In order of most mobile to least mobile, which is the correct sequence: Bunker C, heating oil, diesel, gasoline?

The correct sequence from most mobile to least mobile is accurately represented as gasoline, diesel, heating oil, and then bunker C. Mobility in this context refers to how easily the substance can move through soil and groundwater.

Gasoline is the most mobile due to its lower density and higher volatility, allowing it to quickly migrate through environmental media. Diesel, while less volatile than gasoline, is still fairly mobile and can easily move through soil but not as rapidly as gasoline. Heating oil is denser and more viscous than diesel, resulting in reduced mobility in the environment. Finally, bunker C is a heavy fuel oil with a high viscosity and density, making it the least mobile among these substances as it tends to settle in one location rather than migrate through the soil and groundwater effectively.

This understanding of the properties of each fuel type helps clarify why the sequence provided is correct, demonstrating their relative mobility and potential environmental impact in the context of underground storage tank assessments.