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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.
Chemosphere. 2017 Dec; 188:119-129.C

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.

Authors+Show Affiliations

Environmental Futures Research Institute, Griffith University, Gold Coast Campus, QLD, 4215, Australia.Environmental Futures Research Institute, Griffith University, Gold Coast Campus, QLD, 4215, Australia.Natural and Built Environments Research Centre, School of Natural and Built Environments, University of South Australia, South Australia, 5095, Australia; Future Industries Institute, University of South Australia, SA, 5095, Australia.Natural and Built Environments Research Centre, School of Natural and Built Environments, University of South Australia, South Australia, 5095, Australia; Future Industries Institute, University of South Australia, SA, 5095, Australia.Environmental Futures Research Institute, Griffith University, Gold Coast Campus, QLD, 4215, Australia. Electronic address: d.welsh@griffith.edu.au.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

28881239

Citation

Rathnayake Kankanamge, Nadeeka, et al. "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." Chemosphere, vol. 188, 2017, pp. 119-129.
Rathnayake Kankanamge N, Bennett WW, Teasdale PR, et al. 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. Chemosphere. 2017;188:119-129.
Rathnayake Kankanamge, N., Bennett, W. W., Teasdale, P. R., Huang, J., & Welsh, D. T. (2017). 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. Chemosphere, 188, 119-129. https://doi.org/10.1016/j.chemosphere.2017.08.144
Rathnayake Kankanamge N, et al. 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. Chemosphere. 2017;188:119-129. PubMed PMID: 28881239.
* Article titles in AMA citation format should be in sentence-case
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, Y1 - 2017/08/29/ PY - 2017/05/29/received PY - 2017/08/25/revised PY - 2017/08/28/accepted PY - 2017/9/8/pubmed PY - 2018/1/5/medline PY - 2017/9/8/entrez KW - Diffusive equilibration in thin films KW - Diffusive gradients in thin-films KW - Environmental variability KW - Sediment biogeochemistry in estuaries SP - 119 EP - 129 JF - Chemosphere JO - Chemosphere VL - 188 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. SN - 1879-1298 UR - https://www.unboundmedicine.com/medline/citation/28881239/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_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0045-6535(17)31383-8 DB - PRIME DP - Unbound Medicine ER -