High frequency un-mixing of soil samples using a submerged spectrophotometer in a laboratory setting—implications for sediment fingerprinting

A - Papers appearing in refereed journals

Lake, N. F., Martínez-Carreras, N., Shaw, P. J. and Collins, A. L. 2021. High frequency un-mixing of soil samples using a submerged spectrophotometer in a laboratory setting—implications for sediment fingerprinting. Journal of Soils and Sediments. https://doi.org/10.1007/s11368-021-03107-6

AuthorsLake, N. F., Martínez-Carreras, N., Shaw, P. J. and Collins, A. L.
Abstract

Purpose
This study tests the feasibility of using a submersible spectrophotometer as a novel method to trace and apportion suspended sediment sources in situ and at high temporal frequency.

Methods
Laboratory experiments were designed to identify how absorbance at different wavelengths can be used to un-mix artificial mixtures of soil samples (i.e. sediment sources). The experiment consists of a tank containing 40 L of water, to which the soil samples and soil mixtures of known proportions were added in suspension. Absorbance measurements made using the submersible spectrophotometer were used to elucidate: (i) the effects of concentrations on absorbance, (ii) the relationship between absorbance and particle size and (iii) the linear additivity of absorbance as a prerequisite for un-mixing.

Results
The observed relationships between soil sample concentrations and absorbance in the ultraviolet visible (UV–VIS) wavelength range (200–730 nm) indicated that differences in absorbance patterns are caused by soil-specific properties and particle size. Absorbance was found to be linearly additive and could be used to predict the known soil sample proportions in mixtures using the MixSIAR Bayesian tracer mixing model. Model results indicate that dominant contributions to mixtures containing two and three soil samples could be predicted well, whilst accuracy for four-soil sample mixtures was lower (with respective mean absolute errors of 15.4%, 12.9% and 17.0%).

Conclusion
The results demonstrate the potential for using in situ submersible spectrophotometer sensors to trace suspended sediment sources at high temporal frequency.

KeywordsSediment fingerprinting; UV–VIS spectrophotometer; High temporal frequency; In situ measurements; Sediment source tracing; MixSIAR
Year of Publication2021
JournalJournal of Soils and Sediments
Digital Object Identifier (DOI)https://doi.org/10.1007/s11368-021-03107-6
Web address (URL)https://doi.org/10.1007/s11368-021-03107-6
Open accessPublished as ‘gold’ (paid) open access
FunderBiotechnology and Biological Sciences Research Council
Funder project or codeS2N - Soil to Nutrition - Work package 3 (WP3) - Sustainable intensification - optimisation at multiple scales
PAINLESS project, C17/SR/11699372 from Luxembourg National Research Fund (FNR)
Publisher's version
Output statusPublished
Publication dates
Online22 Nov 2021
Publication process dates
Accepted04 Nov 2021
PublisherSpringer Heidelberg
ISSN1439-0108

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