Thickness slick

This zinc is uscil in lln- )nll>miiu- Initn (it.iKul.iicil, thick slicks, lliin slicks. 

Despite their disadvantages, suction skimmers are the most economical of all skimmers. Their compactness and shallow draft make them particularly useful in shallow water and in confined spaces. They operate best in calm water with thick slicks and no debris. Very large vacuum pumps, called air conveyors, and suction... 

The optimal length of a manually performed spread is 4—7 m. Short markers may be joined and laid as one spread, forming either a traditional or a step spread. The number of fabric plies in a spread depends on the size of the order, the fabric properties (thickness, slickness, friction between the fabric and a cutting device, etc.) and the technical limits of the manual cutting machines (the stroke size, shape of the blade, etc.). Narrow tubular fabrics and interlinings are spreaded by a single worker. 

Dispersants are expensive and contain toxic compounds harmful to aquatic fauna and flora. Furthermore, they are ineffective in calm water where is no sufficient mixing energy needed to mix dispersants with oil and to also aid immediate dispersion of the oil. They are also more effective in thicker oil slicks than thinner ones because the dispersants are easily lost in thinner slicks. Also, thicker slicks subjected to weathering action will become more viscous and thereby reduce the effectiveness of the dispersants, though the effect is less severe than dispersant loss in thick slick. 

They are in no way used to purify water in depth and do not modify an emulsion. They are placed at the surface of a body of water that is assumed to be as calm and constant as possible and can only "recover" a preexisting, fairly thick slick of oil. 

Oil spreads on water to form a film about 100 nm thick (two significant figures). How many square kilometers of ocean will be covered by the slick formed when one barrel of oil is spilled (1 barrel = 31.5 U.S. gal) ... 

Corexit 9527 is a water-and ethylene glycol monobutyl ether-dissolved dispersant. The nature of the surface-active agent has not been disclosed. Laboratory tests were conducted using 0.5-mm thick, fresh Alberta Sweet-Mixed Blend crude oil treated with Corexit 9527 dispersant applied from an overhead spray boom [165]. The effects on dispersion efficiency of mixing jet pressure, mixing jet flow rate, jet standoff distance, and vessel speed were evaluated. The system operates with a nozzle pressure of 7000 kPa, a flow rate of 55 liter/min per nozzle, and nozzles positioned approximately 0.6 m from the water surface. In laboratory tests, such a system was capable of dispersing 80% to 100% of the surface slick. 

Underdosing and overdosing of the slick because of its variable thickness... 

Pierre [60] has reported a study of the characterisation of the surface of oil slicks by infrared reflective spectroscopy. A double-beam spectrophotometer was modified for studying the reflectance spectra (at angles of incidence 45°, 60°, 70°) of oil layers (20-30 xm thick) on the surface of water using pure water as reference. 

As oil enters the environment, it begins to spread immediately. The viscosity of the oil, its pour point, and the ambient temperature will determine how rapidly the oil will spread, but light oils typically spread more rapidly than heavy oils. The rate of spreading and ultimate thickness of the oil slick will affect the rates of the other weathering processes. For example, discharges that occur in geographically contained areas (such as a pond or slow-moving stream) will evaporate more slowly than if the oil were allowed to spread. Most of this process occurs within the first week after the spill. 

Gasoline from a tank truck spill has contaminated a small stream that enters a lake. Although the surface slick (NAPL) has evaporated, some gasoline is now dissolved in the lake water. The lake is stratified, and the epilimnion is 4 m thick. Consider the fate of two specific compounds in the fuel pentane (C5H12) and octane (C8H18), both initially present at concentrations of 100 ppb. 

In a summer boating accident, 10 liters of gasoline is spilled into a lake. A slick, 3 m wide and 7 m long, forms on the water surface. How long will it take to evaporate Assume the slick is of uniform thickness, and that the vapor pressure of the fuel is 25 mm Hg. The wind speed (at 10 m above the ground) is 4 m/sec. Gasoline contains approximately 7 mol/liter of liquid. 

Photo 29 This photo from the Exxon Valdez spill shows how slicks can often contain some emulsified oil, shown here near the edge of the water, and various thickness and weathering states of oil. (National Oceanic and Atmospheric Administration)... 

Tar balls are agglomerations of thick oil less than about 10 cm in diameter. Larger accumulations of the same material ranging from about 10 cm to 1 m in diameter are called tar mats. Tar mats are pancake-shaped, rather than round. Their formation is still not completely understood, but it is known that they are formed from the residuals of heavy crudes and Bunker C. After these oils weather at sea and slicks are broken up, the residuals remain in tar balls or tar mats. 

Thick oil on water absorbs infrared radiation from the sun and thus appears in infrared data as hot on a cold ocean surface. Unfortunately, many other false targets such as weeds, biogenic oils, debris, and oceanic and riverine fronts can interfere with oil detection. The advantage of infrared sensors over visual sensors is that they give information about relative thickness since only thicker slicks, probably greater than 100 pm, show up in the infrared. 

Photo 46 This composite image of an oil slick in both infrared and ultraviolet shows the relative thickness of various areas. The orange areas are the thicker portions mapped in infrared and the thin portions in blue are mapped in ultraviolet. (Environment Canada)... 

The passive microwave sensor detects natural background microwave radiation. Oil slicks on water absorb some of this signal in proportion to their thickness. While this cannot be used to measure thickness absolutely, it can yield a measure of relative thickness. The advantage of this sensor is that it can detect oil through fog and in darkness. The disadvantages are the poor spatial resolution and relatively high cost. 

The effectiveness of a skimmer is rated according to the amount of oil that it recovers, as well as the amount of water picked up with the oil. Removing water from the recovered oil can be as difficult as the initial recovery. Effectiveness depends on a variety of factors including the type of oil spilled, the properties of the oil such as viscosity, the thickness of the slick, sea conditions, wind speed, ambient temperature, and the presence of ice or debris. 

---