A Primer on in Situ Fluorometry to Monitor Dispersed Oil

ABSTRACT A flow-through fluorometry system is a valuable tool for measuring dispersed oil concentrations real-time in freshwater and marine environments. As part of the new Scientific Monitoring of Advanced Response Technologies (SMART), fluorometers are used to investigate dispersant efficacy and dispersed oil transport. Using fluorometers in situ to accurately measure dispersed oil concentrations is not a trivial task: detector response values vary due to oil composition, oil weathering changes response factors, dispersed oil is not a true solution, and natural waters contribute matrix effects and background fluorescence. Based on recent experiences and building upon research conducted in the 1980's, the most effective and accurate method to estimate the dispersed oil concentrations is through real-time water grab samples analyzed by laboratory methodologies for in vitro dispersed oil toxicity quantification. Once analyzed, the field water results can be used to establish a response curve, converting raw field response values into oil concentrations. The continuous record created by the flow-through fluorometer provides a far more comprehensive assessment than collecting a few water samples for laboratory analysis. The combination of using a real-time fluorometer in conjunction with field water sampling is a far superior approach than either method alone. The art and science of in situ fluorometry for measuring dispersed oil will be demonstrated using both laboratory and actual field data.