Size-refractive index distribution of clear coastal water particulates from light scattering

Simultaneous measurements of the size distribution and volume scattering function of particles in clear coastal water are used to estimate a particle size-refractive index distribution. Various possibilities of the refractive index distribution and the observed particle distribution are studied systematically using Mie theory. The resulting model has minerals in mid-sizes and organic material in large and small sizes, but does not yield the correct dependence of scattering on wavelength. By assuming the existence of minerals or organics in sizes too small to be measured by the particle counter, two other models are developed, both of which yield acceptable wavelength dependence of scattering. The results of the three models are combined to provide limits on the size-refractive index distribution of the particles. Within these limits, volume scattering functions computed for the particles show good agreement with the measurements.