Biophysical flocculation reduces variability of cohesive sediment settling velocity

Biophysical cohesion, introduced predominantly by Extracellular Polymeric Substances (EPS) during mineral flocculation in subaqueous environments, plays important role in morphodynamics, biogeochemical cycles and ecosystem processes. However, the mechanism of how EPS functioning with cohesive partic...

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Bibliographic Details
Published in:Communications earth & environment 2023-12, Vol.4 (1), p.138-9, Article 138
Main Authors: Ye, L., Penaloza-Giraldo, J. A., Manning, A. J., Holyoke, J., Hsu, T.-J.
Format: Article
Language:English
Subjects:
Aquatic environment
Biogeochemical cycles
Clay minerals
Cohesion
Cohesive sediments
Extracellular polymers
Flocculation
Jar tests
Laboratories
Mixtures
Physical properties
Settling behavior
Settling velocity
Variability
Velocity
Xanthan
Xanthan gum
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Summary:Biophysical cohesion, introduced predominantly by Extracellular Polymeric Substances (EPS) during mineral flocculation in subaqueous environments, plays important role in morphodynamics, biogeochemical cycles and ecosystem processes. However, the mechanism of how EPS functioning with cohesive particles and affects settling behaviors remain poorly understood. We measure initial flocculation rate, floc size and settling velocity of mineral and artificial EPS (Xanthan gum) mixtures. Combining results from these and previous studies demonstrate coherent intensification of EPS-related flocculation compare with those of pure mineral and oil-mineral mixtures. Importantly, the presence of EPS fundamentally changes floc structure and reduces variability of settling velocity. Measured data shows that ratios of microfloc and macrofloc settling velocity for pure mineral flocs is 3.9 but greatly reduced to a lowest value of 1.6 due to biological EPS addition. The low variability of settling velocity due to EPS participation explains the seemingly inconsistent results previously observed between field and laboratory studies.
ISSN:2662-4435
2662-4435
DOI:10.1038/s43247-023-00801-w