Instrument to measure in situ visible light absorption in natural waters

J. H. M. Hakvoort; A. E. R. Beeker; J. Krijgsman

doi:10.1117/12.190123

26 October 1994 Instrument to measure in situ visible light absorption in natural waters

J. H. M. Hakvoort, A. E. R. Beeker, J. Krijgsman

Proceedings Volume 2258, Ocean Optics XII; (1994) https://doi.org/10.1117/12.190123
Event: Ocean Optics XII, 1994, Bergen, Norway

Abstract

A submersible absorption meter was built to measure the light absorption plus backscattering coefficients of natural waters in one term. The radiance attenuation is measured close to the surface of a Lambertian light source and it is measured along the direction of the net vector irradiance. Photons scattered out of this normal direction are replaced by photons initially travelling at a deviating direction being scattered into the normal direction. Photons scattered in the backward direction are lost. The performance of the absorption meter was tested in the laboratory working with several simple test suspensions and in the field in estuarine and in marine water. Radiance attenuation spectra of clear water and absorption spectra of clear water matched closely. The radiance attenuation of algae increased linearly with concentration of chlorophyll (alpha) in the measured range of 0 - 70 mg m^-3, while the radiance attenuation spectrum was very close to the absorption spectrum of the algal sample as measured with a semi-integrating sphere. An offset between these spectra remained. This was not observed when field data from estuarine and marine water were compared to laboratory measurements.

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J. H. M. Hakvoort, A. E. R. Beeker, and J. Krijgsman "Instrument to measure in situ visible light absorption in natural waters", Proc. SPIE 2258, Ocean Optics XII, (26 October 1994); https://doi.org/10.1117/12.190123

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