european journal of soil science, june 2006,
TRANSCRIPT
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Trace element distributions in soils developed in loessdeposits fromnorthern France
T . S T E R C K E M A N a , F . D O U A Y b , D . B A I Z E c , H . F O U R R I E Rb , N . P R O I X d , C . S C H V A R T Zb & J . C A R I G N A Ne
aENSAIA-INPL/INRA, Laboratoire Sols et Environnement, BP 172, 54505 Vandoeuvre-le`s-Nancy Cedex,
bISA, Laboratoire Sols et
Environnement, 41, rue du Port, 59046 Lille Cedex, cINRA, Unite de Science du Sol, BP 20619, 45166 Olivet Cedex, dINRA,
Laboratoire dAnalyses des Sols, 273, rue de Cambrai, 62000 Arras, and eCNRS, Centre de Recherches Petrographiques et
Geochimiques, 15, rue Notre Dame des Pauvres, 54501 Vandoeuvre-le`s-Nancy, France
Summary
A pedo-geochemical survey was carried out in the Nord-Pas de Calais region (France) on soils developed
in loess deposits. Total concentrations of Al, Fe and 18 trace elements, as well as common soil
characteristics, were determined in samples from 52 surface and 97 deep horizons developed in these
loess deposits. The Pb isotopic composition was determined in two sola. The composition of deep
horizons, compared with that of the upper continental crust, with that of horizons developed from 21
other sedimentary rocks from the region and with that of loess from various parts of the world, confirms
that loess from the Nord-Pas de Calais region derives from multi-recycled and well-mixed ancient
sedimentary rocks. Correlation analysis shows that least mobile (i.e. ionic potential (Z/r) is between 3
and 7) geogenic elements (Bi, Co, Cr, Cu, In, Ni, Pb, Sn, Tl, V, Zn) are associated with the fraction
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few decimetres to about 20 m. The origin of the loess material
of western Europe is still controversial. It has been proposed
that these aeolian sediments were derived locally from
paleoestuaries bordering the English Channel. Alternative
models favour the role of shallow marine shelves that
emerged during glacial times. In either case, a reworking of
Tertiary sediments during the Pleistocene era seems to be
required before the aeolian deposition (Gallet et al., 1998).
Our work deals only with soils developed from typical loess
(Jamagne et al., 1981), excluding those developed in the
transition zone where loamy aeolian formations are mixed
with sand.
In the Nord-Pas de Calais, the development of soils issuing
from loess is quite slight. Soils developed in this recent mate-
rial are attributed to luvic BRUNISOLS or NE OLUVISOLS,
according to the Re fe rentiel Pe dologique (AFES, 1998) or to
Cambisols or Haplic Luvisols according to the WRB (ISSS,
1998). Under forest, the soils are often designated as luvic
BRUNISOLS OLIGOSATURE S or as oligosaturated
NE OLUVISOLS.
The luvic BRUNISOLS are distinguished by incipient clay
illuviation, leading to the formation of a structural horizon
with some clay coatings (St horizon). The NE OLUVISOLS
are characterized by a typical BT horizon, resulting from
marked clay illuviation. The St and BT horizons are brown
to yellow brown (Munsell: 10YR 4/4 to 10YR 4/6), with a
loamy to loamy-clayey texture, and a distinct prismatic and
polyhedral structure. The C horizon generally appears between
0.8 m and 1.2 m. It can be distinguished from the St and BT
horizons by its yellowish colour (Munsell: 10YR 5/6), its
smaller clay content and the absence of structure. The soil
parent material is often calcareous and designated as Cca.
An S or SC horizon may be observed between the BT (or St)
horizons and the Cca horizon. The sola may be truncated as a
consequence of water erosion.
In soils developed in a relatively shallow loess stratum over-
lying an impermeable material (such as clayey Tertiary depos-
its or residual clay with flints), signs of temporary water
excess may appear at depths of less than 0.5 m. When the
loess deposit is thicker, the soils show better natural drainage
and less distinct hydromorphic features appear at greater
depths.
The main use of the loess soils is intensive cultivation for
various crops (cereals, sugar beet, potatoes, vegetables, etc.).
Some of them are under permanent grassland and a very small
portion under forest.
Canche
Authie
Aa
Lys
Scarpe
Esc
aut
Sam
bre
Lille
Valenciennes
Holocene deposits
Loamysandy transition zone
Sands zone (thin mantle)Sands zone (thick mantle)
Loess zone (thin mantle)
Loess zone (thick mantle)
FranceBelgium border
50km
Dunkerque
Calais
Boulogne
Figure 1 Map of the superficial Pleistocene deposits of northern France, adapted from Paepe & Somme (1970).
Trace elements in loess soils 393
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Sampling
Sampling sites were far from potential contamination sources
(industrial plants, busy roads, houses, etc.). There were 38 sites
under cultivation, 11 under permanent grassland and three
under forest. All the horizons were sampled, in soil pits. The
sola were described according to the Pedological Information
System (STIPA, 1982). The horizons were sampled starting at
the bottom of the solum, to avoid contaminating the horizons
to be sampled. A steel blade was used to detach about 1 kg of
soil material, which was poured into a polypropylene bag.
Analysis
In each solum, samples from three horizons were analysed: the
surface organo-mineral horizon (LA horizon for cultivated
soil, A horizon for other soil uses), the C horizon and a
horizon situated between the previous ones, a BT, S or SChorizon. In one solum situated under forest and another one
under cultivation, all the horizons were analysed for the deter-
mination of the lead isotope ratios.
Methods of analysis are presented in Table 1. Quality con-
trol was based on internal control samples whose mean and
uncertainty values were known. For each parameter, a control
sample was analysed every 1520 samples. The total contents
of trace and major elements were determined for batches of
3040 samples. Three blanks, two internal control samples and
two certified samples (GBW 7401 and GBW 7402) in triplicate
were inserted into each batch. Moreover, in each batch two
samples were analysed twice and two others were analysed
thrice. At the INRA Soil Analysis Laboratory, where the
analyses were performed, all the parameters, except Bi, In,
Mo and Sn contents, are controlled by national or interna-
tional inter-laboratory comparisons. The frequency of these
comparisons is one sample a month for the pedological para-
meters (BIPEA, 2000) and four samples every 3 months for
major and trace elements (Van Dijk et al., 2001). The resultswere expressed on a dried soil basis, after deduction of the
moisture content.
Lead isotope ratios were determined using a magnetic sector
and multicollector inductively coupled plasma mass spectro-
meter (MCICPMS) (White et al., 2000) after aqua regia
extraction and lead separation by anionic exchange chromato-
graphy (Manhe` s et al., 1980).
Data processing
Frequency distributions, correlation matrices, principal com-
ponents analysis (PCA) and multiple linear correlations wereperformed using the STATISTICA software (StatSoft, 2002).
Data below the quantification limit were replaced by values of
half this limit (Holmgren et al., 1993; Sanford et al., 1993).
Results and discussion
Soil characteristics
The frequency distributions of nearly all the parameters mea-
sured in the deep horizons are only slightly skewed (data not
shown). Therefore, the data can be reasonably used in regres-
sion analysis without transformation. The particle-size distri-
bution fits that of typical loess as given by Jamagne et al.
Table 1 Methods of analysis. The standards refer to those published by AFNOR (Paris)
Parameter Principle Standard
Pretreatment Drying at room temperature, sieving to 2 mm, grinding to 0.250 mm for total dissolution NF ISO 11464
Residual moisture content Weighing the test portion before and after heating at 105C NF ISO 11465
Particle-size distribution Sedimentation (050 mm) and sieving (>50 mm) NF X31-107
Organic carbon Dry combustion or sulfo-chromic acid oxidation (when CaCO3 >50 g kg1) NF ISO 10694,
NF ISO 14235
Total carbonates Measurement of the volume of CO2 released after reaction with HCl NF ISO 10693
pH pH of a water suspension NF ISO 10390
CEC Percolation of a 1.0 mol l1
ammonium acetate solution, pH 7 NF X31-130Exchangeable cations Extraction with a 1.0 mol l1 ammonium acetate solution, pH 7 NF X31-108
Total Al, Bi, Cd, Co, Cr, Cu, Calcination followed by a HF HClO4 digestion at 180C. Determination by ICPOESa NF ISO 14869-1
Fe, In, Mn, Mo, Ni, Pb, or ICPMSb
Sb, Sn, Tl, V, Zn
Total Hg Digestion by a sulfo-nitric acid mixture at 60C. Determination by CVAFSc INRA methode
Total As and Se Digestion by a sulfo-nitric acid mixture containing V2O5. Determination by CVAASd INRA methode
aICPOES, inductively coupled plasma optical emission spectrometry.bICPMS, inductively coupled plasma mass spectrometry.cCVAFS, cold vapour atomic fluorescence spectrometry.dCVAAS, cold vapour atomic absorption spectrometry.eSterckeman et al. (2002a).
394 T. Sterckeman et al.
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(1981): dominance of coarse silt, and coarse silt to fine silt
ratios are always above 1 and often above 2 (Table 2).
Relationships between trace elements and major mineral
components
The positive correlations of numerous trace element contents
with lutum, Al and Fe contents suggest that trace elements are
specifically associated with phyllosilicates and with iron oxides
and hydroxides of the finest fraction (Table 3). This is sup-
ported by the fact that, in the lutum fraction of two deep
horizons, Sterckeman (2004) found mainly smectites, chlorite
and illite, together with goethite. In the >2 mm fractions, he
found chlorite, micas and feldspars whose content decreased
with increasing fraction size. The quartz content increased
with the fraction size, the >50 mm fraction containing more
than 800 g kg1 quartz. This composition could explain the
negative correlations of trace element contents with the coarse
fraction content, as quartz acts as a diluent of the carryingphases.
In the deep horizons, the correlation between Al and Fe
explains about half of the variance of Bi, Cr, Cu, In, Ni, Pb,
Sn, Tl and Zn contents and about 80% of that of V (Table 3).
It also explains the variance of As, Co, Mo and Sb, but at a
rather smaller level (about 15% to 35%). It does not explain,
or only slightly, that of Cd, Mn, Hg and Se. More or less close
Table 2 Physico-chemical characteristics of the soil horizons from the Nord-Pas de Calais loess deposits (median values)
Horizon type
Variable Unit LA or A BT S, SC or C Cca Subsoil
Cultivation
Size (n) /horizon 38 33 26 11 70
Thickness /cm 20 15 20 20 20
Lutum (
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Table3
Linearcorrelationcoefficients
betweenvariablesmeasuredinthesoilhorizonsfromtheNord-PasdeCalaisloessdep
osits.Coefficientssignificantlydifferentfromzero(
0.05)
areinboldtype.Coarsefraction(202000mm)isthesumofcoarsesiltandsands
Lutum
Finesilt
Coarsesilt
Finesand
Coarsesand
Coarsefraction
OrganicC
pH
CaCO3
CEC
Al
Fe
Mn
Surfacehorizons
Lutum
1.00
0.23
0.6
7
0.4
7
0.20
0.7
7
0
.00
0.23
0.2
7
0.5
6
0.81
0.8
2
0.05
Finesilt
0.23
1.00
0.3
0
0.8
0
0.3
5
0.8
0
0
.24
0.26
0.22
0.24
0.37
0.4
3
0.4
7
Coarsesilt
0.6
7
0
.30
1.00
0.09
0.2
7
0.6
2
0
.12
0.17
0.3
0
0.2
9
0.58
0.6
7
0.3
1
Finesand
0.4
7
0
.80
0.09
1.00
0.4
2
0.8
1
0
.31
0.17
0.16
0.4
3
0.49
0.5
4
0.24
Coarsesand
0.20
0.3
5
0.2
7
0.4
2
1.00
0.3
5
0
.12
0.07
0.25
0.20
0.28
0.08
0.08
Coarsefraction
0.7
7
0
.80
0.6
2
0.8
1
0.3
5
1.00
0
.16
0.03
0.02
0.5
1
0.75
0.7
9
0.3
4
OrganicC
0.00
0.24
0.12
0.3
1
0.12
0.16
1
.00
0.7
5
0.24
0.7
8
0.27
0.17
0.5
4
pH
0.23
0.26
0.17
0.17
0.07
0.03
0.7
5
1.00
0.5
8
0.4
2
0.27
0.20
0.3
4
CaCO3
0.2
7
0.22
0.3
0
0.16
0.25
0.02
0
.24
0.5
8
1.00
0.03
0.07
0.04
0.00
CEC
0.5
6
0.24
0.2
9
0.4
3
0.20
0.5
1
0
.78
0.4
2
0.03
1.00
0.21
0.3
1
0.4
2
Al
0.8
1
0
.37
0.5
8
0.4
9
0.2
8
0.7
5
0
.27
0.2
7
0.07
0.21
1.00
0.8
6
0.3
8
Fe
0.8
2
0
.43
0.6
7
0.5
4
0.08
0.7
9
0
.17
0.20
0.04
0.3
1
0.86
1.00
0.4
2
As
0.4
0
0.03
0.2
8
0.19
0.10
0.2
7
0
.23
0.13
0.13
0.3
6
0.23
0.3
6
0.11
Bi
0.2
7
0
.39
0.09
0.5
1
0.14
0.4
3
0
.69
0.4
8
0.13
0.6
3
0.10
0.21
0.19
Cd
0.07
0.3
3
0.07
0.19
0.3
6
0.17
0.4
2
0.3
8
0.2
7
0.2
9
0.08
0.05
0.17
Co
0.5
0
0
.35
0.6
0
0.3
3
0.16
0.5
4
0
.56
0.4
7
0.15
0.18
0.68
0.7
6
0.7
7
Cr
0.7
1
0
.36
0.6
5
0.3
6
0.14
0.6
8
0
.37
0.3
7
0.06
0.13
0.78
0.8
5
0.5
0
Cu
0.04
0.22
0.19
0.3
0
0.16
0.12
0
.05
0.02
0.13
0.06
0.01
0.01
0.09
Hg
0.01
0.26
0.06
0.11
0.25
0.17
0
.56
0.26
0.16
0.4
3
0.33
0.25
0.6
3
In
0.4
2
0
.42
0.22
0.5
6
0.14
0.5
4
0
.70
0.4
1
0.03
0.7
4
0.22
0.3
1
0.24
Mn
0.05
0
.47
0.3
1
0.24
0.08
0.3
4
0
.54
0.3
4
0.00
0.4
2
0.38
0.4
2
1.00
Mo
0.12
0.25
0.03
0.3
7
0.07
0.24
0
.79
0.6
0
0.21
0.6
2
0.04
0.01
0.3
8
Ni
0.7
7
0.20
0.6
0
0.3
3
0.09
0.6
1
0
.41
0.4
7
0.2
8
0.09
0.86
0.8
1
0.4
4
Pb
0.10
0.08
0.09
0.01
0.2
9
0.12
0
.64
0.4
2
0.03
0.3
9
0.35
0.23
0.4
9
Sb
0.02
0
.30
0.09
0.3
9
0.05
0.21
0
.79
0.5
4
0.12
0.5
7
0.23
0.12
0.3
6
Se
0.02
0.21
0.09
0.2
8
0.02
0.13
0
.91
0.6
9
0.19
0.6
8
0.29
0.13
0.5
1
Sn
0.11
0.19
0.12
0.06
0.3
6
0.06
0
.38
0.14
0.23
0.3
3
0.12
0.07
0.3
6
Tl
0.4
3
0
.45
0.20
0.5
2
0.4
1
0.5
6
0
.24
0.15
0.10
0.3
6
0.48
0.3
8
0.02
V
0.7
0
0
.42
0.6
4
0.4
7
0.03
0.7
1
0
.03
0.08
0.05
0.3
6
0.65
0.8
6
0.3
6
Zn
0.4
0
0.15
0.4
1
0.00
0.4
2
0.15
0
.22
0.25
0.3
0
0.06
0.34
0.3
9
0.23
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Table4
AveragecompositionofsoilhorizonsfromNord-PasdeCalaisloessdepo
sitsandsedimentaryrocks(medianvalues)
,ofloessfromFrance,GreatBritain,Germ
any,Spitsbergen,
Kansas,Argentina,ChinaandNewZe
aland(Worldloess,medianvalue)andofu
ppercontinentalcrust(UCC,meanvalue)
Nord-Pasde
Calais
Loess
Surfacehorizons
Deeph
orizons
21othersedimentary
parentmaterialsa
Worldloessb
UCC
Unit
LACultivation
AGrassland
AForest
BT
S,SCorC
Cca
All
Surfacehorizons
Deephorizons
Value(n)
T&Mc
Wd
Ge
Size
/horizon
38
11
3
47
39
11
97
219
390
Al
/gkg
1
41.2
41.0
37.6
52.6
50.1
42.0
50.3
35.0
36.9
65.2(75)
80.4
77.4
72.2
Fe
20.6
20.1
18.2
29.1
26.6
22.5
27.4
20.5
23.8
31.5(75)
35.0
30.9
39.9
As
/mgkg
1
8.5
9.0
10.0
10.6
9.7
8.4
10.0
8.0
7.6
1.5
2
4.4
Bi
0.16
0.15
0.30
0.17
0.15
0.14
0.16
0.17
0.12
0.127
0.123
0.23
Cd
0.41
0.33
0.15
0.13
0.11
0.12
0.12
0.40
0.10
0.098
0.102
0.079
Co
9.2
8.8
4.7
11.5
10.6
10.0
11.1
9.0
8.5
11.4(54)
10
11.6
17
Cr
54
55
44
68
65
54
65
51
57
56(42)
35
35
80
Cu
15.8
14.8
13.7
14.3
13.9
11.6
13.6
13.6
9.3
13.0(42)
25
14.3
32
Hg
0.065
0.061
0.174
0.031
0.020
0.020
0.024
0.061
0.022
0.056
0.0123
In
0.038
0.041
0.062
0.045
0.041
0.037
0.041
0.038
0.031
0.05
0.061
Mn
642
627
302
593
519
450
523
427
276
620(75)
600
5
27
774
Mo
0.53
0.49
0.93
0.53
0.48
0.44
0.50
0.53
0.43
0.14(7)
1.5
1.4
0.78
Ni
20.5
19.1
12.9
28.6
28.6
23.4
27.8
18.8
20.1
19.5(39)
20
18.6
38
Pb
30.3
32.7
71.6
19.2
17.8
15.1
18.6
29.4
14.6
16.0(71)
20
17
18
Sb
0.65
0.76
1.82
0.57
0.61
0.50
0.55
0.71
0.45
0.2
0.31
0.3
Se
0.22
0.29
0.65
0.13
0.06
0.05
0.10
0.29
0.17
0.05
0.083
0.15
Sn
2.17
2.27
3.20
2.09
2.01
1.65
2.02
2.01
1.46
3.6(18)
5.5
2.5
1.73
Tl
0.46
0.44
0.51
0.51
0.48
0.41
0.50
0.39
0.36
0.75
0.75
0.47
V
59
64
53
75
72
58
72
58
64
66(42)
60
53
98
Zn
66
68
47
58
54
43
55
67
44
55(42)
71
52
70
aFromSterckemanetal.(2002a):limes
tones,chalks,shales,marls,clays,sandsan
dmixedfaciesfromPrimary,Secondary,TertiaryandQuaternaryeras.
bFromLeRiche(1973),Tayloretal.(1983),Galletetal.(1996,1998),Dingetal.
(2001),Jahnetal.(2001)andYokooetal.
(2004).
cFromTaylor&McLennan(1995).
dFromWedepohl(1995).
eFromGaoetal.(1998).
Trace elements in loess soils 399
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the Cd content is less in surface horizons under forest com-
pared with those under permanent grassland and cultivation.
This is consistent with the hypothesis of an exogenous Cdinput in the surface horizons varying with soil use (see next
section).
In the deep horizons, Cd is positively and closely correlated
with Mn and organic C, while it shows few correlations with
other soil characteristics, contrary to the other trace elements.
Considering the absence of link between Cd and organic C in
the surface horizons, and that Cd is known to generally show
little association with organic matter in soil (Adriano, 1986;
Alloway, 1995), the positive correlation between Cd and
organic C in the deep horizons could be a consequence of a
physical link between Cd and Mn, the latter being also asso-
ciated with organic C.
Enrichment of surface horizons
In the deep horizons, close linear correlations exist between the
contents of various trace elements and those of Al or Fe (Table 5).
These relations have the general form:
TEDH aMEDH b; 2
where [TE] represents the concentration of a trace element (in
mg kg1), [ME] the concentration of a reference major element
(Al or Fe, in g kg1), DH indicates that the content refers to
deep horizons, and a and b are the parameters of the linear
regression (least squares method).
If we consider that [TE]DH represents the trace elementcontent of the original soil parent material, i.e. the pedo-
geochemical background (PGB) content, this can be estimated
in any surface horizon ([TE]PGB/SH) assuming that:
TEPGB=SH aMESH b; 3
where SH indicates that the content refers to a surface horizon.
This assumption is possible because there is generally no sig-
nificant contamination with Al and Fe in soils. In the case of
Cd, Hg and Se, which show no correlation with Al or Fe, the
mean content of the deep horizon was taken as [TE]PGB/SH
(Table 5). For Mn, Co was taken instead of Al or Fe.
Subtracting [TE]PGB/SH from the actual trace element contentof the surface horizon ([TE]SH) gives the enrichment (ETE) of the
surface horizon, relative to the soil parent material (Figure 6),
expressed in mg kg1 or in percentage of [TE]PGB/SH.
The bivariate diagrams (e.g. Figures 4a and 6) indicate that the
surface horizons are enriched with all the trace elements deter-
mined, except Co, Cr and Ni. In absolute values (mg kg1) and
without distinguishing between soil use, enrichments with Mn,
Zn, Pb, Cu and V are the greatest (median from 172 mg kg1 to
3.32 mg kg1) (Table 6); the smallest are Se, Mo, Tl, Hg, Bi
and In (from 0.11 mg kg1 to 0.003 mg kg1). When
expressed relative to the pedo-geochemical background, the
Lutum
Al
Fe
Co
Cr
Ni
V(15)
0.8 0.9 1.0
0.2
0.1
0.0
0.1
LutumV(15)
FS
CS
FSa
CSa
org CSe(4).
pH
CaCO3
CEC
AlFe
Mn
Cd(1)
CoCr
Cu(5)
Ni
Pb(3)
Zn(7)
Mo(11)
Sn(9)
Sb(6)
Tl(12)
Bi(10)
In(14)
As(13)
Hg(2)
1.0
1.0 0.5 0.0 0.5 1.0
0.5
0.0
0.5
1.0
PC1: 32.03%
PC2:23.71%
org. C
Pb(3)Sn(9)
Sb(6)
Hg(2)
Se(4)
0.5
0.6
0.6 0.5 0.4 0.3 0.2 0.1
0.7
0.8
0.9
Figure 3 Principal components analysis of the variables measured in surface and deep horizons from loess deposits. FS, fine silt; CS, coarse silt; FSa,
fine sand; CSa, coarse sand. The surface enrichment ranking number is in parentheses.
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estimated from the correlation between the isotopic ratio and
1/[Pb] in the horizon under forest (Figure 9). The results do
not vary significantly whatever the isotopic ratio used and are
close to the mean isotopic composition of the French
industrial Pb emissions and of the main lead ores (Monna
et al., 1997).
In forest soils, the enrichments calculated by the two meth-
ods are close. In the OF horizon EPb/Al is 120.3 mg kg1,
Table 6 Estimated enrichment of the soil surface horizons from the Nord-Pas de Calais loess deposits with 15 elements
All soil uses All Cultivation Grassland Forest
Median 5th percentile 95th percentile Median 5th percentile 95th percentile Median
/mg kg1 /% of the pedo-geochemical background /g m2
As 0.91 1.01 3.89 10.6 13.6 49.8 0.18 0.18 0.17 0.21
Bi 0.030 0.005 0.128 24.8 4.7 99.3 0.005 0.005 0.005 0.009
Cd 0.26 0.09 0.52 220.4 75.3 434.8 0.080 0.085 0.050 0.001
Cu 4.26 0.45 13.43 44.1 4.0 126.9 0.9 1.0 0.8 0.2
Hg 0.035 0.011 0.159 106.4 33.7 482.2 0.009 0.010 0.006 0.007
In 0.003 0.002 0.020 7.6 5.3 66.9 0.001 0.001 0.000 0.002
Mn 172 17 348 37.1 4.7 83.5 47.3 49.8 34.7 2.2
Mo 0.10 0.00 0.39 22.9 0.3 99.3 0.022 0.029 0.022 0.030
Pb 14.93 6.20 48.67 94.6 42.7 337.4 4.0 4.6 3.4 2.4
Sb 0.22 0.03 0.90 42.8 5.8 196.2 0.069 0.071 0.053 0.071
Se 0.113 0.038 0.373 94.2 32.0 311.2 0.029 0.029 0.030 0.024
Sn 0.51 0.18 2.20 28.9 10.4 139.8 0.11 0.12 0.11 0.08
Tl 0.049 0.001 0.117 11.6 0.1 31.6 0.012 0.015 0.009 0.006V 3.32 2.84 12.97 6.6 4.8 22.2 0.6 0.6 1.1 0.2
Zn 18.66 4.42 38.50 41.0 11.1 87.2 5.6 6.5 3.6 0.3
Lutum
FS
CS
FSa
pH
Al
FeECd
0.9 0.8
0.1
0.2
0.3
org. C
ECuEPb
EMo
ESn
ESb
EBi
EIn
EAs
ESe
0.4
0.5
0.6
0.7
0.8
0.5 0.4 0.3 0.2 0.1
EHg
Lutum
FSCS
CSa
org. C
pH
CaCO3CEC
Al FSaFe
ECuEPb
EZn EV
EMo
ESn
ESb
ETl
EBiEInEAs
EMn
EHgESe
ECd
1.0 0.5 0.0 0.5 1.0
1.0
0.5
0.0
0.5
1.0
PC1: 40.11%
PC2:16.40%
Figure 7 Principal components analysis of the characteristics and enrichments [expressed as ln(mass or cmol by m2)] of the surface horizons from
loess deposits. FS, fine silt; CS, coarse silt; FSa, fine sand; CSa, coarse sand; EXX, enrichment with element XX.
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Table7
ContentandisotopiccompositionofPbinthehorizonsoftwosolafrom
theNord-PasdeCalaisloessdeposits
Horizon
Depth/cm
Pb/mgkg
1
208
Pb/206Pb
207Pb/206Pb
206Pb/207Pb
208Pb/204Pb
207Pb/204Pb
206Pb/204Pb
Solumundercultivation
LA
024
42.4
2.0726
0.83990
1.1906
2
38.570
15.630
18.609
BT1
2
445
19.3
2.0417
0.81930
1.2205
6
38.957
15.632
19.080
BT2
4
585
18.6
2.0408
0.82000
1.2195
1
38.950
15.650
19.086
BC
8
5100
20.2
2.0382
0.81987
1.2197
1
38.960
15.672
19.115
C1
10
0130
17.6
2.0522
0.82315
1.2148
5
39.054
15.665
19.031
C2
13
0160
17.2
2.0468
0.82247
1.2158
5
38.967
15.658
19.038
C3ca
16
0180
15.6
2.0499
0.82720
1.2088
9
38.764
15.643
18.910
Solumunderforest
OF
03.5
131.7
2.1042
0.86321
1.1584
7
38.051
15.610
18.084
A
3.58.5
113.5
2.0991
0.85837
1.1649
9
38.199
15.620
18.197
Esg
8.537.5
19.9
2.0451
0.82061
1.2186
1
39.049
15.669
19.094
SCg
37.577.5
18.0
2.0513
0.82124
1.2176
7
39.141
15.670
19.081
Cg
77.5150
16.6
2.0511
0.82341
1.2144
6
38.964
15.642
18.997
Qualitycontrol
NBS981Pb
referencematerial
2.1
677
0.91484
1.09308
36.725
15.499
16.942
Twostandard
deviations(n
17)
0.0
001
0.00004
0.00005
0.008
0.003
0.004
Referencevalues(SE)
2.1677
2
0.91483
7
36.722
8
15.498
3
16.941
2
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whilst EPb/IR is 120.6 mg kg1. In the A horizon, EPb/Al is
99.8 mg kg1, whilst EPb/IR is 92.3 mg kg1. In the LA hor-
izon, EPb/IR is 17.3 mg kg1, i.e. about 36% less than EPb/Al
(27.1 mg kg1). When using a greater 206Pb/207Pb ratio (here
1.175), as suggested by the relationship between this ratio and
1/Pb (Figure 9), EPb/IR becomes 26.5 mg kg1. Figure 9 sug-
gests that, at least under forest, the 206Pb/207Pb ratio of the
exogenous Pb could increase with depth, which could reveal a
variation in exogenous Pb composition (and origin) with time.
Semlali et al. (2001) found the 206Pb/207Pb of exogenous Pb to
increase with depth in a French Andosol. This could be the
consequence of the greater206
Pb/207
Pb of lead depositedbefore petrol lead deposition (Farmer et al., 1996, 2002).
This might explain why the estimated isotopic composition
of anthropogenic Pb in the LA horizon is different from that
in the OF and A horizons (for instance a greater 206Pb/207Pb
ratio), as the LA horizon results from mixing by ploughing of
horizons deeper than those of the forest A horizon. However,
it cannot be excluded that the exogenous Pb could be partly
different in forest soils to that in cultivated soils, because of
different sources or interceptions of the fallout. Nevertheless,
it is reasonable to consider that the Pb enrichment in the
surface horizons is completely due to exogenous, mostly
anthropogenic, input.
Comparison with continental crust and other sedimentary
deposits
The composition of the loess horizons is close to that of thehorizons developed in 21 other sedimentary parent materials
from the Nord-Pas de Calais, particularly when comparing the
deep horizons which can be considered to be uncontaminated
(Table 4). This composition is not so very far from the average
composition of loess deposits from various places in the world
(Argentina, China, France, Germany, Great Britain, Kansas,
New Zealand, Spitsbergen) calculated from the results of var-
ious researches. A close agreement is also found when compar-
ing the composition of the Nord-Pas de Calais loess horizons
with those of the upper continental crust (UCC), though this
varies according to the authors (Taylor & McLennan, 1995;
Wedepohl, 1995; Gao et al., 1998). This is consistent with theconclusion reached by Taylor et al. (1983) and confirmed by
Gallet et al. (1998), that the average composition of the upper
continental crust can be obtained from aeolian deposits as well
as from fine-grained clastic sediments.
Enrichment factors (EF) of the loess deep horizons were
calculated for all the elements, using the classical formula
(see for instance Shotyk et al., 2003):
EF EDH=REDH=EUCC=REUCC; 7
where REis one of the reference elements, here Al and Fe, and
UCC refers to the upper continental crust.
0.75
0.80
0.85
0.90
0.95
1.00
1.05
2.00 2.05 2.10 2.15 2.20 2.25 2.30
208Pb/206Pb
207Pb/206Pb
Soils, Germany, surface horizons
Soils, Germany, deep horizons
Pb in gasoline, average, France
Industrial emissions, average,France
Aerosols, N-PdC
Peat bogs, Norway
Pb ores, Australia, Idaho, Canada
Loess, N-PdC, cultivation, LA
Loess, N-PdC, forest, OF
Loess, N-PdC, forest, A
Loess, N-PdC, deep horizons
European Standard Lead Pollution(Haack et al., 2003)
Figure 8 Relationship between 207Pb/206Pb and208Pb/206Pb in horizons from two sola in loess
deposits and in other samples (references in the
text). N-PdC, Nord-Pas de Calais.
Under foresty=1.1424x+1.1531R2=0.96
1.15
1.16
1.17
1.18
1.191.20
1.21
1.22
1.23
0 0.03 0.05 0.07
1/[Pb] / mg1kg2
206Pb/207P
b
Cultivation
Forest
Figure 9 Relationship between 206Pb/207Pb and 1/[Pb] in horizons
from two sola on loess deposits.
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Enrichment factors using the composition of UCC from Gao
et al. (1998) are closer to 1 than the EF based on the data from
Taylor & McLennan (1995) and Wedepohl (1995) (Figure 10).
Whatever the REand the UCC composition used, the loess soils
from the Nord-Pas de Calais appear richer in As and Sb than
the upper continental crust, and also seem to be slightly
enriched with Cd. When based on the values from Taylor &
McLennan (1995) and Wedepohl (1995), the EF indicates a
slight enrichment with Bi, Cr, Ni and Se, which is not confirmed
by the EF based on the data from Gao et al. (1998).
The enrichment factors have also been calculated using the
average composition of world loess as a reference (Figure 10).They indicate no or only slight enrichment of the Nord-Pas de
Calais loess compared with the available data, except for Mo.
However, the reference data for Mo come from only one loess
deposit of Great Britain (Le Riche, 1973), analysed with a
method which may not be comparable to the methods used
in the other more recent work. The relative composition of
loess from the Nord-Pas de Calais is close to that of the other
loess from distant parts of the world. Again, this is consistent
with the fact that loess is a representative sample of the con-
tinental crust, more or less diluted with quartz and carbonates.
Their ionic potentials make As, Cd, Mo and Sb relatively more
mobile (less conservative) elements (Goldschmidt, 1958; Pedro
& Delmas, 1970), susceptible to accumulation in sedimentary
rocks. This may be why loess appears enriched with these
elements in comparison with UCC.
Bivariate diagrams give a generally positive correlation
between Al and Fe in the various loess deposits. However,Fe/Al ratio varies according to the location of the deposit
(Figure 11). Loess deposits from the Nord-Pas de Calais,
together with those from France and southwestern Germany
(Kaiserstuhl), appear to be slightly richer in Fe than those
from the rest of the world. Whatever the deposit, the
0
5
10
15
20
25
30
35
40
45
50
30 40 50 60 70 80 90 100
Al / gkg1
Fe/gkg1
Nord-Pas de Calais
France
Great Britain
Germany
Spitsbergen
Kansas
Argentina
China
New Zealand Figure 11 Relationship between Fe and Al con-
tents in loess deposits from Nord-Pas de Calais,
France, Great Britain, Germany, Spitsbergen,
Kansas, Argentina, China and New Zealand
(see Table 4 for sources).
0
1
2
3
4
5
6
7
8
9
10
11
12
Al Fe As Bi Cd Co Cr Cu Hg In Mn Mo Ni Pb Sb Se Sn Tl V Zn
EFAl
UCC, Taylor & McLennan, 1995
UCC, Wedepohl, 1995
UCC, Gao et al., 1998
World loess depositsSedimentary rocks from N-PdC
Figure 10 Average enrichment factors (EFAl) of
elements in deeper horizons from loess deposits,
against different materials, using Al as reference
element. UCC, upper continental crust; N-PdC,
Nord-Pas de Calais.
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correlations between Fe and Al show negative y-axis inter-
cepts, indicating an impoverishment in Fe. This could be the
consequence of sedimentary differentiation and the moderate
chemical weathering undergone by the loess protoliths (Gallet
et al., 1998). These differentiation and weathering processes
might have been slightly weaker in northwestern Europe thanin the other parts of the Earths surface.
There is often a close correlation between Al and most of the
trace element contents in the loess deep horizons from the
Nord-Pas de Calais (Table 4). In the other loess deposits, the
correlation is generally not as good and does not fit that found
in the Nord-Pas de Calais horizons (Figure 12a). However,
several trace element contents from the various deposits corre-
late with Fe more uniformly, as if there were a unique relation-
ship between the Fe and TE of the loess from various regions
of the Earths surface. Figure 12(b) illustrates this phenom-
enon in the case of Zn and is similar to that observed for Co,
Cu, Pb and V. These elements behave more like Fe than Al
and could be more associated with iron (oxy-)hydroxides than
with phyllosilicates. Chromium content appears to be more
closely correlated to Al than to Fe (Figure 13). In this case, as
well as in the case of Ni and Sn, loess from Argentina, Kansas,
Spitsbergen and New Zealand does not fall along with the
correlations with Al or with Fe. This connects with the Nd
and Sr isotopic compositions measured by Gallet et al. (1998),
which clearly distinguished the Argentinean loess from the
other deposits they studied. The rare earth elements and theisotopic results from these authors indicate a significant con-
tribution of young Andean volcanic rocks to the Argentinean
loess deposits, whereas multi-recycled and well-mixed ancient
sediments are the principal sources for the other loess deposits.
Note that the New Zealand loess rests upon two eroded vol-
canoes of basaltic composition (Taylor et al., 1983).
The manganese content clearly does not correlate with that of
Al or Fe because of its great mobility (Pedro & Delmas, 1970).
However, Mn varies similarly in the different loess deposits. No
data were available about the As, Bi, Cd, Hg, In, Sb, Se and Tl
contents of loess from the other parts of the world. If loess
deposits from the Nord-Pas de Calais are considered to derive
from sedimentary rocks similar to those found in this region, EFs
based on these sediments average composition show that loess is
not enriched with As, Sb and Cd, nor with any other element.
0
10
20
30
40
50
60
70
80
90
30 40 50 60 70 80 90 100
Zn
/gkg1
Zn/gkg1
Fe / gkg1
AI / gkg1
(a)
0
10
20
30
40
50
60
70
80
90
10 15 20 25 30 35 40 45
Nord-Pas de Calais
France
Great BritainGermany
Spitsbergen
Kansas
Argentina
China
New Zealand
(b)
Figure 12 Relationship between Zn content
and (a) Al content, (b) Fe content in loess
deposits from Nord-Pas de Calais, France,
Great Britain, Germany, Spitsbergen, Kansas,
Argentina, China and New Zealand (see Table
4 for sources).
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They show an impoverishment in Se, due to the large Se content
in some peat horizons fromthe region (Sterckeman etal., 2002a).
These results suggest that the ratios between trace element
contents and those of Al or Fe in deep loess horizons from
northern France (Table 8) give an acceptable characterization
of the pedo-geochemical background of soils developed in
most sedimentary rocks from northwestern Europe.
Conclusions
In the north of France, the contents of the least mobile ele-
ments in the deep horizons of soils from loess deposits are
close to those in the upper continental crust. In contrast, loess
appears to be enriched with mobile elements, such as As or Cd.
The composition of Nord-Pas de Calais loess is close to that of
loess from other parts of the world (the rest of France, Great
Britain, Germany, Spitsbergen, Kansas, Argentina, China,
New Zealand). However, whatever the mobility of the element,
the average composition of the loess from the Nord-Pas de
Calais is closer to that of the 21 other sedimentary rocks of the
region than to that of the loess from the rest of the world. Our
results highlight the fact that, to some extent, loess composi-
tion reflects the composition of the various rocks it is derived
from, which can be slightly different from those of the upper
continental crust.
In the deep horizons, Bi, Co, Cr, Cu, In, Ni, Pb, Sn, Tl, V and
Zn are associated with phyllosilicates and, probably even moreclosely, with iron oxy-hydroxides of the fine fraction. This is
suggested by the correlation of these element contents (except
Cr and Sn) with Fe, which is closer than that with Al, when
considering the loess deposits from the rest of the world. More
mobile elements such as As, Cd, Hg, Mn, Mo, Sb and Se seem
less or unassociated with these carrying phases. Cadmium, as
well as Co, seems to be particularly linked to Mn. The distribu-
tion of trace element/Al or trace element/Fe in loess could be
used as an estimate of the background contents for soils devel-
oped from most of the sedimentary materials in the north of
France and also in northwestern Europe.
0
20
40
60
80
100
120
140
160
180
30 40 50 60 70 80 90 100
Cr/gkg1
Cr/gkg1
Fe / gkg1
AI / gkg1
(a)
(b)
0
20
40
60
80
100
120
140
160
180
10 15 20 25 30 35 40 45
Nord-Pas de Calais
France
Great Britain
Germany
Spitsbergen
Kansas
Argentina
China
New Zealand
Figure 13 Relationship between Cr content and
(a) Al content, (b) Fe content in loess deposits
from Nord-Pas de Calais, France, Great
Britain, Germany, Spitsbergen, Kansas,
Argentina, China and New Zealand (see Table
4 for sources).
408 T. Sterckeman et al.
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Surface horizons are enriched with exogenous input of all the
trace elements examined, except Co, Cr and Ni. Isotopic com-
position demonstrates that Pb enrichment is almost totally due
to human contamination through atmospheric fallout fromvarious emission sources. Enrichments with Cd, Cu, Mn and
Zn are greater in cultivated soils than in forest soils.
Enrichments with Pb and with Cu, Hg, Mo, Sb, Se and Sn are
due mainly to human contamination through atmospheric fall-
out. Humic substances seem to act as a sink for all these
exogenous elements.
Acknowledgements
We gratefully acknowledge the financial support of the Conseil
Re gional du Nord Pas de Calais and of the Ministe` re de
lAme nagement du Territoire et de lEnvironnement.
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Table 8 Distribution parameters of the ratios between trace element contents (in mg kg1) and Al or Fe contents (in g kg1) in deep soil horizons
from Nord-Pas de Calais loess deposits
[Element]/[Al] [Element]/[Fe]
Element Arithmetic mean Median 5th percentile 95th percentile Arithmetic mean Median 5th percentile 95th percentile
Al 1.00 1.00 1.00 1.00 1.86 1.85 1.71 2.08
Fe 0.54 0.54 0.48 0.59 1.00 1.00 1.00 1.00
As 0.20 0.20 0.14 0.23 0.36 0.36 0.27 0.44
Bi 0.0033 0.0033 0.0027 0.0039 0.0061 0.0060 0.0051 0.0071
Cd 0.0024 0.0024 0.0013 0.0038 0.0046 0.0046 0.0023 0.0072
Co 0.22 0.22 0.19 0.27 0.41 0.40 0.35 0.49
Cr 1.30 1.29 1.16 1.43 2.42 2.42 2.18 2.74
Cu 0.27 0.27 0.22 0.31 0.50 0.50 0.41 0.58
Hg 0.0007 0.0005 0.0002 0.0027 0.0012 0.0009 0.0004 0.0052
In 0.0009 0.0009 0.0007 0.0010 0.0016 0.0016 0.0014 0.0019
Mn 10.6 10.8 6.0 16.3 19.8 19.9 10.8 28.8
Mo 0.010 0.010 0.008 0.012 0.019 0.019 0.015 0.022
Ni 0.56 0.56 0.46 0.65 1.03 1.03 0.86 1.23Pb 0.37 0.37 0.33 0.42 0.69 0.68 0.59 0.82
Sb 0.011 0.011 0.008 0.014 0.021 0.021 0.015 0.026
Se 0.0024 0.0021 0.0010 0.0051 0.0044 0.0038 0.0017 0.0099
Sn 0.040 0.040 0.036 0.044 0.075 0.074 0.067 0.082
Tl 0.010 0.010 0.009 0.011 0.019 0.018 0.016 0.021
V 1.43 1.43 1.29 1.55 2.65 2.65 2.44 2.85
Zn 1.09 1.09 0.97 1.21 2.04 2.03 1.73 2.39
Trace elements in loess soils 409
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