Isolation,biodegradation ability and molecular detection of hydrocarbon degrading bacteria in petroleum samples from a Brazilian offshore basin

The detection of microorganisms with potential for biodeterioration and biodegradation in petroleum fields is of great relevance, since these organisms may be related to a decrease in petroleum quality in the reservoirs or damage in the production facilities. In this sense, petroleum formation water and oil samples were collected from the Campos Basin, Brazil, with the aim of isolating microorganisms and evaluating their ability to degrade distinct classes of hydrocarbon biomarkers (9,10-dihydrophenanthrene, phytane, nonadecanoic acid and 5α-cholestane). Twenty eight bacterial isolates were recovered and identified by sequencing their 16S rRNA genes. Biodegradation assays revealed that bacterial metabolism of hydrocarbons occurred through reactions based on oxidation, carbon–carbon bond cleavage and generation of new bonds or by the physical incorporation of hydrocarbons into microbial cell walls. Based on the biodegradation results, selective PCR-based systems were developed for direct detection in petroleum samples of bacterial groups of interest, namely Bacillus spp., Micrococcus spp., Achromobacter xylosoxidans, Dietzia spp. and Bacillus pumilus. Primer sets targeting 16S rRNA genes were designed and their specificity was confirmed in silico (i.e. computational analysis) and in PCR reactions using DNA from reference strains as positive and negative controls. Total DNA from oil was purified and the amplification tests revealed the presence of the target bacteria in the samples, unraveling a significant potential for petroleum deterioration in the reservoirs sampled, once proper conditions are present for hydrocarbon degradation. The application of molecular methods for rapid detection of specific microorganisms in environmental samples would be valuable as a supporting tool for the evaluation of oil quality in production reservoirs.     

Aeolian dune migration along the Ceará coast, north-eastern Brazil

Aeolian dune dimensions and migration rates are analysed along the Ceará coast, north-east Brazil. Dunes that are currently mobile along the Ceará coast are composed of barchans and sand sheets. The results show that barchans maintain an equilibrium form, which can be characterized by values of dimensionless shape parameters H/W and W/L , where H is the dune height, W is the wing-to-wing width and L is the dune length. Dunes are highly mobile, with average migration rates of 17·5 m year⁻¹ for barchans and 10 m year⁻¹ for sand sheets. The calculated migration rates were found to depend strongly on dune dimensions for both barchans and sand sheets, i.e. the larger the dune is, the lower the migration rate will be. This size dependence was associated with the existence of a representative common transport rate along the dune fields, which induces a different dune migration rate dependent on dune size. Finally, from the observed dune evolution, an aggregated scale aeolian sediment transport was inferred. This bulk transport rate, of the order of 90–100 m³ m⁻¹ year⁻¹, is only valid for a timescale of years to decades, which is the timescale used in dune evolution analysis.     

Nonlinear FE model updating and reconstruction of the response of an instrumented seismic isolated bridge to the 2010 Maule Chile earthquake

Nonlinear finite element (FE) modeling has been widely used to investigate the effects of seismic isolation on the response of bridges to earthquakes. However, most FE models of seismic isolated bridges (SIB) have used seismic isolator models calibrated from component test data, while the prediction accuracy of nonlinear FE models of SIB is rarely addressed by using data recorded from instrumented bridges. In this paper, the accuracy of a state‐of‐the‐art FE model is studied through nonlinear FE model updating (FEMU) of an existing instrumented SIB, the Marga‐Marga Bridge located in Viña del Mar, Chile. The seismic isolator models are updated in 2 phases: component‐wise and system‐wise FEMU. The isolator model parameters obtained from 23 isolator component tests show large scatter, and poor goodness of fit of the FE‐predicted bridge response to the 2010 Mw 8.8 Maule, Chile Earthquake is obtained when most of those parameter sets are used for the isolator elements of the bridge model. In contrast, good agreement is obtained between the FE‐predicted and measured bridge response when the isolator model parameters are calibrated using the bridge response data recorded during the mega‐earthquake. Nonlinear FEMU is conducted by solving single‐ and multiobjective optimization problems using high‐throughput cloud computing. The updated FE model is then used to reconstruct response quantities not recorded during the earthquake, gaining more insight into the effects of seismic isolation on the response of the bridge during the strong earthquake.     

Spectroscopic Characterization of Organic Structures and Organic‐Inorganic Interactions in Paper Mill Sludge

The organic composition and organic‐inorganic interaction in paper mill sludge (PS) solvent extracts (hexane, ethyl acetate, acetone and ethanol) and humic fractions, humic acid (HA) and humin (HU) were studied by electron paramagnetic resonance spectroscopy (EPR), proton and carbon‐13 nuclear magnetic resonance spectroscopy (¹H NMR; ¹³C NMR), Fourier‐transformed infrared spectroscopy (FTIR), and ultraviolet‐visible spectroscopy (UV‐vis). The strategy of fractionating the PS, sequentially, with organic solvents of increasing polarity is a reliable analytical procedure for humic substance sample separation because it results in more purified fractions. FTIR, ¹H NMR and ¹³C NMR results showed that hexane extract consisted mainly of aliphatic hydrocarbon structures. Their contents in the extracts decreased as the polarity of the extracting solvent increased and the content of oxygen functional groups increased. Carboxylic and carboxylate functional groups were found in the acetone extract, and ester and ether functions were predominantly found in the ethanol extract. EPR spectra revealed some Fe³⁺ complexes with rhombic structure (g₁ = 4.3; g₂ = 9.0) in the humic fractions and in all solvent extracts, except hexane. Quasi‐octahedral Fe³⁺ complexes (g = 2.3; ΔH_pp ≤ 400 G) were found in the HU fraction and in the acetone extract. The organic free radical content in the HA fraction was higher than the non‐fractionated PS sample and HU fraction.     

Climatic signals in lacustrine deposits of the Upper Yacoraite Formation,Western Argentina: Evidence from clay minerals,analcime, dolomite and fibrous calcite

Authigenic clays are an important control on reservoir quality in lacustrine carbonates but remain challenging to predict. Lacustrine depositional systems respond to climatic variations in rainfall, surface runoff and groundwater input, and evaporation, and result in rapid and frequent changes in lake volume; this is expressed through changing water depth and shoreline position. In the upper portion of the Early Palaeocene Yacoraite Formation of the Salta Basin in Argentina, extensive lacustrine deposits were deposited during the sag phase of rifting. Prior high-resolution stratigraphic studies have suggested that climatic factors control microbial carbonate sequences within a ‘balanced fill’ lake, with variation in the lake level having a major influence on facies association changes. This study characterizes the evolution of facies and mineralogy within the Yacoraite Formation, focusing on the distribution of clay minerals, making a link between the high, medium and low-frequency sequence stratigraphic cycles. The low-frequency transgressive hemicycle of the upper portion of the Yacoraite Formation is comprised of abundant siliciclastic facies, suggesting a wetter period. Microbialites occurring in this interval are coarse-grained and agglutinated. Detrital clay minerals such as illite and chlorite and associated siliciclastic sediments were input to the lake during high-frequency transgressive periods. During high-frequency regressive hemicycles, sedimentation was dominated by carbonate facies with Ca-rich dolomite and the authigenic clays are comprised of chlorite/smectite mixed-layers. By contrast, the low frequency regressive hemicycle records fine-grained agglutinated microbialite with horizons of fibrous calcite, more stoichiometric dolomite, barite and authigenic magnesian smectite. This indicates elevated ion concentrations in the lake under intense evaporation during an arid period. Understanding the conditions that are favourable for formation and preservation of authigenic clays within the lacustrine environment can improve understanding of reservoir quality in comparable economically important deposits.     

Adjustability of exposed elements by updating their capacity for resistance after a damaging event: application to an earthquake–tsunami cascade scenario

Natural Hazards - The 2011 Great East Japan earthquake and tsunami remind us once again that these types of cascade event can occur and cause considerable damage. The scientific community realizes...     

Digital mapping of coastal boulders – high-resolution data acquisition to infer past and recent transport dynamics

Coastal boulder fields provide clues to long-term frequency-magnitude patterns of coastal flooding events and have the potential to play an important role in coastal hazard assessment. Mapping boulders in the field is time and labour-intensive, and work on intertidal reef platforms, as in the present study, is physically challenging. By addressing coastal scientists who are not specialists in remote sensing, this contribution reports on the possibilities and limitations of digital applications in boulder mapping in Eastern Samar, Philippines, where recent supertyphoons Haiyan and Hagupit induced high waves, coastal flooding and boulder transport. It is demonstrated how satellite imagery of sub-metre resolution (from Pléiades and WorldView-3 imagery) enables efficient analysis of transport vectors and distances of larger boulders, reflecting variation in latitudes of both typhoon tracks and approaching angles of typhoon-generated waves. During the investigated events, boulders with a-axes of up to 8 m were clearly identified to have been shifted for up to 32 m, mostly along the seaward margin of the boulder field. It is, however, hard to keep track of smaller boulders, and the length of a-axes and b-axes including their orientation is often impossible to map with sufficient accuracy. Orthophotographs and digital surface models created through the application of an unmanned aerial vehicle and the ‘Structure from Motion’ technique provide ultra-high-resolution data, and have the potential to not only improve the results of satellite image analysis, but also those from field mapping and may significantly reduce overall time in the field. Orthophotographs permit unequivocal mapping of a-axes and b-axes including their orientation, while precise values for c-axes can be derived from the respective digital surface models. Volume of boulders is best inferred from boulder-specific Structure from Motion-based three-dimensional models. Battery power, flight speed and altitude determine the limits of the area covered, while patches shielded by the boulders are difficult to resolve. For some tasks, field mapping remains mandatory and cannot be replaced by currently available remote sensing tools: for example, sampling for rock type, density and age dating, recording of lithological separation of boulders from the underlying geological unit and of geomorphic features on a millimetre to decimetre-scale, or documentation of fine-grained sediment transport in between the boulders in supratidal settings. In terms of future events, the digital products presented here will provide a valuable reference to track boulder transport on a centimetre to decimetre-scale and to better understand the hydrodynamics of extreme-wave events on a fringing reef coastline.