Effects of elevated sulfate in eutrophic waters on the internal phosphate release under oxic conditions across the sediment-water interface

Chen, J., Zhang, H., Liu, L., Zhang, J., Cooper, M. ORCID: 0000-0002-1864-1434, Mortimer, R.J.G. and Pan, G. ORCID: 0000-0003-0920-3018, 2021. Effects of elevated sulfate in eutrophic waters on the internal phosphate release under oxic conditions across the sediment-water interface. Science of The Total Environment, 790: 148010. ISSN 0048-9697

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Abstract

Eutrophication in freshwater environments may be enhanced by the elevation of sulfate in waters, through the release of internal phosphorus (P) from anoxic sediments. However, the influence of increasing but modest sulfate concentrations (less than 3000 μM) on P release under oxic conditions across the sediment-water interface (SWI) in eutrophic freshwater is poorly understood. In this study, the profiles of P, iron (Fe), sulfur (S) and physicochemical parameters were measured in a simulated lacustrine system with varying concentrations of sulfate (970–2600 μM) in overlying water. The results indicated that elevated concentrations of sulfate increased the soluble reactive P in overlying waters under oxic conditions across the SWI. A 100 μM increase of sulfate was found to induce a 0.128 mgm−2d−1 increase of P flux from surface sediments into overlying waters under oxic conditions. Higher sulfate concentrations in the overlying waters increased the concentrations of labile S(-II) in the deep sediments, due to sulfate penetration and subsequent reduction to S(-II). We also found the fluxes of labile Fe (10.34 to 18.33 mgm−2d−1) and P (2.70 to 1.33 mgm−2d−1) from deep to surface sediment were both positive and greater than the corresponding fluxes (Fe, 2.2 to 3.51 and P, 2.6 to 0.39 mgm−2d−1, respectively) from surface sediment to the overlying water, suggesting that reduction of P-bearing Fe(III)(oxyhydr)oxides in deep anoxic sediment acted as a major source of internal P release. In addition, the upward flux of Fe(II) was significantly lower under higher sulfate conditions, indicating that the Fe(II) flux could be mitigated by formation of Fe(II) sulfides in the deep sediment. Under these conditions, less Fe(II) from deep sediments could be re-oxidized and combine with P in the surface, oxic sediment, thereby reducing the retention capacity for P and leading to higher release of internal P to the water column.

Item Type: Journal article
Publication Title: Science of The Total Environment
Creators: Chen, J., Zhang, H., Liu, L., Zhang, J., Cooper, M., Mortimer, R.J.G. and Pan, G.
Publisher: Elsevier BV
Date: 10 October 2021
Volume: 790
ISSN: 0048-9697
Identifiers:
NumberType
10.1016/j.scitotenv.2021.148010DOI
1444216Other
Divisions: Schools > School of Animal, Rural and Environmental Sciences
Record created by: Laura Ward
Date Added: 08 Jun 2021 09:19
Last Modified: 08 Jun 2021 09:19
URI: http://irep.ntu.ac.uk/id/eprint/43014

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