Towards high temporal and in situ estimates of suspended sediment properties


CALL: 2017

DOMAIN: SR - Water Resources under Change


LAST NAME: Martínez Carreras




KEYWORDS: suspended sediment, monitoring, UV-VIS spectrophotometer, sediment fingerprinting, uncertainty, hydrology

START: 2018-01-01



Submitted Abstract

Accurate estimates of the river fluxes and loads of suspended sediments and its associated chemical constituents are required for many reasons, e.g. to better quantify sediment-associated nutrient and contaminant transfers, and to address problems associated to the quantity and quality of sediments. However, while devices to measure discharge and suspended sediment concentration (or a surrogate variable as turbidity) at high temporal resolution and over long periods of time are currently at hand, affordable instruments to measure sediment-associated chemical concentrations are still lacking. As a consequence, sediment-associated chemical concentrations are commonly measured in the laboratory on grab stream water samples. The number of samples analysed is then commonly limited by the often labour intensive and expensive analytical procedures. This restricts high frequency sampling campaigns to a limited number of events and reduces accuracy when aiming to estimate fluxes and loads. In this context, we have recently demonstrated that submersible UV-VIS spectrophotometers (220-730 nm) can be used to estimate suspended sediment properties in situ and at high temporal resolution [Martínez-Carreras et al., 2016]. Currently commercialized spectrophotometers can measure light absorption spectra at high frequency (i.e. several minutes) directly submersed in a liquid media and are mainly used in wastewater drainage systems to measure several water quality parameters. The PAINLESS research project envisages to leverage our proof-of-concept investigations and aims to (1) determine which suspended sediment properties – including sediment-associated chemical constituents (e.g. total phosphorous) and physical properties (e.g. colour) – can we estimate from in situ measurements of light absorbance in the UV-VIS range, (2) calculate fluxes and loads of the sediment-associated chemical constituents that can be estimated from the in situ light absorbance data, and (3) investigate if in situ light absorbance measurements can be used to trace suspended sediment sources. To test the project’s hypothesis and achieve the project objectives we intend to rely on laboratory and field experiments. We will use chemometric regression techniques (e.g. partial least-squares regressions) to find relationships between the spectrophotometer readings and the suspended sediment properties.

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