There's no such thing as 'undisturbed' soil and sediment sampling: sampler-induced deformation of salt-marsh sediments revealed by 3D x-ray computed tomography

Carr, Simon, Diggens, Lucy M. and Spencer, Kate L. (2019) There's no such thing as 'undisturbed' soil and sediment sampling: sampler-induced deformation of salt-marsh sediments revealed by 3D x-ray computed tomography. Journal of Soils and Sediments . [in press]. Item availability may be restricted.

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Abstract

Purpose: Within most environmental contexts, the collection of 'undisturbed' samples is widely relied-upon in studies of soil and sediment properties and structure. However, the impact of sampler-induced disturbance is rarely acknowledged, despite the potential significance of modification to sediment structure for the robustness of data interpretation. In this study, 3D-computed X-ray microtomography (μCT) is used to evaluate and compare the disturbance imparted by four commonly-used sediment sampling methods within a coastal salt-marsh.

Materials and methods: Paired sediment core samples from a restored salt-marsh at Orplands Farm, Essex, UK were collected using four common sampling methods (push, cut, hammer and gouge methods). Sampling using two different area-ratio cores resulted in a total of 16 cores that were scanned using 3D X-Ray computed tomography, to identify and evaluate sediment structural properties of samples that can be attributed to sampling method.

Results and discussion: 3D qualitative analysis identifies a suite of sampling-disturbance structures including gross-scale changes to sediment integrity and substantial modification of pore-space, structure and distribution, independent of sediment strength and stiffness. Quantitative assessment of changes to pore-space and sediment density arising from the four sampling methods offer a means of direct comparison between the impact of depth-sampling methods. Considerable disturbance to samples result from use of push, hammer and auguring samplers, whilst least disturbance is found in samples recovered by cutting and advanced trimming approaches.

Conclusions: It is evident that with the small-bore tubes and samplers commonly used in environmental studies, all techniques result in disturbance to sediment structure to a far greater extent than previously reported, revealed by μCT. This work identifies and evaluates for the first time the full nature, extent and significance of internal sediment disturbance arising from common sampling methods.

Item Type: Article
Journal / Publication Title: Journal of Soils and Sediments
Publisher: Springer Verlag
ISSN: 1614-7480
Departments: STEM
Depositing User: Anna Lupton
Date Deposited: 10 Oct 2019 12:27
Last Modified: 12 Oct 2019 18:23
URI: http://insight.cumbria.ac.uk/id/eprint/5140

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