Kenneth Pye
Associates
Ltd.
Scientific Research,
Consultancy and Investigations
.
..
Particle Size Analysis
...
|
|
Laser DiffractionRapid, reliable and highly reproducible results are achieved using the Coulter™ LS230 Laser Granulometer. This instrument covers the range 0.04 µm to 2000 µm, which provides accurate determination of the sand, silt and clay fractions. Generally 0.1 g to 4 g of sediment is required, suspended in water and ultrasonically disaggregated for the analysis. For very small samples (<0.1 g), or where samples need to be recovered after analysis, a small volume module can be used.
Sieve Analysis Samples containing gravel particles, greater than 2000 µm in diameter, can be analysed by wet or dry sieving to determine the complete grain size distribution. The British Standards BS1377 method is followed, using standard Endecotts™ test sieves in the range 63 µm to 63 mm, nested and agitated on mechanical shakers. The required sample size varies depending on the coarseness of the sediment, but is generally between 5 g and 1 kg.
Microscopy
and Image Analysis
Particle Size Analysis Software Particle size statistics and parameters are efficiently calculated using our in-house software, GRADISTAT. The software using a combination of Microsoft Excel and VisualBasic to analyse data obtained from sieve, laser granulometer, or many other particle sizing techniques. The user is required to input the mass or percentage of sediment retained on sieves spaced at any intervals, or the percentage of sediment detected in each bin of a Laser Granulometer. The following sample statistics are then calculated using the Method of Moments: mean, mode(s), sorting (standard deviation), skewness, kurtosis, D10, D50, D90, D90/D10, D90-D10, D75/D25 and D75-D25. Grain size parameters are calculated arithmetically and geometrically (in microns) and logarithmically (using the phi scale) (Krumbein and Pettijohn, 1938). The program also calculates statistical parameters by the Folk and Ward (1957) graphical method and determines the physical description (such as “very coarse sand” and “moderately sorted”). The program also provides a physical description of the textural group which the sample belongs to and the sediment name (such as “fine gravelly coarse sand”) after Folk (1954). Also included is a table giving the percentage of grains falling into each size fraction, modified from Udden (1914) and Wentworth (1922). In terms of graphical output, the program provides graphs of the grain size distribution and cumulative distribution of the data in both metric and phi units, and displays the sample grain size on triangular diagrams. Samples may be analysed singularly, or up to 250 samples may be analysed together. A copy of the software can be downloaded here (Microsoft Excel document, 301 KB). Full instructions are included.
Publications Blott, S.J.
and Pye,
K. (2006).
Particle
size distribution analysis of sand-sized particles by laser diffraction: an
experimental investigation of instrument sensitivity and the effects of particle
shape. Sedimentology 53, 671-685. Pye,
K., Blott, S.J.,
Croft, D.J. and Carter, J.F. (2006). Forensic comparison of soil samples:
assessment of small-scale spatial variability in elemental composition, carbon
and nitrogen isotope ratios, colour, and particle size distribution.
Forensic Science International 163, 59-80. Pye, K. and Blott,
S.J. (2004). Particle size analysis of
sediments, soils and related particulate materials for forensic purposes using
laser granulometry. Forensic Science International 144, 19-27. Blott, S.J.,
Croft, D.J., Pye, K., Saye,
S.E. and Wilson, H.E. (2004). Particle size analysis
by laser
diffraction. In:
Pye, K.
and
Croft, D. (Eds.) Forensic Geoscience - Principles, Techniques and
Applications.
Geological Society Special Publication No. 232, Geological Society
Publishing House, Bath, 63-73. Blott, S.J.
and Pye, K. (2001).
GRADISTAT: a grain size distribution and statistics package for the analysis of
unconsolidated sediments. Earth Surface Processes and Landforms 26,
1237-1248. |
|
|
