DEVELOPMENT OF A PROTOTYPE MONOCHROMATIC IN SITU LIGHT ABSORPTION METER.

AN INSTRUMENT WILL BE DEVELOPED FOR THE IN SITU MEASUREMENT OF ABSORPTION OF 670 NM WAVELENGTH LIGHT BY MARINE PARTICLES. THE INSTRUMENT WILL MAKE USE OF A LARGE AREA DETECTOR AND A REFLECTING TUBE ALIGNED COAXIALLY WITH THE MAIN LIGHT BEAM. INITIAL RESEARCH WILL FOCUS ON THE OPTIMIZATION OF TECHNIQUE AND MATERIAL FOR THE DESIGN OF THEREFLECTING TUBE TO TRANSMIT ALL OF THE LIGHT SCATTERED FORWARD BY SUSPENDED PARTICLES WITHIN A WATER MASS. THE REFLECTING TUBE MUST MEET THE CRITERIA OF EASE OF PROCUREMENT OR MANUFACTURE, RESISTANCE OF THE OPTICAL SURFACE TO FOULING AND CORROSION, AND HIGH REFLECTANCE. TESTS OF A PUMP FLOW-THROUGH SYSTEM WILL ALSO BE PERFORMED ON SEVERAL MARINE PARTICULATES (INCLUDING ALGAL POPULATIONS)TO DETERMINE THE FEASIBILITY OF SUCH A SAMPLE DELIVERY/FLUSHING MECHANISM FOR THE ABSORPTION METER. FINALTESTING WILL AIM AT OBTAINING AN ABSOLUTE CALIBRATION OF THEABSORPTION METER USING MATERIALS OF KNOWN ABSORPTION AND SCATTERING AS WELL AS SOME NATURALLY OCCURRING PARTICLE MIXTURES.