Distribution of Polycyclic Aromatic Hydrocarbons in Sunken Oils in the Presence of Chemical Dispersant and Sediment

Modulatory effects of quercetin on histological changes, biochemical and oxidative stress of rat placenta induced by inhalation exposure to crude oil vapor

The inhalation exposure to crude oil vapor (COV) has been shown to have adverse effects on the placenta and fetal development. The modulatory effects of quercetin (QUE) as a natural phenolic compound with antioxidant properties are promising for the protection of placental structure. This study aimed to investigate the modulatory role of QUE in mitigating histopathological damage, oxidative stress, and biochemical alteration in the placenta of COV-exposed pregnant rats. Forty-eight pregnant rats were divided into eight groups (days 15 and 20) as follows: 1-2) Control groups, 3-4) COV groups, 5-6) COV+QUE groups, and 7-8) QUE-treated groups (50 mg/kg). The inhalation method was used to expose pregnant rats to COV, and QUE was administered orally. On the 15th and 20th days of gestation, placental tissue was analyzed using PAS and H&E staining and immunohistochemistry. The expression of the caspase-3 gene and oxidative stress biomarkers including TAC, CAT, MDA, GPx, and SOD were investigated in the placental tissue. The COV significantly decreased the weight, diameter, and thickness of the placenta as well as the thickness of the junctional zone and labyrinth and the number of trophoblast giant cells in 15- and 20-day-old placentas (P<0.05). Also, COV significantly increased placental expression of caspase-3 and the oxidative stress biomarkers (P<0.05). The administration of QUE along with exposure to COV reduced morphometric and histological alteration, oxidative stress, and caspase-3 expression (P<0.05). Our findings indicated that QUE in COV-exposed pregnant rats can prevent placental histopathological alternations by increasing the activity of the antioxidant system.

Formation and sedimentation of oil-mineral aggregates in the presence of chemical dispersant

The formation and sedimentation of oil-mineral aggregates (OMAs) is the major method to transport spilled oil to the seafloor. In this study, the formation and sedimentation experiments of OMA using montmorillonite and four crude oils were performed in a wave tank in the presence of chemical dispersant. Most of the formed OMAs were droplet OMAs, and single droplet OMA would aggregate into multiple ones under the action of the dispersant. The size of the oil droplets trapped in the OMA increased with time and was larger for the oil with higher viscosity. The sinking velocities of OMAs formed in this study were between 100-1200 μm s-1 and they were positively correlated with their diameter. The density of OMA was of the same order as that of the crude oil that formed them. An increase in the dispersant dosage could promote the formation of OMAs. The oil content in OMAs was higher for the denser oil in the presence of a dispersant. The maximum oil trapping efficiency of OMAs was 48.05%. This study provides fundamental data on the formation kinetics of OMAs.

Protective effect of quercetin on fetal development and congenital skeletal anomalies against exposure of pregnant Wistar rats to crude oil vapor

BACKGROUND

Epidemiological evidence indicates a relationship between maternal exposure to crude oil vapors (COV) during pregnancy and adverse pregnancy outcomes. Quercetin (QUE) is a plant flavonoid with purported antioxidant and anti-inflammatory effects, which has been shown to prevent birth defects. This study was aimed to investigate the protective role of QUE on fetal development and congenital skeletal anomalies caused by exposure of pregnant rats to COV.

METHODS

Twenty-four pregnant Wistar rats were randomly categorized into four groups of control, COV, COV + QUE, and QUE (50 mg/kg). The inhalation method was used to expose pregnant rats to COV from day 0 to 20 of pregnancy, and QUE was administered orally during this period. On day 20 of gestation, the animals were anesthetized and a laparotomy was performed, and then the weight and crown rump length (CRL) of the fetuses were determined. Skeletal stereomicroscopic evaluations of fetuses were performed using Alcian blue/Alizarin red staining method, and the expression of osteogenesis-related genes (Runx2 and BMP-4) was evaluated using qPCR.

RESULTS

This study showed that prenatal exposure to COV significantly reduced fetal weight and CRL, and expression of Runx2 and BMP-4 genes. Moreover, COV significantly increased the incidence of congenital skeletal anomalies such as cleft palate, spina bifida and non-ossification of the fetal bones. However, administration of QUE with exposure to COV improved fetal bone development and reduced congenital skeletal anomalies.

CONCLUSION

QUE can ameliorate the teratogenic effects of prenatal exposure to COV by increasing the expression of osteogenesis-related genes.

Formation of oil-particle aggregates in the presence of marine algae

After an oil spill, the formation of oil-particle aggregates (OPAs) is associated with the interaction between dispersed oil and marine particulate matter such as phytoplankton, bacteria and mineral particles. Until recently, the combined effect of minerals and marine algae in influencing oil dispersion and OPA formation has rarely been investigated in detail. In this paper, the impacts of a species of flagellate algae Heterosigma akashiwo on oil dispersion and aggregation with montmorillonite were investigated. This study has found that oil coalescence is inhibited due to the adhesion of algal cells on the droplet surface, causing fewer large droplets to be dispersed into the water column and small OPAs to form. Due to the role of biosurfactants in the algae and the inhibition of algae on the swelling of mineral particles, both the oil dispersion efficiency and oil sinking efficiency were improved, which reached 77.6% and 23.5%, respectively at an algal cell concentration (Ca) of 1.0 × 106 cells per mL and a mineral concentration of 300 mg L-1. The volumetric mean diameter of the OPAs decreased from 38.4 μm to 31.5 μm when Ca increased from 0 to 1.0 × 106 cells per mL. At higher turbulent energy, more oil tended to form larger OPAs. The findings may add knowledge about the fate and transport of spilled oil and provide fundamental data for oil spill migration modelling.

Inhalation exposure to crude oil vapor induces behavioural deficits by increasing oxidative stress and histopathological changes in rat hippocampus: Quercetin therapeutic approach

OBJECTIVE

Inhalation exposure to crude oil vapor (COV) and petroleum products is considered responsible for neurobehavioral toxicity in human and animal models. The antioxidant activity of quercetin (Que) and its derivatives are promising for protecting the hippocampus. This study aimed to evaluate the neuroprotective role of Que against COV-induced behavioral alterations and hippocampus damage.

METHODS

Eighteen adult male Wistar rats were randomly divided into the following three groups (n = 6): the control, the COV, and the COV + Que group. The inhalation method was used to expose the rats to crude oil vapors for 5 h daily, and Que (50 mg/kg) was administered orally. After 30 days of treatment, the spatial working memory and anxiety levels were evaluated using the cross-arm maze and elevated plus maze (EPM), respectively. TUNEL assay and hematoxylin-eosin (H&E) staining were used to identify the necrosis, normal and apoptotic cells in the hippocampus. Moreover, the levels of oxidative stress biomarkers including malondialdehyde (MDA), glutathione peroxidase (GPx), superoxide dismutase (SOD), catalase (CAT), and total antioxidant capacity (TAC) were investigated in the hippocampus tissue.

RESULTS

The results indicated that exposure to COV was associated with a significant decrease in spatial working memory and activity of CAT, TAC, SOD, and GPx enzymes compared to the control (P < 0.05). Moreover, COV significantly increased the level of anxiety, MDA, and hippocampal apoptosis (P < 0.05). The simultaneous administration of quercetin along with exposure to COV improved the behavioral alterations, activity of antioxidant enzymes, and hippocampal apoptosis.

CONCLUSIONS

These findings suggest that quercetin prevents COV-induced hippocampal damage by enhancing the antioxidant system and preventing cell apoptosis.

Concentration of polycyclic aromatic hydrocarbons (PAHs) and histological changes in Anomalocardia brasiliana and Crassostrea rhizophorae from Pernambuco, Brazil after the 2019 oil spill

The present study aimed to analyze the concentrations of polycyclic aromatic hydrocarbons (PAHs) in populations of the shellfish Anomalocardia brasiliana and oysters Crassostrea rhizophorae three years after the 2019 oil spill, as well as evaluate histopathological changes on the gill tissues of the bivalves. Individuals of both species were sampled at points along the northern and southern coast of Pernambuco, Brazil. The permanence of oil residues was confirmed, evidenced by the total concentration of PAHs in the shellfish from the northern coast, which was roughly four times higher than the southern one. Among the PAHs analyzed, the low molecular weight compounds naphthalene and anthracene were the main contributors to the total concentration. Histological changes in the gills of the bivalves, were more severe in the specimens sampled on the north coast indicating alterations in the bivalve's health, mainly on the state's northern coast.

Effects of oil properties on the formation of oil-particle aggregates at the presence of chemical dispersant in baffled flask tests

The formation of oil-particle aggregates (OPA) is the major sedimental pathway of spilled oil, which can bring great harm to both the benthic communities and marine environment. In this paper, effects of GM-2 chemical dispersant and oil properties on the formation of OPA was investigated by the EPA baffled flask test. The addition of dispersant can promote the formation of OPA from montmorillonite and five test oils obviously. With the increase of the dispersant dosage, the size of trapped oil in OPA increased and the density of OPA decreased. The dispersant can increase the kinematic viscosity of crude oil, and high viscosity of the oil is advantageous for the formation of OPA. The oil-seawater interfacial tension is reduced after the addition of dispersant, which makes oil dispersed into the water column easier. A kinematic equation of dispersed oil concentration attenuation was modified by introducing the oil property coefficient β. The modified empirical equation can calculate the mass of oil in sunken OPA in oil spill accidents.

Effects of chemical dispersant on the surface properties of kaolin and aggregation with spilled oil

After oil spills occur, dispersed oil droplets can collide with suspended particles in the water column to form the oil-mineral aggregate (OMA) and settle to the seafloor. However, only a few studies have concerned the effect of chemical dispersant on this process. In this paper, the mechanism by which dispersant affects the surface properties of kaolin and the viscosity and oil-seawater interfacial tension (IFT_ow) of Roncador crude oil were separately investigated by small-scale tests. The results indicated that the presence of dispersant impairs the zeta potential and enhances the hydrophobicity of kaolin. The viscosity of Roncador crude oil rose slightly as the dosage of dispersant increased, while IFT_ow decreased significantly. Furthermore, the oil dispersion and OMA formation at different dispersant-to-oil ratio (DOR) were evaluated in a wave tank. When DOR was less than 1:40, the effect of dispersant on the dispersion of spilled oil was not obvious. With the increasing DOR, the effect became more pronounced, and the adhesion between oil droplets and kaolin was inhibited. The size ratio between oil droplets and particles is the significant factor for OMA formation. The closer the oil-mineral size ratio is to 1, the more difficultly the OMA forms.

Cellular accumulation of crude oil compounds reduces the competitive fitness of the coral symbiont Symbiodinium glynnii

Oil spill events in the marine environment can have a deleterious impact on the affected ecosystems, such as coral reefs, with direct consequences for their socioeconomic value. The mutualistic relationship between tropical corals and their dinoflagellate symbionts (Symbiodiniaceae) provide structural and nutritional basis for a high local biodiversity in oligotrophic waters. Here, we investigated effects of crude oil water-accommodated fraction on the competitive fitness of the model zooxanthellae species Symbiodinium glynnii. Results of laboratory essays demonstrate that crude oil carbon is incorporated into the cellular biomass with a concomitant change of δ¹³C isotopic value. Carcinogenic/mutagenic polycyclic aromatic hydrocarbons were identified in the culture media and were responsible for a linear reduction in population growth of S. glynnii, presumably related to energy relocation for DNA repair. Additionally, the experiments revealed that physiological effects induced by crude oil compounds are genetically inherited by the following generations under non-contaminated growth conditions, and induce a reduction in the competitive fitness to cope with other environmental parameters, such as low salinity. We suggest that the effects of crude oil contamination represent an imparing factor for S. glynnii coping with anthropogenic drivers (e.g. warming and acidification) and interfere with the delicate symbiont-host relationship of tropical corals. This is especially relevant in the coastal areas of northeastern Brazil where an oil spill event deposited crude oil on shallow water sediments with the potential to be resuspended to the water column by physical and/or biological activity, enhancing the risk of future coral bleaching events.

Oil dispersion and aggregation with suspended particles in a wave tank

Suspended particulate matter (SPM) in marine environments plays an important role in determining the fate of spilled oil via the generation of oil-particle aggregates (OPAs). A series of mesoscale wave tank experiments and sedimentation tests were conducted to fill the knowledge gap on how the turbulent mixing, temperature, and oil type affect the dispersion of spilled oil and properties of OPAs. Generally, the oil dispersing efficiency was significantly enhanced by high wave energy, which also led to effective oil sinking, large size of OPAs and wide distribution of trapped oil. Nonlinear fitting results indicated that the oil sinking efficiency followed an exponential growth over time. The effect of temperature on oil dispersion and formation of OPAs is primarily attributed to its influence on oil viscosity and interfacial tension. Viscous oils are more likely to interact with particles above 25 °C. However, below 20 °C, a specific oil viscosity that will bring about the maximum OPAs exists. Excessive oil viscosity will lead to a weak binding between oil and SPM and a centralized distribution of trapped oil. Furthermore, spilled oil with a high asphaltene can interact more effectively with particles. Our finding suggested that early prevention of offshore oil sinking is key in summer.

Antioxidant Response and Oxidative Stress in the Respiratory Tree of Sea Cucumber (Apostichopus japonicus) Following Exposure to Crude Oil and Chemical Dispersant

Sea cucumber (Apostichopus japonicus) is mainly cultured in the coastal zone, where it is easily threatened by accidental oil spills. Chemical dispersant is one of the efficient oil spill responses for mitigating the overall environmental damage of oil spills. However, the impact of crude oil and chemical dispersants on sea cucumber is less well known. Hence, the present study focused on exploring the antioxidant response and oxidative stress in the respiratory tree of sea cucumber following exposure to GM-2 chemical dispersant (DISP), water-accommodated fractions (WAF), and chemically enhanced WAF (CEWAF) of Oman crude oil for 24 h. Results manifested that WAF exposure caused a significant increase in the reactive oxygen species (ROS) level (5.29 ± 0.30 AU·mgprot−1), and the effect was much more obvious in CEWAF treatment (5.73 ± 0.16 AU·mgprot−1). Total antioxidant capacity (T-AOC), as an important biomarker of the antioxidant defense capacity, showed an increasing trend following WAF exposure (0.95 ± 0.12 U·mgprot−1) while a significant reduction in T-AOC was observed following CEWAF exposure (0.23 ± 0.13 U·mgprot−1). Moreover, we also evaluated the oxidative damage of the macromolecules (DNA, protein, and lipid), and our results revealed that the presence of chemical dispersant enhanced oxidative damage caused by crude oil to sea cucumber.

Effect of the concentration and size of suspended particulate matter on oil-particle aggregation

After spill, the dispersed oil droplets may collide with suspended particulate matter in the water column to form oil-particle aggregates (OPAs) in turbulent environments. It may be an effective pathway to stabilize the oil by taking advantage of the particulate matter to clean up the contaminated waters. A theoretical model in Payne et al. (2003) is adopted to describe the oil-particle aggregation, and a solution method is proposed and validated against a group of experiments. The effect of the particle size and mass concentration on the aggregation has been examined quantitatively in detail. The particles and the oil droplets are consumed at a fixed ratio. Under the same mass concentration, smaller particles can trap more oil droplets, while larger particles tend to interact more quickly with the oil. The oil-particle aggregation rate and the oil trapping efficiency mainly depend on the particle concentration. The theoretical model is applied to predict the decrease of the dispersed oil in nearshore environments, based on the parameters obtained from the experiments. It is efficient to promote the oil-particle aggregation by increasing the particle concentration in the closed bay. In the open sea, the decrease of the dispersed oil can be effectively enhanced by increasing the particle concentration when it is below 0.50 kg/m³. The information presented in this paper can serve to predict the fate of the dispersed oil in coastal waters and provide technical support for oil spill management strategies.