Environmental vulnerability to oil spills in Itapuã State Park, Rio Grande do Sul, Brazil: An approach using two-dimensional numerical simulation.

The growing use of coastal areas for different economic purposes is responsible for increasing pollution by hydrocarbons in marine environments. As a consequence of these activities, accidents during fuel extraction, transport, and storage can occur, causing intense environmental degradation. Numerical modeling of the trajectory of oil stains becomes an important tool with low operational costs, providing powerful support to the government agencies in charge of risk management associated with possible oil accidents, by helping to generate scenarios and strategies for containment and cleaning of affected environments. In this sense, the aim of this study is to estimate environmental vulnerability to oil at beaches located in the Itapuã State Park (PEI), a Protection Conservation Unit. This work focused on describing a methodology to estimate the vulnerability of coastal areas, with emphasis on the fact that the study was carried out in a closed environment. For that, an approach was used based on the integration of: (1) an intrinsic variable to the environment; (2) a dynamic variable determined through diesel oil surface dispersion scenarios. Four hypothetical accident scenarios with 20 m³ of diesel oil were simulated in 2018, during five days of simulations with instant dumping in the navigation channel of the local waterway near the PEI. The results suggest the forcing of the field of intensity and direction of the local winds as preponderant for the dynamics of movement and structure of the spots, with the zonal and meridional components of the fields of superficial currents acting in this process as a secondary factor. The study showed that all beaches in the park are susceptible to contact with oil throughout the simulated year, with Pombas Beach, Pedreira Beach, and Onça Beach being affected in all simulated scenarios, which classifies them as very high vulnerability and defines them as priority protection areas.

Integrated environmental vulnerability to oil spills in sensitive areas.

As the typical range of influence of oil spills surrounds urbanised and economically active areas, it is likely that fragile regions may not be part of the most vulnerable zones. This premise is remediated in this paper with the adoption of a vulnerability approach based on the integration of static and dynamic information, such as oil pollution susceptibility. Susceptibility is a poorly consolidated term and is often used as synonym for environmental sensitivity; it is considered here to be the distribution areas of oil slicks. To test the proposed approach, an integrated estimation of environmental vulnerability is carried out for an environmentally sensitive area in the south of Brazil by merging static data inherent to the medium with information of a dynamic nature related to trajectory, behaviour and the fate of oil at sea. Moreover, the oil pollution intensity and environmental sensitivity data in susceptible areas are addressed. Subsequently, the environmental vulnerability is estimated by integrating hazard maps, concentrations and losses of the mass of the oil slick, oil beaching time and the littoral sensitivity index hierarchy. Results will prove to be useful to highlight critical areas for which the highest levels of severity are expected, which can lead to improvements in decision-making processes to support oil-spill prevention, as well as improve response readiness, especially in developing countries that have historically under-protected their sensitive regions.

Oil permeability variations on lagoon sand beaches in the Patos-Guaíba system in Rio Grande do Sul, Brazil.

Permeability is the ability of a sediment deposit to allow fluids to pass through it. It depends on the local types of sediments. When the fluid is oil, high permeability implies greater interaction with the site and more extensive damage, which makes recovery most difficult. Knowledge of permeability oscillations is necessary to understand oil behavior and improve cleanup techniques. The goal is to determine oil permeability variations on lagoon sand beaches. Oil permeability tests were performed at the beach face, using a Modified Phillip Dunne Permeameter and parameters were sampled. Permeability of lagoon beaches is driven by grain diameter and roundness, soil compaction, and depth of the water table. Factors that enhance permeability include: sand sorting, vertical distribution of sediments and gravel percentage. High permeability on lagoon beaches is related to polymodal distribution, to the sediment package, and to the system's low mobility.