[en] Short communication

[en] The feasibility of developing natural dispersants (biodispersants) for use in response to a marine oil spill was discussed. In this study biochemical tests were conducted with Bacillus and Coccus Gram Positive bacteria in order to select the one marine microorganism which is capable of producing biodispersants to degrade crude oil. Different carbon sources and salt concentrations were used in the experiments. A second experiment was conducted in which the production of biodispersants by the pure microbial strain were studied by measuring interfacial tension, determined by using the Longman method. The surfactant efficacy and the dispersant stability of Arabian Light crude oil was also studied. The biological oxygen demand at five days, biological oxygen demand at the end of the biodegradation, the biodegradation constant and the biochemical stabilization constant were determined during the degradation process. 23 refs., 9 tabs.,4 figs

[en] The physical and chemical properties of Pina crude oil are analyzed, and the evaporation of this same crude oil spilled at sea and on calcareous type beach sand is described. The properties were analyzed for future uses in simulations of oil spills at sea. Among the parameters used in the characterization are specific gravity, viscosity, flash point, hydrocarbon groups, sulphur content, distillation, and interfacial and surface tension. In the evaporation process, the influence of layer thickness of crude oil and the influence of the height of the air chamber for the same thickness of crude oil at different wind velocities and conditions was of particular interest. The evaporated fraction was also correlated with the time and qualitative and quantitative variation of the components of the crude oil were studied by gas chromatography. The maximum per cent of evaporation over a 28 day period was 39 per cent at sea and 35.4 per cent when the same crude was spilled on sand. 5 refs., 6 figs

[en] Creation of a geographic information system (GIS), connected to the OILMAP simulation model, and specific for the Balearic Islands is described. The resulting GIS includes information about the coastal areas of the islands, indicating the most sensitive areas (fisheries, natural parks, beaches and their sand type, dimensions, potential occupancy and services). The natural parks bordering the littoral region of the Balearic sea (in Majorca, Menorca, Formentera and Cabrera) are classified by extension, flora and fauna and other characteristics. Data concerning the tanker routes that pass through the Balearic Sea are entered. With the aid of the computer program OILMAP (developed by Applied Science Associates) different types of tanker oil spills are simulated to evaluate the potential risk zones and the effects that an oil spill could create for the Islands

[en] Synchronization of periodic and chaotic oscillations between two coupled rotating baroclinic fluid systems will be presented. The numerical part of the study involves a pair of coupled two-layer quasigeostrophic models, and the experimental part comprises two thermally coupled baroclinic fluid annuli, rotating one above the other on the same turntable. Phase synchronization and imperfect synchronization (phase slips) have been found in both model and experiments, and model simulations also exhibit chaos-destroying synchronization.

[en] This work is about the anthropogenic historic impacts in subtidal environments in Montevideo Bay. The studies carried out in the sediments enable to conclude that the increase of the industrial discharges (nutrients, heavy metals) are the cause of the chemical changes in the sediment of the Montevideo Bay

[en] The ability of a mixed marine bacteria culture to degrade Pina Cuban crude oil in the presence of nutrients and sea water was studied. Laboratory experiments were conducted in flasks with 100 ml of saline liquid containing 1 per cent crude. The flasks were inoculated with marine bacteria (IDO-225, IDO-226, and IDO-229) at a final concentration of 10⁶ cell/ml. The cultures were grown at 29 degrees C for 21 days. Bacterial growth, and surface and interfacial tension were measured after 5, 13 and 21 days. Results showed that the marine bacteria were effective in accelerating the biodegradation process of Pina Cuban oil. The efficiency of the process increased when nutrients were added to the system. This biopreparation also accelerated emulsification of the oil without any negative effects to the natural microbiota. The biological oxygen demand at five days and at the end of the experiment was determined. The biodegradation constant and the biochemical stabilization constant were also measured. 14 refs., 5 tabs., 4 figs

[en] Highlights: • Humid tropical forests are often ill-adapted to fire. • Post-fire restoration strategies depend strongly on context. • Restoration practice should account for fire severity. • Fire poses a recurring and intensifying threat throughout the recovery process. • Landscape approaches are crucial to address the spatiotemporal dynamics of fire. Humid tropical forests are increasingly exposed to devastating wildfires. Major efforts are needed to prevent fire-related tipping points and to enable the effective recovery of fire-affected areas. Here, we provide a synthesis of the most common forest restoration strategies, thereby focusing on post-fire forest dynamics in the humid tropics. A variety of restoration strategies can be adopted in restoring humid tropical forests, including natural regeneration, assisted natural regeneration (i.e. fire breaks, weed control, erosion control, topsoil replacement, peatland rewetting), enrichment planting (i.e. planting nursery-raised seedlings, direct seeding) and commercial restoration (i.e. plantation forests, agroforestry). Our analysis shows that while natural regeneration can be effective under favourable ecological conditions, humid tropical forests are often ill-adapted to fire, and therefore less likely to recover unassisted after a wildfire event. Active restoration practices may be more effective, but can be costly and challenging to implement. We also identify gaps in knowledge needed for effective restoration of humid tropical forests after fire, hereby taking into account the ecosystems and socio-economic conditions in which these fires occur. We suggest to incorporate fire severity in future studies, to better understand and predict post-fire ecosystem responses. In addition, as fire poses a recurring and intensifying threat throughout the recovery process, more emphasis should be placed on post-restoration management and the prevention of fire throughout the different phases of the restoration process. Furthermore, as tropical wildfires are increasing in scale, establishing collaborative capacity and setting priorities for efficient resource allocation should become a major priority for restoration practitioners in the humid tropics. Finally, as global fire regimes are changing and expected to intensify in the context of climate change, land use and land cover change, we suggest to put continuous effort into fire monitoring and modelling to inform the development of effective restoration strategies in the long-run.

[en] The electron drift velocity, the longitudinal diffusion coefficient and the effective ionization coefficients in C₂F₆ and its mixtures with Ar and N₂ have been studied in a pulsed Townsend experiment. The density-reduced electric field strength E/N, was varied widely in the range 0.1-500 Td (1 Td = 10^-17 V cm²). In all cases, negative differential conductivity (NDC) regions were found in the plots of the electron drift velocity as a function of E/N. Our drift velocity values were found to be in good agreement with previous work on C₂F₆ and its mixtures. In some cases, the E/N range was increased. The longitudinal diffusion coefficient also displays the NDC effects; these are more pronounced as the C₂F₆ content in the mixture decreases. The effective ionization coefficient for C₂F₆ was measured over a wider range of E/N than that covered by previous studies. Our effective ionization coefficients for C₂F₆ and those derived previously disagree strongly. We are not aware of any previously published data on effective ionization coefficients for the mixtures herein studied. The limiting field strength for C₂F₆-N₂ turned out to be nearly a factor of two higher than that for C₂F₆-Ar, for C₂F₆ concentrations being less than 10% in both mixtures