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The method controls the story: sampling method impacts on the detection of pore-water nitrogen concentrations in streambeds

Comer-Warner, Sophie; Knapp, Julia L.A.; Blaen, Phillip; Klaar, Megan; Shelley, Felicity; Zarnetske, Jay; Lee-Cullin, Joseph; Folegot, Silvia; Kurz, Marie; Lewandowski, Jorg; Harvey, Judson; Ward, Adam; Mendoza-Lera, Clara; Ullah, Sami; Datry, Thibault; Kettridge, Nicholas; Gooddy, Daren; Drummond, Jennifer; Martí, Eugènia; Milner, Alexander; Hannah, David; Krause, Stefan. 2020 The method controls the story: sampling method impacts on the detection of pore-water nitrogen concentrations in streambeds. Science of The Total Environment, 709, 136075. https://doi.org/10.1016/j.scitotenv.2019.136075

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Abstract/Summary

Biogeochemical gradients in streambeds are steep and can vary over short distances often making adequate characterisation of sediment biogeochemical processes challenging. This paper provides an overview and comparison of streambed pore-water sampling methods, highlighting their capacity to address gaps in our understanding of streambed biogeochemical processes. This work reviews and critiques available pore-water sampling techniques to characterise streambed biogeochemical conditions, including their characteristic spatial and temporal resolutions, and associated advantages and limitations. A field study comparing three commonly-used pore-water sampling techniques (multilevel mini-piezometers, miniature drivepoint samplers and diffusive equilibrium in thin-film gels) was conducted to assess differences in observed nitrate and ammonium concentration profiles. Pore-water nitrate concentrations did not differ significantly between sampling methods (p-value = 0.54) with mean concentrations of 2.53, 4.08 and 4.02 mg l−1 observed with the multilevel mini-piezometers, miniature drivepoint samplers and diffusive equilibrium in thin-film gel samplers, respectively. Pore-water ammonium concentrations, however, were significantly higher in pore-water extracted by multilevel mini-piezometers (3.83 mg l−1) and significantly lower where sampled with miniature drivepoint samplers (1.05 mg l−1, p-values <0.01). Differences in observed pore-water ammonium concentration profiles between active (suction: multilevel mini-piezometers) and passive (equilibrium; diffusive equilibrium in thin-film gels) samplers were further explored under laboratory conditions. Measured pore-water ammonium concentrations were significantly greater when sampled by diffusive equilibrium in thin-film gels than with multilevel mini-piezometers (all p-values ≤0.02).

Item Type: Publication - Article
Digital Object Identifier (DOI): https://doi.org/10.1016/j.scitotenv.2019.136075
ISSN: 00489697
Date made live: 19 Mar 2020 16:16 +0 (UTC)
URI: http://nora.nerc.ac.uk/id/eprint/527282

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