Report about the Analysis of Soil Samples from the Test Lanes in Ispra, Italy

prepared for the project network Humin/MD

J. Igel, H. Preetz

Hannover, September 2005

Leibniz Institute for Applied Geosciences Stilleweg 2 30655 Hannover, Germany www.gga-hannover.de

1

Content Page 1. Introduction 1

2. Material and Methods of Investigation 1

2.1 Soil sampling 2

2.2 Methods of Investigation 2

3. Experimental Results 3

3.1 Soil physical and chemical properties 3

3.2 Physical Specification 5

4. Discussion and Conclusions 12

5. References 15

6. Appendix 16

A Total substance contents analysed by X-ray fluorescence 16 spectroscopy

B Multi frequency complex magnetic susceptibility and 18 dual frequency magnetic susceptibility 1. Introduction The soil investigation has been carried out within the joint research project Humin/MD (Metal detectors for Humanitarian Demining, www.humin-md.de) fi-nanced by the German Federal Ministry of Education and Research (BMBF). The test lanes of the Joint Research Centre (JRC) Ispra were used by the project net-work for measurements with metal detectors. Even though there exist several reports on the petrophysical properties of the test lanes in Ispra (KATSUBE et al. 2003a, 2003b, 2005), this report will give a more extensive pedological and mineralogical description of the different substrates and a more detailed classification of the material. Therefore, soil samples were taken in October 2004 and analysed in the laborato-ries of the Federal Institute for Geosciences and Natural Resources (BGR) in Han-nover.

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2. Material and Methods of Investigation 2.1 Soil Sampling The soil samples were taken on October 22th 2004 by a member of the project network (Mr. A. Yashan from the Saarland University) according to a continuous sampling pattern. The sampling depth was 5 cm and 12 specimens were taken from each test lane. Afterwards, the samples were merged and homogenised and the composite samples were used for the laboratory analyses. The JRC in Ispra possesses 8 test lanes with soils consisting of different partial-size structure, 6 of them being used for the investigations of HuMin/MD. Table 1 shows the list of the selected plots including a very short description and classification respectively. In addition a more detailed description by Dr. A. Lewis, JRC Ispra is listed. Table 1: Test lane and sample numbers including the soil description by JRC Test Lane/ Sample No

Description/ Classification

Additional Description

Plot 2 loamy Local Ispra soil, unmodified. Contains some metal clutter

Plot 3 sandy Local Ispra soil, cleaned Plot 4 pure sand Sandy subsoil from a location inside the

JRC Ispra site at a depth of about 1 - 2 m Plot 5 clay Clay from a location near to Vercelli,

Piemonte region of Italy (west of Ispra) Plot 6 high organic content Local Ispra soil with addition of horticul-

tural peat moss Plot 7 ferromagnetic Volcanic soil from a location near to

Napoli, Italy 2.1 Methods of Investigation A wide range of tests have been performed in the laboratory. Pedological character-istics like grain size distribution and organic matter content have been measured in all samples. Further tests such as X-ray fluorescence spectroscopy and the meas-urement of frequency dependent magnetic susceptibility have also been carried out for all plots. For better understanding the type of iron oxides in particular of the "ferromagnetic" soil the sample from Plot 7 was analysed by more methods like magnetic iron extraction, XRD, IR-spectroscopy, REM, Curie-temperature and IRM. Table 2 summarizes the laboratory analyses that have been carried out at the different soil samples.

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Table 2: Soil samples and tests that have been performed

Method Plot2

Plot3

Plot4

Plot5

Plot6

Plot7

Grain size distribution x x x x x x Organic matter content x x x x x x Calcium carbonate content x x x x x x Dual frequency magnetic susceptibility Bartington MS 2 B sensor x x x x x x

Multi frequency magnetic susceptibility Magnon sensor x x

X-ray fluorescence spectroscopy (XRF) x x x x x x Magnetic extraction x Scanning electron microscopy (SEM) x X-ray-diffraction (XRD) x x Infrared-spectroscopy x x Curie-temperature x x Isothermal remanent magnetisation (IRM) x x

3. Experimental Results 3.1 Soil physical and chemical properties In this chapter the results of the following measurements are listed: grain size dis-tribution, organic matter, calcium carbonate and some selected metal contents.

Table 3: Soil physical and chemical properties

Grain size distribution Sample

sand silt clay Organic matter CaCO3

% of humus-free soil %

Plot 2 80.8 15.8 3.4 2,30 0,66

Plot 3 91.3 8.7 0 0,07 0,80

Plot 4 97.1 2.9 0 0,00 0,74

Plot 5 12.7 75.2 12.1 0,34 1,14

Plot 6 69.1 26.8 4.1 3,29 0,79

Plot 7 79.9 17.3 2.8 0,17 6,60 Sand: 63 - 2000 μm Silt: 2 - 63 μm Clay: < 2 μm

4

0 10 20 30 40 50 60 70 80 90 100

% Silt

100

90

80

70

60

50

40

30

20

10

0

% Clay

100

90

80

70

60

50

40

30

20

10

0

% S

and

Plot 5

Plot 6Plot 2

Plot 7

Plot 3Plot 4

Fig. 1: Grain size triangle with the results of Plot 2 - 7

0

20

40

60

80

100

%

2 6,3 20 63 200 630 2000

Clay Silt Sand

Plot 2

µm

Plot 3

Plot 4

Fig.2: Grain size curves of Plot 2 - 4

5

0

20

40

60

80

100

%

2 6,3 20 63 200 630 2000

Clay Silt Sand

µm

Plot 5

Plot 6

Plot 7

Fig. 3: Grain size curves of Plot 5 - 7 Table 4: Metal contents for the characterisation of susceptibility and further soil

properties analysed by X-ray fluorescence spectroscopy

Sample TiO2 Al2O3 Fe2O3 MnO Co Ni

% mg/kg

Plot 2 0,43 12,7 2,88 0,06 8 18

Plot 3 0,44 13,2 2,56 0,08 6 13

Plot 4 0,85 13,1 5,39 0,10 16 28

Plot 5 0,88 17,2 6,13 0,04 16 47

Plot 6 0,42 12,5 2,87 0,05 5 18

Plot 7 0,75 15,6 6,37 0,13 20 41 3.1 Physical Specification The most important parameter affecting the detection of landmines adversely is the magnetic susceptibility. It has been measured with the multi frequency magnetic susceptibility sensor Magnon SM200. The major results are shown in figure 4. Ap-pendix B contains the complete measurements as well as the results achieved with the well-known dual frequency kappa meter MS 2B from Bartington.

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10 100 1000 10000frequency [Hz]

2000

4000

6000

8000

10000

sus

[10-6

SI]

real partimaginarypart

Plot 4Plot 7

Fig. 4: Frequency dependent complex magnetic susceptibility (Magnon sensor) The susceptibility of Plot 4 shows no frequency dependence. This can be explained as the soil texture is coarse sand which does not seem to contain any superpara-magnetic grain fraction. Plot 7 shows a small frequency dependence of the real part of the susceptibility of approximately 2% per decade. While the real part decreases the imaginary part increases. As a conclusion one can state that the frequency dependence of the mag-netic susceptibility of both magnetic soils in Ispra is low compared to other soils being problematic for landmine detection with metal detectors. The reason might be that they contain no or at least a poor content of very small (superparamagnetic) magnetic minerals. The results listed in Appendix B show that Plot 4 and 7 are the only ones with an eminent susceptibility. For this reason further tests concerning the constituent min-erals in these samples were performed. The aim was to identify the magnetic Fe-minerals which are causing the magnetic behaviour of the soil samples.

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Fig. 5: X-Ray diffractogram of Plot 4, sample without magnetic separation.

Fig. 6: Infrared spectroscopy of Plot 4, sample without magnetic separation.

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Fig. 7: X-Ray diffractogram of Plot 7, sample without magnetic separation.

Fig. 8: Infrared spectroscopy of Plot 7, sample without magnetic separation.

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Table 5: Summary of the mineral compound defined by IR-spectroscopy and X-ray diffractography of samples from Plot 4 and 7 without magnetic separation

Sample or

gani

c m

at-

ter

quar

tz

feld

spar

calc

ite

mus

covi

te/

illite

hem

atite

mag

netit

e/

mag

hem

ite

chlo

rite

horn

blen

de

leuc

ite

diop

side

biot

ite

Plot7 IR x x x Plot7 XRD x x x x x

Plot4 IR x x x Plot4 XRD x x x x x

As shown in the compilation of the XRD- and the IR-determinations, the magnetic Fe-minerals could not be identified in the untreated soil samples as their content is lower than about 2 %. In the X-ray diffractogram of Plot 7 there is possibly a peak coincidence between magnetite and diopside. This means that the peak of magnetite is covered by the one of diopside. In order to concentrate the magnetic fraction for further analyses a magnetic separation of the soil was carried out. Unfortunately the amount of magnetic substrate in the sample Plot 7 was too small for a XRD- and IR-determination, but still sufficient for scanning electron microscopy (SEM).

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Fig. 9: SEM of magnetic separated substrate of Plot7: titanomagnetites em-

bedded in feldspar (large grey mineral in the centre of the picture with bright inclusions).

Fig. 10: SEM of magnetic separated substrate of Plot7: isomorphic and

rounded titanomagnetites in the centre of the figure.

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Further methods were selected for the analysis of the untreated samples. In the fol-lowing the results of the determination of the Curie-temperature are shown.

0 200 400 600T [°C]

-0.2

0

0.2

0.4

0.6

0.8

1

Mre

l [ ]

Plot 7Plot 4

magnetiteFe3O4

Fig. 9: Determination of the Curie-temperature of Plot 4 and Plot 7: the normalised

magnetisation is plotted versus the temperature. The curve of demagnetisation of Plot 7 shows no distinct attribution to a specific mineral. The curve probably visualises the presence of various titanomagnetites and contingently maghemite. Whereas the intense decline of the curve from Plot 4 at 500 °C indicates magnetite being the main cause for the magnetic properties of the sample.

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0 400 800 1200 1600 2000B [mT]

0

0.2

0.4

0.6

0.8

1

IRM

norm

[ ]

Plot 4Plot 7

Fig. 10: Isothermal remanent magnetisation of Plot 4 and Plot 7: the normalised

magnetisation is plotted versus the applied outer magnetic field. The determination of the isothermal remanent magnetisation (IRM) can be used to distinguish between high coercitive minerals (hematite, goethite) and low coer-citive minerals (magnetite, titanomagnetite). The latter are magnetised readily when applying an outer magnetic field. Thus, their magnetisation rises steeply and reaches a saturation plateau at relatively low magnetic fields. As both graphs show such a behaviour the magnetic properties of Plot 4 as well as Plot 7 are caused by low coercitive minerals, most likely magnetite and titanomagnetite. 4. Discussion and Conclusions Grain size distribution The results of the grain size analysis as shown in fig. 1 - 3 are demonstrating that the plots are consisting of predominantly sandy substrates. The only exception is Plot 5 which is made up of silty loam. The conformity of most of the implemented soils implicates a small variety of related parameters such as the electrical conduc-tivity.

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As a conclusion of these results a more detailed description of the textures accord-ing to the US Soil Taxonomy is given in table 7. A description according to the German soil classification system is listed in addition for the purpose of compari-son (AG BODEN 1994). The fact that the boundary between silt and sand is at 50 μm in the US Soil taxonomy and at 60 μm in the German system remains uncon-sidered because it does not influence the classification in that case (s. fig. 2 and 3). Table 6: Classification of the texture of the soil material Test Lane/ Sample No

JRC: Description/ Classification

US Soil Taxonomy German Soil Taxon-omy

Plot 2 loamy loamy sand moderate silty sand Plot 3 sandy sand sand Plot 4 pure sand sand sand Plot 5 clay silty loam clayey silt Plot 6 high organic content sandy loam silty sand Plot 7 ferromagnetic loamy sand moderate silty sand To find terms for the dimension of the pedological results they are classified in table 8 following the US and the German classification system. Table 7: Classification of the texture (US classification) and the organic matter and

CaCO3 content (German classification) of the soil material Test Lane/ Sample No

texture organic matter content

CaCO3 content

Plot 2 loamy sand medium (2,30 %) low (0,66 %) Plot 3 sand very low (0,07 %) low (0,80 %) Plot 4 sand humus-free (0,0 %) low (0,74 %) Plot 5 silty loam very low (0,34 %) low (1,14 %) Plot 6 sandy loam medium (3,29 %) low (0,79 %) Plot 7 loamy sand very low (0,17 %) medium (6,60 %) Chemical analysis: The organic matter and the CaCO3 content of the soils have been analysed and classified (table4). Table 4 shows the amounts of the major metals in the soils which range between normal to low values. The amounts of heavy metals as well as aluminium show a correlation to the clay content (Plot 5) or the volcanic origin (Plot 7) of the material as expected. Even though magnetic properties are present in two test lanes there is no clear correlation to specific metals.

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The complete results of the analysis with XRF are listed in appendix A. There is a noticeable result that however does not influence the magnetic properties of the soils. The measured concentrations of arsenic (76 - 127 mg/kg) are in all the test lanes pretty high. Common total amounts of arsenic in soils without contamination are between 0.1 - 20 mg/kg (e.g. CHEN & HARRIS 2002). The maximum permis-sible value for arsenic in soils in several European countries is 20 mg/kg respec-tively. The reason for the contamination of the plots with arsenic is unknown. Nev-ertheless, these results do not mean any hazard for persons working on the test lanes. Mineralogical analysis: With the XRD and IR spectroscopy alone the magnetic Fe-minerals could not be identified in the untreated soil samples as their content is lower than about 2 %. But with the determination of the Curie-temperature and the Isothermal remanent mag-netisation the cause of the magnetic properties could be detected. In Plot 4 magnet-ite was identified to be the reason. This mineral derives from the unknown parent material of the soil. In Plot 7 titanomagnetite and contingently maghemite are the magnetic minerals. The former is often contained in vulcanites like the parent ma-terial of this test lane and maghemite is supposed to be a product of the weathering of titanomagnetite in this case. Magnetic properties: The magnetic properties of both magnetic soils (Plot 4 and Plot 7) which show a relatively high magnetic susceptibility are most likely caused by magnetite and some content of titanomagnetite. The frequency dependence of the susceptibility is low for both soils due to a low content of superparamagnetic minerals i.e. particles smaller than approx. 100 nm. Beside a high spatial variability of magnetic soil properties the frequency dependence of the magnetic susceptibility is the main rea-son for the failure of metal detectors. Therefore, it is questionable if the two mag-netic Ispra soils are representative for the so called “incooperative soils” causing most of the problems when using metal detectors for mine detection as their fre-quency dependence is negligible.

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5. References AG BODEN (1994): Bodenkundliche Kartieranleitung.- 4. Aufl., 392 S.; Han-

nover. CHEN, M., MA, L.Q. & HARRIS, W.G. (2002): Arsenic Concentrations in Florida

Surface Soils - Influence of Soil Type and Properties.- Soil Sci. Soc. Am. J., 66: 632 - 640.

KATSUBE, T.J. (2003a): Petrophysical Property (MS & EC) Determination of Soil

Samples from JRC.- Interim Report #1 prepared for Dr. A. Lewis, JRC Ispra, Italy.

KATSUBE, T.J., CONELL, S. & SCROMEDA-PEREZ, N. (2003b): Petrophysical

Property Determination of Soil Samples from JRC: Resistivity - Soil Mois-ture Relationship.- Interim Report #2 prepared for Dr. A. Lewis, JRC Ispra, Italy.

KATSUBE, T.J. & ERNST, R. (2005): Petrophysical Property (MS & EC) Deter-

mination of Soil Samples from JRC.- Additional Report (Revised) prepared for Dr. A. Lewis, JRC Ispra, Italy.

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Appendix A Table I: Total substance contents analysed by X-ray fluorescence spectroscopy

SiO2 TiO2 Al2O3 Fe2O3 MnO MgO % % % % % %

Plot 2 71.11 0.43 12.7 2.88 0.055 1.08 Plot 3 73.23 0.44 13.22 2.56 0.075 0.89 Plot 4 68.5 0.852 13.17 5.39 0.101 2.35 Plot 5 62.8 0.881 17.24 6.13 0.04 0.99 Plot 6 69.55 0.417 12.49 2.87 0.054 1.07 Plot 7 46.54 0.752 15.63 6.37 0.127 4.72

CaO Na2O K2O P2O5 (SO3) (Cl) % % % % % %

Plot 2 1.592 2.66 2.022 0.17 <0.01 0.007 Plot 3 2.361 3.31 1.9 0.211 <0.01 0.008 Plot 4 3.238 2.57 1.833 0.114 0.01 0.006 Plot 5 0.707 0.86 1.639 0.048 <0.01 0.005 Plot 6 1.612 2.55 2.038 0.17 <0.01 0.007 Plot 7 11.416 2.4 5.146 0.507 0.09 0.045

(F) LOI Sum_XRF (As) Ba Bi % % % mg/kg mg/kg mg/kg

Plot 2 <0.05 4.94 99.67 95 416 <3 Plot 3 0.09 1.38 99.68 96 391 <3 Plot 4 <0.05 1.49 99.62 92 477 <3 Plot 5 <0.05 8.26 99.6 104 442 <3 Plot 6 <0.05 6.83 99.65 76 417 <3 Plot 7 0.11 5.61 99.45 127 1584 <3

Ce Co Cr Cs Cu Ga mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg

Plot 2 29 8 50 6 <10 12 Plot 3 36 6 53 <5 <10 13 Plot 4 50 16 96 <5 13 14 Plot 5 64 16 117 10 14 22 Plot 6 77 5 49 <5 <10 14 Plot 7 109 20 103 10 55 16

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Hf La Mo Nb Nd Ni

mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg Plot 2 5 34 <2 10 <50 18 Plot 3 <5 42 <2 9 <50 13 Plot 4 <5 27 <2 7 <50 28 Plot 5 8 38 <2 17 <50 47 Plot 6 <5 34 <2 7 55 18 Plot 7 7 72 7 38 <50 41

Pb Pr Rb Sb Sc Sm mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg

Plot 2 26 <50 71 7 9 <50 Plot 3 19 <50 58 <5 8 <50 Plot 4 7 <50 62 <5 14 <50 Plot 5 31 <50 111 5 14 <50 Plot 6 24 <50 76 <5 9 <50 Plot 7 32 <50 212 <5 21 <50

Sn Sr Ta Th U V mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg

Plot 2 <2 164 <5 11 5 43 Plot 3 <2 214 <5 13 6 30 Plot 4 <2 221 <5 11 <3 104 Plot 5 4 83 <5 18 11 113 Plot 6 <2 165 <5 11 8 38 Plot 7 <2 889 <5 18 10 174

W Y Zn Zr mg/kg mg/kg mg/kg mg/kg

Plot 2 <5 16 55 181 Plot 3 <5 17 37 169 Plot 4 <5 13 60 210 Plot 5 <5 25 59 343 Plot 6 <5 15 54 184 Plot 7 <5 15 77 217 ( ): residual concentration after ignition with 1030 °C LOI: ignition lost

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Appendix B Table II: Multi frequency complex magnetic susceptibility (Magnon sensor)

Sample f [Hz] H [A/m] Real part X'

Imaginary partX''

Plot4 54 161 3373.9 23.1 Plot4 105 161 3333.8 0.3 Plot4 205 161 3327.9 10.8 Plot4 310 161 3324.3 9 Plot4 510 161 3318.1 21.5 Plot4 804 161 3322.4 33.8 Plot4 1060 161 3346.5 44.2 Plot4 2020 161 3317.7 76.5 Plot4 3013 161 3330.8 106.5 Plot4 4993 161 3300.8 144.9 Plot4 7991 161 3280.7 158.2 Plot4 9991 161 3275.9 135.7 Plot7 54 161 9226.8 87.9 Plot7 105 161 9195 133.4 Plot7 205 161 9184.4 139.2 Plot7 310 161 9135.3 147.7 Plot7 510 161 9110.1 168.8 Plot7 804 161 9090.4 200.1 Plot7 1060 161 9067.7 227.4 Plot7 2020 161 9081.8 319.5 Plot7 2020 161 9040.2 317.3 Plot7 3013 161 8961.3 394 Plot7 3013 161 8965.9 393.5 Plot7 4993 161 8900.3 498.5 Plot7 7991 161 8858.8 534.8 Plot7 9991 161 8822.8 471.1

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Table III: Dual frequency magnetic susceptibility (Bartington MS 2 B sensor)

LF (465 Hz) HF (4650 Hz) Sample SI * 10-6

frequency effect (LF-HF)/LF*100

Plot 2 265 255 3,8 % Plot 3 70 65 - * Plot 4 2475 2465 0,4 % Plot 5 145 145 - Plot 6 260 245 5,8 % Plot 7 5950 5820 2,2 % * Values of susceptibility too low for reliable determination