Inferring Suspended Sediment Carbon Content and Particle Size at High Frequency From the Optical Response of a Submerged Spectrometer
Real time monitoring of suspended sediment (SS) carbon content and particle size information is essential to understand SS transport mechanisms and processes. However, limited in situ methods are available, and manual and unattended sampling makes high frequency observation challenging. Based on evidence that optical measurements of SS concentration are dependent on particle size and composition, we hypothesize that SS carbon content and mean particle size (Formula presented.) can simultaneously be inferred from the absorbance data measured with a submerged spectrometer at high frequency. With the aim to predict both parameters, we investigate if global calibrations can be obtained and used instead of site-dependent local calibrations. To test this, we created a laboratory data set using a tank setup, and an in situ field data set. Sediment samples varying in composition were collected and used in a tank setup to obtain global (all sites grouped together) calibrations between absorbance, particle size and carbon content. Two sites were instrumented to collect in situ field data, to generate local (site-specific) calibrations and to validate the global calibrations obtained in the laboratory. A procedure to account for the effect of SS concentration when using the global calibration to predict (Formula presented.) is also presented. Our findings indicate that global calibrations can accurately predict (Formula presented.) from in situ absorbance readings, with a median absolute error of 17.3 μm, versus 10.5 μm for a local calibration. Local calibrations are indispensable to reliably predict carbon content, with a median absolute error of 1.3%.
| Main Authors: | , , , , |
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| Format: | Article/Letter to editor biblioteca |
| Language: | English |
| Subjects: | absorbance, carbon content, in situ, particle size, spectrometer, suspended sediment, |
| Online Access: | https://research.wur.nl/en/publications/inferring-suspended-sediment-carbon-content-and-particle-size-at- |
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