The refractive index of particulate matter suspended in seawater
is nonuniform and potentially is an indicator of composition and
origin. A method is described for determining the refractive index
distribution. The method requires the measurement of the volume
scattering function and assumes the total size distribution to be
capable of being reproduced as a linear superposition of hyperbolic
size distributions. The procedure utilizes 40 theoretical volume
scattering functions computed for a range of refractive indices and
particle size distributions. Each one represents a particular combination
of index and distribution. The eight values for the refractive
index (relative to that of water) range from 1.02 to 1.15. The
distribution of refractive index and the total particle size distribution
are determined by finding the best possible representation of the
measured volume scattering function as a linear superposition of the
40 computed functions. An iterative descent method is used to
minimize the error between the measured curve and the superposition
of component scattering functions. If the particle size distribution is
known beforehand, the determination can be restricted to reproduce
the measured distribution to within limits set by a weighting factor.
A similar technique is given for finding the refractive index composition
for phytoplankton populations using measured scattering and
size-distribution data.
Twelve volume scattering functions measured in oceanic
environments (Sargasso Sea, Mediterranean Sea and Baltic Sea) and
three measured in cultured phytoplankton populations (the dinoflaggelate
Amphidinium carterae, and unidentified unicellular alga labeled
T-24, and a centric diatom of the genus Biddulphia) were analyzed.
Determinations for the Mediterranean Sea were performed at a series
of depths extending from near surface to 2OO m. All the determinations
showed the refractive index distributions to be essentially
bimodal with components of refractive indices near 1.05 and 1.15.
The method reproduced measured scattering curves with an average
absolute error less than the experimental uncertainty.
Suggestions for obtaining better results using the same technique
are given. / Graduation date: 1975
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/28572 |
| Date | 09 August 1974 |
| Creators | Roach, David Michael |
| Contributors | Zaneveld, J. Ronald V. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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