Biochemical tests to determine the biodegradability potential of bacterial strains in PAH polluted sites.

Although the use of degrading-bacteria is one of the most efficient methods for the bioremediation of polluted sites, detection, selection and proliferation of the most efficient and competing bacteria is still a challenge. The objective of this multi-stage research was to investigate the effects of the selected bacterial strains on the degradation of anthracene, florentine, naphthalene, and oil, determined by biochemical tests. In the first stage, using the following tests: (a) biosurfactant production (emulsification, oil spreading, number of drops, drop collapse, and surface tension), (b) biofilm production, (c) activity of laccase enzyme, and (d) exopolysaccaride production, the three bacterial strains with the highest degrading potential including Bacillus pumilus, B. aerophilus, and Marinobacter hydrocarbonoclasticus were chosen. In the second stage using the following tests: (a) bacterial growth, (b) laccase enzyme activity, and (c) biosurfactant production (emulsification, oil spreading, and collapse of droplet) the degrading ability of the three selected bacterial strains plus Escherichia coli were compared. Different bacterial strains were able to degrade anthracene, florentine, naphthalene, and oil by the highest rate, three days after inoculation (DAI). However, M. hydrocarbonoclasticus showed the highest rate of florentine degradation. Although with increasing pollutant concentration the degrading potential of the bacterial strains significantly decreased, M. hydrocarbonoclasticus was determined as the most efficient bacterial strain.

Oil Transport Following the Deepwater Horizon Blowout.

The Deepwater Horizon oil spill in the Gulf of Mexico in 2010 was the largest in US history, covering more than 1,000 km of shorelines and causing losses that exceeded $50 billion. While oil transformation processes are understood at the laboratory scale, the extent of the Deepwater Horizon spill made it challenging to integrate these processes in the field. This review tracks the Deepwater Horizon oil during its journey from the Mississippi Canyon block 252 (MC252) wellhead, first discussing the formation of the oil and gas plume and the ensuing oil droplet size distribution, then focusing on the behavior of the oil on the water surface with and without waves. It then reports on massive drifter experiments in the Gulf of Mexico and the impact of the Mississippi River on the oil transport. Finally, it concludes by addressing the formation of oil-particle aggregates. Although physical processes lend themselves to numerical modeling, we attempted to elucidate them without using advanced modeling, as our goal is to enhance communication among scientists, engineers, and other entities interested in oil spills.

Characterization of the physical and weathering properties of low sulfur fuel oil (LSFO) and its spreading on water surface.

Effective countermeasures against the marine pollution caused by spilled oil are enabled based on the understanding of its physical and weathering characteristics. In that sense, our knowledge of the newly enforced low-sulfur fuel oil (LSFO) needs to be secured urgently. First, we show that the oil viscosity increases with decreasing temperature, following the William-Landel-Ferry law developed for bunker oil. The meso-stable emulsion is achieved from the emulsion test, of which the viscosity is 10-100 times larger than the normal one. On the other hand, the portion of the evaporation of LSFO was insignificant (less than 3%), and thus, its effect on the oil properties is not substantial except the increase of the viscosity. In addition, we experimentally examine the spreading features (e.g., spreading area and rate) of LSFO on the water surface in the circulating water bath. We find that initially, the oil spreading area increases quite fast but saturates, of which the details are explained in terms of the driving and retarding forces involved in the spreading processes. Finally, considering the procured properties of the LSFO, we performed a numerical simulation of spreading LSFO on the water surface with a scale of hundred meters, which shows that our analysis can be extended to larger scales.

Stretchable skin hydrating PVB patches with controlled pores' size and shape for deliberate evening primrose oil spreading, transport and release.

With the increasing number of skin problems such as atopic dermatitis and the number of affected people, scientists are looking for alternative treatments to standard ointment or cream applications. Electrospun membranes are known for their high porosity and surface to volume area, which leads to a great loading capacity and their applications as skin patches. Polymer fibers are widely used for biomedical applications such as drug delivery systems or regenerative medicine. Importantly, fibrous meshes are used as oil reservoirs due to their excellent absorption properties. In our study, nano- and microfibers of poly (vinyl butyral-co-vinyl alcohol-co-vinyl acetate) (PVB) were electrospun. The biocompatibility of PVB fibers was confirmed with the keratinocytes culture studies, including cells' proliferation and replication tests. To verify the usability and stretchability of electrospun membranes, they were tested in two forms as-spun and elongated after uniaxially stretched. We examine oil transport through the patches for as-spun fibers and compare it with the numerical simulation of oil flow in the 3D reconstruction of nano- and microfiber networks. Evening primrose oil spreading and water vapor transmission rate (WVTR) tests were performed too. Finally, for skin hydration tests, manufactured materials loaded with evening primrose oil were applied to the forearm of volunteers for 6 h, showing increased skin moisture after using patches. This study clearly demonstrates that pore size and shape, together with fiber diameter, influence oil transport in the electrospun patches allowing to understand the key driving process of electrospun PVB patches for skin hydration applications. The oil release improves skin moisture and can be designed regarding the needs, by manufacturing different fibers' sizes and arrangements. The fibrous based patches loaded with oils are easy to handle and could remain on the altered skin for a long time and deliver the oil, therefore they are an ideal material for overnight bandages for skin treatment.

A Lagrangian analysis of the gravity-inertial oil spreading on the calm sea using the reflective oil-water interface treatment.

Negative impacts are caused by oil spills on coastal ecosystems. In the phenomenon of oil spreading, the knowledge of the physical properties of the pollutant, such as velocities and positions, is of fundamental importance for the adoption of timely contingency measures to protect the environment (Fraga Filho, Smoothed Particle Hydrodynamics: Fundamentals and Basic Applications in Continuum Mechanics, 2019). This paper presents a Lagrangian particle modelling for the prediction of the oil slick diameter in the first stage of the oil spreading on a calm sea. At the first studies on the oil spreading (Fay, The Spread of Oil Slicks on a Calm Sea, 1969; Fay, Physical Processes in the Spread of Oil on a Water Surface, 1971), curves were adjusted to laboratory experimental data. The modelling employed in this work is based on the continuum Navier-Stokes equations, and the Smoothed Particle Hydrodynamics (SPH) method has been used to obtain the solution for the conservation equations of mass and momentum. The oil-water interface was treated using a reflective treatment. The solution achieved was compared to the oil slick diameter predicted by Fay's equation, and an error lower than 1% was found.

Extended oil spill spreading with Langmuir circulation.

When spilled in the ocean, most crude oils quickly spread into a thin film that ruptures into smaller slicks distributed over a larger area. Observers have also reported the film tearing apart into streaks that eventually merge forming fewer but longer bands of floating oil. Understanding this process is important to model oil spill transport. First, slick area is calculated using a spreading model. Next, Langmuir circulation models are used to approximate the merging of oiled bands. Calculations are performed on Troll blended and Alaska North Slope crude oils and results compared with measurements from the 1990s North Sea field experiments. Langmuir circulation increases the oil area but decreases the surface coverage of oil. This work modifies existing oil spreading formulas by providing a surface area correction due to the effects of Langmuir circulation. The model's simplicity is advantageous in situations with limited data, such as emergency oil spill response.

Role of self-assembled surfactant structure on the spreading of oil on flat solid surfaces.

Uniform spreading of oil on solid surfaces is important in many processes where proper lubrication is required and this can be controlled using surfactants. The role of oil-solid interfacial self-assembled surfactant structure (SASS) in oil spreading is examined in this study for the case of hexadecane-surfactant droplet spreading on a flat horizontal copper surface, with triphenyl phosphorothionate surfactants having varying chain lengths (0 to 9). It is shown that the frictional forces (F(SASS)) as determined by the SASS regulate droplet spreading rate according to surfactant chain length; surfactants with longer chains led to higher reduction in the spreading rate. The extent of such forces, F(SASS), depends on the surfactant density of the evolving SASS, and specific configuration the evolving SASS exhibit as per the orientations of the surfactant chains therein. Thus, F(SASS)=[k(1)+k(2(t))] Γ(δ(t)), where Γ(δ(t)) is the surfactant adsorption density of SASS at time 't' during evolution, and, k(1) and k(2(t)) are the force coefficients for Γ(δ(t)) and orientations (as a function of spreading time) of the surfactant chains respectively. As a SASS evolves/grows along with adsorption of surfactants at the spreading induced fresh interface, the k1Γ(δ(t)) component of F(SASS) increases and contributes to reduction in the net spreading force (S). With a decrease in the net spreading force, the existence of a cross-over period, during which the transition of the spatial dynamics of the chains from disordered to realignment/packing induced ordered orientation occurs, has been inferred from the F(SASS) vs. chain length relationships. Such relationships also suggested that the rate of realignment/packing is increased progressively particularly due the realignment/packing induced decrease in the net spreading force. Therefore, the realignment process is a self-induced process, which spans a measurable period of time (several minutes), the cross-over period, during which the net spreading force decreases essentially due to such self-induced process.