Absolute tracer dye concentration using airborne laser-induced water Raman backscatter

Abstract

Reported here for the first time is the use of simultaneous airborne laser-induced dye fluorescence and the 3400-cm(-1) OH-stretch water Raman backscatter spectra to yield the absolute concentration of an ocean-dispersed tracer dye. Using a straightforward theoretical model, the concentration is calculated by numerically comparing the airborne laser-induced fluorescence and Raman backscatter spectra to similar laboratory data for a known dye concentration measured under comparable environmental and instrumental conditions. The dye is assumed to be uniformly mixed throughout the water column together with other interfering, fluorescent, organic matter. A minimum detectable integrated water column dye concentration of approximately 2 ppb by weight as limited by background and instrument noise is obtained. A dye concentration contour map produced from the conical scan lidar data is given.