Rare earth elements in groundwater from different Alpine aquifers

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Chemie der Erde 69 (2009) 327–339 www.elsevier.de/chemer

Rare earth elements in groundwater from different Alpine aquifers Riccardo Biddaua,, Michael Bensimonb, Rosa Cidua, Aurele Parriauxb a

Department of Earth Sciences, Via Trentino 51, 09127 Cagliari, Italy Laboratory of Engineering and Environmental Geology, Federal Institute of Technology, 1015 Lausanne, Switzerland

b

Received 30 March 2009; accepted 20 May 2009

Abstract Rare earth elements (REE) were determined in 39 groundwater samples collected at 14 sites under low- and highflow conditions. Water samples derived from aquifers hosted in crystalline, molasse, flysch, carbonate and evaporite rocks located in Western Switzerland. The concentration of REE in groundwater circulating in different rocks showed large variations: lowest concentrations (SREEr10 ng/L) occurred in groundwater from evaporite aquifers; highest concentrations (SREE up to 516 ng/L) were observed in carbonate aquifers, although REE in these waters do vary under different hydrological conditions; groundwater from other aquifers had SREE from 10 to 100 ng/L. Distinct REE signatures were observed in waters draining specific rocks. The REE patterns in groundwater from crystalline, molasse and flysch aquifers showed heavy-REE enrichment at different degrees. Groundwaters circulating in crystalline rocks were distinguished by negative anomalies in Ce and Eu, whereas those from carbonate aquifers were nearly flat with SREE and the magnitude of negative anomaly in Ce is likely to be controlled by iron concentrations. The REE-Post-Archean Australian Shales (PAAS) normalized patterns appear useful to recognize the aquifer type and suggest the possibility to use the REE as geochemical tracers. r 2009 Elsevier GmbH. All rights reserved. Keywords: Rare earth elements; Groundwater; High-resolution ICP-MS; Rare earth elements geochemistry; Colloidal and particulate fractions; Iron; Normalized patterns; Alps; Switzerland

1. Introduction Rare earth elements (REE) are of interest in hydrogeochemistry because of their potential use to study water–rock interaction between groundwater and rocks hosting the aquifer and, in some cases, to trace the groundwater flow (De Boer et al., 1996; Banks et al., 1999; Mo¨ller et al., 2000, 2003; Tang and Johannesson, 2006). Some investigations on the REE geochemistry have shown that groundwater exhibits typical signatures Corresponding author.

E-mail address: [email protected] (R. Biddau). 0009-2819/$ - see front matter r 2009 Elsevier GmbH. All rights reserved. doi:10.1016/j.chemer.2009.05.002

(i.e., aqueous REE normalized to a common rock standard) that closely resemble the rocks through which they have flowed (Fee et al., 1992; Johannesson et al., 1997a, b) and the REE-pattern similarities between groundwater and the parent rock suggest that the REE can be useful tracers of water–rock interaction processes (Banner et al., 1989; Smedley, 1991). The aqueous REE geochemistry can be controlled directly or indirectly by different factors, such as pH, redox conditions, solution chemistry, complexation, colloidal and particulate matter transport (Goldstein and Jacobsen, 1988; German and Elderfield, 1989; Tricca et al., 1999; Nelson et al., 2003; Quinn et al., 2004). Several studies demonstrate the relevance of such factors on the

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REE signatures in groundwater, as compared to the REE signatures in parent rocks (Gosselin et al., 1992; Dia et al., 2000; Mo¨ller et al., 2003; Janssen and Verweij, 2003). Some authors have observed that aquifer rocklike REE fractionation patterns occur towards the end of groundwater flow paths and, hence, proximal to discharge zones (Banner et al., 1989). Others suggest that groundwater inherits aquifer rock-like signatures in the recharge zones, and with subsequent flow down gradient, additional chemical weathering, adsorption, and solution complexation reactions modify REE concentrations and fractionation patterns in the groundwater (Johannesson et al., 1999, 2005; Leybourne et al., 2000; Mo¨ller et al., 2003; Tang and Johannesson, 2005). Overall results suggest that depending on the considered system both rock source and solution chemistry can play important roles in controlling patterns and amount of REE in groundwater. In this study, the determination of REE in groundwater from different aquifer types in the Alpine belt was carried out. The aim was to identify the main factors that control the geochemical behavior of REE in groundwater and, possibly, to use the REE signatures to distinguish the aquifer that hosts the groundwater.

2. Sampling and analytical methods 2.1. Sampling Among several hydrochemical studies carried out in Switzerland over the past 20 years, the AQUITYP project conducted at the Federal Institute of Technology in Lausanne, EPFL, investigated the chemistry of recent groundwater in the Alpine belt (Parriaux et al., 1990). Different aquifers, including crystalline, molasse, flysch, carbonate and evaporite aquifers, were identified on the basis of lithological and hydrogeological data. A groundwater-monitoring network comprising several hundred samples, most of which are used as drinking waters, was established. These waters were characterized for major element composition, degree of mineralization and several trace elements (Kilchmann, 2001). The water samples were non-filtered and acidified in the laboratory soon after sampling; so that, element contents determined in the water can be considered as total amounts, as consumed by the user. This decision was consciously chosen to meet the objectives of the AQUITYP project as a whole (i.e. to check compliance of bedrock groundwater with regulations established for drinking water), but is obviously not ideal for the purposes of a detailed study on REE geochemistry, where a significant particulate component would have a large impact on the REE concentration and profiles. This limitation will be considered in the following discussion; nevertheless,

the waters were generally free of particulate matter and appeared well preserved, i.e. no solid deposit was observed in the container when bottles were opened for REE analysis. Rare earth elements were determined in 2006 on acidified aliquots of 39 water samples collected in groundwater from 14 sites during different sampling campaigns carried out since 2001. The location of water samples is shown in Fig. 1. These sites were selected on the basis of previous records, i.e. taking into account the relative abundance of major ions and salinity, and concentrations of minor and trace components. The selected samples comprise perennial springs from aquifers hosted in defined lithological and tectonic units (Table 1) and are mostly located in remote regions to minimize anthropogenic impacts. Therefore, REE concentrations in the selected waters should reflect the examples of natural processes occurring in specific aquifers. The analyzed waters include 10 samples taken in May 2001 and 15 samples in October 2001. Water samples taken in May and October represent high- and low-flow conditions, respectively. Groundwater at Sarve was investigated in more detail to better understand the REE behavior in waters from the carbonate aquifers; specifically, REE and Fe concentrations were also determined in the water collected twice a year (May and October) from 2002 to 2005 (8 samples). At 6 sites, a sampling campaign was repeated in May 2006 to collect both non-filtered and filtered through 0.4 mm pore-size filters aliquots; both aliquots were acidified in situ with HNO3.

2.2. Analytical Rare earth elements were determined by Sector-Field Inductively Coupled Plasma Mass Spectrometry (SF-ICP-MS, Element2 Thermo Finnigan), using the ESI Apex-Q High Sensitivity Sample Introduction. The latter allows to increase the sensitivity, to lower the sample volume required for analyses, and to reduce interferences from oxides generated in the plasma. Water samples nebulized into the heated spray chamber were completely evaporated; the sample aerosol was passed through an air-cooled condenser loop, and then to a Peltier condenser cooled at a temperature of 2 1C. The desolvated, dry sample aerosol was transferred to the Element2 torch, via a short length of PTFE tubing, using dry Ar at low flow. This operation was able to suppress solvent condensation in the transfer tube, and allowed more flexibility in selecting the Ar flow and plasma conditions. An additional N2 gas flow was added within the last loop of the condenser to improve the stability of the signal, and also to reduce the oxide formation in the plasma. The Apex was used with an ESI PFA-ST micro-concentric nebulizer, with sample

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Fig. 1. Map showing the main geological features of the Western Swiss Alps (simplified from Epard, 2001; Schmid et al., 2004) and the location of groundwater samples.

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Table 1.

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Description of the groundwater samples selected for this study and characteristics of their aquifers.

Aquifer type

Lithology

Main minerals

Accessory minerals

Predominant groundwaters flow of the aquifers

Residence timea

Crystalline

Granites

Quartz, K-feldspar plagioclase (mainly oligoclase

Chloritised biotite, hornblende, epidote and sericite

Fracture flow Range: o0.1–10 L/s Mean: 1 L/s (n ¼ 54)

One–two years

Flysch

Turbidite sediments (conglomerates, breccias and sandstone with intercalated shale and limestone)

Quartz, feldspar, Barite, tourmaline, calcite, dolomite and zircon, apatite and clay minerals (illite and TiO2-minerals Fe-chlorite micas)

Fracture flow Range: o0.1–10 L/s Mean: 1 L/s (n ¼ 50)

Months

Molasse

Conglomerates and sandstones intercalated with marls layers and locally with limestone and coal seams

Apatite , biotite, Detrital quartz, feldspar, micas and clay spinels, pyroxenes, minerals (illite, chlorite, amphiboles smectite), calcite, (glauconite)

Intergranular and fracture flow Range: o0.1–10 L/s Mean: 0.1 L/s (n ¼ 95)

From few days to several years

Evaporite

Gypsum and anhydrite rocks and dolomitic limestones associated with shales and sandstone

Gypsum or anhydrite, dolomite and calcite with detrital quartz, feldspar, micas and clay minerals (illite, chlorite, smectite)

Conduit and fracture flow, karst Range: o0.1–10 L/s Mean: 1 L/s (n ¼ 35)

Hours or few months

Carbonate

Marly and dolomitic limestone and dolostone

Calcite, dolomite, Sulphides, fossil organic matter, barite, detrital quartz, feldspar, micas and clay gypsum minerals

Conduit and fracture flow, karst Range: o0.1–1000 L/s Mean: 10 L/s (n ¼ 44)

Hours or few months

a

Celestite, fluorite, apatite, barite, chalcedony and sulphides (pyrite, chalcopyrite, galena)

Based on tracer tests and tritium data.

uptake monitored by an EPOND Pluto micro-flow meter. Operating conditions of the Finnigan Element2 and the ESI Apex are reported in Table 2. The isotopes 89Y, 139La, 140Ce, 141Pr, 142Nd, 147Sm, 152 Sm, 151Eu, 153Eu, 158Gd, 159Tb, 164Dy, 165Ho, 166Er, 168 Er, 169Tm, 172Yb, 174Yb and 175Lu were used to quantify the REE in the groundwater samples. All these isotopes were monitored at low-resolution mode (resolution power, R ¼ 300). In addition, 151Eu and 153Eu isotopes were also monitored at high-resolution mode (R ¼ 10,000) in order to eliminate potential interferences due to Ba-oxide formation. The R value necessary to eliminate the interference can be calculated from R ¼ M/DM, where M is the mass of the thought element reported in atomic mass unit (amu), and DM is its the mass difference with respect to the interference ion (Jarvis et al., 1994). As an example, the resolution power required to separate the 153Eu (152.921225 amu) from 137Ba16O (152.900727 amu) is equal to 7460 [i.e. R ¼ 153Eu/(153Eu137Ba16O)]. Therefore, the high-resolution mode is able to distinguish the specific Eu isotope from the interference caused by Ba present in the sample. A few results on water samples having different

Ba concentrations are reported in Table 2. Only the high-resolution results for Eu are reported. Standard solutions for REE calibration were prepared from a certified multi-standard (Spectrascan REE), and blank solutions from high-purity water (Milli-Q o0.1 mS/cm). Detection limit was estimated at 0.01 ng/L for all REE.

3. Results and discussion 3.1. Physical–chemical features of groundwater Detailed results are reported elsewhere for groundwater from crystalline (Dubois, 1993), flysch (Basabe, 1993), molasse (Hesske, 1995; Hesske et al., 1997), evaporite (Mandia, 1993) and carbonate (Dematteis, 1995) aquifers. Overall results are reported in Kilchmann et al. (2004). The main characteristics of specific aquifers are reported in Table 3, whereas the relevant chemical features are reported in Table 4, and summarized below.

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Table 2. SF-ICP-MS operating conditions for the determination of REE and Y in groundwater samples (above) and results on Eu determination at low- and high-resolution mode in groundwater samples having different Ba concentration (below). Plasma RF power Coolant argon flow Auxiliary argon flow Carrier gas Argon added at start of transfer tube to torch Sample uptake Apex-Q heating chamber temperature Apex-Q condenser stage temperature Flow of added N2 CeO+/Ce ratio

W L/min L/min L/min L/min mL/min 1C 1C ml/min %

Groundwater

Ba (mg/L)

151

Cornalle Pierre-Ozaire Lutry

150 8.4 15

3.8 1.0 1.0

Eu (LR) (ng/L)

153

Eu (LR) (ng/L)

7.6 1.1 1.3

1250 16 1 0.65 0.2 100 140 2 5 0.3 153

Eu (HR) (ng/L)

0.72 0.70 0.56

LR ¼ low resolution (resolving power ¼ 300). HR ¼ high resolution (resolving power ¼ 10,000).

Table 3.

Lithological and hydrological features in the Alpine aquifers (modified by Kilchmann et al., 2004).

Water samples

Aquifer type

Geografic unit

Tectonic or lithostratigraphic unit

Age

BON BRO

Bonette Broccard

Crystalline Crystalline

Alpes Alpes

M.te Blanc M.te Blanc

Carboniferous Carboniferous

TRE LLI

Treyvaux Lac Lioson

Flysch Flysch

Prealpes Prealpes

Gurnigel Nappe Niesen Nappe

Late Cret-Eocene Late Cret-Eocene

COR LRY POZ

Cornalle Lutry Pierre-Ozaire

Molasse Molasse Molasse

Plateau Plateau Plateau

Molasse subalpine (USM)a Molasse subalpine (OMM)b Molasse subalpine (OMM)

Lower Chattian Burdigalian Burdigalian

BLE NOC

Bains de Leytron Noche

Evaporite Evaporite

Alpes Prealpes

Helvetic Ultrahelvetic

Trias Trias

TIL LIO MAL SAR BOR

Tilenet Lionne Malagne Sarve Bornels

Carbonate Carbonate Carbonate Carbonate Carbonate

Jura Jura Jura Alpes Prealpes

Folded Jura Folded Jura Folded Jura Morcles Nappe Medianes Rigides Nappe

Cretaceous Malm Malm Trias-Cretaceous Trias-Malm

a

USM ¼ Lower Freshwater Molasse (Hesske et al., 1997). OMM ¼ Upper Marine Molasse (Hesske et al., 1997).

b

Groundwater samples considered in this study have near neutral or slightly alkaline pH (6.8–7.8), and Eh values in the range of 0.2–0.5 V. Electrical conductivity (in the range of 0.03–1.4 mS/cm) varies significantly among samples, depending on the lithological composition of the aquifer. The lowest values were observed in groundwater from crystalline aquifers (0.03–0.09 mS/cm), the highest values in groundwater from evaporite aquifers (1.1–1.4 mS/cm) and intermediate values (0.30–0.65 mS/cm) in groundwater from flysch, molasse and carbonate aquifers. The relative proportions of major ions in a given aquifer, did not change significantly when waters were

sampled at different time. The Piper diagram in Fig. 2 shows the major ionic composition of groundwater samples from the different aquifers. The waters from crystalline, flysch, molasse and carbonate aquifers have a dominant Ca–HCO3 composition. Sulphate is the dominant anion in groundwater from evaporite aquifers. Groundwater at Cornalle has a distinguished Ca–Mg–HCO3 composition and reflects heterogeneity in the molasse rocks (Hesske et al., 1997). Specifically, Cornalle circulates in the Lower Freshwater Molasse (USM) having Mg-rich chlorite and rock fragments with serpentinite composition (Henry et al., 1997).

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Table 4.

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Physical–chemical parameters and major ionic components in groundwater from different Alpine aquifers.

Groundwater

Cond

T (1C)

pH

mS/cm

Eh

Ca

Mg

Na

V

K

Cl

SO4

HCO3

mg/L

Crystalline-Rock Aquifers Bonette 0.09 Broccard 0.03

6.8 6.9

7.3 7.3

0.31 0.30

17 11

0.7 0.7

1.75 1.0

1.73 1.8

0.4 0.4

11 6.3

46 34

Flysch-Rock Aquifers Treyvaux Lac Lioson

0.27 0.17

5.7 3.7

7.0 7.8

0.45 0.44

56 33

3.2 2.7

0.8 0.3

0.4 0.4

0.3 0.3

8.2 4.8

187 116

Molasse-Rock Aquifers Cornalle 0.56 Pierre-Ozaire 0.30 Lutry 0.29

11 9.8 9.0

7.8 7.3 7.2

0.44 0.45 0.46

67 60 55

25 6.8 5.5

30 4.5 2.1

1.3 1.7 0.5

12 16 2.0

22 10 13

371 154 184

Evaporite-Rock Aquifers Bains de Leytron 1.10 Noches 1.40

24 11

7.3 7.2

0.47 0.20

226 300

43 60

8.7 15

0.7 1.4

2.6 21

535 706

171 251

7.0 7.0 7.5 6.8 7.0

0.44 0.44 0.43 0.39 0.43

68 77 125 45 41

0.3 0.9 3.7 0.3 0.6

0.3 0.6 1.5 0.2 0.5

2.0 14 14 0.1 0.1

Carbonate-Rock Aquifers Lionne 0.29 Malagne 0.34 Tilenet 0.64 Sarve 0.24 Bornels 0.39

6.4 6.8 8.8 7.0 5.7

2.9 5.1 7.8 5.7 5.6

4.0 nd 9.9 38 34

216 257 343 131 142

nd ¼ not determined.

3.2. REE geochemistry Results of REE and Y determined in non-filtered samples taken in May and October 2001 are reported in Table 5. The most abundant elements are Y, La, Ce and Nd. A large range in concentrations occurs in the groundwater from different aquifers, with SREE values varying more than one order of magnitude. Waters from evaporite aquifers exhibit low concentrations (SREEr12 ng/L); those from crystalline, flysch and molasse aquifers have SREE between 9 and 58 ng/L; those from carbonate aquifers exhibit the highest REE concentrations (SREE up to 516 ng/L), with the exception of Bornels that shows SREE ¼ 14 ng/L. When the sample taken in May 2001 at high flow is compared with that taken in October 2001 at low flow, significant differences in concentrations of REE are observed. Waters from carbonate aquifers show large variations in REE abundance, probably due to variable amounts of solid particles dissolved prior to analysis. Table 6 reports the concentrations of REE and Fe determined in non-filtered water samples taken at Sarve; values of SREE at different sampling times vary significantly and appear correlated with Fe concentrations and flow, as it can be observed in Fig. 3. Taking into account that Fe in neutral to alkaline waters occurs prevalently as colloidal particles, the correlation of SREE with Fe suggests an aqueous

transport of the REE via sorption onto iron colloids. Although this process is particularly relevant in surface waters (Cidu and Biddau, 2007; Leybourne and Johannesson, 2008), where Fe concentrations depend on the amount of suspended materials, which increase as flow and turbulence increases, sorption processes may also occur in groundwater (Dia et al., 2000; Nelson et al., 2003; Janssen and Verweij, 2003). In carbonate aquifers the groundwater flow through conduits and fissures occurs more readily than through matrix porosity, as noted by the relatively short residence time (see Table 3). Hence, from the hydrological point of view, carbonate groundwater behaves similarly to surface waters, and might explain the marked differences observed among non-filtered samples taken at Sarve under different flow conditions (Table 6). These observations indicate that the role of fine particles on the aqueous transport of REE need to be assessed.

3.3. Aqueous REE in filtered and non-filtered water samples Table 7 shows results of REE and Y in filtered and non-filtered water samples collected in May 2006. Taking into account the lack of data on filtered water samples collected in 2001–2005, the results on the 2006 sampling campaign may be used as an estimate of the

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Fig. 2. Piper diagram showing the distribution of major ions in groundwaters from the different Alpine aquifers. The shaded areas represent the major chemical composition of all groundwaters considered in the AQUITIP project (from Kilchmann et al., 2004). Symbols in triangular plots and size of circles in the diamond plot indicating TDS values refer to the samples considered in this study.

relative proportions between the REE concentrations in filtered and non-filtered fractions in the groundwater from the different aquifers. When non-filtered samples are compared with filtered ones, it can be seen that REE concentrations in non-filtered samples are generally higher than those in samples filtered through 0.4 mm pore-size filters. Values of SREE show either small differences or variations within the same order of magnitude in groundwater samples from crystalline, flysch, molasse and evaporite rocks. At Sarve, a large REE amount occurs in non-filtered samples, i.e. REE appear preferentially transported in the water fraction 40.4 mm.

These results suggest that fractionation processes may affect the REE transport depending on the corresponding REE occurrences in the different aqueous fractions: dissolved species, colloidal particles and suspended matter. Indeed, literature data on aqueous REE show that fractionation processes result in distinct REE signatures when REE concentrations in the water are normalized to the corresponding concentration in common solid materials, such as the Post-Archean Australian Shales (PAAS; McLennan, 1989). The dissolved fraction generally shows normalized patterns enriched in heavy REE (HREE), the colloidal fraction displays a shale-like distribution and the suspended

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Table 5.

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Concentrations of Y, each REE and SREE (La to Lu) in non-filtered samples collected in May and October 2001.

Groundwaters

Sampling date Y

La

Ce

Pr

Nd

Sm

Eu Gd

Tb Dy

Ho Er

Tm Yb Lu

SREE ng/L

ng/L Crystalline-rock aquifers Bonette May 2001 Bonette Oct 2001 Broccard Oct 2001

54 40 19

13 8.2 3.7

5.4 2.3 2.9

3.3 2.0 1.1

Flysch-rock aquifers Treyvaux May 2001 Treyvaux Oct 2001 Lac Lioson Oct 2001

14 6.0 17 8.5 7.0 3.8

3.5 5.6 1.4

1.4 2.3 0.69

Molasse-rock aquifers Cornalle May 2001 Cornalle Oct 2001 Pierre-Ozaire May 2001 Pierre-Ozaire Oct 2001 Lutry Oct 2001

13 13 34 42 35

1.2 3.1 0.95 3.9 1.4

0.27 1.2 0.48 2.6 2.4 8.1 3.2 11 2.1 7.3

0.48 0.85 2.6 2.7 2.2

0.64 0.72 0.62 0.70 0.56

0.48 0.70 3.0 3.9 3.1

0.09 0.11 0.44 0.57 0.44

0.70 0.81 3.1 4.2 3.3

0.20 0.20 0.90 1.2 0.72

0.55 0.59 2.9 3.9 2.5

0.06 0.08 0.44 0.64 0.37

0.54 0.54 3.4 4.5 2.4

Evaporite-rock aquifers Bains de Leytron May 2001 Bains de Leytron Oct 2001 Noches May 2001 Noches Oct 2001

17 16 27 30

2.5 1.4 4.3 2.2

0.46 0.25 0.51 0.23

1.9 1.3 2.8 2.5

0.36 0.20 0.22 0.30

0.18 0.01 0.06 0.01

0.55 0.17 0.54 0.89

0.15 0.10 0.11 0.10

0.58 0.26 0.33 0.31

0.68 2.7 0.24 0.05

0.43 0.24 0.33 0.13

0.06 0.02 0.01 0.03

0.32 0.05 10 0.12 o0.01 7.5 0.13 0.03 12 0.07 o0.01 7.9

Carbonate-rock aquifers Lionne May 2001 Lionne Oct 2001 Sarve May 2001 Sarve Oct 2001 Tilenet May 2001 Tilenet Oct 2001 Malagne Oct 2001 Bornels Oct 2001

84 109 52 40 98 64 56 7.5

64 96 86 90 41 67 32 49 80 194 48 109 43 52 2.9 3.8

17 20 10 7.9 24 15 11 0.53

71 89 48 38 122 71 46 3.2

13 17 8.3 7.0 23 14 9.5 0.61

3.1 3.9 1.9 1.8 5.7 3.5 2.3 0.14

13 17 8.4 7.6 23 14 9.3 0.77

1.8 2.5 1.2 1.0 3.3 2.1 1.4 0.14

11 15 7.0 6.9 18 11 8.4 0.70

2.3 3.2 1.5 1.3 3.5 2.2 1.7 0.34

6.4 8.9 4.3 3.8 9.5 5.9 5.1 0.46

0.91 1.3 0.61 0.48 1.3 0.80 0.70 0.06

5.4 7.2 3.6 3.2 7.6 5.0 4.3 0.40

2.5 3.6 9.9 14 10 1.7 0.81 2.3 1.2

12 3.3 0.33 4.5 0.70 5.1 1.3 4.0 0.59 4.0 7.0 2.3 0.10 2.8 0.53 3.2 1.4 2.6 0.38 2.7 4.5 1.4 0.20 1.7 0.29 2.0 0.57 1.4 0.22 1.4 5.2 1.2 0.51 1.2 0.18 1.2 0.28 0.84 0.11 0.67 8.8 2.1 0.51 2.1 0.32 2.1 0.44 1.3 0.22 1.0 2.4 0.54 0.11 0.44 0.10 0.55 0.14 0.40 0.06 0.30

matter is characterized by the relative enrichment in light REE (LREE; Goldstein and Jacobsen, 1988; Elderfield et al., 1990). When the bulk composition of water is considered, as in the case of this study where most water samples were non-filtered, different REE patterns might be expected.

3.4. REE patterns in non-filtered water samples Fig. 4 shows the concentration of each REE in the non-filtered groundwater samples normalized to the corresponding concentration in the PAAS. Despite some similarities, a closer inspection of patterns in Fig. 4 shows that different REE signatures are observed in the water from each aquifer. REE patterns of crystalline (Fig. 4a) and Upper Marine Molasse (OMM, Hesske et al., 1997; Fig. 4b) waters show a marked negative Ce anomaly and an enrichment in

0.79 58 0.48 36 0.27 21 0.11 22 0.13 35 0.06 11 0.09 0.10 0.62 0.87 0.38

0.82 1.1 0.51 0.39 1.1 0.74 0.67 0.05

9.0 14 39 56 37

305 361 204 161 516 301 196 14

HREE. The negative Ce anomaly is frequently observed in groundwater under oxidizing conditions, and results from the preferential retention of Ce in solid phases, due to the poor solubility of Ce4+ species (Sholkovitz, 1992). The HREE enrichments reflect the greater solubility of the HREE as compared with the LREE (Nelson et al., 2003). The negative Eu anomaly in groundwater from the crystalline aquifers (Fig. 4a) mirrors the negative Eu anomaly generally observed in granite (e.g.: Tricca et al., 1999); this anomaly distinguishes the crystalline groundwater from the OMM molasse groundwater. These observations indicate that REE in groundwater from the crystalline and Upper Marine Molasse are mainly transported in the dissolved fraction rather than the colloidal and particulate fractions, which would be in agreement with the results derived from the 2006 campaign showing small differences among filtered and non-filtered water samples (see Table 7).

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Table 6.

335

Concentrations of Y, each REE and SREE (La to Lu) in non-filtered samples collected at Sarve from 2001 to 2006.

Groundwaters

La

Ce

Pr

Nd

Sm

Eu

Gd

Tb

Dy

Ho

Er

Tm

Yb

Lu

ng/L

ng/L Crystalline-rock aquifers Broccard F 2.85 0.96 Broccard nF 3.69 1.99

0.78 1.03

Molasse-rock aquifers Lutry F 17.29 4.84 Lutry nF 19.61 6.32 Pierre-Ozaire F 8.90 0.49 Pierre-Ozaire nF 9.48 0.54

3.30 11.42 3.84 13.88 1.98 7.36 2.15 7.91

Evaporite-rock aquifers Noche F Noche nF Bains de Leitron F Bains de Leitron nF

0.10 0.08 0.22 0.25

0.18 o0.01 0.45 o0.01 0.49 o0.01 0.43 0.01

Carbonate-rock aquifers Sarve F 4.60 1.27 Sarve nF 7.84 7.39

0.75 1.66

4.20 4.91

1.12 0.03 1.61 0.21 1.73 1.44 o0.01 1.97 0.28 2.07

0.17 0.25

1.26 o0.01 1.61 1.49 o0.01 1.76

0.15 17 0.17 21

3.19 3.84 2.06 2.13

0.70 0.86 0.34 0.42

4.11 4.90 2.50 2.67

0.67 0.71 0.30 0.34

4.28 4.88 2.46 2.57

0.80 1.01 0.40 0.43

3.06 3.41 2.11 2.13

0.19 0.17 0.07 0.11

2.83 3.03 2.35 2.45

0.42 0.33 0.38 0.36

1.51 0.03 o0.01 1.70 0.03 o0.01 1.06 o0.01 o0.01 1.05 0.04 o0.01

0.75 0.86 0.61 0.57

0.11 0.22 0.08 0.08

0.13 0.14 0.10 0.15

o0.01 o0.01 o0.01 o0.01

o0.01 o0.01 o0.01 o0.01

o0.01 o0.01 o0.01 o0.01

0.05 0.02 0.06 0.05

o0.01 o0.01 o0.01 o0.01

4.15 8.36

SREE

0.73 o0.01 1.35 0.19 0.91 o0.01 1.50 o0.01 2.16 0.26 1.45 0.14

57 67 32 34 2.9 3.7 2.6 2.6

0.55 o0.01 0.55 o0.01 15 0.78 o0.01 0.77 o0.01 32

F ¼ filtered through 0.4 mm pore-size filters. nF ¼ non filtered.

Fig. 3. Plot showing Fe concentrations and flow rates versus SREE (La to Lu) in non-filtered water samples collected at Sarve from 2001 to 2006 (see Table 6).

Fig. 4c shows the pattern of the Cornalle groundwater, flowing out of the USM molasses; the most striking feature in this pattern is the marked positive Eu

anomaly, which is absent in groundwater from the OMM molasse (Fig. 4b). Positive Eu anomalies are uncommon in groundwater and may occur under strong

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Table 7. Concentrations of each REE and SREE (La to Lu) in samples filtered through 0.4 mm pore-size filters and non-filtered samples collected in May 2006. Sampling date Flow Fe

May 2001 Oct 2001 May 2002 Oct 2002 May 2003 Oct 2003 May 2004 Oct 2004 May 2005 Oct 2005 May 2006

L/s

mg/L

400 1500 2400 500 1000 300 4500 100 3500 100 100

40 4.0 80 30 160 15 580 4.0 230 30 30

Y

La

Ce

Pr

Nd

Sm Eu

Gd Tb

Dy Ho

Er

Tm

Yb

Lu

ng/L

ng/L 40 52 80 42 170 40 900 14 380 77 o0.01

32 41 68 30 150 22 860 7.1 370 59 7.8

49 67 130 51 290 37 1770 8.3 680 110 7.4

8 10 17 7.2 39 5.7 240 1.5 97 16 1.7

38 48 86 36 200 28 1200 7.2 480 77 8.4

7.0 8.3 15 6.2 34 5.9 215 1.3 86 15 1.5

reducing conditions (e.g. Lee et al., 2003). Because the Cornalle groundwater is not reducing (Eh ¼ 0.44 V, Table 4), the positive Eu anomaly should be related to peculiar characteristics in the host rocks. Data on the REE content in the USM molasse are not available. However, taking into account that the USM molasse contains mafic components (serpentinites) and that these components may have a positive anomaly in Eu (e.g. Dwijesh et al., 2005), it might be argued that the positive Eu anomaly observed in the Cornalle groundwater might derive from the weathering of specific minerals, such as Eu-enriched plagioclase. The PAAS-normalized REE patterns in waters from flysch (Fig. 4d) are relatively smooth, showing a negative Ce anomaly only. The groundwater from carbonate aquifers with high REE concentrations (SREE 4100 ng/L) show patterns with a small Ce anomaly (Fig. 4e) and a slight convex-up shape, especially evident in the water at Sarve taken at different sampling times (Fig. 4f). These patterns, generally observed in waters where the REE are predominantly associated with colloids (Smedley, 1991; Sholkovitz, 1992; Protano and Riccobono, 2002), would be in agreement with the results derived from the 2006 campaign showing much higher REE concentrations in the non-filtered water samples (see Table 7). In evaporite groundwaters, the very low REE concentrations (SREEr10 ng/L) are probably due to the fast flushing rates and the relatively low residence time of water in this aquifer (see Table 1). The PAAS-normalized plots (Fig. 4g) are characterized by a small negative Ce anomaly and a more marked negative Eu anomaly. According to major and accessory minerals in evaporitic rocks (see Table 1), the observed pattern in these waters might reflect the gypsum dissolution, although the knowledge of REE concentrations in gypsum is very limited (Playa` et al.,

1.8 1.9 3.4 1.4 7.5 1.0 46 0.32 19 3.2 o0.01

7.6 8.4 15 6.5 34 6.4 210 1.7 85 15 2.2

SREE

1.0 1.2 2.1 0.9 4.9 1.1 29 0.3 12 2.2 0.26

6.9 7.0 12 5.6 29 6.0 170 1.4 69 12 1.5

1.3 1.5 2.5 1.2 5.7 1.1 33 0.3 13 2.5 0.14

3.8 4.3 6.8 3.2 16 3.0 88 0.83 35 6.7 0.78

0.48 0.61 0.91 0.44 2.1 0.44 12 0.12 4.6 0.9 o0.01

3.2 3.6 5.6 2.7 13 2.4 72 0.7 29 5.6 0.77

0.39 0.51 0.77 0.40 1.8 0.32 9.9 0.08 4.1 0.78 o0.01

160 200 360 150 830 120 4900 31 1990 330 32

2007), and/or apatite weathering (Rasmussen et al., 1998; Kemp and Trueman, 2003). We are unable to explain the high Ho observed in the Bains de Leytron groundwater (Fig. 4g); it could be due to an analytical artifact.

4. Conclusions This study showed that groundwater samples from different Alpine aquifers have distinct REE signatures. Specifically, PAAS-normalized patterns of groundwater from crystalline and molasse aquifers show HREEenrichment with a negative Ce anomaly, but the former are distinguished by a negative anomaly in Eu. Groundwaters interacting with flysch and carbonate rocks show relatively smooth PAAS-normalized patterns with a negative Ce anomaly; but the SREE in carbonate groundwater are usually much higher. In carbonate rocks, variations in REE concentrations are likely to be controlled by sorption process onto Fe-rich and/or organic colloids. Major uncertainties may be found when REE concentrations in the water occur at very low levels (i.e. SREE o10 ng/L) that may imply higher analytical errors. Although few water samples have been considered in this study, the aqueous REE concentrations appear as a promising tool to identify the aquifer hosting the groundwater. Lessons learnt from this study will be carefully considered in forthcoming REE researches to be carried out at the EPFL, especially the sampling strategy that appears to be a key factor to avoid misinterpretations of data. Also, the determination of REE in the rocks hosting each aquifer will be useful to evaluate the partitioning of REE between aqueous and solid phases.

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Fig. 4. Patterns of REE in non-filtered groundwater from the different Alpine aquifers, samples taken in October 2001, unless specified. Concentrations normalized to the Post-Archean average Australian Shale (PAAS).

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Acknowledgements R. Biddau thanks EPFL for invitation to carry out this study. Authors wish to thank Alan Rube Eastergate from EPOND SA for his contribution in the optimization of the APEX experimental conditions. Authors wish to thank the Anonymous reviewers for their useful suggestions.

References Banner, J.L., Wasserburg, G.J., Dobson, P.F., Carpenter, A.B., Moore, C.H., 1989. Isotopic and trace element constraints on the origin and evolution of saline groundwaters from central Missouri. Geochimica et Cosmochimica Acta 53, 383–398. Banks, D., Hall, G., Reinmann, C., Siewers, U., 1999. Distribution of rare earth elements in crystalline bedrock groundwaters: Oslo and Bergen regions, Norway. Applied Geochemistry 14, 27–39. Basabe, P.P., 1993. Typologie des eaux souterraines du flysch de la nappe tectonique du Niesen (Pre`alpes Suisses). [Typology of groundwaters derived from the flysch of the Niesen tectonic nappe (Swiss Prealps)] Ph.D., Federal Institute of Technology Lausanne, Switzerland. Cidu, R., Biddau, R., 2007. Transport of trace elements under different seasonal conditions: effects on the quality of river water in a Mediterranean area. Applied Geochemistry 22, 2777–2794. De Boer, J.L.M., Verweij, W., Velde-Koerts, T., Mennes, W., 1996. Levels of rare earth elements in Dutch drinking water and its sources. Determination by ICP-MS and toxicological implications. A pilot study. Water Research 30, 190–198. Dematteis, A., 1995. Typologie ge`ochimique des eaux des aquife`res carbonate`s des chae`nes alpines d’Europe centrale et me`ridionale. (Geochemical typology of groundwaters derived from Alpine carbonate-rock aquifers of central and southern Europe) Ph.D., Federal Institute of Technology Lausanne, Switzerland. Dia, A., Gruau, G., Olivie´-Lauquet, G., Riou, C., Mole´nat, J., Curmi, P., 2000. The distribution of rare earth elements in groundwaters: assessing the role of source-rock composition, redox changes, and colloidal particles. Geochimica et Cosmochimica Acta 64, 4131–4152. Dubois, J.D., 1993. Typologie des aquife`res du cristallin: Exemple des massifs des Aiguilles Rouges et du Mont Blanc (France, Italie et Suisse). [Typology of crystalline-rock aquifers: Example of the Aiguilles Rouges and Mont Blanc massifs (France, Italy and Switzerland)] Ph.D., Federal Institute of Technology Lausanne, Switzerland. Dwijesh, R., Ranadip, B., Sridhar, D.I., Rao, T.G., 2005. Serpentinites from the Northern Central Indian Ridge: implications on low temperature hydrothermal alteration. Workshop on Tectonic & Oceanic Processes along the Indian Ocean Ridge System, National Institute of Oceanography, Dona Paula, Goa 403 004, India, 19–21 January 2005.

Elderfield, H., Upstill-Goddard, R., Sholkovitz, E.R., 1990. The rare earth elements in rivers, estuaries, and coastal seas and their significance to the composition of ocean water. Geochimica et Cosmochimica Acta 54, 971–991. Epard, J.L., 2001. The overall tectonic framework of the externides domain. In: Stampfli G.M. (Ed.) Geology of the western Swiss Alps, a guide book. Me´moires de Ge´ologie (Lausanne) 36, pp. 43–51. Fee, J.A., Gaudette, H.E., Lyons, W.B., Long, D.T., 1992. Rare-earth element distribution in lake Tyrrell groundwaters, Victoria, Australia. Chemical Geology 96, 67–93. German, C.R., Elderfield, H., 1989. Rare earth elements in Saanich Inlet, British Columbia, a seasonally anoxic basin. Geochimica et Cosmochimica Acta 53, 2561–2571. Goldstein, S.J., Jacobsen, S.B., 1988. Rare earth elements in river waters. Earth Planetary Science Letters 89, 35–47. Gosselin, D.C., Smith, M.R., Lepel, E.A., Laul, J., 1992. Rare earth elements in chloride-rich groundwater, Palo Duro Basin, Texas, USA. Geochimica et Cosmochimica Acta 56, 1495–1505. Henry, P., Deloule, E., Michard, A., 1997. The erosion of the Alps: Nd isotopic and geochemical constraints on the sources of the peri-Alpine molasse sediments. Earth and Planetary Science Letters 146, 627–644. Hesske, S., 1995. Typologie des eaux souterraines de la Molasse entre Chambe`ry et Linz (France, Suisse, Allemagne, Autriche). [Typology of groundwaters derived from molasse aquifers between Chambe`ry and Linz (France, Switzerland, Germany, Austria)] Ph.D., Federal Institute of Technology Lausanne, Switzerland. Hesske, S., Parriaux, A., Bensimon, M., 1997. Geochemistry of springwaters in Molasse aquifers: typical mineral trace elements. Eclogae Geologicae Helvetiae 90, 151–171. Janssen, R.P.T., Verweij, W., 2003. Geochemistry of some rare earth elements in groundwater, Vierlingsbeek, The Netherlands. Water Research 37, 1320–1350. Jarvis, K.E., Gray, A.L., Houk, R.S., 1994. Handbook of Inductively Coupled Plasma Mass Spectrometry. Chapman & Hall, London, p 380. Johannesson, K.H., Stetzenbach, K.J., Hodge, V.F., 1997a. Rare earth elements as geochemical tracers of regional groundwater mixing. Geochimica et Cosmochimica Acta 61, 3605–3618. Johannesson, K.H., Stetzenbach, K.J., Hodge, V.F., Kreamer, D.K., Zhou, X., 1997b. Delineation of groundwater flow systems in the southern Great Basin using aqueous rare earth element distributions. Ground Water 35, 807–819. Johannesson, K.H., Farnham, I.M., Guo, C., Stetzenbach, K.J., 1999. Rare earth fractionation and concentration variations along a groundwater flow path within a shallow, basin-fill aquifer, southern Nevada, USA. Geochimica et Cosmochimica Acta 63, 2697–2708. Johannesson, K.H., Cortes, A., Leal, J.A.R., Ramirez, A.G., Durazo, J., 2005. Geochemistry of rare earth elements in groundwaters from a Rhyolite aquifer, central Mexico. In: Johannesson, K.H. (Ed.), Rare Earth Elements in Groundwater Flow Systems. Springer, Dordrecht, The Netherlands, pp. 187–222.

ARTICLE IN PRESS R. Biddau et al. / Chemie der Erde 69 (2009) 327–339

Kemp, R.A., Trueman, C.N., 2003. Rare earth elements in Solnhofen biogenic apatite: geochemical clues to the palaeoenvironment. Sedimentary Geology 155, 109–127. Kilchmann, S., 2001. Typology of recent groundwaters from different aquifer environments based on geogenic tracer elements. Ph.D., Federal Institute of Technology Lausanne, Switzerland. Kilchmann, S., Waber, H.N., Parriaux, A., Bensimon, M., 2004. Natural tracers in recent groundwaters from different Alpine aquifers. Hydrogeology Journal 12, 643–661. Lee, S.G., Lee, D.H., Kim, Y., Chae, B.G., Kim, W.Y., Woo, N.C., 2003. Rare earth elements indicators of groundwater environment changes in fractured rock system: evidence from fracture-filling calcite. Applied Geochemistry 18, 135–143. Leybourne, M.I., Johannesson, K.H., 2008. Rare earth elements (REE) and yttrium in stream waters, stream sediments, and Fe–Mn oxyhydroxides: Fractionation, speciation, and controls over REE+Y patterns in the surface environment. Geochimica et Cosmochimica Acta 72, 5962–5983. Leybourne, M.I., Goodfellow, W.D., Boyle, D.R., Hall, G.M., 2000. Rapid development of negative Ce anomalies in surface waters and contrasting REE patterns in groundwaters associated with Zn–Pb massive sulphide deposits. Applied Geochemistry 15, 695–723. Mandia, Y., 1993. Typologie des aquife`res e´vaporitiques du Trias dans le Bassin le´manique du Rhoˆne (Alpes occidentales). [Typology of Triassic evaporite-rock aquifers in the Swiss Rhoˆne Valley (western Alps)] Ph.D., Federal Institute of Technology Lausanne, Switzerland. McLennan, S.M., 1989. Rare earth elements in sedimentary rocks. Influence of provenance and sedimentary processes. In: Lipin, B.R., McKay G.A. (Eds.), Geochemistry and Mineralogy of Rare Earth Elements. Mineralogical Society of America, Washington, Review in Mineralogy 21, pp. 169–200. Mo¨ller, P., Dulski, P., Bau, M., Knappe, A., Pekdeger, A., Sommervon Jarmersted, C., 2000. Anthropogenic gadolinium as a conservative tracers in hydrology. Journal of Geochemical Exploration 69–70, 409–414. Mo¨ller, P., Rosenthal, E., Dulski, P., Geyerc, S., Guttmand, Y., 2003. Rare earths and yttrium hydrostratigraphy along the Lake Kinneret–Dead Sea–Arava transform fault, Israel and adjoining territories. Applied Geochemistry 18, 1613–1628. Nelson, B.J., Wood, S.A., Osiensky, J.L., 2003. Partitioning of REE between solution and particulate matter in natural

339

waters: a filtration study. Journal of Solid State Chemistry 171, 51–56. Parriaux, A., Dubois, J.D., Mandia, Y., Basabe, P., Bensimon, M., 1990. The AQUITYP Project: Towards an aquifer typology in the alpine orogen. In: Parriaux A. (Ed.), Proceedings of the 22nd Congress of IAH: Water Resources in Mountainous Regions 1, pp. 254–262. Playa`, E., Cendo´n, D.I., Trave´, A., Chivas, A.R., Garcı´a, A., 2007. Non-marine evaporites with both inherited marine and continental signatures: the Gulf of Carpentaria, Australia, at 70 ka. Sedimentary Geology 201, 267–285. Protano, G., Riccobono, F., 2002. High contents of rare earth elements (REEs) in stream waters of a Cu–Pb–Zn mining area. Environmental Pollution 117, 499–514. Quinn, K.A., Byrne, R.H., Schijf, J., 2004. Comparative scavenging of yttrium and the rare earth elements in seawater: competitive influences of solution and surface chemistry. Aquatic Geochemistry 10, 59–80. Rasmussen, B., Buick, R., Taylor, W.R., 1998. Removal of oceanic REE by authigenic precipitation of phosphatic minerals. Earth and Planetary Science Letters 164, 135–149. Sholkovitz, E.R., 1992. Chemical evolution of rare earth elements: fractionation between colloidal and solution phases of filtered river water. Earth and Planetary Science Letters 114, 77–84. Schmid, S.M., Fu¨genschuh, B., Kissling, E., Schuster, R., 2004. Tectonic map and overall architecture of the Alpine orogen. Eclogae Geologicae Helvetiae 97, 93–117. Smedley, P.L., 1991. The geochemistry of rare earth elements in groundwater from the Carnmenellis area, southwest England. Geochimica et Cosmochimica Acta 55, 2767–2779. Tang, J., Johannesson, K.H., 2005. Rare earth element concentrations, speciation, and fractionation along groundwater flow paths: the Carrizo Sand (Texas) and Upper Floridan aquifers. In: Johannesson, K.H. (Ed.), Rare Earth Elements in Groundwater Flow Systems. Springer, Dordrecht, The Netherlands, pp. 223–251. Tang, J., Johannesson, K.H., 2006. Controls on the geochemistry of rare earth elements along a groundwater flow path in the Carrizo Sand aquifer, Texas, USA. Chemical Geology 225, 156–171. Tricca, A., Stille, P., Steinmann, M., Kiefel, B., Samuel, J., Eikenberg, J., 1999. Rare earth elements and Sr and Nd isotopic compositions of dissolved and suspended loads from small river systems in the Vosges mountains (France), the river Rhine and groundwater. Chemical Geology 160, 139–158.