Naphthalene Research Articles

Syntheses and Structures of 6,13-Dihydro-6,13-diborapentacenes: π-Stacking in Heterocyclic Analogues of Pentacene

6,13-Dibromo-6,13-dihydro-6,13-diborapentacene (1) has been prepared by the reaction of 2,3-bis(trimethylsilyl)naphthalene with BBr3. The reaction of 1 with Me4Sn or mesityllithium afforded the dim...

The Alkylation of Naphthalene over One-Dimensional Twelve-Membered Ring Zeolites. The Influence of Zeolite Structure and Alkylating Agent on the Selectivity for Dialkylnaphthalenes

Abstract Alkylation, i.e., isopropylation, s-butylation, and t-butylation, of naphthalene (NP) was examined over one-dimensional twelve-membered (12-MR) zeolites: H-mordenite (MOR), SSZ-24 (AFI), SSZ-55 (ATS), and SSZ-42 (IFR) in order to elucidate how zeolite structure and alkylating agent play roles in the shape-selective catalysis. The β,β-selectivities (for β,β-dialkylnaphthalene (2,6- and 2,7-dialkylnaphthalenes, β,β-DAN)) and the 2,6-selectivities (for 2,6-DAN) were varied with the types of zeolite and of alkylating agent. MOR and AFI gave high β,β-selectivities by using alkylating agents, propene, 1-butene, and 2-methylpropene. However, the β,β-selectivities were changed over ATS and IFR at 250 °C: 40% for the isopropylation, 80% for the s-butylation, and almost 100% for the t-butylation. The 2,6-selectivities in the isopropylation were as high as 60% over MOR and 50% over AFI at 250 °C; however, they were less than 20% over ATS and IFR. The selectivities increased by using bulky alkylating agents over these one-dimensional zeolites: selective formation of 2,6-DAN occurred in the s-butylation and t-butylation. The different features among zeolites are explained by the zeolite channel and the bulkiness of alkylating agent. MOR and AFI with straight channels gave smaller reaction spaces than ATS and IFR with corrugated channels. Bulky alkylating agent also enhances the discrimination of the isomers, particularly between 2,6- and 2,7-DAN. The β,β- and 2,6-selectivities are synergetically governed by the zeolite channel and the bulkiness of alkylating agents.

Determination of naphthalene by competitive fluorescence immunoassay

A reliable and sensitive competitive fluorescence immunoassay for the quantitative determination of naphthalene (NA) was developed. 2-naphthoxy acetic acid (NAA) was selected as the hapten of naphthalene. Active ester method (AEM) was used to couple the NAA to carrier proteins (bovine serum albumin) to form artificial immune antigen. Male New Zealand white rabbits were immunized with this antigen to obtain polyclonal antibodies, with which, a novel fluorescence immunoassay for detection of NA was described. Under best conditions, NA can be determined in the concentration range of 0.1-100 microg/L with a detection limit of 0.05 microg/L. The cross-reactivities of the anti-NA antibody to seven structurally related compounds were below 15%. Some environmental samples were analyzed with satisfactory results. It shows a good accuracy and suitability to analyze NA in environmental water.

Interaction of naphthalene and naphthol with soil organic matrix

The sorption of naphthalene and naphthol from water solutions by peat, chernozem, and humic and fulvic acids was studied. The sorption isotherms of naphthalene and naphthol by chernozem corresponded to the Langmuir isotherms. More complex nonlinear isotherms were obtained for peat. Binding of naphthalene and naphthol by humic and fulvic acids can proceed through hydrophobic interactions with aromatic fragments of humic substances and hydrogen bonds between the polar groups of humic molecules and naphthol OH groups.

Keratinocyte growth factor protects against Clara cell injury induced by naphthalene

Airway epithelial cells are exposed to environmental toxicants that result in airway injury. Naphthalene (NA) causes site-selective damage to Clara cells in mouse distal airways. N-terminally truncated recombinant human keratinocyte growth factor (DeltaN23-KGF) protects against acute lung injury. The present study investigated whether or not DeltaN23-KGF protects against NA-induced acute Clara cell damage by measuring airway responses specifically and in order to identify underlying molecular mechanisms. Mice were treated with DeltaN23-KGF or PBS 33 h prior to injection of 200 mg.kg body weight(-1) NA. Lung function was analysed by head-out body plethysmography. Distal airways isolated by microdissection were assessed for cell permeability using ethidium homodimer-1. Immunohistochemistry of Clara cell-specific protein in conjunction with a physical dissector was used to quantify Clara cell numbers. RNA was isolated from frozen airways in order to analyse gene expression using quantitative RT-PCR. DeltaN23-KGF prevented NA-induced airflow limitation and Clara cell permeability, and resulted in twice as many Clara cells compared with PBS pre-treatment. DeltaN23-KGF-pre-treated mice exhibited increased expression of proliferating cell nuclear antigen mRNA. Cytochrome P(450) isoform 2F2, which converts NA into its toxic metabolite, was reduced by approximately 50%. The present results demonstrate that pre-treatment with N-terminally truncated recombinant human keratinocyte growth factor protects against naphthalene-induced injury. This suggests that N-terminally truncated recombinant human keratinocyte growth factor exerts its beneficial effect through a decrease in the expression of cytochrome P(450) isoform 2F2.

Mechanisms of Pulmonary Tolerance in Female Mice to the Cytotoxicant 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. Chronic exposures to compounds like NA can have both toxic and conditioning effects. Tolerance is the emergence of a resistant cell phenotype after prior exposure. Research in male mice has found the development of tolerance to NA involves upregulation of gamma‐glutamylcysteine synthetase, the rate limiting enzyme in glutathione synthesis. Tolerance has not been studied in females. Females have sex differences in airway epithelial responses and in the prevalence of airway diseases. To address female specific airway responses, mice were injected with a tolerizing regimen of NA and gene and protein expression of enzymes involved in NA bioactivation and detoxification were assessed. We found decreased gene/protein expression for CYP2F2, a P450 that metabolizes NA to a toxic epoxide, as well as increased gene/protein expression of glutathione s‐transferase pi, an enzyme involved in detoxification of the epoxide, in the airways of NA tolerant female mice. We conclude that mechanisms contributing to the development of NA tolerance in female mice include changes in airway epithelial specific metabolizing and detoxifying enzymes. Funded by NIH ES013066, ES012720, TRDRP 14RT‐0132, EPA RD‐832414

Comparison of nasal proteins adducted by reactive metabolites of naphthalene (NA) in rat and rhesus macaque using 2 dimensional gel electrophoresis and MALDI TOF/TOF

NA is a volatile pollutant classified by NTP as a ‘reasonably anticipated human carcinogen’ based on concentration‐dependent, rare olfactory epithelial neuroblastomas and respiratory (nasal) epithelial adenomas in rats (NTP 2000). However, epidemiologic studies have not provided a convincing link between exposure and cancer. Reactive metabolites of NA bind covalently to proteins in target cells; good correlations between adducted protein levels and injury have been observed (Drug Metab Rev 34:791, 2002). Accordingly, these studies compared adducted proteins in nasal epithelium of rats and rhesus macaques to develop biomarkers mechanistically associated with toxicity which could be applied to human populations. Rat and monkey nasal tissues were incubated with 14C ‐NA, proteins were resolved by 2D gel electrophoresis, and labeled proteins were imaged and subsequently identified. The adducted protein patterns between rat and rhesus macaque are remarkably similar. 45 adducted proteins identified in rat olfactory incubations include those involved in cell structure, transcription, protein synthesis/folding, ATP synthesis, and cell signaling; similar work is ongoing in monkeys. These studies suggest that several of these adducts may be good biomarker targets for assessing the potential for NA toxicity in humans. Supported by EPRI, NIEHS 04311, 04699 and RR00169.

Importance of microsomal epoxide hydrolase (mEH) in toxicity, metabolism and formation of covalent protein adducts from the volatile air pollutant, naphthalene (NA): Comparison of mEH null and wild type (WT) mice

Human exposure to NA is due to combustion of both environmental and man‐made materials. Toxicity of NA is P450‐dependent, occurring in murine, but not rat, airways. However, the extent to which specific metabolic pathways (to epoxides, quinones and diol epoxides) contribute to cytotoxicity and the formation of covalent protein adducts is unknown. Upon inhalation exposure to NA (4h at 5–20 ppm) male mEH null animals had increased cytotoxicity in the bronchioles, but decreased susceptibility in the trachea and lobar bronchus as compared to WT mice, despite having a normal pattern of P450‐containing CC10 positive Clara cells. Formation rates of NA metabolites (conjugates plus diol) in the trachea were lower in EH null animals, but equivalent in the airways compared to WT. As expected, rates of diol formation were undetected/low in mEH null animals. Protein adducts detected after ip administration of NA were 2–4 fold higher in airway epithelium than elsewhere in the lung, and EH null animals showed significantly higher levels compared to WT. Bound liver adducts showed no differences between mEH and WT animals. These studies suggest that metabolites (1,2‐quinone, diol epoxide) arising via the diol pathway are not critical to NA toxicity or formation of covalent adducts in distal airway epithelium. This work also suggests that there are compensatory changes associated with disruption of mEH. NIEHS 04311, 12720 and 04699.

Hormonal Influences on Airway Biology and Naphthalene‐ Mediated Clara Cell Injury

Women have a greater chance of developing adult onset asthma, COPD, and some forms of lung cancer than men. Naphthalene (NA), a bioactivated cytotoxicant, is used to model distal Clara cell airway injury and repair. Our laboratory has shown that female mice are more sensitive than male mice to NA toxicity. The objective of the current study was to evaluate the role of hormones in normal airway biology and in NA mediated injury. This was achieved by 1) measuring estrogen receptors (ESR) gene expression by RT PCR in airways by estrus cycle stage, 2) measuring glutathione levels in airways by cycle stage, and 3) comparing airway damage in response to NA in intact vs. gonadectomized animals. Airway level specific responses were defined in microdissected airways. In comparison to non‐cycling mice, ESR expression was decreased in both diestrus and proestrus and increased in the estrus phase of the cycle. Glutathione levels were decreased in the airways of mice during diestrus and metestrus compared to male mice. Depletion of glutathione within the Clara cell plays a major role in NA cytotoxity. Confocal microscopy of microdissected airways as well as high resolution resin sections showed less extensive injury in ovariectomized mice compared to intact female mice. These findings support the hypothesis that sex differences in lung injury are influenced by hormones. Funded by NIH grants ES012720, HL007013‐29, and TRDRP 14RT‐0191.

Urinary protein/peptide adducts as markers of reactive naphthalene (NA) metabolite formation in male mice

NA, an abundant PAH generated during combustion, has been shown to produce dose dependent cytotoxicity in murine airways and in rat and murine nasal epithelium. The relevance of findings in these animal models to human health is not clear, in part due to a high background of human lung diseases. Previous work has shown metabolism of NA in target tissues of rodents to reactive metabolites that covalently bind to such proteins as redox, extracellular, and cytoskeletal (Chem Res.Tox 18: 802, 2005). The current work focuses on monitoring urinary protein/peptide adducts as markers of key processes associated with NA toxicity. 24‐hour urine collected from male mice following ip administration of 14C‐NA revealed specific activities of covalently adducted proteins that exceed those observed in lung. On SDS PAGE gels, these adducted proteins varied in size from 5–70 kDa. Much of the adducted protein in male mouse urine was approximately 12 kDa and is consistent with the formation of adducts with major urinary protein (MUP). Female mice, lacking MUPs, have significantly less protein which was adducted at lower specific activity in the urine. Resolution of urinary proteins by 2D electrophoresis and their subsequent identification by mass spectrometry is ongoing. We conclude that adducted proteins eliminated in the urine may be excellent markers of processes critical to target tissue toxicity. Supported by NIEHS 04311 and 04699.

Gel electrophoresis and multiplexed fluorescent imaging analysis for the measurement of protein thiol oxidation induced in murine airway epithelial cells after treatment with the Clara cell toxicant, naphthalene (NA) or the non cytotoxic thiol depletor, diethylmaleate (DEM)

Oxidative stress leading to alterations in airway cell protein thiol (PSH) status has been implicated in NA cytotoxicity. This study identified specific thiol containing proteins altered by NA or DEM. Murine airway epithelial PSH and formation of oxidized thiols (PSSP, PSSG, PSOH, PSO3) in response to NA (200 mg/kg, ip) or DEM (1 g/kg, ip) was measured using multiplexed fluorescent 2D gel electrophoresis. Proteins were labeled with SH reactive Cy3, disulfides and sulfenic acids were reduced and labeled with Cy5. Proteins were separated to measure significant changes in the SH/oxidized ratios of each spot using the ratio of maleimide labels. NA and DEM caused significant changes in PSH of 82 proteins total compared to control (p<0.05). DEM oxidized more proteins to a greater extent than those recovered from murine airway epithelial samples after NA. However, several proteins containing reactive thiols are oxidized to a greater extent by NA compared to DEM including those involved in transcription regulation (zinc finger proteins), protein synthesis/folding (ribosomal proteins, serine peptidase inhibitor), cell growth/cycle control, and apoptosis (Suv39h2 Histone‐lysine N‐methyltransferase, Bcl2‐associated transcription factor 1). We conclude that specific proteins/protein pathways are disrupted by oxidation/arylation in response to NA that are less affected by nontoxic doses of DEM. NIEHS 04311/04699

Effects of naphthalene and phenanthrene on visual and prey capture endpoints during early stages of the dourado Salminus Brasiliensis

Naphthalene (NAP) and phenanthrene (PHE) effects on Salminus brasiliensis, a carnivorous freshwater fish, were investigated using behavioral tests. Larval stages of S. brasiliensis were exposed to water concentrations of 0, 0.04 mg/l, 0.20 mg/l and 0.50 mg/l for naphthalene and 0, 0.01 mg/l, 0.05 mg/l and 0.1 mg/l for phenanthrene during two developmental phases. The prey fish Prochilodus lineatus were not exposed. Visual acuity was measured at the end of phase 2 in individual S. brasiliensis, which were also tested at the end of each phase for number of attacks on prey, number of prey captured, prey capture efficiency, and distance swam. Vision was impaired by PHE exposure, as acuity angles increased in exposed fish. At Stage I 2.3 ± 1.2 prey were captured with 46% efficiency in controls compared to 0.4 ± 0.3 prey captured with 13.4% efficiency in fish exposed to 0.05 mg PHE l −1, the LOEL for both endpoints. At Stage II 4.0 ± 1.1 preys were captured in controls compared to 2.5 ± 0.9 preys captured in fish exposed to 0.01 mg PHE l −1, the LOEL. Stage II control fish captured prey with 70% efficiency compared to 30% efficiency at Stage II fish exposed to 0.05 mg PHE l −1, the LOEL. Distance swam was not affected by either NAP or PHE exposure. The exposure of larval stages of S. brasiliensis to realistic water concentrations of PHE impairs foraging skills and could affect recruitment of the species.

The alkylation of naphthalene over three-dimensional large pore zeolites: The influence of zeolite structure and alkylating agent on the selectivity for dialkylnaphthalenes

In order to elucidate how zeolite structure and alkylating agent play roles in the shape-selective catalysis, the alkylation, i.e., isopropylation, sec-butylation, and tert-butylation, of naphthalene (NP) was examined over three-dimensional twelve-membered (12-MR) zeolites, Y (FAU), Beta (BEA), and CIT-1 (CON), and compared to that of H-mordenite (MOR). The β,β-selectivities (for β,β-dialkylnapthalene (β,β-DAN)) and the 2,6-selctivities (for 2,6-dialkylnaphthalene (2,6-DAN)) among DAN isomers varied with the types of zeolites and alkylating agents. FAU, BEA, and CON gave only low selectivities for 2,6-diisopropylnaphthalene (2,6-DIPN) in the isopropylation, and predominant isomers were bulky and thermodynamically unstable α,β-DIPN (1,3-, 1,6-, and 1,7-DIPN) and α,α-DIPN (1,4- and 1,5-DIPN) at lower temperatures, and the formation of the less bulky and thermodynamically stable β,β-DIPN (2,6- and 2,7-DIPN) increased with increasing the temperature: they have quite different features from the shape-selective catalysis over MOR. These results suggest that FAU, BEA, and CON are not shape-selective in the isopropylation, and that the isopropylation is principally controlled kinetically at lower temperatures, and thermodynamically at higher temperatures. The β,β-selectivities over FAU, BEA, and CON increased with increasing the bulkiness of alkylating agents, and were almost 100% in the tert-butylation. On the other hand, the 2,6-selectivities over these zeolites were much lower than those over MOR at a typically moderate temperature, 250 °C. These results mean that FAU, BEA, and CON have the shape-selective nature to give the less bulky isomers, β,β-DAN, in the sec-butylation and tert-butylation by using bulkier alkylating agents, particularly 2-methyl-2-propene: they can differentiate β,β-DAN from their isomers at the transition states by the steric restriction of zeolite channels. However, the channels of these zeolites are too large for differentiating 2,6- and 2,7-DAN even with 2-methyl-2-propene.

Behavior of catalysts with rhodium in simultaneous hydrodesulfurization and hydrogenation reactions

The behavior of catalysts containing rhodium was evaluated in hydrotreating (HDT) reactions at 583 K and 5 MPa. The influence of the temperature and the nature of the activating agent were analyzed for the monometallic Rh/γ-Al 2O 3 catalyst in simultaneous hydrodesulfurization (HDS) of dibenzothiophene (DBT) and hydrogenation (HYD) of naphthalene (NT). H 2, H 2S, N 2 and H 2S (15 vol.%)/H 2, H 2S (85 vol.%)/H 2 mixtures were used as activating agents. Bimetallic RhMo/γ-Al 2O 3 catalysts with different Rh/Mo ratios were also tested in the same reactions. Some of the catalysts were characterized by XPS. The results show that for the Rh monometallic catalyst, the H 2S present in the activating mixture leads to an increase in the selectivity to HDS. Synergy in both HDS and HYD reactions was detected for the bimetallic catalysts, and it presents a slight increase with the Rh/(Rh + Mo) atomic ratio. These results lead to speculate about the possible role of Rh in bimetallic catalysts.

Enhanced Sorption of Polycyclic Aromatic Hydrocarbons to Tetra-Alkyl Ammonium Modified Smectites via Cation−π Interactions

The objective of this study was to characterize molecular sorptive interactions of polycyclic aromatic hydrocarbons (PAHs) by organoclays modified with quaternary ammonium cations. Three PAHs, naphthalene (NAPH), phenanthrene (PHEN), and pyrene (PYR), and three chlorobenzenes, 1,2-dichlorobenzene (DCB), 1,2,4,5-tetrachlorobenzene (TeCB), and pentachlorobenzene (PtCB), were sorbed from aqueous solution to reference montmorillonite clays (SWy-2) exchanged respectively with tetramethyl ammonium (TMA), tetraethyl ammonium (TEA), tetra-n-butyl ammonium (TBA), and hexadecyltrimethyl ammonium (HDTMA) cations. Solute hydrophobicities are compared between PAHs and chlorobenzenes using the solute n-octanol-water partition coefficient, n-hexadecane-water partition coefficient, and polyethylene-water distribution coefficient. The PAHs show several- to more than 10-fold greater sorption than the chlorobenzenes having close hydrophobicities but fewer delocalized pi electrons (NAPH/DCB, PHEN/TeCB, and PYR/ PtCB) by TEA-, TBA-, and HDTMA-clays. Furthermore, the PAHs show greater trends of solubility enhancement than the compared chlorobenzenes by TMA, TEA, and TBA in aqueous solution. The enhanced sorption and aqueous solubility of PAHs are best described by cation-pi interactions between ammonium cations and PAHs relative to chlorobenzenes that are incapable of such interactions. Cation-pi complexation between PAHs and tetra-alkyl ammonium cations in chloroform was verified by ring-current-induced upfield chemical shifts of the alkyl groups of cations in the 1H NMR spectrum.

Gama-Tocopherol Accumulation and Floral Differentiation of Medicinal Pumpkin (Cucurbita pepo L.) in Response to Plant Growth Regulators

Changes in biochemical and agronomical characteristics were studied in medicinal pumpkin (Cucurbita pepo L.) plants under different treatments with plant growth regulators (PGRs). The seeds were subjected to priming with PGRs before planting and plants unerwent foliar sprays with different solutions of PGRs at 10 day-intervals after flowering. y-tocopherol (y-toc) content of grains was found to be increased under gibberellic acid (GA3) treatment. The accumulation of y-tocopherol in the grains of GA3 treated plants was approximately 19.5 % higher than the control and reached 220.2 mg kg-1 dry pumpkin grains. The number of female flowers per plant was positively affected by PGRs and was 10.1 and 1.89 respectively, in the naphthalene acetic acid (NAA) and GA3 treated plants. A significant efficiency of treatments was observed upon fresh fruit yield. The yield increased from 4831 t ha-1 in the control to 6820 t ha-1 with NAA treatment. Priming treatments increased seedling emergence rate and percent. The highest seedling emergence rate was found in GA3 treated seeds.

An interdigitated functionally rigid [2]rotaxane

The synthesis of a functionally rigid [2]rotaxane incorporating pi-electron rich 1,5-disubstituted naphthalene (NP) ring systems, encircled by the pi-electron deficient tetracationic cyclophane, cyclobis(paraquat-p-phenylene), is described; in the solid state, the molecules of this donor-acceptor [2]rotaxane line themselves up in parallel pi-pi stacks of alternating NP ring systems and bipyridinium units, affording an interdigitated superstructure.

Acute and prolonged stress responses of brain monoaminergic activity and plasma cortisol levels in rainbow trout are modified by PAHs (naphthalene, β-naphthoflavone and benzo( a)pyrene) treatment

We have investigated if treatment with two different PAHs such as naphthalene (NAP) and benzo( a)pyrene (BaP), and the PAH-like compound β-naphthoflavone (BNF), may modify the stress responses elicited in rainbow trout by acute or prolonged stress stimuli, and the possible involvement of brain monoamines in those responses. Two experiments (acute and prolonged stress) were performed. In the acute stress experiment, fish were i.p. injected with vegetable oil alone (control) or oil containing NAP, BNF or BaP (10 mg kg −1), and 72 h after injection fish were acutely stressed by chasing for 15 min. In the prolonged stress experiment, a similar group-design and injection protocol were followed, but fish were submitted to severe confinement stress by maintaining fish under high stock density (70 kg fish mass m −3) for 72 h. The levels of cortisol, glucose and lactate were assayed in plasma. In addition, the contents of dopamine (DA), noradrenaline (NA) and serotonin (5HT), as well as their oxidized amine metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and 5-hydroxy-3-indoleacetic acid (5HIAA) were assayed in telencephalon, hypothalamus, preoptic region, optic tectum and brain stem, as well as the pituitary. Both acute and prolonged stress stimuli increased plasma levels of cortisol, which further increase with NAP and BNF treatments after acute stress. In contrast, cortisol levels of fish exposed to prolonged stress showed a clear tendency to decrease after the treatment with BNF and BaP. Stress stimuli also increased plasma glucose levels, which were not affected by PAHs in acute stressed fish but decreased in fish exposed to prolonged stress. Increased plasma levels of lactate in fish exposed to stress decreased after PAHs treatment in acute stress but not in prolonged stress. With respect to monoaminergic systems, major changes induced by both acute and prolonged stress were increases of the metabolites DOPAC and 5HIAA and DOPAC/DA or 5HIAA/5HT ratios in several brain regions. PAHs induced alterations in the normal responses of monoaminergic systems to stress, with dopaminergic system being the most affected after acute stress, and serotonergic system after prolonged stress. Those alterations, especially after prolonged stress, showed certain parallelism with alterations of plasma cortisol levels. Thus, results suggest that in stressed fish PAH effects on plasma cortisol levels (and its derived metabolic actions) could be in part mediated by alterations on the monoaminergic systems at the CNS of rainbow trout.

Potential of the Trad-MCN assay applied with inflorescences of Tradescantia pallida ‘Purpurea’ for evaluating air contamination by naphthalene

The aims of this study were to determine clastogenic responses of Tradescantia pallida cv. Purpurea to naphthalene (NAPH) by means of the bioassay Trad-MCN with inflorescences of T. pallida cv. Purpurea and to verify if this assay might be an indicator of the potential risk imposed in a workplace, where solid insecticide containing NAPH is usually applied. The clastogenic potential of NAPH was assessed by using static and dynamic experimental systems. In both systems, increased micronucleus frequencies were observed in inflorescences submitted to increasing concentrations of solid or gaseous NAPH. The evident clastogenicity verified in inflorescences exposed experimentally to 25–50 mg m −3 of NAPH during 6 h points to a narrow threshold of plant sensitivity, indicating risks under lower NAPH levels than the standards established by OSHA and therefore revealing its suitability for biomonitoring purposes. However, the clastogenic risk should be carefully investigated by other monitoring methods if human health is taken into consideration.

Influences of polycyclic aromatic hydrocarbons (PAHs) on soil microbial community composition with or without Vegetation

Uptake of three polycyclic aromatic hydrocarbons (PAHs), naphthalene (NAP), phenanthrene (PHN), and pyrene (PYR), from soils by ryegrass, white clover and soybean were investigated in an 8-week pot experiment. The microbial phospholipid-fatty-acid (PLFA) patterns in PAHs-contaminated soil were analyzed. Contamination with PAHs inhibited the soil microbial activity. In non-vegetated soils, the total PLFA showed 87% reduction on the addition of PAHs after an 8-week incubation compared to the PAH-free soil; the concentrations of NAP, PHN, and PYR in soils showed 19.4%, 25.5% and 24.3% reduction, respectively, due mainly to the evaporative loss and microbial degradation. In vegetated soils, the reduction of added NAP and PHN levels was not related to the plant biomass nor to the total PLFA. However, the reduction in PYR concentrations in soil mediated by soybean growth was much pronounced than those by ryegrass or white clover growth, but thisis not related to the total microbial biomass as revealed by PLFAs. The principal-component analysis (PCA) of the PLFA signatures revealed significant changes in the PLFA pattern in PAH-spiked soils when different vegetations were planted. Using the PLFA as a biomarker, it was found that the Gram-negative bacteria were more sensitive to PAHs than Gram-positive bacteria and fungi.