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The amplification of light absorption by aquatic particles retained on glass-fibre filters, the so-called beta factor, has been measured for 29 stations located in the varying coastal environment of the northern basin of the Adriatic Sea. The spectral values of the optical density of particles have been determined on glass-fibre filters by the standard transmittance (T) method as well as by the transmittance-reflectance (T-R) method, which performs an accurate correction for light back scattering by the particles, and on glass slides by the modified filter-transfer-freeze (FTF) method, which eliminates the path length amplification. It has been shown that the relationships between the optical densities of particles on glass slides (OD(sus)) and on glass-fibre filters OD(f) have a low dispersion when OD(f) is measured by the T-R method: in this case, the use of a single expression for all stations adds an error that does not exceed the typical uncertainty of the measurement of the filter-retained particle absorption. On the contrary, the OD(sus) versus OD(f) plots obtained by the T method exhibit considerable variability, apparently due to the approximate correction for light backscattering performed by this method, and do not permit the use of a single equation for all stations.

Additional information

Authors: TASSAN ET AL, Space Applications Insititute, JRC Ispra (IT);BRICAUD ET AL, Universite P. et M. Curie, Villefranche-sur-Mer (FR)
Bibliographic Reference: Article: Journal of Plankton Research, vol.22, no.4 pp 659-668
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