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

Area of Science:

• Oceanography
• Environmental Monitoring
• Spectroscopy

Background:

• Accurate measurement of ocean-dispersed tracers is crucial for understanding marine processes.
• Existing methods may lack precision or real-time capabilities for airborne applications.

Purpose of the Study:

• To report the first use of simultaneous airborne laser-induced dye fluorescence and Raman backscatter for absolute tracer dye concentration measurement.
• To establish a method for quantifying dye dispersion in oceanic environments.

Main Methods:

• Utilized simultaneous airborne laser-induced dye fluorescence and 3400-cm(-1) OH-stretch water Raman backscatter spectra.
• Employed a theoretical model comparing airborne spectra to laboratory data for known concentrations.
• Assumed uniform dye mixing with interfering organic matter in the water column.

Main Results:

• Achieved absolute concentration measurement of an ocean-dispersed tracer dye.
• Determined a minimum detectable integrated water column dye concentration of approximately 2 ppb by weight.
• Generated a dye concentration contour map using conical scan lidar data.

Conclusions:

• The combined spectroscopic technique provides a reliable method for airborne oceanic tracer dye quantification.
• The developed approach offers a sensitive tool for studying dye dispersion dynamics.
• The 2 ppb detection limit supports detailed environmental monitoring applications.