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Oil Spill Dispersants: Efficacy and Effects (2005)

Chapter: Appendix D: Definitions and Unit Conversions

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Suggested Citation:"Appendix D: Definitions and Unit Conversions." National Research Council. 2005. Oil Spill Dispersants: Efficacy and Effects. Washington, DC: The National Academies Press. doi: 10.17226/11283.
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D
Definitions and Unit Conversions

Conversions reported in the text conserve the number of significant figures of the original reported value using rules consistent with the NRC report on Oil in the Sea III: Inputs, Fates and Effects (NRC, 2003) and available on the following Massachusetts Institute of Technology website: http://web.mit.edu/10.001/Web/Course_Notes/Statistics_Notes/Significant_Figures.html.

We are reporting everything in metric units except where common or regular usage requires that values be reported in English units. In these cases, metric equivalents are provided in parenthesis.


barrels × 42 = US gallons

liters × 0.264 = US gallons

cubic meters × 264.2 = US gallons

cubic feet × 7.481 = US gallons

liters × 0.0009 = tonnes*

(note tonnes = metric tons)

tonnes × 294 = US gallons*

tonnes × 7.33 = barrels

US gallons × 0.0034 = tonnes*

US gallons × 3.785 = liters

*  

NOTE: The gallon is a volume measurement. The tonne is a weight measurement. For truly precise conversions between gallons and tonnes, it is important to take into account that equal volumes of different types of oil differ in their densities. The specific gravity (sp gr), or density in relation to pure water is generally less than 1.0. Specific gravity of petroleum products varies from about 0.735 for gasoline to about 0.90 for heavy crude to 0.95 for Bunker C (No. 6 fuel). In some cases the oil is even heavier than water, especially with some of the heavy No. 6 fuels. These oils can sink. The volume that a particular weight of oil takes up varies with temperature and atmospheric pressure.

Suggested Citation:"Appendix D: Definitions and Unit Conversions." National Research Council. 2005. Oil Spill Dispersants: Efficacy and Effects. Washington, DC: The National Academies Press. doi: 10.17226/11283.
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Some common metric unites and their english equivalents:


miles × 1.609 = kilometers

miles × 1.1 = nautical miles

nautical miles × 1.852 = kilometers

feet × 0.304 = meters

nautical miles per hour (knots) × 1.852 = kilometers per hour

miles per hour × 1.609 = kilometers per hour

gallons/acre × 9.35 = liters/hectare

acre × 0.404 = hectare

inches × 25.4 = millimeters

fathom × 1.8288 = meters

   

The conversion factor of 294 gallons per tonne is derived from an average specific gravity of 0.83, which corresponds to an API gravity or degree API of 39. Note that API gravity and specific gravity are inversely proportional as per the formulae below. The 294 gallons/tonne conversion unit is also convenient because it happens that 294 gallons = 7 barrels.

API = (141.5/sp gr) − 131.5

sp gr = 141.5/(API + 131.5)

Suggested Citation:"Appendix D: Definitions and Unit Conversions." National Research Council. 2005. Oil Spill Dispersants: Efficacy and Effects. Washington, DC: The National Academies Press. doi: 10.17226/11283.
×
Page 353
Suggested Citation:"Appendix D: Definitions and Unit Conversions." National Research Council. 2005. Oil Spill Dispersants: Efficacy and Effects. Washington, DC: The National Academies Press. doi: 10.17226/11283.
×
Page 354
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Approximately 3 million gallons of oil or refined petroleum products are spilled into U.S. waters every year. Oil dispersants (chemical agents such as surfactants, solvents, and other compounds) are used to reduce the effect of oil spills by changing the chemical and physical properties of the oil. By enhancing the amount of oil that physically mixes into the water, dispersants can reduce the potential that a surface slick will contaminate shoreline habitats. Although called for in the Oil Pollution Act of 1990 as a tool for minimizing the impact of oil spills, the use of chemical dispersants has long been controversial. This book reviews the adequacy of existing information and ongoing research regarding the effectiveness of dispersants as an oil spill response technique, as well as the effect of dispersed oil on marine and coastal ecosystems. Oil Spill Dispersants also includes recommended steps for policy makers faced with making hard choices regarding the use of dispersants as part of spill contingency planning efforts or during actual spills.

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