A novel gel-based technique for the high resolution, two-dimensional determination of iron (II) and sulfide in sediment

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Author(s)
Robertson, David
Teasdale, Peter R
Welsh, David T
Year published
2008
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Many coastal marine sediments display highly heterogeneous biogeochemistry due to complex biological and chemical interactions. Existing measurement techniques are limited in their ability to characterise the distributions of reduced species at high resolution in two dimensions. To obtain more detailed information than existing methods, a novel technique for the simultaneous high-resolution (1 mm), 2D determination of porewater iron (II) and sulfide using a gel-based diffusive sampler was developed. A diffusive equilibration in a thin-film (DET) hydrogel was colourised by Ferrozine reagent, imaged electronically and analysed ...
View more >Many coastal marine sediments display highly heterogeneous biogeochemistry due to complex biological and chemical interactions. Existing measurement techniques are limited in their ability to characterise the distributions of reduced species at high resolution in two dimensions. To obtain more detailed information than existing methods, a novel technique for the simultaneous high-resolution (1 mm), 2D determination of porewater iron (II) and sulfide using a gel-based diffusive sampler was developed. A diffusive equilibration in a thin-film (DET) hydrogel was colourised by Ferrozine reagent, imaged electronically and analysed using Computer Imaging Densitometry (CID). With the selected gel parameters, the method detection limit for iron (II) was 0.6 ?mol L-1, with an upper calibration limit of 500 孯l L-1 and relative standard deviations below 10% across the calibration range. This method was integrated into the existing diffusive gradient in a thin film (DGT) method for sulfide determination. Field deployments of a prototype probe, which measured an area of 170 נ80 mm, in estuarine sediment revealed complex, fine-scale, interlocking zones of iron (II) and sulfide. This confirms the need to assess more than a single dimension, at appropriately high resolution, to obtain an accurate representation of sediment geochemistry. Advantages of the technique include its high spatial resolution, minimal sample handling, flexible probe size, simultaneous measurement of two analytes at exactly the same location in the sediment and the rapid production of data without requiring expensive analytical instrumentation.
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View more >Many coastal marine sediments display highly heterogeneous biogeochemistry due to complex biological and chemical interactions. Existing measurement techniques are limited in their ability to characterise the distributions of reduced species at high resolution in two dimensions. To obtain more detailed information than existing methods, a novel technique for the simultaneous high-resolution (1 mm), 2D determination of porewater iron (II) and sulfide using a gel-based diffusive sampler was developed. A diffusive equilibration in a thin-film (DET) hydrogel was colourised by Ferrozine reagent, imaged electronically and analysed using Computer Imaging Densitometry (CID). With the selected gel parameters, the method detection limit for iron (II) was 0.6 ?mol L-1, with an upper calibration limit of 500 孯l L-1 and relative standard deviations below 10% across the calibration range. This method was integrated into the existing diffusive gradient in a thin film (DGT) method for sulfide determination. Field deployments of a prototype probe, which measured an area of 170 נ80 mm, in estuarine sediment revealed complex, fine-scale, interlocking zones of iron (II) and sulfide. This confirms the need to assess more than a single dimension, at appropriately high resolution, to obtain an accurate representation of sediment geochemistry. Advantages of the technique include its high spatial resolution, minimal sample handling, flexible probe size, simultaneous measurement of two analytes at exactly the same location in the sediment and the rapid production of data without requiring expensive analytical instrumentation.
View less >
Journal Title
Limnology and Oceanography: Methods
Volume
6
Copyright Statement
© 2008 by the American Society of Limnology and Oceanography, Inc.. The attached file is reproduced here in accordance with the copyright policy of the publisher. Please refer to the journal's website for access to the definitive, published version.
Subject
Sensor technology (incl. chemical aspects)
Earth sciences
Other environmental sciences not elsewhere classified
Biological sciences