Transcript Анализ на състоянието на почвите в район

COMPARISON OF DIFFERENT ANALYTICAL TECHNIQUES FOR
ENVIRONMENTAL MONITORING OF CONTAMINATED SOILS
Metodi Mladenov, Daria Ilieva
University of Chemical Technology and Metallurgy – Sofia, Bulgaria, 1756, Sofia, 8 “St. Kliment Ohridski” blvd., e-mail: [email protected]
Introduction
Environmental monitoring of contaminated soils is a different task, because of the using of different analytical techniques for analysis depending on the type of the
contaminants. There are many types of analysis which are used for preparation of the samples. Still the most used and standardized in many countries is method
for extraction with “aqua regia”, and next analysis through inductively coupled plasma (ICP) technique. Some other analytical technique is the wave dispersive X-ray
fluorescence (WD-XRF) analysis. That method has very high possibilities for determination of concentration of heavy metals and metalloids in different kinds of
samples and has some advantages over the other analytical methods.
In current work the done experiments for environmental monitoring of contaminated soil are described. The presence and concentrations of elements Cu, Fe, Mn,
Pb, As, Zn, Ni and Cr, through “aqua regia” extraction and ICP-OES (optical emission spectrometry) analysis and WD-XRF analysis are investigated.
Experimental
Nineteen samples from region of old metallurgical plant, which proven are contaminated with heavy metals and metalloids, are analyzed. The presence and
concentrations of elements Cu, Fe, Mn, Pb, As, Zn, Ni and Cr, through “aqua regia” extraction and ICP-OES analysis and XRF analysis are investigated.
Schemes of principal work of the two techniques are showed on figs. 1 and 2. Comparison of the performances of the two used method is showed in Table 1.
The sampling and sample preparation
for XRF analysis are detailed in [1]. The
samples were analysed with a Carl
Zeiss, Jena (Germany) “VRA 20”
wavelength-dispersive
XRF
spectrometer. Working conditions: X-ray
tube with Rh anode; current 50 mA;
voltage 35 kV; crystalline analyzer
LiF200; detector SC and FC; collimator
0.70; measuring time of each step 30 s;
measuring reiteration 3 times. For the
quantitative analysis measurements
were performed at the characteristic line
for each analyte [2]. The extraction with
“aqua regia” solution was done
according to [3]. It was used Prodigy
ICP_OES, Teledyne, Leeman Labs
apparatus with next plasma operation
Fig. 1. Scheme of principle work of ICP-OES
conditions: coolant gas – 18 L/min;
Fig. 2. Scheme of principle work of WD-XRF
spectrometer
auxiliary gas – 0.5 L/min; nebulizer gas
spectrometer
– psi; power – 1,2 kW; sample uptake
time – 30 sec.
Results
Table 1. Comparison of performances of the used methods in analysis of current
Obtained intervals for results from both methods are showed in table
samples
Performance
Method
2. Obtained results haven’t good accordance between themselves.
Aqua reqia extraction
WD-XRF analysis*
The reason for that can be contain in a different sample preparation
with next ICP-OES
procedure for both method.
analysis
Accuracy
Up to 0.0001 % for ICP
Up to 0.01 %
Table 2. Obtained intervals of concentrations by the two methods.
Precision
Very good
Very good
Element
ICP-OES, %
WD-XRF, %
Sensitivity
Up to 0.0001 %
Up to 0.01 %
As
0.001
–
0.21
<
0.01 – 0.23
Selectivity
Very high
Very high for elements
Scale of operation
From ppm to 100 %
with atom number up to
15
From 0.02 to 100 %
Extraction of the sample
in liquid
Yes
Not necessary
Time for sample
preparation
Time for analysis**
16-18 hours
15-30 min
30 min
30 min
Error possibility
High – mainly in the
sample preparation stage
Lower – it haven’t some
extraction procedure
*The new apparatus for WD-XRF have comparable instrumental performance with
used in current analysis ICP-OES technique.
** time for five parallel measurements of one sample.
Cu
0.005 – 0.14
0.22 – 0.47
Cr
0.002 – 0.008
0.04 – 0.06
Ni
0.001 – 0.01
0.02 – 0.03
Pb
0.005 – 0.05
< 0.01 – 0.16
Zn
0.01 – 0.06
0.01 – 0.08
Mn
0.03 – 0.13
0.02 – 0.12
Fe
-
1.23 – 3.72
On the basis of the obtained results, next conclusions may be drawn:
The obtained results from the two methods are with good accordance for elements As, Zn, Ni and Mn.
Sample preparation for ICP-OES analysis needs from special treatment, which not every time is appropriate for treatment of the analyzed soil
samples. For example when the carbonate soils are treated often it is necessary double portion of aqua regia to be used.
Used ICP-OES analysis have very high accuracy, high sensitivity and scale of operation up to ppm, which is advantage to the used apparatus for WDXRF. That advantage can be equalize if for WD-XRF analysis s use new generation of apparatus.
Even used old generation of apparatus for WD-XRF analysis, the advantages of this analysis is consist in lower time for sample preparation and
elimination of error which can be permit form stage of extraction.
References
1. Mladenov M., Jordanov J., Pelovski Y., X-ray spectroscopy analysis of soils in the region of “Eliseina” metallurgical
plant, Journal of Environmental Protection and Ecology (2010) 11 (4), 1246-1252.
2. Mladenov M., Jordanov J., Ivanova E., X-ray spectroscopy analysis of soils in the region of Eliseina metallurgical
plant – Part 2, Journal of Environmental Protection and Ecology (2012) 13 (3A), 1887-1895.
3. ISO 11466 :1995. Soil quality – Extraction of trace elements soluble in aqua regia.
Acknowledgements
This poster has been produced with the financial
assistance of the European Social Fund, project
number BG051PO001-3.3.06-0014. The author is
responsible for the content of this material, and under
no circumstances can be considered as an official
position of the European Union and the Ministry of
Education and Science of Bulgaria