Inferring Suspended Sediment Carbon Content and Particle Size at High Frequency From the Optical Response of a Submerged Spectrometer

Abstract

Riverine suspended sediments (SSs) are a complex composite of mineral particles (clay, silt, and fine sand), living organisms, natural organic matter (humic substances, extracellular polymers) and contaminants (Droppo, 2001;Paterson, 2001;Tao et al., 2018;Walling & Moorehead, 1989). The physical, chemical and biological interaction among SS components changes the structure (dis-/aggregation) and properties of SS such as particle size, density and composition (Maggi & Tang, 2015), and might result in flocculation (Spearman et al., 2011). These interactions are also influenced by meteorological, hydrological, ecological and anthropogenic pressures (Aleixo et al., 2020;Ankers et al., 2003). Recent studies showed that information on SS size and composition, also considered as primary floc characteristics, is important in physics-based modeling studies (e.g.

A Generic Relation Between Turbidity, Suspended Particulate Matter Concentration, and Sediment Characteristics

“…A generic calibration largely reduces the sampling and re‐calibration effort, but requires ex situ measurements of SPMC, C , and color, as well as in situ measurements of turbidity and particle size. We argue that the proposed generic calibration approach may be specifically useful when using submersible spectrometers, which measure absorbance in the UV‐Visible range (200–750 nm) to simultaneously predict turbidity, particle size and carbon (Sehgal, Martínez‐Carreras, Hissler, Bense, & Hoitink, 2022).…”

“…Three sub‐filters were drawn out of each filter using a round hole punch (1/2”/12.7 mm; Tedpella Inc., Redding, USA) to make three replicates per sample and to calculate measurement uncertainties. This method was adopted from Sehgal, Martínez‐Carreras, Hissler, Bense, and Hoitink (2022). SPM carbon content is an appropriate substitute for organic carbon only at sites with no or negligible influence of inorganic carbon.…”

“…org/10.5281/zenodo.7393129 (Sehgal, Martínez-Carreras, & Hissler, 2022b). Most of the data for site 1 was taken from https://doi.org/10.5281/zenodo.6509837 (Sehgal, Martínez-Carreras, & Hissler, 2022a).…”

“…argued that the dominance of particulate organic matter can have serious consequences for the estimates of SPM loads, due to resulting high amount of sidescatter in the measurements. In this context, Sehgal, Martínez-Carreras, Hissler, Bense, and Hoitink (2022) recently demonstrated that a submersible spectrometer can simultaneously provide quick in situ information on turbidity, particle size and carbon content, which can help understanding the deviations in turbidity-SPMC relations due to organic content. SPM organic content is know to exert an influence on turbidity, yet an explicit formulation of turbidity accounting for SPM organic content is not available in the literature.…”

The Impact of Flocculation on In Situ and Ex Situ Particle Size Measurements by Laser Diffraction

“…Both data sets, except for a few experiments from the second data set (oxidized, tank setup), were taken from Sehgal et al (2022d). A detailed description of the tank setup and measurement protocol is available in Sehgal et al (2022b). The same measurement protocol and samples were used to characterize the sediment samples that were oxidized using hydrogen peroxide (H 2 O 2 ) 60% at 1:1 solution (H 2 O 2 and Mili-Q water) for 15 days, with intermittent stirring and warming at 30°C.…”