U.S. EPA Contaminated Site Cleanup Information (CLU-IN)

U.S. Environmental Protection Agency
U.S. EPA Technology Innovation and Field Services Division

Dense Nonaqueous Phase Liquids (DNAPLs)

Chemistry and Behavior

Multi-Component Waste

Heavy Oils

Heavy oils, which are sold as marine, bunker C, and No. 6 fuel oil, are residual hydrocarbon materials blended with middle distillates. Because of the different composition of the residuals and lighter blending oils, the actual compounds found in heavy oils and their percent by weight is highly variable. For example, if the residual components are from atmospheric or vacuum distillation refining columns, the concentration of three to seven ring aromatic hydrocarbons is on the order of six to eight percent. If the residual is from catalytically or steam cracked units, the level of three to seven ring aromatic hydrocarbons may approach 20 percent (CANCAWE 1998). The origin of the crude being refined will also affect the type of hydrocarbon found in the residual and cutting oils as well as the type of contaminant (e.g., sulfur compounds like hydrogen sulfide and heavy metals).

CANCAWE (1998) describes the composition of residual fuels as a "complex mixture of high molecular weight compounds having a typical boiling range from 350 to 650° C. They consist of aromatic, aliphatic and naphthenic hydrocarbons, typically having carbon numbers from C20 to C50, together with asphaltenes and smaller amounts of heterocyclic compounds containing sulfur, nitrogen, and oxygen."

The density of heavy oil products typically varies between 0.88 g/cc and 1.03 g/cc or somewhat higher for some products. At 50° C the kinematic viscosity of No. 6 fuel oil can vary between 97.4 and 660 centistokes, compared with 0.553 for water (Engineering Tool Box).

The log Kow values for components of heavy fuel oils range from about 2.7 to over 6, which suggests that some of them may bioaccumulate (CANCAWE 1998). The range in densities also suggests that heavy fuel oils released to surface or ground water may float, be neutrally buoyant, or sink through the water column.

Fuels like bunker C can be aerobically degraded. This process occurs as the lighter compounds dissolve or volatilize in areas where they can be biologically or chemically attacked. Fuels like bunker C, in which the great majority of the oil is concentrated in the heavier compounds that do not volatilize or dissolve, degrade very slowly, if at all.

For Further Information

Heavy Fuel Oils
Conservation of Clean Air and Water in Europe (CONCAWE) 1998

Adobe PDF LogoHeavy Fuel Oils Category Analysis and Hazard Characterization
American Petroleum Institute (API), Petroleum HPV Testing Group. 138 pp, 2012

This document summarizes the physical-chemical properties, environmental fate, environmental effects, and human health effects of a variety of heavy fuel oils, some of which may be characterized as DNAPLs. More extensive information is detailed in API's Robust Summary of Information on Heavy Fuel Oil CategoryAdobe PDF Logo (370 pp, 2012).

Fluids - Kinematic Viscosities: Kinematic Viscosities of Some Common Fluids - Motor Oil, Diesel Fuel, Peanut Oil and Many More
Engineering Tool Box

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