The spatial and temporal dynamics of sediment phosphorus attenuation and release in impacted stream catchments

Shijie Li, J. Arnscheidt, R. Cassidy, R.W. Douglas, H.J. McGrogan, P. Jordan

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7 Citations (Scopus)
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Abstract

Sediments can attenuate phosphorus (P) from overlying water and reduce trophic status in zero and first order ditches and streams. These features can be considered as intermediate mitigation features between P mobilised from land, and onward delivery to river systems, if the risk of chemical P release from sediments is minimal. However, risk assessments are rarely based on temporal scale dynamics and especially at fine scale in both sediment and water column environments. In this study, in eutrophic stream catchments, bed sediments were tested fortnightly and spatially over one year for EPC0 (to derive phosphate exchange potential—PEP) and for P across a spectrum from labile to recalcitrant fractions. At the same time stream discharge and P concentrations were measured synchronously at high frequency and resolved to 1-hour intervals and indicated high water quality pressures at all flow rates. PEP indicated spatial and temporal changes most likely caused by periods of source disconnection/reconnection and sediment mobilisation during storm events, moving from periods of high attenuation potential to near saturation. Despite these spatial and temporal changes, PEP did not indicate much potential for chemical P release from the sediments (distributing mostly below or close to zero). However, this may be a misleading risk assessment by itself as physical P release, especially of the labile bicarbonate-dithionite (B-D) P fraction of sediments, was a more dominant process mobilised during storm events reducing by up to 84 % during a succession of summer storm events. The total P and total reactive P loads monitored leaving the catchments were coincident with these changes. The specific downstream trophic effects of this episodic P release will need to be assessed in terms of its bioavailability, in combination with other more noted diffuse and point P source processes.
Original languageEnglish
Article number120663
Pages (from-to)1-12
Number of pages12
JournalWater Research
Volume245
Early online date24 Sept 2023
DOIs
Publication statusPublished (in print/issue) - 15 Oct 2023

Bibliographical note

Funding Information:
We thank Pete Devlin, School of Geography and Environmental Sciences, Ulster University for technical and field work assistance, Colleen Ward currently at AFBI for project management, and landowners in the Blackwater River sub-catchments for access to stream sites. This study was funded by the Special EU Programmes Body under EU INTERREG IIIa 20204 ‘BlackwaterTRACE’ and an Ulster University VCRS award.

Funding Information:
We thank Pete Devlin, School of Geography and Environmental Sciences, Ulster University for technical and field work assistance, Colleen Ward currently at AFBI for project management, and landowners in the Blackwater River sub-catchments for access to stream sites. This study was funded by the Special EU Programmes Body under EU INTERREG IIIa 20204 ‘BlackwaterTRACE’ and an Ulster University VCRS award.

Publisher Copyright:
© 2023 The Author(s)

Keywords

  • Phosphorus
  • Fractionation
  • EPC
  • Phosphate exchange potential
  • Stream sediments
  • Water quality

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