Aquatic Geochemistry

, Volume 7, Issue 2, pp 155-171

First online:

Particle Size Distributions of Clay-rich Sediments and Pure Clay Minerals: A Comparison of Grain Size Analysis with Sedimentation Field-Flow Fractionation

  • Martin HassellövAffiliated withAnalytical and Marine Chemistry, Göteborg University
  • , Benny LyvénAffiliated withAnalytical and Marine Chemistry, Göteborg University
  • , Henrik BengtssonAffiliated withDepartment of Earth Sciences, Göteborg University
  • , Ragna JansenAffiliated withAnalytical and Marine Chemistry, Göteborg University
  • , David R TurnerAffiliated withAnalytical and Marine Chemistry, Göteborg University
  • , Ronald BeckettAffiliated withCRC for Freshwater Ecology, Water Studies Centre and Department of Chemistry, Monash University

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Two clay-rich coastal sediment samples have been characterised together with three pure clays identified as major components of the sediment samples. The mineralogy of the sediments was determined by X-ray diffraction, and their bulk properties measured (organic carbon content, leachable iron and manganese, surface area and cation exchange capacity). A simple approach is used to model the properties of the sediments from those of their pure clay components. Good agreement is found for cation exchange capacity and specific surface area indicating that the clay minerals are the most important constituents influencing the sediments' surface properties. Particle size distributions were assessed by conventional grain size analysis, and also by Sedimentation Field-Flow Fractionation (SedFFF). These two approaches yield sharply differing size distributions; in particular, conventional grainsize analysis indicates a much greater proportion of submicron particles. Similar results are obtained from analysis of pure clays. The most likely reason for this is artifacts introduced in the unavoidable 1 μm prefractionation used for SedFFF.

Sediment size distribution field-flow fractionation XRD clay mineralogy specific surface area cation exchange capacity