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Measurement of soluble reactive phosphorus concentration profiles and fluxes in river-bed sediments using DET gel probes

Jarvie, Helen P; Mortimer, Robert J. G.; Palmer-Felgate, Elizabeth J.; St Quinton, Katherine; Harman, Sarah A.; Carbo, Patricia. 2008 Measurement of soluble reactive phosphorus concentration profiles and fluxes in river-bed sediments using DET gel probes. Journal of Hydrology, 350. 261-273. 10.1016/j.jhydrol.2007.10.041

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Abstract/Summary

DET (diffusive equilibrium in thin films) gel probes were used for sampling river-bed sediment porewaters, to characterise in situ soluble reactive phosphorus (SRP) concentration profiles and fluxes. DET probes were deployed in three contrasting rural streams: (1) a headwater ‘pristine’ stream, with minimal P inputs from low intensity grassland and no point sources, (2) an intensively cultivated arable catchment, and (3) a stream subject to high P loadings from sewage effluent and intensive arable farming. The DET results showed highly enriched porewater SRP concentrations of between ca. 400 and 5000 ug-P/1 in the sewage-impacted stream. In contrast, the arable and pristine streams had porewater SRP concentrations <70 ug-P/1 and <20 ug-P/1, respectively. Porewater SRP concentration profiles in both the sewage-impacted and arable-impacted streams showed well-defined vertical structure, indicating internal sources and sinks of SRP within the sediment. However, there was little variability in porewater SRP concentrations in the pristine stream. The DET porewater profiles indicated net diffusion of SRP (a) from the overlying river water into the surface sediment and (b) from subsurface sediment upwards towards the sediment–water interface. A mass balance for the sewage-impacted site showed that the influx of SRP into the surface sediments from the overlying river water was small (ca. 1% of the daily river SRP load). The DET results indicated that, in the arable and sewage-impacted streams, the surface ‘cap’ of fine sediment may play an important role in inhibiting upward movement of SRP from subsurface porewaters into the overlying river water, under steady-state, low-flow conditions.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1016/j.jhydrol.2007.10.041
Programmes: CEH Programmes pre-2009 publications > Water > WA02 Quantifying processes that link water quality and quantity, biota and physical environment > WA02.2 Hydrochemical and sediment processes
CEH Programmes pre-2009 publications > Water > WA02 Quantifying processes that link water quality and quantity, biota and physical environment > WA02.3 Physico-chemical processes and effects on freshwater biot
CEH Sections: Acreman
ISSN: 0022-1694
Additional Keywords: DET, gel probe, soluble reactive phosphorus (SRP), river, sediment, flux
NORA Subject Terms: Ecology and Environment
Hydrology
Chemistry
Date made live: 12 Jun 2008 12:39
URI: http://nora.nerc.ac.uk/id/eprint/3201

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