Analyze soils and sediments for the presence of liquid hydrocarbons; the sample is extracted with a solvent and the extract is analyzed for the presence of aromatic hydrocarbons, specifically the 2-ring (naphthalene) and 3-ring (phenanthrene) aromatics. Crude oils usually contain appreciable amounts of aromatic compounds including naphthalenes (two ring) and phenanthrenes (three ring).

The concentration of these aromatics and their fluorescence intensity has been found a useful indicator of liquid hydrocarbons in sediment and soil extracts, and under some conditions these data can be used to predict the approximate API Gravity of the source oils and condensates.