We propose to clean the areas, the sand and the vegetation "In Site" with Biodegradable Chemicals MPCD and Biological Acceptable Products BIOSINFO that are Environmentally Friendly to accelerate the process of Biodegradation. To do that we need heavy machinery to mix the products with the soil and sand and a lot of hand labor "In Site".

Modelling of the likely fate and behaviour of oil once spilled can follow a number of different approaches. These range from a simple vector calculation, to estimate the probable two–dimensional trajectory of the centre point of a slick, to sophisticated computer models of the movement and distribution of the oil in three dimensions with the concurrent predictions of the change in properties as the oil weathers. The main properties which affect the fate of spilled oil at sea are specific gravity (its density relative to pure water - often expressed as ° API* or API gravity); distillation characteristics (its volatility); viscosity (its resistance to flow); and pour point (the temperature below which it will not flow). In addition the wax and asphaltene content influence the likelihood that the oil will mix with water to form a water-in-oil emulsion. Oils which form stable oil-in-water emulsions persist longer at the water surface.

The graph above represents a simple empirical model based upon the properties of different oil types. For this purpose, it is convenient to classify the most commonly transported oils into four main groups, roughly according to their specific gravity (see table below). Having classified the oils, the expected rate at which the volume of oil at the sea surface decreases can be estimated. These four groups are shown in the above graph, where account is also taken of the competing process of emulsification which, for most oils, leads to an increase in volume.

Group   Density   Examples
GroupI   less than 0.8   Gasoline, Kerosene
GroupII   0.8 - 0.85   Gas Oil, Abu Dhabi Crude
GroupIII   0.85 - 0.95   Arabian Light Crude, North Sea Crude Oils (e.g Forties)
GroupIV   greater than 0.95   Heavy Fuel,Venezuelan Crude Oils

Group I oils (non-persistent) tend to dissipate completely through evaporation within a few hours and do not normally form emulsions. Group II and III oils can lose up to 40% by volume through evaporation but, because of their tendency to form viscous emulsions, there is an initial volume increase as well as a curtailment of natural dispersion, particularly in the case of Group III oils. Group IV oils are very persistent due to their lack of volatile material and high viscosity, which preclude both evaporation and dispersion.

To model the movement of oil, the most important input parameters include the type and quantity of oil spilled, along with the rate of release. Key environmental input data include wind, ocean currents, tides and air and sea temperatures. While this does not sound particularly onerous, one must keep in mind that there are numerous variables associated with each of these parameters and usually this type of information is not readily available. The reliability of a trajectory model will depend on the availability of a detailed hydraulic model from which water movement data can be drawn and these require detailed knowledge of water depths (bathymetry), currents at various depths and tidal streams. Although trajectory models exist where such basic data can be input to generate hydraulic models, this takes considerable time and most are limited to those geographic areas where such hydraulic models already exist.

The other component required to model the transport of oil spilled at sea is wind data. During the period over which the incident is modelled the wind strength and direction is likely to change and can vary at different locations across the spill area as time progresses. As far as possible this information also has to be input to the model although often, average values are used for set time intervals.

It is important to appreciate the assumptions upon which models are based and not to place complete reliance on the results. However, they can serve as a useful guide to understanding how a particular oil is likely to behave and help in assessing the scale of the problem which a spill might present. The principle uses of such models are for planning, training, emergency response, and impact assessment. The suitability of computer modelling for each of these applications differs.

Computer models are widely used for contingency planning where they are particularly helpful for decision makers who need to link their site-specific, pre-identified risks with decisions concerning the locations and make-up of the planned response measures, including equipment, materials and manpower. This can be done by running the model over and over using a range of the most likely scenarios and then observing the predicted oil movement and behaviour. Based on the results, those locations shown to be the most vulnerable can be identified, the logistics of responding to these locations studied and response assets placed accordingly. There is, of course, no guarantee that these resources will be best placed in the event of a spill, but the planners will have made the best judgement based on available information.

Spill response training is another key application for models. The model is used to help course participants feel as if they are involved in a real-life situation, even if they are only taking part in a table-top exercise. Trainers use the models in a variety of ways, but one approach is to run the model at real-time speed for 20-30 minutes so that participants can make some decisions about what measures should be taken and what equipment should be mobilised. Then the model is fast-forwarded to a later period and participants are asked to deal with the updated situation. In this way, an event of 2-3 days can be collapsed down to an hour or so.

The use of computer models in emergency response itself is much more challenging, depending on the particular details of the case, because it requires the timely acquisition of the numerous input parameters. Usually the release occurs immediately after an incident occurs, for example, following a collision. Little will be known about the oil types or the quantities involved. As the incident develops better information will improve the outcome of the model. However, one immediate application is to inform decisions on the scope of initial aerial surveillance flights where the movement of oil may not be immediately obvious, for example, following an instantaneous release of oil at night the oil may have moved a considerable distance from the source.

Perhaps the most controversial application of computer modelling is for damage assessment. Computer modelling in this case is used to show where the oil might have gone as it spread, drifted, dissolved, and evaporated. In the simplest cases, reference is made to, for example, the threshold levels for the contaminants in marine products for safe human consumption. The geographic areas simulated to have been exposed to concentration levels in excess of these standards are assumed to have been impacted. In more sophisticated models, input data for related toxicological studies is used together with ecological sub-models to predict what sort of acute exposure and impact may have been experienced. The trouble with this approach is that the models do not actually show damage, they simply predict it based on a host of simplifying assumptions. Many years of field experience have made it clear that when there is real impact, it can be observed on site. While before-the-fact impact assessment might be a useful planning tool, for example to study the need for specialist wildlife cleaning equipment and expertise, it is no replacement for scientific field work and post–spill surveys.

*°API = (141.5/SG) -131.5

Note: API gravity values increase with decreasing density eg. SG 1 = 10° API & SG 0.8 = 45.4° API


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