Amount Of Pyrene Research Articles

Iron Oxide-Activated Carbon Composites for Enhanced Microwave-Assisted Pyrolysis of Hardwood

A commercial activated carbon (AC) was modified through iron oxide incorporation to obtain microwave absorbers (MWAs) for microwave-assisted pyrolysis. The influence of iron oxide content (5 and 20 wt% Fe3O4) and the modification methods were tested as follows: (1) in situ co-precipitation + washing step with Milli-Q; (2) in situ co-precipitation + washing step with Milli-Q/ethanol; and (3) physical iron oxide blending. The resulting MWAs were evaluated on the microwave-assisted pyrolysis of hardwood in a Milestone Flexiwave microwave reactor. The biochar yield varied from 24 wt% to 89 wt% and was influenced by the modification method rather than the iron oxide addition. The MWAs with physically blended iron oxide resulted in biochar yields comparable to conventional biochar (450 °C). Furthermore, the addition of iron oxide-activated carbon composites during the microwave-assisted pyrolysis caused a significant decrease in the biochar’s 16 EPA polycyclic aromatic hydrocarbons, mainly by reducing the amount of pyrene in the biochar.

Insights into the accumulation, distribution and toxicity of pyrene associated with microplastics in rice (Oryza sativa L.) seedlings

Microplastic and polycyclic aromatic hydrocarbons (PAHs) can be introduced into agroecosystems through various agricultural activities and may threaten food safety and human health. However, little research has focused on the behavior of microplastics-associated PAHs and their toxicity effects in agroecosystems, especially in crops. In the present study, we investigated the accumulation, distribution and toxicity of pyrene associated with polyethylene (PE) microplastics in rice (Oryza sativa L.). With quantitative analysis using 14C isotope labelling, the total accumulation efficiency of 14C-pyrene in rice seedlings was 22.4 ± 1.2% and 14.5 ± 0.3% when exposed to freely dissolved pyrene and PE-associated pyrene, respectively. The translocation of 14C-pyrene was significantly decreased by microplastics adsorption even when the amount of pyrene in the rice roots had no significant difference. Subcellular distribution of 14C-pyrene in rice suggested that PE microplastics-associated pyrene located more on cell walls than free dissolved pyrene. Furthermore, results showed free pyrene, but not PE-associated pyrene, significantly decreased the length and biomass of rice roots as well as increased the activities of antioxidant enzymes (superoxide dismutase and catalase). It indicated that the association with microplastics alleviated the phytotoxicity of pyrene in rice seedlings. These findings shed new light on the environmental behavior and effects of PAHs associated with microplastics in crops and will be helpful to its comprehensive risks assessment.

Fire Phoenix plant mediated microbial degradation of pyrene: Increased expression of functional genes and diminishing of degraded products

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental pollutants, and bioremediation is an eco-friendly means of removing pollutants from contaminated soils. This study investigated mechanisms underlying plant mediated microbial degradation of pyrene. Fire Phoenix (Festuca spp.) plants were grown in soils contaminated by two levels of pyrene. Degraded products, expression of functional genes of microbial organisms, and pyrene removal rates were monitored before planting and after 60, 90, and 120 days of plant growth. Results showed that the removal rates of pyrene from soils contaminated with 22.4 mg/kg and 35.3 mg/kg of pyrene were 89.7% and 92.1%, respectively. Detected degraded products included 1-hydroxy pyrene, dihydroxylated pyrene, 1-hydroxy-2-naphthoic acid, and phthalic acid. As far as is known, this is the first report of 1-hydroxypyrene as an epoxidation product of pyrene. Pyrene degradation occurred through both double-oxygen and single-oxygen pathways in the rhizosphere of Fire Phoenix. The expression of microbial 16S rDNA, PAH-RHDα-GP, nidA, and nidB genes were analyzed. The copy numbers of 16S rDNA increased over time, and the highest occurred in soil with higher pyrene. Microbial nidA, nidB, and PAH-RHDα-GP genes were highly expressed in rhizosphere on day 60 of plant growth, and their copy numbers were 32, 49, and 320 times greater than those before plant cultivation. The higher levels of expression were significantly correlated with the residual amount of pyrene and the content of total PAH metabolites in the soil. Our research shows that that microbial RHDα-GP, nidA, and nidB genes are important factors influencing the degradation of pyrene and pyrene degradation products in rhizosphere. Based on the results, a two-pathway model for biodegradation of pyrene in Fire Phoenix rhizosphere is proposed.

Enhanced pyrene degradation by a biosurfactant producing Acinetobacter baumannii BJ5: Growth kinetics, toxicity and substrate inhibition studies

Abstract Microbial community isolated from petroleum oil contaminated soil was enriched in minimal medium with pyrene as the only carbon source. One of the isolates exhibiting growth with increased concentrations of pyrene was identified as Acinetobacter baumannii BJ5 by 16S rRNA analysis. Growth, toxicity, and substrate inhibition models were studied with the enriched strain BJ5 over the range of 10–600 mg/L of pyrene. The specific growth rate increased linearly from 0.0163–0.0346 h−1 up to a concentration of 300 mg/L, with a decrease at higher levels, as confirmed by cell viability test. However, the absolute amount of pyrene metabolised increased linearly with an increase in initial concentration to the maximum of 336 mg/L in 14 days ( C initial = 600 mg/L). Kinetic parameters derived by nonlinear regression of the substrate inhibition model (Haldane Andrew model) were μ max = 0 . 033 , Ks=16.58 mg/L, and Ki=503.9 mg/L, respectively, indicating good tolerance and adaptation of the BJ5 strain to high concentrations of pyrene. With the production of a glycolipid biosurfactant (as characterised by FTIR, NMR and GC–MS) during growth with pyrene, the strain BJ5 exhibits a promising application for reclamation of Polyaromatic Hydrocarbons contaminated sites, adversely affecting the health of the exposed.

Biotransformation of pyrene in soil in the presence of earthworm Eisenia fetida

Abstract Pyrene, a toxic four benzene ring polycyclic aromatic hydrocarbons (PAHs) that persists in the environment, is highly resistant to degradation. Hence, this study aims to investigate the pyrene degradation by the combination of earthworm (Eisenia fetida) and some microbes in the soil. The artificially contaminated soil (200 g) was prepared in a container box by the addition of pyrene and combined with the addition of the earthworms and some microbes. The results showed that no mortality of earthworms in all soil conditions. The largest amount of pyrene (68.7%) was removed by earthworm microbes in the unsterilized soil. Twelve enzymes were produced such as peroxidase, laccase, invertase, glucosidase, phosphatase, phytase, urease, hydrolase, chitinase, nitrogenase, aminopeptidase, and arylsulfatase. The combination of earthworm and microbes transformed pyrene to protocatechuic acid via pyrene-4,5-dione, phenanthrene-4,5-dicarboxylic acid, and phenanthrene-4-carboxylic acid. But, these compounds were not confirmed in our extract.

Comparative evaluation of growth kinetics for pyrene degradation by Acinetobacter pittii NFL and Enterobacter cloacae BT in the presence of biosurfactant

In the present study, Acinetobacter pittii NFL and Enterobacter cloacae BT were studied for the first time for growth kinetics and biodegradation of pyrene over a range of 10–500 mg/L. E. cloacae BT and A. pittii NFL showed increase in specific growth rate from 0.0087 to 0.0318 h−1 and 0.0182 to 0.0320 h−1 up till 300 mg/L and 200 mg/L concentration, respectively. Maximum amount of pyrene degraded by the strain BT and NFL was found to be 241.7 ± 7.7 and 193.7 ± 2.1 mg/L, as determined by HPTLC. This high amount of pyrene degradation was facilitated by the biosurfactant released during growth with the compound. Biosurfactant production was validated by emulsification index (24 ± 4.8 and 36 ± 5.7% for BT and NFL, respectively) and drop collapse test, and, identified by FTIR analysis. Results indicated excellent efficiency of the acclimatized strains for pyrene degradation within few days, even when present at initial concentrations of high toxicity.

Novel 2-naphthol luminophors for optoelectronics

A new class of 2-naphthol luminophors doped with varying amounts of pyrene were prepared by applying standard solid-state reaction method to sight new luminophors which emit at a higher wavelength. The optical and electrochemical properties of prepared luminophors were studied by fluorimetry and cyclic voltammetry technique, respectively. The fluorescence spectrum of doped 2-naphthol showed broad fluorescence band at maximum wavelength 450 nm for 1 × 10–1 mol pyrene per mole 2-naphthol. The shifted broad spectra confirmed the exciplex formation between 2-naphthol and pyrene in the excitation state. On the basis of electrochemical data, energy levels of HOMO and LUMO were obtained for the prepared luminophors. The observed values fit between 5.70–5.72 eV and 3.02–3.09 eV, respectively. Their thermal stability was studied by TGA–DSC analysis. The SEM images evidenced crystal size of ~ 115 nm. Thus, the overall study proposes that the prepared novel luminophors are useful in optoelectronics.

Isolation of diverse pyrene-degrading bacteria via introducing readily utilized phenanthrene

Bacteria able to degrade pyrene play a critical role in the biodegradation of high-molecular-weight polycyclic aromatic hydrocarbons (PAHs). However, the traditional isolation procedure only obtains strains related to the genus Mycobacterium. The aim of the present study was to develop a modified method to isolate taxonomically distinct pyrene-degrading strains. The results indicated that replacing pyrene with phenanthrene in the isolation step improved the isolation efficiency. Using the modified method, six PAH degraders belonging to the genera Bosea, Arthrobacter, Paenibacillus, Bacillus, and Rhodococcus were obtained. They were capable of effectively utilizing pyrene (∼100%) as their sole carbon source, and could co-metabolize the degradation of benzo [a]pyrene (26.9–71.5%). In contrast, a small amount of pyrene (5.6%) and benzo [a]pyrene (8.6%) were degraded by a phenanthrene-degrading Sphingobium sp. NS7 under the same conditions. The difference in PAHs degradation between agar plate culture and liquid culture may lead to the low isolation efficiency in the traditional procedure. Hereditary stability analysis showed that PAH degradation capability of the Bosea, Paenibacillus, and Rhodococcus strains were easily lost without PAH pressure, which may partly explain why those strains were difficult to obtain using the traditional method.

Quantifying the bioaccumulation of nanoplastics and PAHs in the clamworm Perinereis aibuhitensis

The impact of nanometer-scale plastics (<1000 nm nanoplastics, NPs) on the bioaccumulation of hydrophobic organic pollutants, and especially polycyclic aromatic hydrocarbons (PAHs), in marine organisms has become of urgent concern. However, simultaneous determinations of the bioaccumulation of NPs and PAHs have been hindered by the lack of an efficient digestion method that removes background interference from the tissue without altering the surface properties of the plastic and destroying the PAHs. To solve this problem, an enzymatic digestion-based protocol using proteinase K and subsequent quantification methods were developed on a typical marine benthic invertebrate – the clamworm Perinereis aibuhitensis. Enzymatic digestion removed 91% of the biological tissues, comparable to the amount removed using 65% HNO3 (93% removed) and better than that removed using 30% H2O2 or 10% KOH digestion (76% and 66%, respectively). After enzymatic digestion, roughly 92% of the NPs and 88% of the amount of pyrene were recovered, without significant modification of the NPs or pyrene degradation. By contrast, the NP and pyrene recovery achieved with HNO3 digestion was only 1.4% and 0.1%, respectively. The newly developed protocol was successfully applied to a 96-h bioaccumulation study. The use of radioactively labeled 14C-pyrene and fluorescently labeled NPs allowed the simultaneous quantification of NPs and PAHs in the clamworm and revealed a bioconcentration factor (BCF) of 1.96 ± 0.93 and 402.7 ± 47.0, respectively. The quantification of NPs and pyrene indicated that NP-adsorbed pyrene accounted for <1% of the total pyrene accumulation in the clamworm body when the concentration of NPs in seawater was as low as 0.4 mg/L. Our enzymatic digestion and dual-labeling technique thus provides the first reported BCF value of NPs in a marine benthic organism and new insights into the vector effects of these particles on the bioaccumulation of organic contaminants in a marine ecosystem.

Content of Polycyclic Aromatic Hydrocarbons in Smoked Common Carp (Cyprinus Carpio) in Direct Conditions Using Different Filters vs Indirect Conditions

In this study, the common carp fish were smoked in direct and indirect smoke chambers. Direct smokings in craft chamber were conducted in four ways: smoked without filter (Fo), with zeolite filter (Fz), filter with granular activated carbon (Fc) and gravel filter (Fg). The content of 16 different PAHs in smoked common carp was analyzed using GCMS method. Addition of zeolite, activated carbon and gravel filters significantly reduced PAH levels (P < 0.05). Levels of naphthalene, acenaphthylene, fluorine, phenanthrene and fluoranthene were reduced using zeolite, activated carbon and gravel filters by 42.14, 40.64, 42.5 (Naph), 49.81, 48.96, 48.96 (Acy), 32.71, 30.79, 26.15 (Fln), 28.79, 31.68, 18.34 (Phe) and 4.14, 3.87 and 1.12 (Flt) µg/kg, respectively. The addition of zeolite and activated carbon filters reduced amount of anthracene by 15.28 and 11.89 µg/kg and amount of pyrene by 1.25 and 0.6 µg/kg, while addition of gravel filters did not influence significantly these PAHs (P > 0.05). However all filters decreased acenaphthene, benz[a]anthracene and chrysene below detection limits. Zeolite was the most effective adsorbent for PAHs. All samples were under maximum limit of BaP (2 μg/kg) and PAH4 (12 μg/kg) set by European Commission Regulation 835/2011. Based on results in the present study it can be stated that common carp smoked in both direct and indirect conditions can be considered to be safe for consumption.

Pyrene-Functionalized PTMA by NRC for Greater π-π Stacking with rGO and Enhanced Electrochemical Properties.

Nitroxide radical polymers can undergo both excellent electrochemical redox reactions and a rapid "click" coupling reaction with carbon-centered radicals (i.e., nitroxide radical coupling (NRC) reaction). In this work, we report a strategy to functionalize poly(2,2,6,6,-tetramethylpiperidinyl-1-oxyl methacrylate) (PTMA) with pyrene side groups through a rapid and near quantitative NRC reaction. This resulted in P(TMA-co-PyMA) random copolymers with near quantitative amounts of pyrene along the PTMA chain for greater π-π interaction with rGO, while the nitroxide radicals on the polymer could simultaneously be used for energy storage. These copolymers can bind with reduced graphene oxide (rGO) and form layered composites through noncovalent π-π stacking, attaining molecular-level dispersion. Electrochemical performance of the composites with different polymer contents (24, 35, and 45 wt %), tested in lithium ion batteries, indicated that the layered structures consisting of P(TMA-co-PyMA) maintained greater capacities at high C-rates. This simple and efficient strategy to synthesize pyrene-functionalized polymers will provide new opportunities to fabricate many other polymer composite electrodes for desired electrochemical performance.

Gold Catalysts with Polyaromatic-NHC ligands. Enhancement of Activity by Addition of Pyrene

Three Au(I) complexes with N-heterocyclic carbene ligands fused to polycyclic aromatic hydrocarbons (pyrene and phenanthrophenazine) have been obtained and fully characterized. The complexes were tested as catalysts in the hydroamination of terminal alkynes, where they showed moderate to good activity. The addition of a catalytic amount of pyrene to the reaction mixtures produced an improvement in the performance of the catalysts. The study of the reaction order of the catalyst in this reaction indicated that the order is 0.5, indicating that an off-cycle inactive catalyst dimer is formed, as consequence of the self-association of the complex by π–π stacking interactions. The reaction order in catalyst when pyrene is added to the reaction mixture is 1 > n > 0.5, therefore being higher than that in the absence of pyrene. Studies made by 1H NMR spectroscopy demonstrate that an important self-association of the catalyst occurs at the concentrations used in the catalytic reactions. The association of pyrene w...

Toxicokinetics of pyrene in the freshwater alga Chara rudis

Chara has been suggested a good model to study uptake of xenobiotics into cytoplasm due to their large internode cells surrounded by a layer of cortex cells. We studied the uptake and elimination of pyrene (nominal concentration of 5 μg L−1) in the freshwater alga Chara rudis during 22 days in two treatments mimicking epilimnetic (warm and light) and hypolimnetic (cold and dark) conditions. The growth of Chara during the exposure was higher in epilimnetic conditions (40%) compared to both hypolimnetic pyrene exposed Chara and controls (epilimnetic and hypolimnetic, no pyrene). In the water, a more rapid dissipation of pyrene was observed in epilimnetic conditions, possibly as a result of the increased algal growth. In the cortex, pyrene, 1-OH-pyrene (minor metabolite) and an unknown hydrophobic major metabolite was measured. Pyrene amounts decreased over time, while amounts of the unknown metabolite increased. In internode cytoplasm, pyrene and 1-OH-pyrene showed initially increasing followed by decreasing trends, while the unknown metabolite was not detected. The total mass balance showed that we were able to account for the applied pyrene until 4 days of exposure. However, after this time, there was a significant decrease in amounts accounted for by fluorescence, suggesting that the metabolism of pyrene involves degradation of the ring structure. The degradation was larger in epilimnetic than hypolimnetic conditions.

Enhanced Scirpus triqueter phytoremediation of pyrene and lead co-contaminated soil with alkyl polyglucoside and nitrilotriacetic acid combined application

This study aimed to evaluate the effect of combination of alkyl polyglucoside (APG) and nitrilotriacetic acid (NTA) on improving the efficiency of phytoremediation for pyrene and lead (Pb) co-contaminated soil by Scirpus triqueter. Seedlings of S. triqueter with a similar size and biomass (3 g/pot) were grown on 2-month aged soil contaminated with 184.5 mg kg−1of pyrene and 454.3 mg kg−1 of Pb at pH = 8.3. After growth for 10 days, different doses of APG and NTA were added into the soil. After 60 days, the height of plants, Pb concentrations in plants, and pyrene amounts in soil were determined. Combined application of NTA and APG with lower dosage (1 + 1 g kg−1 soil and 1 + 2 g kg−1 soil) had no notable negative influence on the growth of S. triqueter. Moreover, significant synergy on Pb accumulation in S. triqueter was achieved with APG and NTA combined application. Besides, the dissipation of pyrene from soil after 60-day planting was increased in APG and NTA treatments when compared with the control treatments. Application of APG alone or combined with NTA had greater effect on enhancing dissipation of pyrene from soil than NTA alone. This study demonstrated that the remediation of Pb and pyrene co-contaminated soil by S. triqueter can be enhanced by combined application of APG and NTA. Long-term evaluation of this strategy is needed in co-contaminated field sites.

Unveiling the Importance of π-Stacking in Borrowing-Hydrogen Processes Catalysed by Iridium Complexes with Pyrene Tags.

This work describes the preparation of a series of pyrene-tagged N-heterocyclic carbene complexes of iridium, and their use in two benchmark borrowing hydrogen reactions: the reduction of ketones by transfer hydrogenation and the β-alkylation of secondary alcohols with primary alcohols. The detailed study of these homogeneously catalysed reactions reveals several important implications regarding the strong influence of the pyrene tags in the catalysts. First, the catalytic activity is partially inhibited by addition of an external amount of pyrene, but only when pyrene-tagged catalysts and aromatic substrates are used. Second, the rate order of the reaction is highly dependent on the nature of the substrates and the ligand. When pyrene-tagged catalysts and aromatic substrates are used, the reaction follows a zero-order dependence on the concentration of the substrate. All other combinations afford a second-order rate in the substrates. And third, the presence or absence of the pyrene functionality in the catalyst also influences the reaction order with respect to the concentration of the catalyst. Pyrene-containing catalysts display a fractional rate order of below 1. Finally, two pyrene-tagged catalysts were supported onto reduced-graphene oxide (rGO), and used as heterogeneous catalysts. While the dimetallic catalyst was effectively recycled 12 times, the monometallic catalyst maintained its activity for only three runs.

Biosorption and biodegradation of pyrene by Brevibacillus brevis and cellular responses to pyrene treatment

Biodegradation has been proposed as an effective approach to remove pyrene, however, the information regarding cellular responses to pyrene treatment is limited thus far. In this study, the biodegradation and biosorption of pyrene by Brevibacillus brevis, along with cellular responses caused by pollutant were investigated by means of flow cytometry assay and scanning electron microscopy. The experimental results showed that pyrene was initially adsorbed by B. brevis and subsequently transported and intracellularly degraded. During this process, pyrene removal was primarily dependent on biodegradation. Cell invagination and cell surface corrugation occurred due to pyrene exposure. Nevertheless, cell regrowth after 96h treatment was observed, and the proportion of necrotic cell was only 2.8% after pyrene exposure for 120h, confirming that B. brevis could utilize pyrene as a sole carbon source for growth. The removal and biodegradation amount of pyrene (1mg/L) at 168h were 0.75 and 0.69mg/L, respectively, and the biosorption amount by inactivated cells was 0.41mg/L at this time.

Tuning the Interfacial Area and Porosity of TiO2 Film for Enhanced Light Harvesting in DSSC

Pyrene is used as the template material in the preparation of porosity in TiO2 films. Pores are created in the TiO2 film, using a range of pyrene amounts (0, 2, 3, 4 wt%), to increase the light harvesting efficiency and electron charge capabilities at the TiO2 film/dye/electrolyte interface. The specific surface area of the TiO2 film increases from 49.2 to 115.8 m2 g−1 as the porosity are created with 3% pyrene added TiO2 film (TiO2-pyrene-3). The pore volume of TiO2-pyrene-3 is 0.35 cm3 g−1. The charge transfer of TiO2-pyrene-3 based dye-sensitized solar cell (DSSC) is faster than the other TiO2 films. For TiO2-pyrene-3, the electron transport time is 4.19 ms and the electron recombination time is 34.82 ms. The diffusion coefficient is 8.36 × 10−5 cm2 s−1 for TiO2-pyrene-0 and increases to 1.39 × 10−4 cm2 s−1 for TiO2-pyrene-3. TiO2-pyrene-3 has the highest solar conversion efficiency of 7.58%, an increase of 11.47% over that of TiO2-pyrene-0, 6.80%.

Phenylene- and Biphenylene-Bridged Bis-Imidazolylidenes of Palladium. Influence of the Presence of Pyrene Tags on the Catalytic Activity of the Complexes

A series of dimetallic complexes with N-heterocyclic carbene ligands with formally identical stereoelectronic properties have been obtained and fully characterized. The dimetallic complexes were bridged by bis-imidazolylidenes, with different spacers (phenylene and biphenylene). The N substituents were methyl or methylpyrene groups. The related monometallic complexes were also obtained. The catalytic properties of the complexes were tested in the acylation of aryl halides with hydrocinnamaldehyde and in the Suzuki–Miyaura coupling between aryl halides and arylboronic acids. In general, the dimetallic complexes display better activities than the monometallic analogues. The results also indicate that those complexes with pyrene groups at the N substituents display better catalytic activities than those with N-methyl groups. These observations are interpreted as a consequence of the π stacking interaction between the substrates and the pyrene groups in the pyrene-containing catalysts, which may provide some beneficial catalytic properties. The addition of a catalytic amount of pyrene to the Suzuki–Miyaura coupling reactions results in a partial inhibition of the activities of the complexes with the pyrene substituents, while the activity of the complexes with the N-methyl groups is not affected.

Preparation of calcium carbonate microparticles containing organic fluorescent molecules from vaterite

The encapsulation of fluorescent organic molecules into crystalline calcium carbonate was examined using calcium carbonate microcapsule, whose crystalline phase is vaterite as a metastable phase of calcium carbonate. A calcium carbonate microcapsule with impregnated pyrene that is a water insoluble fluorescent molecule was soaked into suitable aqueous solutions to promote the phase transition of vaterite toward calcite as the stable phase of calcium carbonate. When 0.2M calcium chloride solution was used, the largest amount of pyrene (approximately 0.06wt%) was encapsulated into the calcite particle. Pyrene thus included was not eliminated even after thorough washing with THF. The calcite particle thus prepared produced the excimer emission of pyrene by UV irradiation. Rhodamine B was also introduced into calcium carbonate by the immersion of the microcapsule into the aqueous solutions of Rhodamine B. The fluorescence of rhodamine B was observed from the calcium carbonate particles by visible light irradiation. Acetaminophen, a common drug poorly soluble in water, was also included in the calcium carbonate particle by the same procedures as the pyrene encapsulation. As acetaminophen thus encapsulated was released by the dissolution of the calcium carbonate particle in acidic solution, the particle is expected to be applied for a dissolution-triggered drug delivery.

Promotion of pyrene removal from soils by Bidens maximowicziana

A pot experiment was conducted to investigate the potential of removal of pyrene from spiked soils planted with Bidens maximowicziana. The removal of pyrene from the spiked soils planted with B. maximowicziana was obviously higher than that from the unplanted soils. After 50 d, the removal ratio of pyrene in the planted soils was 79%, which was 28% higher than that of the unplanted soils. Pyrene was both accumulated at roots and shoots of B. maximowicziana. The RCFs (root concentration factors) were 1.64–2.20, whereas the SCFs (shoot concentration factors) were 0.8–1.1. Though the plant-enhanced removal of soil pyrene may be the result of plant-promoted microbial degradation, an amount of pyrene was still accumulated in plants. For example, 21.6 mg kg–1 was accumulated in plants when soil pyrene concentration was 121.3 mg kg–1. In addition, the soil dehydrogenase activity, microbial population and phenolic compounds were all improved in planted soils relative to unplanted soil. The increased microbial population and activities of the soil enzymes are presumed to be important for the removal of pyrene.