X-Ray
Fluorescence
Analysis
by Gergana Hristozova
Project supervisor: s. eng. M. Gustova
FLNR
Aim of the project
• To establish the content and concentration of heavy
metals in soil samples. The specimens used were
taken from Bulgaria. The first sample was obtained in
Plovdiv, right in the center of town. The second- from
a field near a metalworks, located outside of Plovdiv.
• The same method can be used to determine the
quantity of micro-admixtures in objects of the
surrounding environment (e.g. minerals, ashes of
plants, dry residua of water samples)
Equipment description
• The multicomponent X-Ray
Fluorescence analysis involves
detection and measurment of the
secondary emission of x-rays by
the atoms of the elements in the
specimen. They are being excited
by gamma rays or x-rays of a
standard radioactive isotope
source such as Cd109 (emanation
energy E =22,16keV, T1/2=453
days) or Am241 (E=59,57keV,
T1/2=458y). A semi-conductive
silicon /lithium spectrometer is
used, with an area of about
30mm2 and thickness of 3mm.
This is a photo of the
standard ring-shaped
radioisotope source 109Cd
(E=22,16 keV, T1/2=453
days) used for excitation
of X-ray radiation.
The characteristic X-ray
radiation is registered
using a semi-conductive
Si(Li) detector with full
width at half maximum
(FWHM) resolution 145eV
for a line of Fe (6,4 keV).
The software settings are done
according to the geometry of the
experiment.
Sample
cassette, ,
S=3cm2
Source stand
Al
Specimen stand
Source
 3mm,
h=3mm
Pb
(protection)
Ag
(protection)
Be window
Si (Li) – detector
Setting the detector and the source
In this picture you can see the pulseheight analyzer and the analysis
software being used: Canberra’s WinAxil
and WinFund.
And these are the two
soil samples taken
from Bulgaria.
The soil needs to be dried out. Both
samples were put in an oven for two hours
at a temperature of 1050C. Afterwards,
both soil specimens were ground, put into
cassettes, signed and weighed out, which
concluded the preparation of the
samples.
Two kinds of samples were examined.
In the first picture you can see a
prepared sample, put on the source. It
contains 2-3g of soil put in a cassette
(saturated layer specimen).
The other type of specimen
is actually a thin layer of the
same soil, baked and ground,
and stuck on a piece of tape.
The spectra of the soils display the need of having two different types of
sample preparation:
WinFund:
Spectrum of
the
saturated
layer,
sample #1.
Spectrum of
the thin
layer,
sample #1.
Spectrum of
the
saturated
layer,
sample #2.
Spectrum
of the thin
layer,
sample #2.
Using Canberra’s Winaxil, the spectra are
analyzed further. A fitting model and the
chemical elements of interest are set,
afterwards, the area of each peak is
calculated.
Spectrum of sample #1, saturated layer:
Spectrum of sample #2, saturated layer:
Calibration curves were used to calculate the exact values of Se, Cr and Ni concentration.
Интенсивность для 1% элемента с учётом распада источника на 01.08.2011
источник Cd-109, образцы почв, время измерения 600 с, n=1.
1.0E+06
1.0E+05
ENO
belg
1.0E+04
GNA
SG1-A
SGH
soil-5
1.0E+03
SCHT-3
F(x)=10^(3,06*lg(x-1,87)+1,49)
SP-1
эталонная кривая
1.0E+02
1.0E+01
0
2
4
6
8
10
12
14
16
18
20
Using thin and saturated layers, and several calibrational curves, the
following results were obtained:
elements
Pb
Ca
Ti
Fe
Cu
Rb
Sr
Y
Zr
K
Mn
Zn
Cr
Ni
Se
concentration
[%]
sample #1
concentration
[%]
sample #2
< 0,004
0,045 ± 0,004
2,3 ± 0,3
11,3 ± 1,0
0,41 ± 0,07
0,37 ± 0,07
2,34 ± 0,03
2,62 ± 0,04
0,0062 ± 0,0007 0,0077 ± 0,0008
0,017 ± 0,001
0,045 ± 0,004
0,0243 ±0,0009
0,0154 ± 0,0007
0,0026 ±0,0004
0,0020 ± 0,0003
0,0143 ± 0,0006
0,0103 ± 0,0005
0,44 ± 0,04
0,61 ± 0,03
0,042 ± 0,004
0,061 ± 0,003
<0,0005
0,0103 ± 0,0005
<0,005
< 0,005
< 0,0002
0,0208 ± 0,0002
< 0,005
0,021 ± 0,005
Due to the low
concentration and the
characteristics of elements
of lower Z, not all elements
of interest were found in the
saturated layer of sample
#1. This is why thin layer
samples were used, too.
Conclusion:
• The following elements were detected: Pb, Ca, Ti, Fe, Cu, Rb, Sr, Y, Zr, K,
Mn, Zn, Cr, Ni, Se.
• Data were analyzed in 3 different ways:
– Using saturated layers and by comparison to reference samples.
– Using calibration curves for elements not present in the reference
samples.
– Using thin layers (for elements such as K, Ca, Cr, Mn).
• It was determined that the soil taken from Plovdiv (sample #1) has a
standard content and concentration.
• The soil taken in proximity to the metalworks (sample #2) contains more
Pb than usual and should not be used for planting fruits.
Acknowledgements
I would like to thank my supervisor
M. Gustova and Natasha Gustova, a student at
the Moscow State University in her third year,
for the patience, the guidance and the help.
It was a pleasure.