Comparing in situ colorimetric DET and DGT techniques with ex situ core slicing and centrifugation for measuring ferrous iron and dissolved sulfide in coastal sediment pore waters

Nadeeka Rathnayake Kankanamge, William W. Bennett, Peter R. Teasdale, Jianyin Huang, David T. Welsh*

*Kontaktforfatter for dette arbejde

Publikation: Bidrag til tidsskriftTidsskriftartikelForskningpeer review

Resumé

In productive coastal sediments the separation between different biogeochemical zones (e.g. oxic, iron(III)-reducing and sulfate-reducing) may be on the scale of millimetres. Conventional measurement techniques simply cannot resolve changes in pore water solute concentrations over such small distances. The diffusive equilibration in thin films (DET) and the diffusive gradients in thin films (DGT) techniques allow in situ determination of pore water solute concentration profiles with one-dimensional profiles and/or two-dimensional distributions on the millimetre scale. Here we compare measurements of pore water iron(II) and sulfide using conventional core sampling (slicing and centrifugation) and colorimetric DET-DGT techniques. DET-DGT samplers were deployed within replicate sediment cores from three different sites, which were processed by slicing and centrifugation following retrieval of the samplers, so that the measurements were approximately co-located. Iron(II) concentrations were determined by DET at all three sites (0.3–262 μmol L−1), while dissolved sulfide was consistently measured by DGT at one site only (0.003–112 μmol L−1). Pore water concentrations of iron(II) and sulfide determined conventionally following pore water extraction (iron(II); 0.4–88 μmol L−1 and sulfide; 0.05–36 μmol L−1), were systematically lower than the colorimetric DET and DGT measurements in the same sample. This underestimation was most likely due to the mixing of sediment from different biogeochemical zones during pore water extraction, which resulted in the precipitation of iron(II) and sulfide. This study shows that conventional pore water extraction methods can be unreliable for the determination of redox-active solutes due to artefacts associated with pore water mixing.

OriginalsprogEngelsk
TidsskriftChemosphere
Vol/bind188
Sider (fra-til)119-129
ISSN0045-6535
DOI
StatusUdgivet - 2017
Udgivet eksterntJa

Fingeraftryk

coastal sediment
porewater
sulfide
iron
solute
sampler
centrifugation
in situ
measuring
extraction method
sediment core
artifact
sulfate

Citer dette

@article{40c0205cd387413b9ae71ff795befe4c,
title = "Comparing in situ colorimetric DET and DGT techniques with ex situ core slicing and centrifugation for measuring ferrous iron and dissolved sulfide in coastal sediment pore waters",
abstract = "In productive coastal sediments the separation between different biogeochemical zones (e.g. oxic, iron(III)-reducing and sulfate-reducing) may be on the scale of millimetres. Conventional measurement techniques simply cannot resolve changes in pore water solute concentrations over such small distances. The diffusive equilibration in thin films (DET) and the diffusive gradients in thin films (DGT) techniques allow in situ determination of pore water solute concentration profiles with one-dimensional profiles and/or two-dimensional distributions on the millimetre scale. Here we compare measurements of pore water iron(II) and sulfide using conventional core sampling (slicing and centrifugation) and colorimetric DET-DGT techniques. DET-DGT samplers were deployed within replicate sediment cores from three different sites, which were processed by slicing and centrifugation following retrieval of the samplers, so that the measurements were approximately co-located. Iron(II) concentrations were determined by DET at all three sites (0.3–262 μmol L−1), while dissolved sulfide was consistently measured by DGT at one site only (0.003–112 μmol L−1). Pore water concentrations of iron(II) and sulfide determined conventionally following pore water extraction (iron(II); 0.4–88 μmol L−1 and sulfide; 0.05–36 μmol L−1), were systematically lower than the colorimetric DET and DGT measurements in the same sample. This underestimation was most likely due to the mixing of sediment from different biogeochemical zones during pore water extraction, which resulted in the precipitation of iron(II) and sulfide. This study shows that conventional pore water extraction methods can be unreliable for the determination of redox-active solutes due to artefacts associated with pore water mixing.",
keywords = "Diffusive equilibration in thin films, Diffusive gradients in thin-films, Environmental variability, Sediment biogeochemistry in estuaries",
author = "{Rathnayake Kankanamge}, Nadeeka and Bennett, {William W.} and Teasdale, {Peter R.} and Jianyin Huang and Welsh, {David T.}",
year = "2017",
doi = "10.1016/j.chemosphere.2017.08.144",
language = "English",
volume = "188",
pages = "119--129",
journal = "Chemosphere",
issn = "0045-6535",
publisher = "Pergamon Press",

}

Comparing in situ colorimetric DET and DGT techniques with ex situ core slicing and centrifugation for measuring ferrous iron and dissolved sulfide in coastal sediment pore waters. / Rathnayake Kankanamge, Nadeeka; Bennett, William W.; Teasdale, Peter R.; Huang, Jianyin; Welsh, David T.

I: Chemosphere, Bind 188, 2017, s. 119-129.

Publikation: Bidrag til tidsskriftTidsskriftartikelForskningpeer review

TY - JOUR

T1 - Comparing in situ colorimetric DET and DGT techniques with ex situ core slicing and centrifugation for measuring ferrous iron and dissolved sulfide in coastal sediment pore waters

AU - Rathnayake Kankanamge, Nadeeka

AU - Bennett, William W.

AU - Teasdale, Peter R.

AU - Huang, Jianyin

AU - Welsh, David T.

PY - 2017

Y1 - 2017

N2 - In productive coastal sediments the separation between different biogeochemical zones (e.g. oxic, iron(III)-reducing and sulfate-reducing) may be on the scale of millimetres. Conventional measurement techniques simply cannot resolve changes in pore water solute concentrations over such small distances. The diffusive equilibration in thin films (DET) and the diffusive gradients in thin films (DGT) techniques allow in situ determination of pore water solute concentration profiles with one-dimensional profiles and/or two-dimensional distributions on the millimetre scale. Here we compare measurements of pore water iron(II) and sulfide using conventional core sampling (slicing and centrifugation) and colorimetric DET-DGT techniques. DET-DGT samplers were deployed within replicate sediment cores from three different sites, which were processed by slicing and centrifugation following retrieval of the samplers, so that the measurements were approximately co-located. Iron(II) concentrations were determined by DET at all three sites (0.3–262 μmol L−1), while dissolved sulfide was consistently measured by DGT at one site only (0.003–112 μmol L−1). Pore water concentrations of iron(II) and sulfide determined conventionally following pore water extraction (iron(II); 0.4–88 μmol L−1 and sulfide; 0.05–36 μmol L−1), were systematically lower than the colorimetric DET and DGT measurements in the same sample. This underestimation was most likely due to the mixing of sediment from different biogeochemical zones during pore water extraction, which resulted in the precipitation of iron(II) and sulfide. This study shows that conventional pore water extraction methods can be unreliable for the determination of redox-active solutes due to artefacts associated with pore water mixing.

AB - In productive coastal sediments the separation between different biogeochemical zones (e.g. oxic, iron(III)-reducing and sulfate-reducing) may be on the scale of millimetres. Conventional measurement techniques simply cannot resolve changes in pore water solute concentrations over such small distances. The diffusive equilibration in thin films (DET) and the diffusive gradients in thin films (DGT) techniques allow in situ determination of pore water solute concentration profiles with one-dimensional profiles and/or two-dimensional distributions on the millimetre scale. Here we compare measurements of pore water iron(II) and sulfide using conventional core sampling (slicing and centrifugation) and colorimetric DET-DGT techniques. DET-DGT samplers were deployed within replicate sediment cores from three different sites, which were processed by slicing and centrifugation following retrieval of the samplers, so that the measurements were approximately co-located. Iron(II) concentrations were determined by DET at all three sites (0.3–262 μmol L−1), while dissolved sulfide was consistently measured by DGT at one site only (0.003–112 μmol L−1). Pore water concentrations of iron(II) and sulfide determined conventionally following pore water extraction (iron(II); 0.4–88 μmol L−1 and sulfide; 0.05–36 μmol L−1), were systematically lower than the colorimetric DET and DGT measurements in the same sample. This underestimation was most likely due to the mixing of sediment from different biogeochemical zones during pore water extraction, which resulted in the precipitation of iron(II) and sulfide. This study shows that conventional pore water extraction methods can be unreliable for the determination of redox-active solutes due to artefacts associated with pore water mixing.

KW - Diffusive equilibration in thin films

KW - Diffusive gradients in thin-films

KW - Environmental variability

KW - Sediment biogeochemistry in estuaries

U2 - 10.1016/j.chemosphere.2017.08.144

DO - 10.1016/j.chemosphere.2017.08.144

M3 - Journal article

VL - 188

SP - 119

EP - 129

JO - Chemosphere

JF - Chemosphere

SN - 0045-6535

ER -