Naphthenic Oil Research Articles

GTL synthetic paraffin oil shows low liver and tissue retention compared to mineral oil

Oral exposure to mineral oil may result in a narrow fraction of mineral oil saturated hydrocarbon (MOSH) being retained in tissues. Excess of MOSH hepatic retention may lead to the formation of lipogranuloma caused by predominantly multiring cycloalkanes (naphthenics) in a critical range of C25–C35. Although hepatic lipogranuloma is of low pathological concern, MOSH tissue deposition could be minimized by using an oil of similar quality but devoid of naphthenic structures to decrease hepatic retention.Synthetic Gas to liquid (GTL) oils offer an alternative to petroleum derived mineral oils, because they do not contain naphthenic structures. To demonstrate this point, SD rats were fed either GTL oil (99% iso-alkanes) or naphthenic mineral oil (84% cycloalkanes) at 200 mg/kg bw/day for 90 or 134 days with a recovery group. Liver, fat and mesenteric lymph nodes were analyzed for alkane sub-type levels using Online-HPLC-GC-FID and GCxGC-TOF-MS.Results indicate that at equal external dose, GTL hydrocarbons result in lower tissue levels and more rapid excretion than MOSH. GTL retained hepatic fractions were also qualitatively different than MOSH constituents. Because chemical composition differences, GTL oil show low absorption and tissue retention potential and thus an advantageous alternative to conventional mineral oil.

Microbial Community Dynamics during Biodegradation of Crude Oil and Its Response to Biostimulation in Svalbard Seawater at Low Temperature.

The development of oil exploration activities and an increase in shipping in Arctic areas have increased the risk of oil spills in this cold marine environment. The objective of this experimental study was to assess the effect of biostimulation on microbial community abundance, structure, dynamics, and metabolic potential for oil hydrocarbon degradation in oil-contaminated Arctic seawater. The combination of amplicon-based and shotgun sequencing, together with the integration of genome-resolved metagenomics and omics data, was applied to assess microbial community structure and metabolic properties in naphthenic crude oil-amended microcosms. The comparison of estimates for oil-degrading microbial taxa obtained with different sequencing and taxonomic assignment methods showed substantial discrepancies between applied methods. Consequently, the data acquired with different methods was integrated for the analysis of microbial community structure, and amended with quantitative PCR, producing a more objective description of microbial community dynamics and evaluation of the effect of biostimulation on particular microbial taxa. Implementing biostimulation of the seawater microbial community with the addition of nutrients resulted in substantially elevated prokaryotic community abundance (103-fold), a distinctly different bacterial community structure from that in the initial seawater, 1.3-fold elevation in the normalized abundance of hydrocarbon degradation genes, and 12% enhancement of crude oil biodegradation. The bacterial communities in biostimulated microcosms after four months of incubation were dominated by Gammaproteobacterial genera Pseudomonas, Marinomonas, and Oleispira, which were succeeded by Cycloclasticus and Paraperlucidibaca after eight months of incubation. The majority of 195 compiled good-quality metagenome-assembled genomes (MAGs) exhibited diverse hydrocarbon degradation gene profiles. The results reveal that biostimulation with nutrients promotes naphthenic oil degradation in Arctic seawater, but this strategy alone might not be sufficient to effectively achieve bioremediation goals within a reasonable timeframe.

Effects of Petroleum-Based Oils as Dispersing Aids on Physicochemical Characteristics of Magnetorheological Elastomers.

This paper investigated the effects of petroleum-based oils (PBOs) as a dispersing aid on the physicochemical characteristics of natural rubber (NR)-based magnetorheological elastomers (MREs). The addition of PBOs was expected to overcome the low performance of magnetorheological (MR) elastomers due to their inhomogeneous dispersion and the mobility of magnetic particles within the elastomer matrix. The NR-based MREs were firstly fabricated by mixing the NR compounds homogeneously with different ratios of naphthenic oil (NO), light mineral oil (LMO), and paraffin oil (PO) to aromatic oil (AO), with weight percentage ratios of 100:0, 70:30, 50:50, and 30:70, respectively. From the obtained results, the ratios of NO mixed with low amounts of AO improved the material physicochemical characteristics, such as thermal properties. Meanwhile, LMO mixed the AO led to the best results for curing characteristics, microstructure observation, and magnetic properties of the MREs. We found that the LMO mixed with a high content of AO could provide good compatibility between the rubber molecular and magnetic particles due to similar chemical structures, which apparently enhance the physicochemical characteristics of MREs. In conclusion, the 30:70 ratio of LMO:AO is considered the preferable dispersing aid for MREs due to structural compounds present in the oil that enhance the physicochemical characteristics of the NR-based MREs.

Oil-mediated oxidative-stress responses in a keystone zooplanktonic species, Calanus finmarchicus

The copepod Calanus finmarchicus is an ecologically important species in the North Atlantic, Norwegian and Barents seas. Accidental or continuous petroleum pollution from oil and gas production in these seas may pose a significant threat to this low trophic level keystone species.Responses related to oxidative stress, protein damage and lipid peroxidation were investigated in C. finmarchicus exposed to a water-accommodated fraction (WAF) of a naphthenic North Atlantic crude oil. The exposure concentration corresponded to 50% of the 96 h LC50, and samples were obtained at 0, 24, 48, 72 and 96 h after exposure initiation. Gene expressions (superoxide dismutase, catalase, glutathione S-transferase, glutathione synthetase, heat shock protein 70 and 90, ubiquitin and cytochrome P-450 330A1), enzyme activities (superoxide dismutase, catalase, glutathione S-transferase) and concentrations of total glutathione and malondialdehyde were analyzed. Gene expression analyses showed no differences between controls and the exposed animals, however significantly higher glutathione S-transferase activity and malondialdehyde concentrations were found in the exposed group, suggests lipid peroxidation as main toxic effect.

Influence of dispersant application on the toxicity to sea urchin embryos of crude and bunker oils representative of prospective oil spill threats in Arctic and Sub-Arctic seas

This study deals with the toxicity assessment of crude and bunker oils representative of prospective oil spill threats in Arctic and Sub-Arctic seas (NNA: Naphthenic North-Atlantic crude oil; MGO: Marine Gas Oil; IFO: Intermediate Fuel Oil 180), alone or in combination with a third-generation dispersant (Finasol OSR52®). Early life stages of sea urchin, Paracentrotus lividus, were selected for toxicity testing of oil low-energy water accommodated fractions. A multi-index approach, including larval size increase and malformation, and developmental disruption as endpoints, was sensitive to discriminate from slight to severe toxicity caused by the tested aqueous fractions. IFO (heavy bunker oil) was more toxic than NNA (light crude oil), with MGO (light bunker oil) in between. The dispersant was toxic and further on it enhanced oil toxicity. Toxic units revealed that identified PAHs were not the main cause for toxicity, most likely exerted by individual or combined toxic action of non-measured compounds.

Multilevel responses of adult zebrafish to crude and chemically dispersed oil exposure

BackgroundThe application of chemical dispersants is a common remediation strategy when accidental oil spills occur in aquatic environments. Breaking down the oil slick into small droplets, dispersants facilitate the increase of particulate and dissolved oil compounds, enhancing the bioavailability of toxic oil constituents. The aim of the present work was to explore the effects of water accommodated fractions (WAF) of a naphthenic North Sea crude oil produced with and without the addition of the chemical dispersant FINASOL OSR 52 to adult zebrafish exposed for 3 and 21 d. Fish were exposed to environmentally relevant concentrations of 5% and 25% WAFOIL (1:200) and to 5% WAFOIL+D (dispersant–oil ratio 1:10) in a semi-static exposure setup.ResultsThe chemically dispersed WAF presented a 20-fold increase of target polycyclic aromatic hydrocarbons (PAHs) in the water phase compared to the corresponding treatment without dispersant and was the only treatment resulting in markedly bioaccumulation of PAHs in carcass after 21 d compared to the control. Furthermore, only 5% WAFOIL+D caused fish mortality. In general, the undispersed oil treatments did not lead to significant effects compared to control, while the dispersed oil induced significant alterations at gene transcription and enzyme activity levels. Significant up-regulation of biotransformation and oxidative stress response genes (cyp1a, gstp1, sod1 and gpx1a) was recorded in the livers. For the same group, a significant increment in EROD activity was detected in liver along with significant increased GST and CAT activities in gills. The addition of the chemical dispersant also reduced brain AChE activity and showed a potential genotoxic effect as indicated by the increased frequency of micronuclei in erythrocytes after 21 d of exposure.ConclusionsThe results demonstrate that the addition of chemical dispersants accentuates the effect of toxic compounds present in oil as it increases PAH bioavailability resulting in diverse alterations on different levels of biological organization in zebrafish. Furthermore, the study emphasizes the importance to combine multilevel endpoints for a reliable risk assessment due to high variable biomarker responses. The present results of dispersant impact on oil toxicity can support decision making for oil spill response strategies.

Electrical and acoustic investigation of partial discharges in two types of nanofluids

Measurements of partial discharges in liquid dielectrics are important for prediction of a serious failure of electrical equipment. Recent research findings show that application of nanoparticles in dielectric liquids may increase their resistance to partial discharges. However, physical properties of a host liquid are expected to play a decisive role in the effective suppression of partial discharges by nanoparticles. In this paper, a transformer oil prepared by a gas-to-liquid technology and a standard naphthenic transformer oil are doped with an equal amount of iron oxide nanoparticles. Determination of basic physical properties of the oils and the nanofluids is followed by an experimental investigation of partial discharges under various alternating voltage levels. The detection of partial discharges is approached by two independent methods, electrically and acoustically. Both methods revealed occurrence of partial discharges in the gas-to-liquid oil at higher voltages, as compared with the naphthenic oil. Acoustic emission energy is found one order of magnitude greater in the gas-to-liquid oil than in the naphthenic oil. The acoustic wave propagation dependence on the physical properties of the liquid is considered in the qualitative explanation of the observed phenomenon. The presence of nanoparticles can suppress partial discharges in the naphthenic oil, but not in the gas-to-liquid oil.

Effect of Petroleum-Based Oil Towards Physicochemical Properties of Natural Rubber-Based Magnetorheological Elastomers

This study presents an investigation of the effect of magnetorheological elastomers (MREs) using petroleum based-oil (PBO) as dispersing aids. The inhomogeneous dispersion and mobility of magnetic particles within the elastomer matrix result in poor MREs performance. Isotropic natural rubber (NR) based MREs were fabricated by homogeneously mixed with the addition of different ratios of naphthenic oil (NO) to aromatic oil (AO), whereby NO 1(100:0), NO 2 (70:30), NO 3 (50:50), and NO 4 (30:70), correspondingly. The cure characteristics, morphological, magnetic properties and thermal analyses were conducted. Based on the results, NO 1 leads the best results for microstructure observation and magnetic properties of the MREs. Meanwhile, NO 2 mixed with AO showed an improvement in curing characteristics and thermal analyses compared to other samples. In summary, the ratio of NO 1 and NO 2 is considered the preferable dispersing aids for MREs compared to NO 3 and NO 4 due to the structural compound in the oil that enhanced the characteristics of the NR-based MREs.

Development of fiber flow finishing (FFF) process for polishing hip prostheses

In this paper, a new polishing process has been developed based on a smart polishing media called fiber flow finishing (FFF). The proposed polishing media included styrene butadiene rubber (SBR), coarse sisal fibers, and naphthenic oil. During the process, the rheological behavior of the polishing media changes intelligently due to severe mechanical disintegration and chemical treatment. This intelligent behavior is very similar to the behavior of pseudo-plastic materials. To evaluate the polishing performance, experiments were performed on the femoral head of hip prostheses grade ASTM F138 (SS 316L) for the different number of finishing cycles to investigate its effect on the percentage change in surface roughness (%ΔR a ). The experimental results clearly showed that the %ΔR a of the femoral head is low in the initial finishing cycles (i.e., up to 200 working cycles), while the %ΔR a increases to 72.54% with an increase in the number of finishing cycles up to 1000. Moreover, the surface morphology of the specimens well substantiated that the FFF process performed a kind of surface modification on the surface texture of the femoral head, resulting in a smooth and uniform surface finish without surface defects that is as a mirror. • The fiber flow finishing (FFF) process is first developed for polishing hip prostheses. • The surface finish of the femoral head was improved by 72.54% using the FFF process. • The FFF process performed a kind of surface modification on the femoral head surface. • The FFF process has a better performance than the abrasive flow finishing (AFF) process. • The FFF process has a promising future to improve surface integrity of industrial parts.

Determination of viscosity average molar masses of polyethylene in a wide range using rheological measurements with a harmless solvent

Rheological measurements of polyethylene solutions in a novel nontoxic solvent were used to determine the Mark-Houwink parameters for PE of widely different molecular weights to assess the viscosity average molar mass for PE of several millions of g.mol−1. Solutions of high density polyethylene that had been previously characterized by size exclusion chromatography were prepared in a harmless naphthenic oil. The intrinsic viscosities were obtained by varying the concentrations of the different calibration samples solutions using a rotational rheometer equipped with a Couette cell. The intrinsic viscosities were determined by both Huggins and Kraemer descriptions of the viscosity variations with concentration. Subsequently, a calibration curve of intrinsic viscosities versus the molar mass was plotted, and the parameters of the Mark-Houwink-Sakurada equation were obtained for polyethylene in naphthenic oil. Using this equation and the newly estimated parameters, the viscosity average molar mass of a high molar mass polyethylene and a commercial ultra high molar mass polyethylene were been determined by measuring their respective intrinsic viscosities. Finally, the method has been validated by comparing these results to values obtained by standard viscosimetry in 1,2,4-trichlorobenzene and to the values given by the supplier, obtained by other methods.

Assessing the dielectric performance of Sclerocarya birrea (Marula oil) and mineral oil for eco-friendly power transformer applications

The ever increasing power demand has forced the power sector companies to increase their generation, transmission and distribution in turn increasing the number of power transformers in the system where necessary. Depending on the nature of operations, the transformers are chosen as either dry-type or liquid-cooled and the preference is mostly liquid cooled. Naphthenic oils have been the primary choice over the years and alternative solutions in the form of natural esters are researched extensively due to the environmental effects of Mineral Oil (MO). One such ester, Marula is presented in this research. The experiment places its focus on measurement of electrical, physical, chemical and thermal characteristics as per the standards of ASTM and IEC. The results prove the superior dielectric performance of MAO over MO. The antioxidant rich MAO exhibits superior dielectric properties and restores faster than MO after the instances of breakdown phenomena. The antioxidants show stability at both the low and high temperatures, and temperature causes minimum damage to antioxidants. In addition to that the use of such dielectric coolant minimizes the winding damage inside the transformer tank. Thus, it can be said that MAO is an excellent coolant and improves the efficiency of the transformer without the requirements of additional cooling devices.

Source Rock Evaluation and Hydrocarbon Generation Model of a Permian Alkaline Lakes—A Case Study of the Fengcheng Formation in the Mahu Sag, Junggar Basin

The alkaline lake source rocks of the Fengcheng Formation are developed in the Mahu Sag of the Junggar Basin. Different from traditional continental fresh water and saltwater lake source rocks, alkaline lake source rocks lack targeted evaluation criteria, and it is unknown whether their hydrocarbon generation models are consistent with traditional models. Therefore, in the present study, evaluation standards and hydrocarbon generation models of alkaline lake source rocks are discussed based on geological and organic geochemical data and a systematic summary of the geochemical characteristics of the Fengcheng Formation source rocks. The Fengcheng Formation source rocks are mainly diamictite with mixed argillaceous rock and dolomite; most total organic carbon (TOC) values range from 0.2–1.4%; and the kerogen is primarily oil-prone type II, reaching low- to high-maturity stages. Based on the types of organic matter in source rocks and the relationships between organic matter abundance parameters, the evaluation standard of alkaline lake source rocks is proposed. The Fengcheng Formation is mainly composed of good to excellent source rocks (55.5%) with high hydrocarbon generation potential. The single-peak hydrocarbon generation model of the Fengcheng Formation is similar to that of traditional freshwater or saltwater lakes, with a high hydrocarbon generation rate, two to five times that of the traditional model; its main particularity is in the formation of naphthenic crude oil from the kerogen of bacteria and algae. A new understanding of the hydrocarbon generation potential and model of alkaline lake source rocks in the Fengcheng Formation can provide support for tight oil and shale oil exploration in the Mahu Sag.

Application of a biological multilevel response approach in the copepod Acartia tonsa for toxicity testing of three oil Water Accommodated Fractions

Copepods play a critical role in the marine food webs, being a food source for marine organisms. In this study, we investigated the toxic effects of Water Accommodated Fractions (WAFs) from three types of oil: Naphthenic North Sea crude oil (NNS), Intermediate Fuel Oil (IFO 180) and a commercial Marine Gas Oil (MGO). The WAFs were prepared at 10 °C and 30 PSU (practical salinity unit), and tested on the marine copepod Acartia tonsa at different endpoints and at different levels of biological organization. We determined the median lethal concentrations after 96 h (LC50) and reproduction capabilities were calculated in adult females following seven days of exposure to sublethal WAF doses. The total lipid content was measured in reproductive females using Nile red lipophilic dye after 96 h of WAF exposure. We also measured the transcription levels of genes involved in antioxidant response and xenobiotic biotransformation after short exposure for 48 h. High doses (7% WAF) of MGO affected survival, percentage of fecund females, egg hatching success, and total lipid content. The IFO 180 WAF affected, at medium (20%) and high (40%) doses, the number of fecund females, mortality and produced significant effects on gene expression levels. In conclusion, toxicity assays showed that the WAFs prepared from refined oils were more toxic than crude oil WAF to Acartia tonsa.

Catalytic Neutralization of Naphthenic Acid from Petroleum Crude Oil by Using Cerium Oxide Catalyst and 2- Methylimidazole in Polyethylene Glycol

Background: The presence of relatively high naphthenic acid in crude oil may contribute to the major corrosion in oil pipelines and distillation units in crude oil refineries. Thus, high concentration naphthenic acid crude oil is considered to be of low quality and is marketed at lower prices. In order to overcome this problem, the neutralization method had been developed to reduce the TAN value in crude oil. In this study, crude oil from Petronas Penapisan Melaka was investigated. Methods: The parameters studied were reagent concentration, catalyst loading, calcination temperature, and reusability of the potential catalyst. The basic chemical used was 2- methylimidazole in polyethylene glycol (PEG 600) with concentration 100, 500 and 1000 ppm. Cerium oxide-based catalysts were supported onto alumina prepared with different calcination temperatures. Results: The catalyst was characterized by using Brunauer-Emmett-Teller (BET), Fourier Transform Infrared Spectroscopy (FTIR) and Thermogravimetry Analysis-Differential Thermal Gravity (TGA-DTG) to study the physical properties of the catalyst. The Ce/Al2O3 catalyst calcined at 1000°C was the best catalyst due to larger surface area formation which lead to an increment of active sites thus will boost catalytic activity. The result showed that the Ce/Al2O3 catalyst meets the Petronas requirement as the TAN value reduced to 0.6 mgKOH/g from the original TAN value of 4.22 mgKOH/g. Conclusion: The best reduction of TAN was achieved by using catalyst loading of 0.39% and reagent of 1000 ppm.

Co-production of Naphthenic Oil and Phenolic Compounds from Medium- and Low-Temperature Coal Tar

The conversion of medium- and low-temperature coal tar into high-performance fuel and value-added chemicals is one of the main approaches to addressing the current global energy challenges. To this aim, an innovative coal tar processing process has been developed, which enables the efficient transformation. This process is suggested to produce phenolic compounds and naphthenic oil. As the hydrogenation of coal tar involves complex chemical structures and reactions, a systematic matrix of model compounds was presented on the basis of qualitative and quantitative analytics to represent the coal tar and hydrogenation products. The kinetics modeling of tar hydrogenation was proposed to optimize the process parameters and predict the characteristics of products. The energy efficiency (81.62%) and the element utilization (carbon (88.21%), hydrogen (87.13%), and oxygen (31.25%)) associated with the whole process are calculated. From the life cycle assessment, the energy use, the CO₂ emission, and the target costing of the proposed coal tar process are calculated as 10.82 MJ/CNY, 2.71 kg CO₂-eq/CNY, and 3141.2 CNY/t-product, respectively.

New Vegetable Oils with Different Fatty Acids on Natural Rubber Composite Properties.

Owing to the toxicity of polycyclic aromatic (PCA) oils, much attention has been paid to the replacement of PCA oils by other nontoxic oils. This paper reports comparative study of the effects of new vegetable oils, i.e., Moringa oil (MO) and Niger oil (NO), on rheological, physical and dynamic properties of silica–filled natural rubber composite (NRC), in comparison with petroleum–based naphthenic oil (NTO). The results reveal that MO and NO exhibit higher thermal stability and better processability than NTO. Cure characteristics of the rubber compounds are not significantly affected by the oil type. It is also found that the NRCs containing MO or NO have better tensile strength and lower dynamic energy loss than the NRCs containing NTO. This may be because both MO and NO improve filler dispersion to a greater extent than NTO as supported by storage modulus and scanning electron microscopy results. Consequently, the present study suggests that MO and NO could be used as the alternative non–toxic oils for NRC without any loss of the properties evaluated.

Novel boron nitride filler polymer matrix dielectric elastomer composites with enhanced actuation performance

This paper describes novel soft dielectric elastomer composites that exhibits interesting features from the perspective of dielectric-elastomer transducer development, with enhanced actuation performance under an applied electric field that are potentially suitable for actuator applications. Materials solutions described are a combination of ceramic BN platelets, used at low loading levels, and a plasticizer (Naphthenic Oil) in a polymer matrix and synergistic effects between them that leads to enhancement in actuation strain by as high as 328% under applied electric field. Such functional dielectric composites would alleviate several issues such as size, functionality, and performance for many real-world actuator applications.

Study on the mechanical failure of the cellulosic insulation of continuously transposed conductors in power transformers under the influence of short circuits and thermal ageing

The dielectric paper of power transformers is subjected to ageing caused by high temperatures and chemical reactions in the dielectric oil. The electromagnetic forces that affect the conductor can cause the breakage of the paper and even the end of the useful life of the transformer. To improve the understanding of those phenomena, a continuously transposed conductor with four layers of dielectric paper (plain Kraft and crepe papers) was impregnated in naphthenic oil and aged during different periods, representative of its whole lifespan. Samples of the conductor were subjected to bending deformations compatible with a short circuit, and the cracks generated in the paper were analysed. The aged dielectric paper was mechanically characterised (in tensile, compressive and shear modes) and the bending tests of the conductors were simulated in ANSYS Static Structural, to estimate the strains in the paper. The Norris failure criterion was modified to predict the regions in the dielectric paper susceptible to fail for a particular ageing state and deformation level, obtaining a good agreement with the experimental results and thus validating this new version of the Norris approach.

Investigation of the palm oil-solubility in naphthenic insulating oil using density functional theory and COSMO-RS

This paper first uses density functional theory combined with the method of quantum chemistry calculations to obtain the electrostatic potential surfaces of the four main triglyceride molecules in palm oil and the water molecule, which reveals the reactivities of triglyceride molecules and the water molecule from a microscopic perspective. In addition, the conductor-like screening model for real solutions (COSMO-RS) method is used to calculate the σ-profile of the main active components of naphthenic mineral oil and the four main triglycerides in palm oil. Then, the COSMO-RS model of the triglyceride-hydrocarbon system is constructed, which theoretically predicts the solubility of the four main triglyceride molecules tripalmitin, tristearin, triolein, and trilinolein in mineral oil. The results show that triglyceride molecules and the mineral oil molecules have similar intermolecular forces, so triglyceride molecules can easily dissolve into the mineral oil. The results of this paper can provide theoretical reference and calculation support for the development of new-type mixed insulating oil for transformers.

Uptake and effects of graphene oxide nanomaterials alone and in combination with polycyclic aromatic hydrocarbons in zebrafish

Because of its surface characteristics, once in the aquatic environment, graphene could act as a carrier of pollutants, such as polycyclic aromatic hydrocarbons (PAHs), to aquatic organisms. In this study we aimed to (1) assess the capacity of graphene oxide (GO) to sorb PAHs and (2) to evaluate the toxicity of GO alone and in combination with PAHs on zebrafish embryos and adults. GO showed a high sorption capacity for benzo(a)pyrene (B(a)P) (98% of B(a)P sorbed from a nominal concentration of 100 μg/L) and for other PAHs of the water accommodated fraction (WAF) of a naphthenic North Sea crude oil, depending on their log Kow (95.7% of phenanthrene, 84.4% of fluorene and 51.5% of acenaphthene). In embryos exposed to different GO nanomaterials alone and with PAHs, no significant mortality was recorded for any treatment. Nevertheless, malformation rate increased significantly in embryos exposed to the highest concentrations (5 or 10 mg/L) of GO and reduced GO (rGO) alone and with sorbed B(a)P (GO-B(a)P). On the other hand, adults were exposed for 21 days to 2 mg/L of GO, GO-B(a)P and GO co-exposed with WAF (GO + WAF) and to 100 μg/L B(a)P. Fish exposed to GO presented GO in the intestine lumen and liver vacuolisation. Transcription level of genes related to cell cycle regulation and oxidative stress was not altered, but the slight up-regulation of cyp1a measured in fish exposed to B(a)P for 3 days resulted in a significantly increased EROD activity. Fish exposed to GO-B(a)P and to B(a)P for 3 days and to GO + WAF for 21 days showed significantly higher catalase activity in the gills than control fish. Significantly lower acetylcholinesterase activity, indicating neurotoxic effects, was also observed in all fish treated for 21 days. Results demonstrated the capacity of GO to carry PAHs and to exert sublethal effects in zebrafish.