Soil analysis

Hello again monugoyal,

You asked what the difference was between:

XRD (X-Ray Powder Diffraction) to Identify Crystalline Compounds and phases.

XRD (X-Ray Fluorescence) to detect Elemental and Oxide content.

Full description of the two Methods below.

XRD and XRF: A brief early history of the use of x-rays for analysis

XRD
LSM Analytical Services large range of analytical techniques includes instrumentation for XRD analysis; one of two of the most widely applied analytical techniques based on X-rays:

XRF (X-Ray Fluorescence) for the elemental or oxide content of a material

XRD (X-Ray powder Diffraction) for identification of crystalline compounds or phases

The techniques are often considered to be complimentary. For example a sample may be submitted for XRF and found to contain 50% Al 2 O 3 and 30% SiO 2 and this may be sufficient information. However, XRD could then distinguish between samples containing different phases; for example Quartz (SiO 2 ), Corundum (Al 2 O 3 ), Mullite (Al 6 Si 2 O 13 ) or Kaolinite (Al 2 Si 2 O 5 (OH) 4 ) or any combination of these.

The X-rays used for XRD have one wavelength (they are all one "colour"). Normally, a sample is a few grams of powder and is packed into a holder with a flat surface. The beam of x-rays enters the sample surface and is reflected by the very small crystals (crystallites) in the sample. When it is reflected the single beam of x-rays is split so the x-rays come out of the sample in several beams at different angles to the sample. The instrument has a detector that swings round the sample as the sample itself is rotated and registers the position and strength of these beams. This data is plotted by software as strength (intensity) vs. position (angle) to give a series of "peaks" or "lines", which is called the diffraction pattern.

Each chemical compound or phase reflects x-rays slightly differently and so has a different diffraction pattern. A mixture of compounds gives a pattern that is made up of the patterns of all the individual compounds. So to identify the compounds present in a mixture the pattern obtained is compared to a large database of patterns. Often there are overlapping lines so experience and judgement are important. To give a guide when phase identification is complete the peaks are classified as major, minor or trace.

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LSM has developed a suite of programmes internally to allow a range of determinations to be made including:

• phase identification of crystalline materials
• phase quantification, including crystalline silica
• glass content of GGBS (ground granulated blast furnace slag)
• customer specific quality control methods

LSM`s analysis development team also develops new methods to meet customer requirements.

XRF

LSM Analytical Services large range of analytical techniques includes instrumentation for XRF analysis; one of two of the most widely applied analytical techniques based on X-rays:

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X-Ray Fluorescent (XRF) Spectrometers use a spectroscopic technique, which is commonly used for solids, in which x-rays are used to excite a sample and generate secondary x-rays.

XRF provides determination of major and trace elements in solids. There are 2 types of XRF spectrometers:

• Wavelength dispersive (WDX or WDS); superior resolution and detection limits
• Energy dispersive (EDX or EDS); smaller, often portable

As with any analytical method, sample preparation is crucial and LSM was one of the early pioneers of the Borate glass bead technique, developing methodology for analysis of refractory and rare earth oxide mixtures as well as a range of Ferro-alloys, Steels and hard metal Carbide powders. This is a valuable way to eliminate errors with materials, which exhibit varying composition, or are difficult to present in other forms.

The x-rays used for X-Ray Fluorescence (XRF) have as wide a range of wavelengths as possible (i.e. they are as near as possible to white light). The beam of x-rays enters the atoms of the sample and for each different element one wavelength ("colour") of x-rays is given out, the characteristic radiation.

The detector is moved to the position at which the characteristic radiation for each element being analysed leaves the sample and registers the strength of the beam. The intensity (strength) of the characteristic x-rays given out measures the amount of that element in the sample. In reality elements are measured simultaneously using a number of pre-assembled fixed channels placed around the sample. Each is effectively a self-contained spectrometer, with a crystal and detector tuned to receive a specific wavelength.

LSM also provides an excellent semi-quantitative package, which covers all the elements from Fluorine to Uranium measurable by XRF in one analysis. Useful results can be obtained from even small samples. By combining a semi-quantitative analysis with XRD, a cost effective investigative tool is available for deposits, corrosion, contamination or other unknowns.

I hope you find this useful!

hii babybear thank u for information

ur answer is very good

but i hav a query regarding my work

actually some one told me to do SEM and XRD of soil for morphological and mijneralogical properties, and my work is to study adsorption behaviour of soil. Can u tell me that these analysis will help me in my result explations.

if u know please reply...

bye

Hi monugoyal,

You asked:

actually some one told me to do SEM and XRD of soil for morphological and mijneralogical properties, and my work is to study adsorption behaviour of soil. Can u tell me that these analysis will help me in my result explations.

I have included details of 'SEM' (Scanning Electron Microscopy) testing below. (I gather that is what you wanted)?

This is the search field page which offers many sites and explanations. See below:

[BOOK] Soil sampling, preparation, and analysis
KH Tan, 2005 - books.google.com
... Micrographs are provided on soil mineral identification and mineral counts for

additional illustrations on the usefulness of SEM-EDAX in soil analysis. ...A Frostegård, E Bååth - Biology and Fertility of Soils, 1996 - Springer
... recovery of bacterial PLFA was 2.6-16% (mean 8.7%; SEM 0.96 ... our suggested conversion
factor to determine bacterial biomass in soil based on PLEA analysis. ...
S Cengiz, A Cengiz Karaca, İ Çakır, H Bülent … - Forensic science international, 2004 - Elsevier
Soils vary among different areas, and have some characteristics because of the
natural effects and transfers made by human and other living beings in time. So
that forensic examination of soil is not only concerned with the analysis ...
V Laperche, SJ Traina, P Gaddam, TJ Logan - Environ. Sci. Technol, 1996 - pubs.acs.org
... of solid-phase forms of Pb with XRD and SEM. ... Air-dried, homogenized soil samples
were passed through a 2-mm ... 2 μm were freeze-dried prior to further analysis. ...
MGA van der Heijden, JN Klironomos, M Ursic, … - Geol. Soc. Am. Bull, 1988 - uib.no
... simulating North American old-field ecosystems (experiment 2). Squares represent
means ( sem). ... Olsen, SR & Sommers, LE in Methods of Soil Analysis part 2 403 ...
RB Jackson, MM Caldwell - Journal of Ecology, 1993 - jstor.org
... 40 000 pairs were used for each sem- ivariogram ... root mass, soil ammonium, and soil
nitrate were logarithmically transformed prior to analysis because their ...

A book which I think you can use on-line which includes many kinds of soil tests, including SEM and XRD.

I am not able to give direct advice with regard to work in 'the field' as this is a 'subjective' judgement.

You will have to research "How To's" etc, on SEM and XRD, I sent info' on XRD already I believe, and when on site where the test samples are to be taken, it will be your subjective judgement and knowledge which must be used to choose the sample areas and types of actual 'soil' samples taken.

SEM is a very intensive method, and when using this or any other Lab Test, all I can say is good luck! And, make certain the sample are labeled and are in no way confused with other samples. I would make notes on the general site conditions, the depth from the prevailing top surface soil level to the sample level.

It may also be sensible to do a 'Datum' by finding something which is not going to be moved and measuring the distance from that Datum to the test samples, from perhaps three different angles, as, if the site is staying as it is with no change, you can always double check the site and where the various soil depth samples were taken. This may help if there was likely to have been any local water or other liquid or contaminant 'percolation' on the site/s.

One other thing. And you may already do this anyway, but I have to mention, that where a site is tested prior to being cleaned up in some way, you should be certain you have enough samples from each sampling area, each in an air-tight container.

I wish you luck!