Optical properties of inorganic suspended solids and their influence on ocean colour remote sensing in highly turbid coastal waters

Abstract

The influence of the optical properties of inorganic suspended solids (ISS) on in-water algorithms was evaluated using an optical model in highly turbid coastal water, whose ISS concentration reached several hundred grams per cubic metre. The measurements were conducted in the upper Gulf of Thailand. The backscattering coefficient of the ISS was calculated using the Lorenz-Mie scattering theory. On the basis of the measurement, the ISS size distribution was parameterized as a function of ISS concentration, and both the spherical and non-spherical particle shape models were evaluated. For ISS concentrations of 10 g m −3 , an estimate of the chlorophyll-a (chl-a) concentration within a factor of 2 on a logarithmic scale is possible in a [chl-a] range of 4-30 mg m −3 . The differential coefficient of remote sensing reflectance was calculated to evaluate its respective sensitivities for chl-a and ISS concentrations. The use of radiometric data at 670 nm (700-900 nm) is valid for in-water algorithms used to estimate chl-a (ISS) concentration in highly turbid coastal waters.

Spectral absorption properties of mineral particles in western Lake Erie: Insights from individual particle analysis

“…(l) with the inclusion of the effects of absorption, as specified by the n9(l) estimates, are (1) consistent with certain analyses of other investigators; (2) likely representative for many minerogenic particle populations of inland waters; and (3) potentially important to related analytical frameworks, including remote-sensing algorithms. There are only limited reports (Kobayashi et al 2011) of the effects of n9(l) on the spectral characteristics of these scattering properties for real (i.e., measured PSDs) minerogenic particle populations. Kobayashi et al (2011) evaluated the influence of PSD (non-Junge) and n9(l) on the spectral backscattering properties of inorganic suspended solids in coastal waters and reported spectral structure similar to our predictions (Fig.…”

“…There are only limited reports (Kobayashi et al 2011) of the effects of n9(l) on the spectral characteristics of these scattering properties for real (i.e., measured PSDs) minerogenic particle populations. Kobayashi et al (2011) evaluated the influence of PSD (non-Junge) and n9(l) on the spectral backscattering properties of inorganic suspended solids in coastal waters and reported spectral structure similar to our predictions (Fig. 10b).…”

“…3c) are the first reported for natural populations of polydispersed mineral particles of inland waters. Kobayashi et al (2011) applied a similar iterative approach in estimating n9(l) for inorganic suspended solids collected in the coastal waters of the upper Gulf of Thailand. Their reported study averages (e.g., 0.004 at 400 nm, 0.0035 at 440 nm) were comparable to our estimates.…”

“…The a m (l) term has been pursued in the context of the spectral mass-specific coefficient, a à m (l) (m 2 g 21 ), that links the gravimetric concentration of the minerogenic particles to the associated component of absorption (Babin and Stramski 2004;Stramski et al 2007). There have been few attempts to determine a à m (l) experimentally on natural particle assemblages (Bowers et al 1996;Kobayashi et al 2011;Moate et al 2012), such as absorption measurements following loss-on-ignition to remove organic particulate material, an approach shown to affect the optical properties of the remaining mineral particles due to heat exposure (Moate et al 2012). Variability in a à m (l) has been attributed to differences in particle size distribution (PSD) and composition (Stramski et al 2007).…”

“…There have been few attempts to determine a à m (l) experimentally on natural particle assemblages (Bowers et al 1996;Kobayashi et al 2011;Moate et al 2012), such as absorption measurements following loss-on-ignition to remove organic particulate material, an approach shown to affect the optical properties of the remaining mineral particles due to heat exposure (Moate et al 2012). Variability in a à m (l) has been attributed to differences in particle size distribution (PSD) and composition (Stramski et al 2007).…”