Initial Phenanthrene Concentration Research Articles

Enhanced Phenanthrene Biodegradation by Bacillus brevis Using Response Surface Methodology

The current investigation assessed the capability of a well-adapted and enriched bacterial strain known as Bacillus brevis for the biodegradation of phenanthrene. To enhance the removal efficiency of phenanthrene, employed Response Surface Methodology (RSM) in conjunction with a Box-Behnken design (BBD) model. The experiments were designed to explore the impact of pH (6.0 to 9.0), temperature (20 to 40°C), initial phenanthrene concentration (50 and 100 ppm), and incubation time (7 to 21 days) on biodegradation of phenanthrene. The highest level of phenanthrene biodegradation, approximately 55.0%, was achieved by Bacillus brevis when the optimal conditions were met as pH of 7.0, temperature 30oC, and initial phenanthrene concentration (70 ppm) after 21 days of incubation time. This study underscores the significance of employing statistical tools like RSM to enhance the microbial degradation of contaminants.

Optimization of phenanthrene biodegradation process by isolated bacterial strain Rhodococcus sp. using response surface methodology

This research aimed to assess the biodegradation potential of phenanthrene in a simulated aqueous solution using an isolated bacterial strain, Rhodococcus sp., with the assistance of a Box-Behnken design matrix. To gauge the impact of key operational factors, pH (6.0 to 9.0), temperature (20 to 40°C), initial phenanthrene concentration (50 to 100 ppm) and incubation time (7 to 21 days), the Response Surface Methodology (RSM) was employed to design the biodegradation experiment. The experimental findings highlighted incubation time as the most influential variable followed by initial phenanthrene concentration, pH and temperature via Box-Behnken Design (BBD) matrix. To determine the maximum phenanthrene biodegradation, the Desirability Function Methodology (DFM) was applied. Within the designated parameter ranges, the highest phenanthrene biodegradation (70.0%) was observed at pH 7.3, temperature of 30°C and an initial phenanthrene concentration of 70 ppm on the 19th day of incubation. The model's fitness was thoroughly validated, with a correlation coefficient (R²) of 0.9899 and a "Prob>F" value below 0.0500, affirming its suitability for optimization purposes. This study underscores the utility of the RSM in optimizing operational variables, ultimately resulting in significant time and cost savings for experimentation.

The discrepant metabolic pathways of PAHs by facultative anaerobic bacteria under aerobic and nitrate-reducing conditions

Studies regarding the facultative anaerobic biodegradation of polycyclic aromatic hydrocarbons (PAHs) were still in the initial stage. In this study, a facultative anaerobe which was identified as Bacillus Firmus and named as PheN7 was firstly isolated from the mixed petroleum-polluted soil samples using phenanthrene and nitrate as the solo carbon resource and electron acceptor under anaerobic condition. The degradation rates of PheN7 towards phenanthrene were detected as 33.17 μM/d, 13.81 μM/d and 7.11 μM/d at the initial phenanthrene concentration of 250.17 μM with oxygen, nitrate and sulfate as the electron acceptor, respectively. The metabolic pathways toward phenanthrene by PheN7 were deduced combining the metagenome analysis of PheN7 and intermediate metabolites of phenanthrene under aerobic and nitrate-reducing conditions. Dioxygenation and carboxylation were inferred as the initial activation reactions of phenanthrene degradation in these two pathways. This study highlighted the significance of facultative anaerobic bacteria in natural PAHs biodegradation, revealing the discrepant metabolic fates of PAHs by one solo bacteria under aerobic and anaerobic environments.

Peroxydisulfate activation by CuFe2S3 nanocrystal doped C/N catalyst for phenanthrene degradation: Experimental, mechanism, and density functional theory calculation

In Fenton-like reactions, metal-doped catalysts generally have high catalytic activity, but their active sites are always randomly distributed, yielding electron transfer mechanisms between orbitals are difficult to explain. Herein, a CuFe2S3-C/N catalyst was synthesized to activate peroxydisulfate (PDS) for phenanthrene (PHE) degradation. The periodic structure of CuFe2S3 nanocrystals embedded in the C/N skeleton facilitated the cooperation of Fe, Cu, and S, resulting in a more effective degradation of PHE [i.e., maximum degradation rate of up to 93.5% (Initial PHE concentration: 1 mg/L)]. A phenanthrene degradation pathway was then proposed, and the dominant reactive oxygen species were proven to be •OH, SO4•-, 1O2 and O2•-. This pathway was elucidated using density functional theory (DFT) methods, and the negative adsorption energy (-2.05 eV) of S2O82- corresponding to a spontaneous adsorption process. The CuFe2S3 surface stretched the O-O bond from 1.306 to 1.433 Å, and the loss of electrons from the 2p bonding orbital of O atoms led to a lower energy barrier for O-O bond cleavage. Additionally, the electrons were transferred from part of the 3d orbitals of Cu and Fe atoms to the 2p orbital of O atoms in S2O82- and the electron donating capacity of the Cu atom was 3–7 times higher than that of the Fe atom, indicating that the Cu atoms dominated the PDS activation. This study expands on approaches that can be used to modify metal-doped materials to degrade phenanthrene and it contributes towards a clearer understanding of electron transfer mechanisms underlying PDS activation.

Removal of Phenanthrene from wastewater with low-cost adsorbents

The potential to remove Phenanthrene (PHE) from water matrices through adsorption onto natural organic substances (NOSs) and natural inorganic compounds (NICs) was studied. Coffee waste (CW) and activated carbon (AC) produced from CW, and chemically pre-treated with NaOH or H3PO4 were chosen as NOS, and diatomaceous earth (DE) and DE pre-treated with NaOH or H3PO4 was chosen as NIC. Comparative analysis showed that the AC produced from CW pre-treated with NaOH and pyrolyzed at 800 °C (CWAC-NaOH-800) was the most efficient adsorbent, and used for parametric analysis with respect to the initial pH of the solution, the contact time, and initial PHE concentration. The pore structure parameters of adsorbents were determined from nitrogen sorption isotherms. The pseudo-second-order kinetic model was fitted better to the experimental data, showing that chemisorption is the rate-controlling step in the adsorption process. Sips isotherm gave the best fit to the experimental isotherm data indicating that adsorption occurs on a heterogenous system, and adsorption capacity was found qmax = 143.85 mg/g. The results show that CWAC-NaOH-800 with the highest specific surface area (SSA=910 m2/g) is very efficient toward the adsorption of PHE which makes it a well-promising material for the removal of PAHs from waters.

Remediation of a clay soil contaminated with phenanthrene by using MgO and forced carbonation

AbstractBACKGROUNDThe Stabilization and Solidification (S/S) technique is one of the most cost‐effective, low‐risk, and efficient remedial technologies for contaminated soils. In this research, the effect of MgO (Magnesium Oxide) on the remediation of a clay soil contaminated with phenanthrene with and without forced carbonation was studied by the S/S method. The effects of various parameters in reducing the mobility and leaching of phenanthrene were considered, including the percentage of MgO and curing time with and without forced carbonation, as well as the duration of carbonation.RESULTSThe results of the leaching tests showed that by using 5% MgO, the initial concentration of phenanthrene (32.7 mg kg−1) is changed to 9.16, 5.77, and 5.1 mg kg−1 for curing times of 7, 14, and 28 days. In addition, for the mixture of contaminated soil with 0.25% MgO and by using forced carbonation, the initial concentration is changed to 7.9, 4.3, and 3.73 mg kg−1 after 4, 8, and 24 h of injection of CO2. The S/S mechanisms for the removal of phenanthrene from soil include immobilization, adsorption, and encapsulation mechanisms. These stages are dependent on the hydration products of MgO.CONCLUSIONA comparison of the results of the leaching tests without and with forced carbonation showed that forced carbonation can reduce the concentration of phenanthrene in a few hours with a small percent of MgO compared to the case without forced carbonation. Therefore, forced carbonation provides a cost‐effective method for the remediation of contaminated soil. © 2022 Society of Chemical Industry (SCI).

Biodegradation of mixed polycyclic aromatic hydrocarbons by Pseudomonas sp. isolated from estuarine sediment

Polycyclic aromatic hydrocarbons (PAHs) are released into the environment via several natural and anthropogenic sources leading to long-term consequences that severely affect the environment, ecosystem, human and animal health. In this study, the extent of PAH pollution was measured at two estuarine locations of the major rivers of Goa, Zuari and Mandovi. Out of the 16 PAHs marked as carcinogenic, 13 PAHs were detected from the sediment samples collected. Bacterial strains were isolated from these PAH-contaminated sediments using conventional plating method. Six of these selected bacterial isolates were checked for their efficacy to degrade both low (phenanthrene) and high molecular weight (fluoranthene and pyrene) hydrocarbons. Amongst them, two bacterial isolates exhibited over 80% degradation of phenanthrene. Isolate NIOSV7 (Pseudomonas pachastrellae) could degrade 83.33% phenanthrene, 40.22% fluoranthene and 45.28% pyrene, while isolate NIOSV8, identified as Pseudomonas oleovorans, showed 85.09% phenanthrene, 70.61% fluoranthene and 67.18% of pyrene degradation in 120 h, at 100 ppm initial concentration of phenanthrene and 75 ppm of fluoranthane and pyrene. Though many Pseudomonas sp. are documented for PAH degradation, this is the first report showing PAH-degradation by Pseudomonas oleovorans strain. This study also shows that the bacteria isolated from estuarine sediments contaminated with PAH have good potential to degrade low and high molecular weight PAHs. These toxic pollutants can be bio-transformed into nontoxic metabolites with the help of microorganisms isolated from the same habitat.

Phenanthrene biodegradation in a fed–batch reactor treating a spent sediment washing solution: Techno–economic implications for the recovery of ethanol as extracting agent

The continuous dredging of sediments contaminated by polycyclic aromatic hydrocarbons such as phenanthrene (PHE) has required the employment of high–efficiency technologies, including sediment washing (SW). However, the large amount of generated spent SW effluents requires the development of effective, eco–friendly and cost–saving approaches, which can tackle the waste formation in favor of the recovery of chemicals. This study proposes the treatment of a spent SW solution containing ethanol (EtOH) as extracting agent, by testing different initial PHE concentrations (i.e. 20–140 mg L−1) within six consecutive cycles in a fed–batch bioreactor under aerobic conditions. The biological process achieved a PHE removal of 63–91% after the enrichment of PHE–degrading bacteria and the proper supplementation of nutrients, and was mainly affected by the initial PHE concentration value and the excessive decrease of pH and dissolved oxygen. Achromobacter, Sphingobacterium and Dysgonomonas genera were mainly involved in PHE degradation, which followed a first–order kinetic model (R2 = 0.652–0.928) with a degradation rate and half–life time of 0.127–1.177 d−1 and 0.589–2.912 d, respectively. A techno–economic assessment revealed that a virtuous operation of SW, EtOH recovery and biodegradation of the SW solution can allow the recovery of up to 1.35 tons of EtOH per ton of remediated sediment and the decrease of the overall costs by 50%.

Kinetics and regression analysis of phenanthrene adsorption on the nanocomposite of CaO and activated carbon: Characterization, regeneration, and mechanistic approach

In the present study, calcium oxide supported on activated carbon (CaO@AC) nanocomposite was synthesized using Basil leaf extract as a promoter and used to remove phenanthrene, an environmental pollutant, from aqueous solution. The activated carbon (AC) was prepared by the carbonization of Palm shells under pyrolytic conditions. The CaO@AC nanocomposite was characterized by FTIR, SEM-EDX, BET, and PXRD. The characterized CaO@AC nanocomposite was employed as an adsorbent for selective removal of phenanthrene from wastewater, maintaining the optimized conditions at initial phenanthrene concentration (5 mg/L), catalyst dosage (1 g), temperature (30 °C), and pH (7.6) for all batches. The adsorption isotherm and the kinetic studies for regression analysis were well fitted for the Freundlich model (R2 = 0.9956) and non-linear Pseudo (II order) mechanism (R2 = 0.9942). The results showed that the type IV linear form of pseudo-II order kinetic expression was inadequate for the kinetic rate parameters compared to the type I - III models. The CaO@AC was demonstrated as an inexpensive, scalable, recyclable, and eco-friendly adsorbent material for removing phenanthrene from wastewater.

Phenanthrene degradation in soil using biochar hybrid modified bio-microcapsules: Determining the mechanism of action via comparative metagenomic analysis

A strategy involving biochar (BC) hybrid modification was developed to promote the bioremediation effect of degrading bacteria immobilized in layer-by-layer assembly (LBL) microcapsules for the treatment of phenanthrene (PHE) polluted soil. A taxonomic and functional metagenomic approach was used to investigate changes in the microbial community structures and functional gene compositions in the PHE-polluted soil during the bioremediation process. Biofortification with an initial PHE concentration of 100 mg kg−1 dry soil in soils using the BC (3%) hybrid LBL bio-microcapsule (BC-LBL, 2.0 g kg−1 dry soil, 107 colony forming unite cell g−1 dry soil) was faster; further, a higher PHE degradation efficiency (80.5% after 25 d) was achieved when compared with that by the LBL agent (66.2% after 25 d) used. Sphingomonas, Streptomyces, Gemmatirosa, Ramlibacter, Flavisolibacter, Phycicoccus, Micromonospora, Acidobacter, Mycobacterium and Gemmatimonas were more abundant in BC-LBL treatment than those in LBL one. Functional gene annotation results showed that more gene number with BC-LBL treatment than those with LBL one. More abundant functions in the former were primarily related to the growth, reproduction, metabolism, and transportation of bacteria. BC hybridization promoting PHE degradation by microencapsulated bacteria may be due to the strong adsorption property of BC, which results in the enrichment of the nutrients that needed for bacterial growth and reproduction, as well as enhancing the mass transfer performance of PHE to BC-LBL; Meanwhile, BC could also stimulate and improve the metabolism and membrane transportation of the degrading bacteria, and finally improving the degradation function.

Establishing the Order of Importance Factor Based on Optimization of Conditions in PAHs Biodegradation

In environmental study, optimization of different factors is crucial to obtain high removal of specific pollutants. The sequence of important factors that were considered in optimization studies is less concerned, and this part is crucial before proceeding to full-scale bioremediation study. This study focuses on bioremediation of polycyclic aromatic hydrocarbons (PAHs) contaminated soil with the potential bacteria, Corynebacterium urealyticum which is isolated from municipal sludge. The bacterial strain has evaluated the effectiveness of PAHs degradation at various factors on soil pH, soil temperature, initial PAHs concentration, initial bacteria number, and heavy metals concentration. The optimum condition for phenanthrene biodegradation was pH 7, 30 °C, 500 mg/kg of phenanthrene concentration, 109 cells/g soil, and without the addition of Zn. In establishing the ranking, we attempt to use a simple method based on the analysis of p values. Based on the analysis of degradation rates, the initial phenanthrene concentration shows the lowest p value, which means that it shows the highest ranking; the most significant factor to achieve highest degradation. In vice versa, the soil pH shows the highest ranking based on the analysis of bacteria growth rates, which is a very limited study that focuses on growth rates in the optimization study. The establishment of these rankings may reduce time, energy and cost in pilot or field study and at the same time achieve highest degradation in bioremediation work. Thus, it is highly recommended to develop the ranking before proceeding to design work in pilot and field study.

Exploration of the biotransformation processes in the biodegradation of phenanthrene by a facultative anaerobe, strain PheF2, with Fe(III) or O2 as an electron acceptor

The study of biodegradation of polycyclic aromatic hydrocarbons (PAHs) with metal ions as electron acceptors is still in its infancy. Here, a pure culture of PheF2 sharing 99.79% 16S rRNA-sequence similarity with Trichococcus alkaliphilus, which was recently reported to degrade PAHs, was isolated and found to degrade PAHs with Fe (III) or O2 reduction. Phenanthrene was selected as a model of PAH to study the biodegradation process by PheF2 with Fe (III) or O2 as an electron acceptor. PheF2 exhibited nearly 100%, 37.1%, and 28.5% anaerobic biodegradation of phenanthrene at initial concentrations of 280.7 μM, 280.6 μM, and 281.3 μM, respectively, within 10 days under anaerobic conditions with XAD-7 as a carrier, heptamethylnonane (HMN) as a solution, and nothing, respectively. PheF2 could degrade nearly 100% of the initial phenanthrene concentration of 283.4 μM under aerobic conditions within three days. The initial step of phenanthrene biodegradation by PheF2 involved carboxylation and dioxygenation under anaerobic and aerobic conditions, respectively. The biotransformation processes of phenanthrene degradation by PheF2 with Fe(III) or O2 as an electron acceptor were explored by metabolite and genome analysis. These findings provide an important theoretical support for evaluation of PAHs fate and for PAHs pollution control or remediation in anaerobic and aerobic environments.

Characterization of Biofilm Formed by Phenanthrene-Degrading Bacteria on Rice Root Surfaces for Reduction of PAH Contamination in Rice.

One effective method in to reduce the uptake of organic contaminants by plants is the development of a root barrier. In this study, the characterization of biofilm structure and function by phenanthrene-degrading Pseudomonas sp. JM2-gfp on rice root surfaces were carried out. Our results showed that root surfaces from three rice species, namely Liaojing401, Koshihikari, and Zhenzhuhong all present hydrophobicity and a high initial adhesion of strain JM2-gfp. Matured robust biofilm formation occurred at 48 h on the root surfaces. The biofilm exhibited cell dense aggregates and biomass embedded in the extracellular polymeric substance (EPS) matrix. EPS composition results showed that the proteins, carbohydrates, lipids and nucleic acids are produced in the biofilm, while the content varied with rice species. Under the initial concentration of phenanthrene 50 mg·L−1, the residual phenanthrene in plant roots from ‘Zhengzhuhong’, ‘Koshihikari’ and ‘Liaojing401’ with biofilm mediated were significantly decreased by 71.9%, 69.3% and 58.7%, respectively, compared to those without biofilm groups after 10 days of exposure. Thus, the biofilm colonized on roots plays an important role of degradation in order to reduce the level of phenanthrene uptake of plants. Thereby, the present work provides significant new insights into lowering the environmental risks of polycyclic aromatic hydrocarbons (PAHs) in crop products from contaminated agriculture soils.

Optimization of Soil Remediation by Ozonation for PAHs Contaminated Soils

ABSTRACTSoil remediation is one of the most important issues in environmental engineering. In this study, the effect of phenanthrene, anthracene, and benz(a)anthracene chemical structures on their removal from different soil slurries were investigated. Also, the effects of initial pollution concentration, injected ozone, water content and processing time on soil remediation were examined by response surface methodology. In the optimized condition for the soil of industrial site, anthracene, phenanthrene, and benz(a)anthracene have 67.87%, 85.2%, and 45.9% removal efficiencies, respectively. Based on these results, better water solubility, and less fine-grained soil particles are contributors to more efficient soil remediation system by ozonation.Abbreviations: ANOVA: analysis of variance; RSM: response surface methodology; CCD: central composite design; PAHs: polycyclic aromatic hydrocarbons; ANT: anthracene; PHE: phenanthrene; BaA: benz(a)anthracene; Vw: water volume; InjO3: injected ozone; T: time; CANT: initial anthracene concentration; CPHE: initial phenanthrene concentration; Wt: Weight percentage; PGSEZ: persian gulf special economic zone

Ozone-encapsulated colloidal gas aphrons for in situ and targeting remediation of phenanthrene-contaminated sediment-aquifer

The hydrophobic polycyclic aromatic hydrocarbons (PAHs) are apt to adhere tightly to the sediments in aquifer and thus pose great threats to the aquatic environment of groundwater and surface water as well as human health. The present study constructed functionalized microbubbles, named colloidal ozone aphrons (COAs), by dissolving ozone-contained air into the nonionic surfactant (Tween-20) solution at the pressure of 300 kPa for the in situ remediation of phenanthrene (PHE)-contaminated sediments. The COA system aimed at improving the PHE elimination in terms of (i) enhancing the migration and transportation ability of the bubble system in the contaminated aquifer matrix, (ii) accurately desorbing the target hydrophobic contaminants from sediments, and (iii) reinforcing the in situ oxidation degradation immediately after or simultaneously when the PAHs are desorbed into the aqueous phase. Experimental results demonstrated that the COAs exhibited similar characteristics as the classical colloidal gas aphrons (CGAs), including the high stability (half-life time > 200 s), typical morphology and average bubble size (114–162 μm); higher air hold-up of COAs was achieved (i. e. > 20%) compared with the air-microbubbles (1–2%) obtained under the same generation conditions. Although the encapsulated ozone could oxidize the surfactant-layers, the properties and behaviors of COAs were not greatly affected. The surfactant multi-layers endowed the COAs with strong hydrophobic attraction with PHE, great migration capacity and enlarged oxidation area in the sediment matrix. Approximately 96.9% of PHE was removed from the sediments and 84.9% of the overall PHE was oxidized at the high ozone concentration of 0.6 mg/L when the initial PHE concentration was 240.0 μg/kg. The COA-involved remediation technology provided the insight of combining the processes of washing and oxidizing through adopting the particularly conceived microbubbles. The in situ and selective removal of hydrophobic organic contaminants from sediments in aquifer was well achieved in this study.

Desorption kinetics and isotherms of phenanthrene from contaminated soil.

Prediction of polycyclic aromatic hydrocarbons (PAHs) desorption from soil to estimate available fraction regarding to initial concentration of the contaminant is of great important in soil pollution management, which has poorly been understood until now. In the present study estimation of fast desorption fraction which is considered as available fraction was conducted by evaluating desorption kinetics of phenanthrene (a three ring PAH) from artificially contaminated soils through the mathematical models. Desorption rate of phenanthrene (PHE) was investigated by using the nonionic surfactant Tween80 in a series of batch experiments. The effects of reaction time from 5 to 1440min and initial PHE concentration in the range of 100-1600mg/kg were studied. Available fractions of the contaminant were achieved within the first hour of desorption process as the system reached to equilibrium conditions. Experimental data were examined by using kinetic models including pseudo-first-order, pseudo-second-order in four linearized forms, and fractional power. Among the models tested, experimental data were well described by pseudo-second-order model type (III) and (IV) and fractional power equation. Fast desorption rates, as Available fractions were determined 79%, 46%, 40%, 39%, and 35% for initial PHE concentrations of 100, 400, 800, 1200, and 1600mg/kg respectively. Among the evaluated isotherm models, including Freundlich, Langmuir in four linearized forms, and Temkin, the equilibrium data were well fitted by the first one. Applying the nonionic surfactant Tween80 is a useful method to determine available fraction of the contaminant. This method will provide the management of contaminated sites by choosing a proper technique for remediation and predicting achievable treatment efficiency.

A Stepwise-Cluster Inference Model for Phenanthrene Immobilization at the Aqueous/Modified Palygorskite Interface

A stepwise-cluster inference (SI) model was established through introducing stepwise-cluster analysis (SCA) into the phenanthrene immobilization process at the aqueous/modified palygorskite interface. SCA has the advantages of tackling the nonlinear relationships among environmental factors and the phenanthrene sorption amount in the immobilization process. The essence of SCA is to form a tree-based classification on a series of cutting or mergence procedures under given statistical criteria. The results indicated that SI could help develop a statistical relationship between environmental variables and the phenanthrene sorption amount, where discrete and nonlinear complexities exist. During the experiment, data were randomly sampled 10 times for model calibration and verification. The R2 (close to one) and root mean squared error (RMSE) (close to zero) values guaranteed the prediction accuracy of the model. Compared to other statistical methods, the calculation of R2 and RMSEs showed that SI was more straightforward for describing the nonlinear relationships and precisely fitting and predicting the immobilization of phenanthrene. Through the calculation of the input effects on the output in the SI model, the influence of environmental factors on phenanthrene immobilization were ranged in descending order as: initial phenanthrene concentration, ionic strength, pH, added humic acid dose, and temperature. It is revealed that SCA can be used to map the nonlinear and discrete relationships and elucidate the transport patterns of phenanthrene at the aqueous/modified palygorskite interface.

Removal of phenanthrene from coastal waters by green tide algae Ulva prolifera

Ulva prolifera (U. prolifera) has been frequently involved in terrible algal proliferation in coastal areas. Although it is known to be associated with green tide, its contribution to the natural attenuation of the polycyclic aromatic hydrocarbons (PAHs) in seawater has not been evaluated. In this study, the removal of phenanthrene using U. prolifera collected from coastal water with green tide blooming was investigated. The results showed that phenanthrene could be removed efficiently in the presence of both the live and heat-killed U. prolifera. The phenanthrene concentrations of the live algae treatment decreased smoothly from 10.00 to 0.80μgL−1 through the whole process, while those of the heat-killed algae treatment decreased sharply from 10.0 to 2.71μgL−1 in one day and kept constantly after that. The in situ monitoring and visualizing using laser confocal scanning microscopy (LCSM) confirmed the accumulation of phenanthrene in U. prolifera. The increase in nutrient and temperature led to the increase of phenanthrene removal rate, while the salinity had less influence on the removal of phenanthrene. The removal efficiency by U. prolifera had a good linear relationship with phenanthrene initial concentration (r2=0.999) even at 100μgL−1 which was higher than its environmentally relevant concentrations. High removal efficiency (91.3%) was observed when the initial phenanthrene concentration was set at environmental relevant concentration (5μgL−1). Results of this study demonstrate a potential new natural attenuation process for typical PAHs in coastal water during the outbreak of green tide. These findings indicate that the outbreak of harmful green tide algae may bring positive environmental benefits in the terms of the removal of harmful organic pollutants from coastal waters.

Biodegradation of PAHs in Soil: Influence of Initial PAHs Concentration

Most studies on biodegradation of Polycyclic Aromatic Hydrocarbons (PAHs) evaluate the effect of initial PAHs concentration in liquid medium. There are limited studies on evaluation in solid medium such as contaminated soil. This study investigated the potential of the bacteria, Corynebacterium urealyticum isolated from municipal sludge in degrading phenanthrene contaminated soil in different phenanthrene concentration. Batch experiments were conducted over 20 days in reactors containing artificially contaminated phenanthrene soil at different concentration inoculated with a bacterial culture. This study established the optimum condition for phenanthrene degradation by the bacteria under nonindigenous condition at 500 mg/kg of initial phenanthrene concentration. High initial concentration required longer duration for biodegradation process compared to low initial concentration. The bacteria can survive for three days for all initial phenanthrene concentrations.

Potential of Endophytic Bacterium Paenibacillus sp. PHE-3 Isolated from Plantago asiatica L. for Reduction of PAH Contamination in Plant Tissues.

Endophytes are ubiquitous in plants, and they may have a natural capacity to biodegrade polycyclic aromatic hydrocarbons (PAHs). In our study, a phenanthrene-degrading endophytic Paenibacillus sp. PHE-3 was isolated from P. asiatica L. grown in a PAH-contaminated site. The effects of environmental variables on phenanthrene biodegradation by strain PHE-3 were studied, and the ability of strain PHE-3 to use high molecular weight PAH (HMW-PAH) as a sole carbon source was also evaluated. Our results indicated that pH value of 4.0–8.0, temperature of 30 °C–42 °C, initial phenanthrene concentration less than 100 mg·L−1, and some additional nutrients are favorable for the biodegradation of phenanthrene by strain PHE-3. The maximum biodegradation efficiency of phenanthrene was achieved at 99.9% after 84 h cultivation with additional glutamate. Moreover, the phenanthrene biodegradation by strain PHE-3 was positively correlated with the catechol 2,3-dioxygenase activity (ρ = 0.981, p < 0.05), suggesting that strain PHE-3 had the capability of degrading HMW-PAHs. In the presence of other 2-, 3-ringed PAHs, strain PHE-3 effectively degraded HMW-PAHs through co-metabolism. The results of this study are beneficial in that the re-colonization potential and PAH degradation performance of endophytic Paenibacillus sp. PHE-3 may be applied towards reducing PAH contamination in plants.