TY - JOUR
T1 - The method controls the story - Sampling method impacts on the detection of pore-water nitrogen concentrations in streambeds
AU - Comer-Warner, Sophie
AU - Knapp, Julia L.A.
AU - Blaen, Phillip
AU - Klaar, Megan
AU - Shelley, Felicity
AU - Zarnetske, Jay
AU - Lee-Cullin, Joseph
AU - Folegot, Silvia
AU - Kurz, Marie
AU - Lewandowski, Jorg
AU - Harvey, Judson
AU - Ward, Adam
AU - Mendoza-Lera, Clara
AU - Ullah, Sami
AU - Datry, Thibault
AU - Kettridge, Nicholas
AU - Gooddy, Daren
AU - Drummond, Jennifer
AU - Martí, Eugènia
AU - Milner, Alexander
AU - Hannah, David
AU - Krause, Stefan
PY - 2020/3/20
Y1 - 2020/3/20
N2 - 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). The findings of this study have critical implications for the interpretation of field-based research on hyporheic zone biogeochemical cycling and highlight the need for more systematic testing of sampling protocols. For the first time, the impact of different active and passive pore-water sampling methods is addressed systematically here, highlighting to what degree the choice of pore-water sampling methods affects research outcomes, with relevance for the interpretation of previously published work as well as future studies.
AB - 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). The findings of this study have critical implications for the interpretation of field-based research on hyporheic zone biogeochemical cycling and highlight the need for more systematic testing of sampling protocols. For the first time, the impact of different active and passive pore-water sampling methods is addressed systematically here, highlighting to what degree the choice of pore-water sampling methods affects research outcomes, with relevance for the interpretation of previously published work as well as future studies.
KW - Ammonium
KW - Nitrate
KW - Nutrients
KW - Samplers
KW - Streambed sampling
UR - http://www.scopus.com/inward/record.url?scp=85076921258&partnerID=8YFLogxK
U2 - 10.1016/j.scitotenv.2019.136075
DO - 10.1016/j.scitotenv.2019.136075
M3 - Review article
C2 - 31887527
AN - SCOPUS:85076921258
SN - 0048-9697
VL - 709
JO - Science of the Total Environment
JF - Science of the Total Environment
M1 - 136075
ER -