Uncertainty in predictions of oil spill trajectories in open sea

A method is introduced to calculate and to account for the uncertainties in the predictions of oil spill trajectories using a classic oil spill model. The method considers the output of the oil spill model as a function of random variables, which are the input parameters, and calculates the standard deviation of the output results which gives a measure of the uncertainty of the model given the uncertainties of the input parameters.Instead of a single trajectory that is calculated by the oil spill model using the mean values of the parameters, a band of trajectories can be defined when various simulations are done taking into account the uncertainties of the input parameters. This band of trajectories defines envelopes of the trajectories that are likely to be followed by the spill given the uncertainties of the input.The method is applied to an oil spill that occurred in open sea near Madeira Islands, in the Atlantic Ocean, in December 1989. The simulations allow the understanding of how a change in the wind direction drove the spill towards the Islands.The envelope of likely trajectories that is obtained with the uncertainty modelling shows a band of trajectories that is in better agreement with the observations than the single trajectory simulated by the oil spill model, based on mean parameters.     

Assessment of cytochrome P450 1A in harbour seals (Phoca vitulina) using a minimally-invasive biopsy approach

Biomarkers of organochlorine exposure, such as the induction of cytochrome P450 1A (CYP1A), can be used to assess the impact of environmental contaminants on the health of free-ranging marine mammal populations. The objective of the present study was to measure CYP1A in skin and liver biopsies obtained from live harbour seals (Phoca vitulina). Twelve harbour seal pups, aged three to five weeks, were captured from the Fraser River estuary, British Columbia, Canada, and temporarily held in captivity. Skin ( approximately 60 mg) and liver ( approximately 40 mg) biopsies, obtained while seals were under general anaesthesia, yielded sufficient tissue for the measurement of CYP1A by immunoblot analysis and ethoxyresorufin O-deethylase activity. A short-term exposure experiment, in which harbour seals (n=3) were treated orally with beta-naphthoflavone (BNF), resulted in increased hepatic and cutaneous CYP1A protein levels, consistent with observations in other mammals. This study is the first to measure CYP1A in skin and liver biopsies from live harbour seals and to report in vivo BNF-associated CYP1A induction in a marine mammal. The results demonstrate that microsamples collected using minimally-invasive techniques can provide toxicologically-relevant information form marine mammals.     

Effects of crab–halophytic plant interactions on creek growth in a S.W. Atlantic salt marsh: A Cellular Automata model

The Bahía Blanca Estuary (38° 50′ S, and 62° 30′ W) presents salt marshes where interactions between the local flora (Sarcocornia perennis) and fauna (Chasmagnathus granulatus) generate some kind of salt pans that alter the normal water circulation and condition its flow and course towards tidal creeks. The crab–vegetation dynamics in the salt marsh presents variations that cannot be quantified in a reasonable period of time. The interaction between S. perennis plant and C. granulatus crab is based on simple laws, but its result is a complex biological mechanism that causes an erosive process on the salt marsh and favors the formation of tidal creeks. To study it, a Cellular Automata model is proposed, based on the laws deduced from the observation of these phenomena in the field, and then verified with measurable data within macroscale time units. Therefore, the objective of this article is to model how the interaction between C. granulatus and S. perennis modifies the landscape of the salt marsh and influences the path of tidal creeks. The model copies the basic laws that rule the problem based on purely biological factors.The Cellular Automata model proved capable of reproducing the effects of the interaction between plants and crabs in the salt marsh. A study of the water drainage of the basins showed that this interaction does indeed modify the development of tidal creeks. Model dynamics would likewise follow different laws, which would provide a different formula for the probability of patch dilation. The patch shape can be obtained changing the pattern that dilates.     

Remote sensing and surface POC concentration in the South Atlantic

Several SeaWiFS products have been compared with shipboard data to assess the possibility of using remote sensing to estimate particulate organic carbon (POC) concentration in surface waters. Transmissometer data were collected during six South Atlantic Ventilation Experiment (SAVE) hydrographic expeditions conducted between November 1987 and March 1989 from R/V Knorr, and Melville. A total of 361 beam attenuation profiles were made with a SeaTech transmissometer interfaced with a CTD/rosette. In order to calculate the POC concentration from transmissometer profiles, a regression between beam attenuation and POC for open Atlantic Ocean waters derived from our research in the North Atlantic (North Atlantic Bloom Experiment, NABE) and enhanced by data from the Bermuda Atlantic Time Series Station (BATS) was applied. The profiles were processed and examined as vertical sections of the surface 250 m. The data were collected in two successive years, during the same season, which allowed us to compile a combined data set over the austral summer for examination. Beam attenuation/POC concentrations were integrated down to one attenuation depth with the intent of making comparisons with satellite optical data. No satellite optical data were available for 1987–1989, so the only option was to compare our integrated data with SeaWiFS-derived variables from later years averaged over the same season as SAVE data. Analysis of four SeaWiFS products acquired from 1997 to 2002 demonstrated very low variations from year to year for seasonally averaged data, suggesting that making comparisons of the beam attenuation/POC fields with averaged satellite optical products from later years is a valid (though not optimal) approach for this area. The highest correlation between beam attenuation/POC concentration and remotely derived products was found with normalized water-leaving radiance at 555 nm. Other SeaWiFS-derived variables—chlorophyll concentration, diffuse attenuation coefficient at 490 nm and integral chlorophyll (integrated over one attenuation depth)—were also compared but showed a slightly less satisfactory correlation.     

Hydrogeochemistry and isotope analyses used to determine groundwater recharge and flow in low-gradient catchments of the province of Buenos Aires,Argentina

The region known as Pampa Plain, in Argentina, is a vast area characterized by slopes of less than 0.05%. The surface sediment is silty sand, mainly Aeolian, referred to as Pampean Loess, which is a phreatic aquifer unit of utmost importance for the water supply of the region. On account of the slight gradient, hydrogeological analyses using only hydraulic measurements are difficult to perform, often leading to confusing results. Thus, the study presented relies on hydrochemical modeling and isotopic determinations as well. The study area comprises three catchments in the inter-mountainous area corresponding to El Moro, Tamangueyú and Seco creeks, and covering 2,570 km² in the province of Buenos Aires. Measurements of piezometric levels and samples of groundwater, surface water and rainwater were carried out between January and March 2005. Major ion results were analyzed by means of hydrochemical graphs and hydrogeochemical modelling using NETPATH. The resulting data show that it is possible to identify local changes in recharge, flow direction and stream/groundwater relationship by using hydrochemical and isotopic information, which may become a useful and more precise tool for the study of particularly flat landscapes.     

Geochemical evolution of the Capim River kaolin, Northern Brazil

The Capim River kaolin, located in the eastern Brazilian Amazon, constitutes one of the most important kaolin deposits in the world. Known for its high whiteness, its noble application is in the paper industry. Studies were carried out on samples from the six facies of the deposit (sand kaolin, soft kaolin, lower transition facies, ferruginous crust, upper transition facies and flint kaolin) in order to trace its geochemical evolution. The kaolin developed at the expense of Cretaceous sandy–clayey sediments of the Ipixuna Formation. Intense lateritic processes characterized by ferruginization and deferruginization mechanisms led to the distinction of the different facies.     

Catastrophic debris flows near Machu Picchu village (Aguas Calientes), Peru

Slope movements together with intensive river erosion and the following accumulation are the leading processes in the landscape evolution in the area of Machu Picchu village (former Aguas Calientes), which is located close to the Machu Picchu Sanctuary. Debris flows affect not only the bottoms of valleys or canyons, but also debris fans at the termini of the drainage basins, which are heavily inhabited at some places. The most recent event in the Machu Picchu village occurred in April 2004, but several others were documented in a broader area in the last 50 years. The field inspections at Machu Picchu (May and September 2004; June and September 2005) together with oral testimony revealed the nature and behavior of the debris flow. Machu Picchu village can be assessed as a zone with high landslide risk in relation to its urban development. Despite that, the village recorded a rapid growth (threefold population increase) without urban control within the past two decades. Precipitation, which is the main triggering factor of the debris flows, and natural hazard management of the Machu Picchu village are discussed in this paper.     

Deformability characteristics of brazilian laterites

This paper summarizes the resilient and permanent deformation characteristics of laterite gravels, determined by cyclic loading in triaxial tests of compacted specimens. A study of laterite pavements was carried out on eight paved road sections in the state of Mato Grosso. Also reported is the influence of fine sand admixture, specimen size and soaking in two laterite samples from Roraima and Rondônia in the North of Brazil. The experimental relationships of resilient moduli against applied stresses are interpreted empirically for models what may be incorporated in a structural analysis of full depth of laterite pavement.