Naphthalene Degradation Research Articles

Enhanced Remediation of Phenanthrene and Naphthalene by Corn-Bacterial Consortium in Contaminated Soil.

The persistent and hazardous nature of polycyclic aromatic hydrocarbons (PAHs) released into the soil has become a critical global concern, contributing to environmental pollution. In this study, the removal efficiency of phenanthrene and naphthalene degradation by complex flora or pure bacteria combined with corn and their effects on the growth of corn, pH, and the number of soil bacteria were investigated using a pot experiment. The results indicate that the corn remediation method (P) outperformed degrading bacteria remediation (B) for phenanthrene, yet the combination (PB) exhibited significantly higher removal efficiency. The degradation efficiency of PB methods increased over time, ranging from 58.40% to 75.13% after 30 days. Naphthalene removal showed a similar trend. Soil pH, influenced by remediation methods, experienced slight but non-significant increases. The number of degrading bacteria increased with combined methods, notably with PB-W1 and PB-W2 treatments. Corn accumulated phenanthrene and naphthalene, with higher concentrations in roots. Remediation by the combined corn and degrading bacteria slightly increased PAH accumulation, indicating potential root protection. Biomass yield analysis revealed the inhibitory effects of PAHs on corn growth, decreased by degrading bacteria. PB-W1 and PB-EF3 demonstrated the highest fresh weight and moisture content for stem and leaf biomass, while PB-F2-6 excelled in root biomass. Overall, combined remediation methods proved more effective, which underscores the potential of the corn and degrading bacteria consortium for efficient PAH remediation in contaminated soil.

Overload of dissolved organic matter (DOM) in riparian infiltration zone increasing the pollution risk of naphthalene, insight from the competitive inhibition of naphthalene biodegradation by DOM.

Riparian infiltration zones are crucial for maintaining water quality by reducing the aqueous concentrations of polycyclic aromatic hydrocarbons (PAHs) through adsorption and biodegradation within the aquatic ecosystem. Dissolved organic matter (DOM) are ubiquitous in riparian infiltration zones where they extensively engage in the adsorption and biodegradation of PAHs, thereby influencing PAHs natural attenuation potential within riparian infiltration zones. Few studies have explored the natural attenuation mechanisms of PAHs influenced by DOM in riparian infiltration zones. In this study, the natural attenuation mechanisms of naphthalene (a typical PAHs component), under the influence of DOM, were explored, based on a case riverside source area. Analysis of microbial community structures, and the electron acceptor (e.g., Fe(III), DO/NO3-, SO42-)/electron donor (naphthalene and DOM) concentration changes within the riparian infiltration zone revealed a competitive inhibition relationship between DOM and naphthalene during microbial metabolism. Biodegradation experiments showed that when the concentration of DOM is higher than 4.0 mg·L-1, it inhibits the biodegradation of naphthalene. DOM competitively inhibits the biodegradation of naphthalene through the following mechanisms: (i) triggering microbial antioxidative defense mechanisms, diminishing the available resources for microbial participation in naphthalene degradation; (ii) altering microbial community structure; (iii) modulating microbial EPS composition, reducing the efficiency of microorganisms in utilizing carbon sources; and (iv) inhibiting the expression levels of downstream genes involved in naphthalene degradation. The competitive inhibition constants of DOM with concentrations of 1.0, 2.0, 4.0, 8.0, and 16.0 mg·L-1 on naphthalene biodegradation are -2.0 × 10-3, -5.0 × 10-3,1.0 × 10-3, 4.0 × 10-4, and 1.0 × 10-4, respectively. These findings enhance understanding of PAHs attenuation in riparian infiltration zone, providing a basis for assessing and managing PAHs pollution risks during riparian extraction.

Photocatalytic Luminous Textiles for the Treatment of Wastewater Issued from Petroleum Activity: Photocatalytic Process Extrapolation

In this study, the degradation of naphthalene in water was performed via photocatalysis with two different configurations: UV-irradiated TiO2 deposited on cellulosic tissue and photocatalytic luminous textiles. The photocatalytic performance of these configurations was evaluated in terms of pollutant removal and mineralization yield. Moreover, the influence of key operating parameters, such as the initial pollutant concentration, solution turbidity, the number of tissues, and the type of irradiation, was investigated. The results showed a complete removal of 8 mg/L of naphthalene with photocatalytic luminous textiles after 4 h of UV irradiation, with a mineralization yield of 80%. The impact of the turbidity shows that at 90 NTU, reductions in photocatalytic activity of 30% and 10% were recorded for the UV-irradiated TiO2 deposed on cellulosic tissue and photocatalytic luminous textiles, respectively. The reactive oxygen species (ROS) concentrations were monitored during photocatalysis to better understand the contribution of each active species in the mechanism reaction of naphthalene oxidation. The results show that the hydroxyl radical (•OH) is responsible for 70% of pollutant oxidation. A scaling up of the water treatment with photocatalytic luminous textiles was performed. The extrapolation confirmed the same trends observed at the laboratory scale in terms of degradation and mineralization.

Photocatalytic degradation of naphthalene, using various nanocomposite materials mostly based on metal oxides

Photocatalytic degradation of naphthalene, using various nanocomposite materials mostly based on metal oxides

Lignin-derived compounds assisted with Kocuria marina H-2 and Pseudomonas putida B6-2 co-culture enhanced naphthalene biodegradation

The implementation of environmentally friendly and sustainable remediation strategies positively impacts solid waste management. In this study, the Kocuria marina H-2 and Pseudomonas putida B6-2 co-culture system demonstrated enhanced naphthalene biodegradation efficiency compared to single-strain cultures. Under optimal conditions of 35 °C, 200 rpm/min, and a 1:1 ratio of the co-culture system, the naphthalene biodegradation potential was further increased. Notably, the addition of both ethylenediamine-pretreated lignin and p-hydroxybenzoic acid significantly elevated naphthalene degradation rates to 68.5 %. In addition, the oil-liquid surface tension decreased, while cell surface hydrophobicity and colony-forming units increased with the addition of lignin-derived compounds. The modification of naphthalene bioavailability by ethylenediamine-pretreated lignin would accelerate the uptake and transport of hydrocarbons via ABC transporters and flagellar assembly. Importantly, genes related to bacterial chemotaxis and fatty acid biosynthesis were upregulated during the co-metabolism of naphthalene and p-hydroxybenzoic acid, further enhancing naphthalene bioconversion.

Green biosynthesis of Ag-doped hetero-metallic oxide nanocomposite for efficient sunlight-driven photo-adsorptive degradation of carcinogenic naphthalene and phenanthrene

One of the most significant issues facing the world today is environmental contamination due to the polycyclic aromatic hydrocarbons, or PAHs release of reactive chemicals into the environment. Here, a green technology was used to synthesis the Ag doped Bi2O3@Co3O4 nanocomposite utilizing an extract from Azadirachta indica leaves. The morphological and structural examination of Ag doped Co3O4@Bi2O3 revealed an image in the form of a hollow spherical or flake adsorbed on a Ag surface with an increase surface area. New peaks in the FT-IR spectra of Ag–O and Co–O–Bi at 678 cm−1 and 1130 cm−1, respectively, show the coupling of Ag. Following this, under various reaction conditions (pollutant: 10–30 mg/L; catalyst: 10–30 mg; pH: 3–11, dark sunlight) the doped nanocomposite was assessed for the efficient removal of NAP and PHE. Ag doped Co3O4@Bi2O3 displayed maximum degradation of NAP (96 %) and PHE (94 %) at 10 mg/L conc. of each PAH with a 25 mg catalytic dose at neutral pH in the presence of direct sunlight. First-order kinetics followed by initial Langmuir adsorption constituted the degradation process. Predominant reactive species and safer metabolite formation in the photocatalysis process of PAHs were studied by scavenger and GC–MS analysis. The green nano photocatalyst that was created demonstrated excellent stability, sensitivity, and reusability (up to 8th cycles) during the degrading process, which likely qualified it for use in industrial uses.

The evolution of autonomy from two cooperative specialists in fluctuating environments

From microbes to humans, organisms perform numerous tasks for their survival, including food acquisition, migration, and reproduction. A complex biological task can be performed by either an autonomous organism or by cooperation among several specialized organisms. However, it remains unclear how autonomy and cooperation evolutionarily switch. Specifically, it remains unclear whether and how cooperative specialists can repair deleted genes through direct genetic exchange, thereby regaining metabolic autonomy. Here, we address this question by experimentally evolving a mutualistic microbial consortium composed of two specialists that cooperatively degrade naphthalene. We observed that autonomous genotypes capable of performing the entire naphthalene degradation pathway evolved from two cooperative specialists and dominated the community. This evolutionary transition was driven by the horizontal gene transfer (HGT) between the two specialists. However, this evolution was exclusively observed in the fluctuating environment alternately supplied with naphthalene and pyruvate, where mutualism and competition between the two specialists alternated. The naphthalene-supplied environment exerted selective pressure that favors the expansion of autonomous genotypes. The pyruvate-supplied environment promoted the coexistence and cell density of the cooperative specialists, thereby increasing the likelihood of HGT. Using a mathematical model, we quantitatively demonstrate that environmental fluctuations facilitate the evolution of autonomy through HGT when the relative growth rate and carrying capacity of the cooperative specialists allow enhanced coexistence and higher cell density in the competitive environment. Together, our results demonstrate that cooperative specialists can repair deleted genes through a direct genetic exchange under specific conditions, thereby regaining metabolic autonomy.

Discovery of the 1-naphthylamine biodegradation pathway reveals a broad-substrate-spectrum enzyme catalyzing 1-naphthylamine glutamylation.

1-Naphthylamine (1NA), which is harmful to human and aquatic animals, has been used widely in the manufacturing of dyes, pesticides, and rubber antioxidants. Nevertheless, little is known about its environmental behavior and no bacteria have been reported to use it as the growth substrate. Herein, we describe a pathway for 1NA degradation in the isolate Pseudomonas sp. strain JS3066, determine the structure and mechanism of the enzyme NpaA1 that catalyzes the initial reaction, and reveal how the pathway evolved. From genetic and enzymatic analysis, a five gene-cluster encoding a dioxygenase system was determined to be responsible for the initial steps in 1NA degradation through glutamylation of 1NA. The γ-glutamylated 1NA was subsequently oxidized to 1,2-dihydroxynaphthalene which was further degraded by the well-established pathway of naphthalene degradation via catechol. A glutamine synthetase-like (GS-like) enzyme (NpaA1) initiates 1NA glutamylation, and this enzyme exhibits a broad substrate selectivity toward a variety of anilines and naphthylamine derivatives. Structural analysis revealed that the aromatic residues in the 1NA entry tunnel and the V201 site in the large substrate-binding pocket significantly influence NpaA1's substrate preferences. The findings enhance understanding of degrading polycyclic aromatic amines, and will also enable the application of bioremediation at naphthylamine contaminated sites.

Isolation and Identification of Naphthalene-Degrading Bacteria and its Application in a Two-phase Partitioning Bioreactor.

Naphthalene is a persistent environmental pollutant for its potential teratogenic, carcinogenic and mutagenic effects. In this study, 10 strains of bacteria capable of degrading naphthalene were isolated from crude-oil contaminated soil. Among them, Pseudomonas plecoglossicida 2P exhibited prominent growth with 1000 mg/L naphthalene as the sole carbon source and degraded 94.15% of naphthalene in 36 h. Whole genome sequencing analysis showed that P. plecoglossicida 2P had a total of 22 genes related to naphthalene degradation, of which 8 genes were related to the salicylic acid pathway only, 5 genes were related to the phthalic acid pathway only, 8 genes were common in both the salicylic acid and phthalic acid pathways, and 1 gene was related to the gentisic acid pathway. P. plecoglossicida 2P was applied in a two-phase partition bioreactor (TPPB) to degrade naphthalene in wastewater. The optimal operating conditions of the reactor were obtained through response surface optimization: initial naphthalene concentration (C0) =1600 mg/L, bacterial liquid concentration (OD600) = 1.3, and polymer-to-wastewater mass ratio (PWR) = 2%. Under these conditions, the naphthalene degradation rate was 98.36% at 24 h. The degradation kinetics were fitted using the Haldane equation with a high coefficient of determination (R2=0.94). The present study laid foundations for naphthalene degradation mechanism of genus Pseudomonas and its potential application in TPPB.

Pseudomonas aeruginosa PR23 isolated from oil contaminated soil tolerate and degrades mixture of polyaromatic hydrocarbons and express novel proteins.

Pseudomonas aeruginosa PR23 isolated from the hydrocarbon contaminated soil can tolerate and degrade mixture of polyaromatic hydrocarbons (PAHs) at an initial concentration of 1300ppm. The degradation and intermediates formed were assessed by gas chromatography-mass spectrometry (GC-MS) analysis. The isolated strain was able to degrade 59.2% of the mixture of PAHs in 3days and 71.6% by day 15. Effect of PAHs on protein expression in Pseudomonas aeruginosa PR23 was studied using nano LC-MS/MS. Thirty-six proteins showed a more than 2-fold increase in expression in the presence of mixture of PAHs. Out of these proteins, 7 proteins have been reported for their role in degradation of naphthalene, phenanthrene, and pyrene. The data revealed the presence of 16 proteins that were uniquely expressed in the presence of mixture of PAHs. A twin-arginine translocation signal peptide (Tat system), known for the transportation of folded proteins across the cell membrane, showed more than 8-fold increased expression in the presence of mixture of PAHs. These results indicate that the isolated strain adopts the conditions in the presence of mixture of PAHs by modulating its metabolic and physiological processes. These findings suggest that Pseudomonas aeruginosa PR23 may be a suitable candidate for use in the development of strategies for bioremediation of mixtures of PAHs.

A novel 3D nitrogen-doped porous carbon supported Fe-Cu bimetallic nanoparticles composite derived from lignin: an efficient peroxymonosulfate activator for naphthalene degradation.

A novel 3D nitrogen-doped porous carbon supported Fe-Cu bimetallic nanoparticles composite (Fe-Cu-N-PC) was prepared via direct pyrolysis by employing black liquor lignin as a main precursor, and it was utilized as a novel catalyst for PMS activation in degrading naphthalene. Under the optimum experimental conditions, the naphthalene degradation rate was up to 93.2% within 60 min in the Fe-Cu-N-PC/PMS system. The porous carbon framework of Fe-Cu-N-PC could facilitate the quick molecule diffusion of reactants towards the inner bimetallic nanoparticles and enriched naphthalene molecules from the solution by a specific adsorption, which increased the odds of contact between naphthalene and reactive oxygen species and improved the reaction efficiency. The quenching reaction proved that the non-free radical pathway dominated by 1O2 was the main way in naphthalene degradation, while the free radical pathway involving SO4·- and ·OH only played a secondary role. Moreover, owing to its high magnetization performance, Fe-Cu-N-PC could be magnetically recovered and maintained excellent naphthalene degradation rate after four degradation cycles. This research will offer a theoretical basis for the construction of facile, efficient, and green technologies to remediate persistent organic pollutants in the environment.

Evaluating Natural Source Zone Depletion and Enhanced Source Zone Depletion in laboratory columns via soil redox continuous sensing and microbiome characterization

To optimally employ Natural Source Zone Depletion (NSZD) and Enhanced Source Zone Depletion (ESZD) at sites impacted by light non-aqueous phase liquids (LNAPL), monitoring strategies are required. Emerging use of subsurface oxidation-reduction potential (ORP) sensors shows promise for tracking redox evolution, which reflects ongoing biogeochemical processes. However, further understanding of how soil redox dynamics relate to subsurface microbial activity and LNAPL degradation pathways is needed. In this work, soil ORP sensors and DNA and RNA sequencing-based microbiome analysis were combined to elucidate NSZD and ESZD (biostimulation via periodic sulfate addition and biosparging) processes in columns containing LNAPL-impacted soils from a former petroleum refinery. Results show expected relationships between continuous soil redox and active microbial communities. Continuous data revealed spatial and temporal detail that informed interpretation of the hydrocarbon biodegradation data. Redox increases were transient for sulfate addition, and sequencing revealed how hydrocarbon concentration and composition impacted microbiome structure and naphthalene degradation. Periodic biosparging did not result in fully aerobic conditions suggesting observed biodegradation improvements could be explained by alternative anaerobic metabolisms (e.g., iron reduction due to air oxidizing reduced iron). Collectively, data suggest combining continuous redox sensing with microbiome analysis provides insights beyond those possible with either monitoring tool alone.

Visible Light Enhancement of Biocarbon Quantum-Dot-Decorated TiO2 for Naphthalene Removal.

In this study, carbon-quantum-dot (CQD)-decorated TiO2 was prepared using an ultrasonic doping method and applied in the photocatalytic degradation of naphthalene under sunlight irradiation. The CQDs were synthesized from a typical macroalgae via diluted sulfuric acid pretreatment and hydrothermal synthesis using an optimal design, i.e., 3 wt% and 200 °C, respectively. The CQD/TiO2 composite remarkably enhanced the photocatalytic activity. The degradation of naphthalene under a visible light environment indicated that there is a synergistic mechanism between the CQDs and TiO2, in which the generation of reactive oxygen species is significantly triggered; in addition, the N that originated from the macroalgae accelerated the photocatalytic efficiency. Kinetic analysis showed that the photocatalytic behavior of the CQD/TiO2 composite followed a pseudo-first-order equation. Consequently, our combined experimental approach not only provides a facile pretreatment process for bio-CQDs synthesis, but also delivers a suitable TiO2 photocatalyst for the visible environment along with critical insights into the development of harmful macroalgae resources.

Simultaneous removal of naphthalene and NOx over V-Ce/Ti catalyst: Design of separated active sites for naphthalene degradation and SCR reaction

V-Ce/Ti catalysts were prepared for the removal of naphthalene and NOx in the flue gas. The adverse effects of NH3 and NO on the naphthalene degradation were weakened on V-Ce/Ti, resulting in a decrease of only 2.5 % in COx selectivity. The formation of high molecular weight byproducts was also reduced. Besides the acid sites on the catalysts, Ce introduced new Brønsted basic sites, which could also adsorb and degrade naphthalene into naphthol effectively. With the separated active sites for naphthalene degradation and NO removal, the reaction between NH3 and the intermediates during the naphthalene degradation was also inhibited, decreasing the formation and accumulation of phthalimide. The oxidation of the intermediates was promoted by active V5+ introduced by Ce, inhibiting the transformation of the intermediates to higher molecular weight byproducts. Nearly 100 % conversion of naphthalene and NO, as well as 40.1 % of the COx selectivity were obtained on V-Ce/Ti.

Novel enzymes for biodegradation of polycyclic aromatic hydrocarbons identified by metagenomics and functional analysis in short-term soil microcosm experiments

Polycyclic aromatic hydrocarbons (PAHs) are highly toxic, carcinogenic substances. On soils contaminated with PAHs, crop cultivation, animal husbandry and even the survival of microflora in the soil are greatly perturbed, depending on the degree of contamination. Most microorganisms cannot tolerate PAH-contaminated soils, however, some microbial strains can adapt to these harsh conditions and survive on contaminated soils. Analysis of the metagenomes of contaminated environmental samples may lead to discovery of PAH-degrading enzymes suitable for green biotechnology methodologies ranging from biocatalysis to pollution control. In the present study, our goal was to apply a metagenomic data search to identify efficient novel enzymes in remediation of PAH-contaminated soils. The metagenomic hits were further analyzed using a set of bioinformatics tools to select protein sequences predicted to encode well-folded soluble enzymes. Three novel enzymes (two dioxygenases and one peroxidase) were cloned and used in soil remediation microcosms experiments. The experimental design of the present study aimed at evaluating the effectiveness of the novel enzymes on short-term PAH degradation in the soil microcosmos model. The novel enzymes were found to be efficient for degradation of naphthalene and phenanthrene. Adding the inorganic oxidant CaO2 further increased the degrading potential of the novel enzymes for anthracene and pyrene. We conclude that metagenome mining paired with bioinformatic predictions, structural modelling and functional assays constitutes a powerful approach towards novel enzymes for soil remediation.

A novel plasmonic Z-scheme photocatalyst for solar-light-driven degradation of naphthalene in seawater: Degradation pathways and mechanism insight

In this study, a plasmonic Z-scheme AgBr/Ag/SnO2 photocatalytic system is constructed for the removal of naphthalene (NAP) in seawater under sunlight irradiation by chemical precipitation, photo-reduction, and sol-gel methods. The effects of irradiation time, initial NAP concentration, catalyst dosage, pH value, seawater salinity, reaction solution type, organic pollutant type, and cycle time on the performance of the AgBr/Ag/SnO2 photocatalyst are investigated. The possible degradation pathways of NAP in seawater are speculated. Moreover, a potential mechanism for the plasmonic Z-scheme photocatalytic system is presented. The results demonstrate that the AgBr/Ag/SnO2 photocatalyst achieves a maximal NAP removal efficiency of 95.05 % in seawater under 2.0 g/L catalyst, 8.0 pH, 62.5 gNaCl/L salinity and 120 min sunlight irradiation. The deposited Ag nanoparticles can absorb visible light, which then induces the surface plasmon resonance (SPR) effect and functions as the electronic medium in the plasmonic Z-scheme photocatalytic system. Among all the active species, hydroxyl radical (•OH) contributes the most to the removal of NAP using the AgBr/Ag/SnO2 photocatalyst. Furthermore, the AgBr/Ag/SnO2 photocatalyst exhibits excellent recyclability and good stability. Based on these results, the proposed plasmonic Z-scheme photocatalytic technology has great potential for the removal of polycyclic aromatic hydrocarbons (PAHs) in seawater in practical application.

Enhanced Aerobic Naphthalene Degradation Utilizing Indigenous Microbial Flora as a Biocatalyst in Oil-Contaminated Wastewater

Enhanced Aerobic Naphthalene Degradation Utilizing Indigenous Microbial Flora as a Biocatalyst in Oil-Contaminated Wastewater

Siderite with chelator as high-efficiency Fenton reagent to degrade naphthalene via ferrous liberation and carbon dioxide radical anion-mediated iron redox cycle

Siderite (FeCO3) has been verified to be an effective iron material in Fenton-like process, but large dose of FeCO3 and oxidants limits its application. Here, chelators were successfully used to enhance the degradation of naphthalene (NAP). When 1.0 mM of hydrogen peroxide (H2O2) and 1.0 g L−1 of FeCO3 were applied, in the presence of 0.2 mM oxalic acid (OA), 0.1 mM nitrilotriacetic acid (NTA), or 0.1 mM DL-tartaric acid (DL-TA), 99.3 %, 100 %, or 96.7 % of NAP was degraded within 24 h, respectively. The different roles of chelators were confirmed. For OA and DL-TA, due to weak complexation with iron ions, acid effect and generation of carbon dioxide radical anion (CO2−) contributed to high concentration of Fe2+, while for NTA, chelation and CO2− were two major factors. In addition, the excellent potential application of H2O2/FeCO3/chelator was determined because of (1) lower environmental risk of chemicals; (2) strong tolerance to water matrixes; (3) the excellent stability of FeCO3 confirmed by surface characterizations and cyclic experiment, as NAP was completely degraded after the 6th cycle. At last, H2O2/FeCO3/chelator had superiority over other reduced iron minerals due to lower running cost in lab study, better reusability, and environmental friendliness. Therefore, it is expected that H2O2/FeCO3/chelator technique can provide an effective alternative to Fenton-like process in remediation of NAP contaminated sites.

Naphthalene-Degrading Bacteria with Potential for Remediating Marine Environments

Brazil is one of the largest oil producers in the world, and petroleum exploration is predominant in marine environments, mainly in the city of Rio de Janeiro. These environments become vulnerable to oil spills, which can be remedied by petroleum hydrocarbon-degrading bacteria. To better understand the distribution of polycyclic aromatic hydrocarbon (PAH)-degrading bacteria in these marine environments, water samples were collected from eight beaches (Arpoador, Grumari, Vermelha, Sahy, Itacuruçá, Itaipuaçu, Ferradura, and Itaipu) along the Rio de Janeiro coastline and further contaminated with 0.1% naphthalene, used as a PAH model. Naphthalene-enriched bacteria were isolated in marine agar, identified using 16S rRNA sequencing, and tested for emulsification and naphthalene degradation. Thirty-five different genera were observed among the 231 isolates, most belonging to Proteobacteria. Some genera were found in at least half of the studied beaches, such as Mesoflavibacter, Muricauda, Alteromonas, Salipiger, Pseudooceanicola, and Celeribacter, while others were found in only a few water samples. Seventeen and 18 strains were considered to be positive for naphthalene degradation and emulsification, respectively, making them the most promising strains for naphthalene bioremediation. Five of these strains were positive for both degradation and emulsification. This study contributes to the selection of potential candidates for further studies on the remediation of PAHs in tropical marine environments worldwide.

Simulated study on electrochemical regeneration of ammonium persulfate for naphthalene degradation in soil

Simulated study on electrochemical regeneration of ammonium persulfate for naphthalene degradation in soil