalene (NaP), phenanthrene (Phe), anthracene (Ant) and fluoranthene (Flo) were dominant compounds in fog water. The total PAH concentration in fog water ranged from 0.03 to 6.67 μg L(-1) (mean of 1.06 μg L(-1)), and was much higher in winter than in summer. The concentration of PAHs in fog or rain water decreased after undergoing a pre-rain or pre-fog wash. The average concentration of PAHs was higher in fog than in rain. Diagnostic ratio analysis suggested that petroleum and combustion were the dominant contributors to PAHs in urban Shanghai. Backward trajectories were calculated to determine the origin of the air masses, showing that air masses were mostly from the northeast territory.

Evaluating the functionalities of NiMo/y-Al2O3-B2O3 catalysts in naphthalene hydrodearomatization and dibenzothiophene hydrodesulfurization

The aim of this work is to contribute to the current understanding on the role of the support’s acidic properties in the hydrogenating function of NiMo/-Al2O3 type catalysts during hydrodearomatization (HDA) and dibenzothiophene (DBT) type molecules desulfurization. NiMo/-Al2O3-B2O3 catalysts of different B2O3 (0, 2, 3, 6 and 8 wt.%) contents were prepared and tested in independent and simultaneous naphthalene (NP) HDA and DBT hydrodesulfurization (HDS) reactions. For HDA the catalytic activity as a function of the B2O3 content followed a volcano-shape trend, with a maximum around 3 wt.% of B2O3. In DBT desulfurization boron was found to have a positive effect in the development of the HYD route of desulfurization possibly due to an increase in total acidity. Conversely, the direct desulfurization route (DDS) was negatively affected by boron addition. The presence of NP during the HDS of DBT was found to have a significant effect in neither total HDS activity nor the HYD/DDS selectivity. The findings in this paper are significant for ultra-deep HDS of heavy oil cuts where increasing in the selectivity to HYD is a must because highly refractory alkyl-DBTs mostly react by this reaction route.

Context-Dependent Differentiation of Multipotential Keratin 14–Expressing Tracheal Basal Cells

Multipotential (MP) differentiation is one characteristic of a tissue-specific stem cell (TSC). Lineage tracing of tracheobronchial basal cells after naphthalene (NA) injury or in the postnatal period demonstrated that basal cells were MP progenitors for Clara-like and ciliated cells. These studies, as well as reports of spatially restricted, label-retaining basal cells, and MP differentiation by human bronchial cells support the hypothesis that a TSC maintained and repaired the tracheobronchial epithelium. However, differences in basal cell phenotype (keratin [K] 5+ versus K14+), age (postnatal versus adult), health status (normal versus injured), and injury type (acid, detergent, NA) limited comparisons among studies and thus diminished the strength of the TSC argument. The finding that K14 was up-regulated after NA injury was a caveat to our previous analysis of reparative (r)K14-expressing cells (EC). Thus, the present study lineage traced steady-state (s)K14EC and evaluated differentiation potential in the normal and repairing epithelium. We showed that sK14EC were unipotential in the normal epithelium and MP after NA, sK14EC-dervied clones were not restricted to putative TSC niches, sK14EC cells were a direct progenitor for Clara-like and ciliated cells, MP-sK14EC clones accumulated over time, and sK14EC-derived Clara-like cells were progenitors for ciliated cells.

Novel method for in situ visualization of polycyclic aromatic hydrocarbons in mangrove plants

Two-photon laser confocal scanning microscopy (TPLCSM) was first used to visualize the uptake and movement of naphthalene (NAP), phenanthrene (PHE), and pyrene (PYR), from separately contaminated hydroponics solutions into living Kandelia candel (L.) Druce seedlings. With this non-destructive and non-chemical extraction technique, the experimental results revealed that three types of polycyclic aromatic hydrocarbons (PAH) were observed moving into the K. candel and its translocation to radicle, hypocotyl and leaf, and the transmission rates of these PAH in the K. candel were in the order of NAP > PHE > PYR. Data demonstrate the manner in which PAH enter, transport, and distribute within the K. candel, and provided us some valuable information on uptake and translocation mechanism of PAH. These findings may help to optimize the phytoremediation strategies of PAH in mangrove wetlands.

Model and calculation of rate constants of nonradiative T-S intersystem conversion: Test by example of naphthalene and its chlorine derivatives

For in-plane spin states (s = z, y), the rate constants Kdgs of the nonradiative energy degradation T1 ⇝ S0 of the lowest triplet T1 state of naphthalene (NPH) and its dichloro-substituted derivatives at positions 1,4- and 2,3- of the molecule (1,4-NPH and 2,3-NPH) are calculated. A simple model is proposed for calculations that is based on the nonadiabatic approximation and uses all the out-of-plane vibrational modes of the molecule as promoting vibrational modes. As a result of calculations, the dependences of the rate constants Kdg and Kdgs on the positions of chlorine atoms in the molecule are obtained, which are consistent with the known data of magnetooptical measurements. The inversion of the ratio Kdgz: Kdgy in the 1,4-NPH and 2,3-NPH molecules is established.