Marine petroleum prospecting and pollution monitoring with an airborne Fraunhofer Line Discriminator

Abstract

A suite of twenty-eight crude oils and fourteen refined products were analyzed in the laboratory and in outdoor tank experiments to determine their luminescence properties. Open column and high performance liquid chromatography were employed to classify the crude oils and to determine the types of aromatic molecules present in the crude oils respectively. The only strong positive correlation found between luminescence intensity and the chromatographic data was with percent aliphatic molecules present. Aromatic crude oils generally displayed a slight shift toward higher luminescence intensity at longer emission wavelengths compared to aliphatic crude oils. This shift was not great enough to separate aromatic crudes from aliphatic crudes based only on luminescence data. Refined products showed an increase in luminescence intensity at shorter emission wavelengths compared to crude oils. Fraunhofer Line Discriminator (FLD) data collected from a natural oil slick in the Santa Barbara Channel compared favorably with simultaneous observations made by trained observers. Outdoor tank experiments demonstrated the ability of the FLD to detect small amounts of oil on a water surface. Oil was detected by a strong positive luminescence signal at the 486.1 nm Fraunhofer line for only two samples; sample 1 and Pennzoil, which were among the brightest samples analyzed in the laboratory. Digital image processing and enhancement techniques which are applicable to small data sets are discussed. Although detection of oil films on a water surface by means of airborne luminescence measurements appears feasable, the identification of the material comprising the film requires, at a minimum, an instrument with simultaneous multispectral capabilities and a knowledge of the luminenscence properties of the underlying water column.