Phenanthrene In Soil Research Articles

Impact mechanisms of various surfactants on the biodegradation of phenanthrene in soil: Bioavailability and microbial community responses

The present study was conducted to systematically explore the mechanisms underlying the impact of various surfactants (CTAB, SDBS, Tween 80 and rhamnolipid) at different doses (10, 100 and 1000 mg/kg) on the biodegradation of a model polycyclic aromatic hydrocarbon (PAH) by indigenous soil microorganisms, focusing on bioavailability and community responses. The cationic surfactant CTAB inhibited the biodegradation of phenanthrene within the whole tested dosage range by decreasing its bioavailability and adversely affecting soil microbial communities. Appropriate doses of SDBS (1000 mg/kg), Tween 80 (100, 1000 mg/kg) and rhamnolipid at all amendment levels promoted the transformation of phenanthrene from the very slow desorption fraction (Fvslow) to bioavailable fractions (rapid and slow desorption fractions, Frapid and Fslow), assessed via Tenax extraction. However, only Tween 80 and rhamnolipid at these doses significantly improved both the rates and extents of phenanthrene biodegradation by 22.1–204.3 and 38.4–76.7 %, respectively, while 1000 mg/kg SDBS had little effect on phenanthrene removal. This was because the inhibitory effects of anionic surfactant SDBS, especially at high doses, on the abundance, diversity and activity of soil microbial communities surpassed the bioavailability enhancement in dominating biodegradation. In contrast, the nonionic surfactant Tween 80 and biosurfactant rhamnolipid enhanced the bioavailability of phenanthrene for degradation and also that to specific degrading bacterial genera, which stimulated their growth and increased the abundance of the related nidA degradation gene. Moreover, they promoted the total microbial/bacterial biomass, community diversity and polyphenol oxidase activity by providing available substrates and nutrients. These findings contribute to the design of suitable surfactant types and dosages for mitigating the environmental risk of PAHs and simultaneously benefiting microbial ecology in soil through bioremediation.

Determination of soil phenanthrene degradation through a fungal-bacterial consortium.

Fungal-bacterial consortia enhance organic pollutant removal, but the underlying mechanisms are unclear. We used stable isotope probing (SIP) to explore the mechanism of bioaugmentation involved in polycyclic aromatic hydrocarbon (PAH) biodegradation in petroleum-contaminated soil by introducing the indigenous fungal strain Aspergillus sp. LJD-29 and the bacterial strain Pseudomonas XH-1. While each strain alone increased phenanthrene (PHE) degradation, the simultaneous addition of both strains showed no significant enhancement compared to treatment with XH-1 alone. Nonetheless, the assimilation effect of microorganisms on PHE was significantly enhanced. SIP revealed a role of XH-1 in PHE degradation, while the absence of LJD-29 in 13C-DNA indicated a supporting role. The correlations between fungal abundance, degradation efficiency, and soil extracellular enzyme activity indicated that LJD-29, while not directly involved in PHE assimilation, played a crucial role in the breakdown of PHE through extracellular enzymes, facilitating the assimilation of metabolites by bacteria. This observation was substantiated by the results of metabolite analysis. Furthermore, the combination of fungus and bacterium significantly influenced the diversity of PHE degraders. Taken together, this study highlighted the synergistic effects of fungi and bacteria in PAH degradation, revealed a new fungal-bacterial bioaugmentation mechanism and diversity of PAH-degrading microorganisms, and provided insights for in situ bioremediation of PAH-contaminated soil.IMPORTANCEThis study was performed to explore the mechanism of bioaugmentation by a fungal-bacterial consortium for phenanthrene (PHE) degradation in petroleum-contaminated soil. Using the indigenous fungal strain Aspergillus sp. LJD-29 and bacterial strain Pseudomonas XH-1, we performed stable isotope probing (SIP) to trace active PHE-degrading microorganisms. While inoculation of either organism alone significantly enhanced PHE degradation, the simultaneous addition of both strains revealed complex interactions. The efficiency plateaued, highlighting the nuanced microbial interactions. SIP identified XH-1 as the primary contributor to in situ PHE degradation, in contrast to the limited role of LJD-29. Correlations between fungal abundance, degradation efficiency, and extracellular enzyme activity underscored the pivotal role of LJD-29 in enzymatically facilitating PHE breakdown and enriching bacterial assimilation. Metabolite analysis validated this synergy, unveiling distinct biodegradation mechanisms. Furthermore, this fungal-bacterial alliance significantly impacted PHE-degrading microorganism diversity. These findings advance our understanding of fungal-bacterial bioaugmentation and microorganism diversity in polycyclic aromatic hydrocarbon (PAH) degradation as well as providing insights for theoretical guidance in the in situ bioremediation of PAH-contaminated soil.

Ultrasonically activated persulfate process for the degradation of phenanthrene in soil-washing effluent: Experimental, DFT calculation and toxicity evaluation

Soil-washing (SW) has been widely used to treat PHE in soil, but this has led to the problem of large quantities of contaminated soil-washing effluent (SWE) that are difficult to treat effectively. The primary objective of this study was to investigate the degradation of phenanthrene (PHE) in SWE with Alkyl glycoside (APG) as a surfactant through the implementation of ultrasound (US)/persulfate (PS) oxidation technique. The findings of the study demonstrated the effectiveness of the US/PS system in facilitating the degradation of PHE, with the degradation process accurately described by a first-order kinetic model. With the reaction conditions optimized, an impressive degradation efficiency of 79.8% was achieved for PHE. Notably, the presence of common water components such as Cl-, HCO3-, H2PO4-, and HA had an impact on the degradation process. The degradation mechanism and degradation pathways of PHE were determined by free radical burst test, electron paramagnetic resonance (EPR), density functional theory (DFT) calculations gas chromatography/mass spectrometry (GC/MS) tests, and the eco-toxicological evaluation of PHE and its intermediates was carried out by using ECOSAR software. Most importantly, physicochemical properties were analysed, structural characterisation and DFT calculations were carried out for the high concentration of APG compounds in the solution environment throughout the degradation process. The result showed that as the reaction progressed, the degradation radicals only opened the APG structure and degraded the PHE encapsulated in it. However, the APG compound itself showed little change. These comprehensive investigations contribute novel insights into the green and efficient treatment of PHE-containing SWE.

Visualization of phenanthrene effect on biochar colloids transport in porous media

Biochar colloids (BCs) can be used as adsorbent materials for remediation of phenanthrene due to their high specific surface area and other characteristics. Understanding the effects of phenanthrene on the transport of BCs contributes to facilitate the removal of phenanthrene in soil and water habitats. In this work, the influence of phenanthrene on the transport of BCs under different environmental factors (pH, ionic strength (IS), media size) in a one-dimensional sand column was firstly explored together with a real-time visualization system to explore the transport mechanism of BCs in two-dimensional sand tank. The results show that phenanthrene adsorbed on the surface of BCs, shielded its surface charge and reduced the mobility of BCs in porous media. Acidic conditions promoted the agglomeration of BCs and adsorption of phenanthrene, resulting in a 51.03 % decrease in the maximum breakthrough rate of BCs compared to alkaline conditions. The same was true for the high IS condition, where the maximum breakthrough rate of BCs was only 0.95 % at IS = 50. Additionally, there was a substantial and positive correlation between media particle size and BCs mobility. As the quartz sand particle size increased, the maximum breakthrough rates of BCs were 2.67 %, 33.28 %, and 52.27 % in the 1-D experiment, and 0, 13.88 %, and 13.10 % in the 2-D experiment, respectively. The contact area of BCs with the medium expands under the fine particle size condition, leading to a significant decrease in the mobility of BCs at low potentials influenced by phenanthrene. This finding is significant for biochar application in phenanthrene contaminated soil and groundwater remediation.

A machine learning and experimental-based model for prediction of soil sorption capacity toward phenanthrene

Sorption by soil is the fundamental basis for environment fate of hydrophobic organic contaminants (HOCs), which varies significantly depending on diverse properties of soils. Therefore, a generalized approach to predict HOC sorption by soils is required. In this study, 488 data points were extracted from references and adopted to develop models for estimating the sorption capacities of phenanthrene in soils using six different machine learning (ML) approaches. The extreme gradient boosting (XGBT) model demonstrated the most favorable performance, achieving a coefficient of determination of 0.91 and root-mean-square errors of 0.24 for the testing dataset. The XGBT model's performance was further demonstrated by comparing with experimental data from batch sorption tests conducted on 20 soil samples collected from 17 provinces of China. The differences between the predicted values and the experimental values were statistically equal to zero (p = 0.14). Leveraging the XBGT model together with soil properties from the Harmonized World Soil Database, the distribution of sorption capacities in Chinese soils was successfully depicted on a national scale. This research is expected to contribute to a deeper understanding of the migration of persistent organic pollutants in terrestrial system. Furthermore, the established model holds implications for more precise and scientific soil environmental management.

Flexoelectricity in hydroxyapatite for the enhanced piezocatalytic degradation of phenanthrene in soil

Hydroxyapatite@fluorapatite prepared by ion exchange shows enhanced piezoelectric properties via flexoelectricity arising from the chemical heterogeneities in the crystal lattice.

Laccase as a useful assistant for maize to accelerate the phenanthrene degradation in soil.

Polycyclic aromatic hydrocarbon (PAH) pollution has attracted much attention due to their wide distribution in soil environment and serious harm to human health. In order to establish an efficient and eco-friendly technology for remediation of PAH-contaminated soil, phytoremediation utilizing maize assisted with enzyme remediation was explored in this study. The results showed that the participation of laccase could promote the degradation of phenanthrene (PHE) from soil and significantly reduce the accumulation of PHE in maize. The degradation efficiency of PHE in soil could reach 77.19% under laccase-assisted maize remediation treatment, while the accumulation of PHE in maize roots and leaves decreased by 41.23% and 74.63%, respectively, compared to that without laccase treatment, after 24days of maize cultivation. Moreover, it was found that laccase addition shifted the soil microbial community structure and promoted the relative abundance of some PAH degrading bacteria, such as Pseudomonas and Sphingomonas. In addition, the activities of some enzymes that were involved in PAH degradation process and soil nutrient cycle increased with the treatment of laccase enzyme. Above all, the addition of laccase could not only improve the removal efficiency of PHE in soil, but also alter the soil environment and reduce the accumulation of PHE in maize. This study provided new perspective for exploring the efficiency of the laccase-assisted maize in the remediation of contaminated soil, evaluating the way for reducing the risk of secondary pollution of plants in the phytoremediation process.

The effects of Cu-phenanthrene co-contamination on adsorption-desorption behaviors of phenanthrene in soils

Polycyclic aromatic hydrocarbons (PAHs) are persistent organic pollutants in the environment, which are teratogenic, carcinogenic, and mutagenic. Co-contamination of PAHs and heavy metal commonly exists in soil. In this study, 20 types of soils with different properties in China were collected and comprehensively characterized. Phenanthrene (Phe) and Cu (II) were selected as representatives of PAHs and heavy metals, respectively. The adsorption-desorption behaviors of Phe under Phe contamination and Cu (II)-Phe co-contamination in 20 types of soils were studied. The adsorption-desorption behaviors of Phe in 20 types of soils varied greatly, and adsorption of Phe in the soils followed both linear partitioning and nonlinear surface adsorption. Soil organic matter (SOM) plays an important role in the adsorption-desorption behavior of Phe. When the concentrations of Phe were >50 μg/L, soft carbon (SC) fraction of SOM not black carbon (BC) contributed more to the adsorption of Phe. Soil dissolved organic matter (DOM), especially fulvic acid and humic acid fractions, contributes to the adsorption of Phe. Under the effect of Cu (II) (60 mg/L in solution), the adsorption capacity of soil for Phe increased, which possibly resulted from lowered pH, the existence of the cation-π bonding and the "bonding bridge" effect. The systematic investigation of adsorption-desorption behaviors of Phe in soils under heavy metal-PAHs co-contamination will provide a scientific basis for the calculation of soil environmental capacity in the future.

Mechanism of synergistic remediation of soil phenanthrene contamination in paddy fields by rice-crab coculture and bioaugmentation with Pseudomonas sp.

Polycyclic aromatic hydrocarbons (PAHs) are persistent and harmful pollutants with high priority concern in agricultural fields. This work constructed a rice-crab coculture and bioaugmentation (RCM) system to remediate phenanthrene (a model PAH) contamination in rice fields. The results showed that RCM had a higher remediation performance of phenanthrene in rice paddy compared with rice cultivation alone, microbial addition alone, and crab-rice coculture, reaching a remediation efficiency of 88.92 % in 42 d. The concentration of phenanthrene in the rice plants decreased to 6.58 mg/kg, and its bioconcentration effect was efficiently inhibited in the RCM system. In addition, some low molecular weight organic acids of rice root increased by 12.87 %∼73.87 %, and some amino acids increased by 140 %∼1150 % in RCM. Bioturbation of crabs improves soil aeration structure and microbial migration, and adding Pseudomonas promoted the proliferation of some plant growth-promoting rhizobacteria (PGPRs), which facilitated the degradation of phenanthrene. This coupling rice-crab coculture with bioaugmentation had favorable effects on soil enzyme activity, microbial community structure, and PAH degradation genes in paddy fields, enhancing the removal of and resistance to PAH contamination in paddy fields and providing new strategies for achieving a balance between production and remediation in contaminated paddy fields.

Regulating the electrokinetic delivery of Tween 80 and persulfate for remediating low-permeability phenanthrene contaminated soil: Importance of reducing unproductive consumption

Controllable delivery of persulfate (PS) and the enhancement of oxidative availability of pollutants in in-situ oxidative remediation of low-permeability polycyclic aromatic hydrocarbons (PAHs) contaminated soil are crucial. To tackle the above challenges, the coupling of Tween 80 solubilization enhanced oxidation of phenanthrene (PHE) in low-permeability soil under electrokinetic remediation (EKR) was proposed. Firstly, batch degradation experiments showed that the addition of Tween 80 significantly inhibited the degradation of PHE in soil under thermally activated PS, as the dosage of Tween 80 increased from 0 % to 1 % with the corresponding removal rate declining from 99.19 % to 40.90 %. Accordingly, in-situ electrokinetic delivery of Tween 80 and PS was regulated in further EKR, intending to reduce unproductive consumption. PS was more uniformly delivered to the whole remediation regions from the cathode chamber by electromigration, while Tween 80 was transported into the soil from the anode chamber by electroosmosis, which made Tween 80 solubilization and PS oxidation achieve synergistic effect. And the total removal rate of PHE reached 64.90 % under this strategy, which had increased by 415.90 % and 8.76 %− 130.14 % compared with only EKR or EKR coupling single enhanced technology, respectively. After further thermal activation of transported PS at 50 ℃ by electrical resistance heating, the total removal rate of PHE increased to 71.58 %. EPR spectrum indicated that SO4.- and OH. were responsible for the degradation of PHE.

Role of direct current on thermal activated peroxydisulfate to degrade phenanthrene in soil: Conversion of sulfate radical and hydroxyl radical to singlet oxygen, accelerated degradation rate and reduced efficiency

Electrokinetic (EK) delivery followed by thermal activated peroxydisulfate (PS) has turned out to be a potential in situ chemical oxidation technology for soil remediation, but the activation behavior of PS in an electrical coupled thermal environment and the effect of direct current (DC) intervention on PS in heating soil has not been explored. In this paper, a DC coupled thermal activated PS (DC-heat/PS) system was constructed to degrade Phenanthrene (Phe) in soil. The results indicated that DC could force PS to migrate in soil, changing the degradation rate-limiting step in heat/PS system from PS diffusion to PS decomposition, which greatly accelerated the degradation rate. In DC/PS system, 1O2 was the only reactive species directly detected at platinum (Pt)-anode, confirming that S2O82- could not directly obtain electrons at the Pt-cathode to decompose into SO4•-. By comparing DC/PS and DC-heat/PS system, it was found that DC could significantly promote the conversion of SO4•- and •OH generated by thermal activation of PS to 1O2, which was attributed to the hydrogen evolution caused by DC that destroys the reaction balance in system. It was also the fundamental reason that DC leaded to the reduction of oxidation capacity of DC-heat/PS system. Finally, the possible degradation pathways of phenanthrene were proposed on the basis of seven detected intermediates.

A strategy to reduce the effect of organic matter on fluorescence intensity for improving the detection accuracy of polycyclic aromatic hydrocarbons in soil

Fluorescence spectroscopy has been used for rapid detection of PAHs in soil, but soil organic matter (SOM) produces strong interference to the fluorescence intensity of PAHs, which restricts the application of fluorescence spectroscopy for rapid detection of PAHs in soil. A correction method of reducing the interference of SOM on PAHs fluorescence intensity was proposed combining fluorescence and near-infrared (NIR) spectroscopy. Six soil samples with different concentrations of humic acid (HA) at a given phenanthrene concentration (5 mg/g) were prepared and scanned for obtaining the fluorescence and NIR diffuse reflectance spectra. The spectral data showed that the fluorescence intensity and NIR diffuse reflectance had an approximate trend with the change of HA concentration. It was found that the NIR diffuse reflection at 4672 cm−1 as a calibration factor could effectively reduce the interference of HA on the fluorescence intensity of phenanthrene. Subsequently, a standard curve for the quantitative analysis of phenanthrene in soil was established based on the fluorescence intensity before and after calibration. For the unknown samples, the predicted average relative errors of the standard curves before and after calibration were 27.46 % and 9.00 %, respectively. The results showed that the proposed correction method could reduce the interference of HA on the quantitative analysis of PAHs, and provide a reference for eliminating the interference constraint of fluorescence spectroscopy technique for rapid real-time detection of PAHs in soil.

Impact of biochar coexistence with polar/nonpolar microplastics on phenanthrene sorption in soil

Microplastics and biochar normally coexist in soil. In this study, two microplastics of different polarities (nonpolar polyethylene (PE) and polar polybutylene adipate-co-terephthalate (PBAT)) and two wheat straw biochars produced at 400 (W4) and 700 °C (W7) were selected to investigate the sorption behaviors of phenanthrene in soil where microplastics and biochar coexisted. The results showed that the presence of PE more significantly weakened the adhesion of soil particles onto biochar than the presence of PBAT. Meanwhile, the presence of biochar enhanced the soil particle attachment on the microplastic surface. As a result, the sorption behavior of phenanthrene was significantly different in soil where biochar coexisted with microplastics of different polarities. The Koc values of PE-biochar-soil mixtures at Ce= 0.005 Cs were up to 42 % lower than those of PBAT-biochar-soil mixtures, which is related to lower micropore area of particles isolated from the former. However, at Ce = 0.05 Cs and 0.5 Cs, the Koc values of PE-biochar-soil mixtures were up to 1.4 times higher than those of PBAT-biochar-soil mixtures because of a more significant reduction in biochar surface polarity when it coexisted with nonpolar PE.

Quantitative analysis of phenanthrene in soil by fluorescence spectroscopy coupled with the CARS-PLS model.

Polycyclic aromatic hydrocarbons (PAHs) are typical organic pollutants in soil and are teratogenic and carcinogenic. Therefore, rapid and accurate analysis of PAHs in soil can provide a theoretical basis and data support for soil contamination risk assessment. In this work, a fluorescence spectroscopy technique combined with partial least squares (PLS) was proposed for rapid quantitative analysis of phenanthrene (PHE) in soil. At first, the fluorescence spectra of 29 soil samples with different concentrations (0.3-10 mg g-1) of PHE were collected by RF-5301 PC fluorescence spectrophotometer. Secondly, the effects of different spectral preprocessing methods were investigated on the prediction performance of the PLS calibration model. And then, the influence of competitive adaptive reweighted sampling (CARS) wavelength points on the prediction performance of PLS calibration model was discussed. Finally, according to the selected wavelength points, a quantitative analytical model for PHE content in soil was constructed using the PLS calibration method. To further explore the predictive performance of the CARS-PLS calibration model, the predictive results were compared with those of the RAW spectrum-partial least squares calibration model (RAW-PLS) and the wavelet transform-standard normal variation (WT-SNV) calibration model. The CARS-PLS calibration model showed the optimal predictive performance and its coefficient of determination of cross-validation (R cv 2) and root mean square error of 10-fold cross-validation (RMSEcv) were 0.9957 and 18.98%, respectively. The coefficient of determination of prediction set (R p 2) and root mean square error of prediction set (RMSEp) were 0.9963 and 16.13%, respectively. Hence, the CARS algorithm based on fluorescence spectrum coupled with PLS can give a rapid and accurate quantitative analysis of the PHE content in soil.

Application of a Zero-Valent Iron/Cork as Permeable Reactive Barrier for In Situ Remediation of Phenanthrene in Soil

This paper proposes an eco-efficient treatment technology for removing phenanthrene (PHE) from kaolinite soil, incorporating a permeable reactive barrier (PRB) in an electrokinetic (EK) remediation system, which was made by modifying the granulated cork (GC) with Fe@Fe2O3, identified as EK/Fe@Fe2O3/GC. The novel product Fe@Fe2O3/GC was characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, and element mapping. EK tests were conducted to investigate the performance of the EK/Fe@Fe2O3/GC for removal of PHE from soil. The results showed that PHE was driven by the electro-osmotic flow toward the cathode and reacted with the EK/Fe@Fe2O3/GC. Further, the removal efficiency of PHE in the soil was higher in the presence of H2O2 due to the additional reactions achieved. The results were discussed in light of the existing literature.

Analysis of influencing factors of phenanthrene adsorption by different soils in Guanzhong basin based on response surface method

Adsorption desorption is an important behavior affecting the migration of phenanthrene in soil. In this study, three typical soils of loess, silts and silty sand in Guanzhong Basin, Shaanxi Province, China were used as adsorbents. Batch equilibrium experiments were carried out to study the adsorption desorption kinetics and isotherm of phenanthrene in different soils. Response surface method (RSM) was used to study the effects of temperature, pH, phenanthrene concentration and organic matter content on soil adsorption of phenanthrene. The results showed that after adsorption, the outline of soil particles became more blurred and the degree of cementation increased. The kinetic adsorption of phenanthrene by soil conforms to the quasi second-order kinetic model, and the adsorption desorption isotherm is nonlinear and conforms to the Freundlich model. Due to the difference of soil properties, the adsorption amount of phenanthrene by soil is loess > silty sand > silts. The thermodynamic results show that the adsorption of phenanthrene by soil is spontaneous and endothermic, and the desorption is spontaneous and exothermic. Through RSM, the interaction between phenanthrene concentration and soil organic matter in Loess and silts is significant, and the interaction between temperature and soil organic matter in silty sand is significant. Among the four factors affecting the adsorption rate of loess, silts and silty sand, soil organic matter is the most significant. The theoretical optimum adsorption rates of loess, silts and silty sand are 98.89%, 96.59% and 93.37% respectively.

Insight into the Soil Dissolved Organic Matter Ligand-Phenanthrene-Binding Properties Based on Parallel Faction Analysis Combined with Two-Dimensional Correlation Spectroscopy.

Dissolved organic matter (DOM) can strongly bind to organic contaminants and control phenanthrene in soil. Herein, four individual parallel factor analysis (PARAFAC) components were found in soil DOM. Component C1 was the humic-like component ligand T, and component C2 was a combination of humic fluorophore ligands M1 and M2. Furthermore, components C3 and C4 were characterized as terrestrial and ubiquitous humic substances. Then, the modified Stern-Volmer complexation model was used to reveal soil DOM component-phenanthrene-binding properties. The overall binding characteristics of a PARAFAC component could not express the phenanthrene-binding properties. Therefore, two-dimensional correlation spectroscopy was used to reveal DOM ligand-phenanthrene-binding properties. After binding with phenanthrene, DOM ligands T, M2, A2, and C1 were quenched but DOM ligands M1, A1, and C2 were excited. The ligands with higher humification presented higher phenanthrene-binding ability. With these promising results, the DOM ligand-phenanthrene-binding characteristics offered theoretical support for soil pollution control.

Effects of biodegradable and non-degradable microplastics on microbial availability and degradation of phenanthrene in soil

Biodegradable plastics have been increasingly used, however, may decompose into microplastics (MPs) more quickly than traditional plastics. In this study, biodegradable polybutylene adipate-co-terephthalate (PBAT) MPs were selected, and non-degradable polyethylene (PE) was used as the reference MPs. The impact of PBAT and PE MPs on microbial availability and degradation of phenanthrene in soil was investigated. The results showed that both the type and addition amount (0.2 % and 2 %, w/w) of MPs significantly affected phenanthrene degradation. Degradation ratio was reduced by the addition of MPs (by 10.6–80.2 %), which was in the order of soil with PBAT > soil with aged PE > soil with PE no matter whether earthworms were present or not. Moreover, compared to PE, addition of PBAT more significantly decreased the concentration of phenanthrene in porewater and the polycyclic aromatic hydrocarbon (PAH)-degrader abundance, which is due to higher sorption affinity of phenanthrene to PBAT and more significant increase in the content of dissolved organic carbon in soil with PBAT, respectively. Additionally, compared to soil without MPs, phenanthrene degradation in soil with MPs was more significantly raised by the presence of earthworms, which is due to a more significant increase in the PAH-degrader abundance.

Migration Behavior and Influencing Factors of Petroleum Hydrocarbon Phenanthrene in Soil around Typical Oilfields of China

Petroleum spills and land contamination are becoming increasingly common around the world. Polycyclic aromatic hydrocarbons (PAHs) and other pollutants found in petroleum are constantly migrating underground, making their migration in soil a hot research topic. Therefore, it is of great significance to evaluate the migratory process of petroleum hydrocarbons in petroleum-polluted soil to clarify its ecological and environmental risks. In this study, Phenanthrene (PHE) was used as a typical pollutant of PAHs. The soil was gathered from three typical oilfields in China, and a soil column apparatus was built to simulate the vertical migration of PHE in the soil. The migration law and penetration effect of PHE in various environmental conditions of soil were investigated by varying the ionic strength (IS), pH, particle size, and type of soil. According to the literature, pH has no discernible effect on the migration of PHE. The migration of PHE was adversely and positively linked with changes in IS and soil particle size, respectively. The influence of soil type was mainly manifested in the difference of organic matter and clay content. In the Yanchang Oilfield (YC) soil with the largest soil particle size and the least clay content, the mobility of PHE was the highest. This study may reveal the migration law of PAHs in soils around typical oilfields, establish a new foundation for PAH migration in the soil, and also provide new ideas for the management and control of petroleum pollution in the soil and groundwater.

Biodegradation of Phenanthrene Polluted Soil through Native Strains in the Darkhouvin Oil Field

As a resistant and toxic polycyclic aromatic hydrocarbon (PAHs), phenanthrene is largely distributed in aquatic and terrestrial environments with adverse biological consequences. Mineralization of this toxic component via bioremediation has been vastly studied in recent years and might lead to new hope in the economic clean-up of this contaminant. The aim of this study was the isolation and identification of phenanthrene degrading bacteria from petroleum polluted environments and the assessment of their growth kinetics. Soil samples were collected from the oil-polluted sites of Darkhouvin oilfield, Iran. Bacterial isolates capable of degrading phenanthrene were characterized genetically and morphologically. Optimal level of environmental parameters including pH, time, temperature, nitrogen and phosphate source, and phenanthrene concentration were determined using Taguchi method. The results showed that different bacterial genera were isolated in which Bacillus mojavensis and Lysinibacillus sphaericus were identified as phenanthrene degrading isolates. Isolated strains showed hemolytic activity and deceased surface tension values. The optimal condition was determined as 45 °C, pH 7, nitrate 1 µg/mL, sodium phosphate 0.3 µg/mL, and on the fifth day of culturing for B. mojavensis, which showed prominent activity in phenanthrene biodegradation. In this study, the ability of native strains on the biodegradation of phenanthrene in soil was investigated. The findings suggest that isolated biosurfactant generating bacteria could biodegrade phenanthrene in optimum conditions.