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REMOTE MONITORING OF ORGANIC CARBON IN SURFACE WATERS
Citation:
Bristow, M. AND D. Nielsen. REMOTE MONITORING OF ORGANIC CARBON IN SURFACE WATERS. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/4-81/001 (NTIS PB81168965).
Description:
This study shows that the intensity of the Raman normalized fluorescence emission induced in surface waters by ultraviolet radiation can be used to provide a unique remote sensing capability for airborne monitoring the concentration of dissolved organic carbon (DOC). Trace concentrations of hydrocarbons, both manmade and natural in origin, are the predominant source for this fluorescence. Water, on the other hand, is nonfluorescent under UV irradiation, but emits an intense Raman band of constant amplitude relative to the incident light. This Raman emission can be used as an internal reference or normalizing standard with which to correct the fluorescence emission for the effects of attenuation, for variations in system sensitivity, and for changes in sensor elevation. It is suggested that a direct calibration of the airborne fluorescence data in terms of equivalent DOC concentration be accomplished by making DOC measurements on samples obtained at a small number of reference sites under the aircraft flight path at the time of the airborne survey. Airborne laser fluorosensors that utilize this principle will provide a synoptic survey capability for rapidly and cost-effectively producing isopleth maps that show concentrations of surface water DOC. These isopleths can be used for delineating gradients, temporal changes and anomalies in the distribution of total dissolved organics in the surface layers of rivers, lakes and costal waters.