Reflectance spectra of crude oils and refined petroleum products on a variety of common substrates

Abstract

A variety of crude oils and refined petroleum products were applied to ten common terrestrial substrates with the goal of developing a set of representative reflectance spectra for hydrocarbon-substrate combinations. Similar to previous studies, each hydrocarbon darkened the substrates and produced hydrocarbon absorption features near 1200, 1690-1770, and 2270-2400 nm, along with a host of other minor features in the VIS/NIR/SWIR portion of the spectrum. Some substrate absorption features interfered with hydrocarbon absorptions, complicating spectral signatures. The reflectance spectra varied directly with the amount of liquid on the substrate. Liquid-saturated samples were left to age and regularly re-measured, establishing a relationship between evaporative loss for volatile and semivolatile products and sample reflectance. The results outline temporal windows of opportunity and minimum detection thresholds for volatiles. They also provide a means for remotely distinguishing 1) water from petroleum products on some substrates and 2) some similar hydrocarbons from one another based on their volatility.