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Applied Geochemistry 23 (2008) 1367–1382

www.elsevier.com/locate/apgeochem

AppliedGeochemistry

The influence of extraction rate on the reduced sulphurcontent of Aix-les-Bains’ thermal spring waters:Consequences for resource-quality monitoring

Stephanie Gallino a,*, Myriam Bulloz a, Emmanuel Naffrechoux b,Marc Dzikowski a, Dominique Gasquet a

a Laboratoire EDYTEM, Campus scientifique, F-73376 Le Bourget du Lac Cedex, Franceb Laboratoire LCME, Campus scientifique, F-73376 Le Bourget du Lac Cedex, France

Received 22 February 2007; accepted 7 November 2007Editorial handling by H. Armannsson

Available online 6 February 2008

Abstract

Sulphurous thermal springs account for a few percent of all thermal springs. As each degree of oxidation of elemental Scorresponds to a different S species, sulphurous spring waters may contain a variety of S species. Total S content is one ofthe parameters measured when analysis is carried out for issuing a spa’s operating licence. Under French law these param-eters must be stable over time. The two spas in Aix-les-Bains are fed by a number of natural springs and boreholes, whosewaters have total reduced S concentrations of between 30 and 800 mg L�1. To ensure compliance with the requirements ofthe spas’ operating licences, particularly in terms of total reduced S content, official analysis of the waters is carried outevery month at random dates and times. Monthly analyses have revealed seasonal variations in the S content of someof Aix-les-Bains’ springs; therefore, more frequent monitoring was carried out in order to investigate the extent and causesof these fluctuations. As well as seasonal variations, this monitoring has revealed daily and hourly fluctuations that appearto be related to extraction rates. For some of the springs and boreholes, S concentrations were correlated with extractionrates; for others, an increase in extraction rate led to a reduction in total S content. Concentrations of sulphide ions (one ofthe species included in the total sulphur analyses) were monitored at the same time as the total S content. Variations insulphide ion concentrations and in sulphide concentration/total S ratios did not appear to be linked to variations in flowrate. These tests show that random monthly testing is not suitable for monitoring the stability of S contents, as this param-eter can only be considered stable in terms of its yearly mean value.� 2008 Published by Elsevier Ltd.

1. Introduction/objective of the study

Sulphurous thermal springs are one of the typesin the classification of thermal waters (Cazaux,

0883-2927/$ - see front matter � 2008 Published by Elsevier Ltd.doi:10.1016/j.apgeochem.2007.11.014

* Corresponding author. Fax: +33 (0) 4 79 75 88 77.E-mail address: Stephanie.gallino@univ-savoie.fr (S. Gallino).

1964). The numerous reduced S species in solutionare classified from the most reduced to the most oxi-dized forms as follows: sulphides (H2S, HS�, S2�),polysulphides ðS2�

n ; HS�n Þ, elemental sulphur (S),thiosulphates ðS2O�3 Þ, polythionates ðSnO�6 Þ, sulph-ites ð HSO�3 ; SO�3 Þ and sulphates ðHSO�4 ; SO2�

4 Þ(Orr, 1974). They may be formed by the dissolution

1368 S. Gallino et al. / Applied Geochemistry 23 (2008) 1367–1382

of S minerals, such as pyrites, or by the bacterialreduction of sulphates to sulphides.

Sulphurous springs are quite common in Franceand in other parts of Europe, especially EasternEurope, Slovakia and Turkey (Barut et al., 2003).In the United States their renown is mainly due tothe famous springs of Yellowstone National Park.The sulphide concentrations of sulphurous springscan be quite variable, ranging from a few mg/Lfor the springs of Northern Portugal (2.5 mg L�1,Marques et al., 2000) to thousands of mg/L for theSlovakian springs of Piest’any (10 mg L�1, Franko,1998). In France, S concentrations can reach severaltens of mg/L, as at Bagneres de Luchon (30.3mg L�1) or Challes-les-Eaux (57.6 mg L�1) (BRGM,unpublished data), although Pougues-les-Eaux holdsthe French record with a concentration of 1187mg L�1. The waters of Aix-les-Bains have totalreduced S (sulphides, sulphites, thiosulphates, poly-sulphides, polythionates) concentrations between 30and 800 mg L�1.

Sulphurous springs have been studied extensivelyand regular monitoring of their physicochemicalparameters has been carried out, most notably thesprings of Yellowstone National Park (USA) (Four-nier et al., 2002; Ball et al., 1998, 2001; Rowe et al.,1973). The aim of these studies was to correlate vari-ations in S species with variations in other chemicalparameters, such as other major ions.

In numerous studies the causes of fluctuations inthe distribution of the different S species have alsobeen examined. Webster (1987) first investigatedvariations in thiosulphate concentrations of springsin New Zealand. A similar study has also been car-ried out of the springs in Yellowstone Park (Xuet al., 1998). Because of the complexity of the chem-ical equilibria and reaction kinetics, it may not bepossible to obtain clear information using on-sitetests. Laboratory experiments are often required inorder to pinpoint basic phenomena that may bemasked by the complexity of the natural environ-ment. For example, research has been carried outinto the stability of thiosulphates in the presenceof pyrite (Xu and Schoonen, 1995) and on the oxi-dation of H2S in natural waters (Millero et al.,1989).

In order to understand these different phenom-ena, it is necessary to measure accurately the differ-ent chemical constituents. Several traditionalmethods can be used, including the iodometricmethod (Rodier, 1984), the methylene blue colori-metric method (APHA, 1985; Centre d’Expertise

en Analyse Environnementale du Quebec, 2005),the potentiometric method or the mercuric chloridemethod (Rodier, 1984). In addition, a number ofmore recent methods have been developed in orderto simplify the analytical protocols for measuringS species (Von Wandruszka et al., 1992; Poulyet al., 1999; Cali et al., 2001; Montegrossi et al.,2006). In this study, it was decided to use traditionalmethods because they are the ones used for the rou-tine monitoring carried out by the spa operators andby the government testing service.

Thermal waters used for a spa must have severalcriteria in order to obtain a license:

–have therapeutical properties, recognized by theFrench Academy of Medicine,–have stable physico-chemical characteristics(provisions R 1322-1 to R 1322-4 from theFrench Public Health Code),–be bacteriologically pure,–and for the boreholes, have identical chemicalcharacteristics to the original springs.

The values of the main parameters are laid downin the reference composition contained in the spa’soperating licence. The concentration of totalreduced S is frequently monitored, with regulatoryanalyses being carried out once a month at randomdates and times. These analyses have revealed vari-ations in total reduced S concentrations; therefore,it was decided to investigate the influence of timeof the year, day of the week and sampling time onthe concentrations of total reduced S and of sulp-hides. Analysis was carried out using the iodometricand sulphide selective electrode potentiometrymethods. Variations in concentrations were com-pared to water extraction rates.

2. Geographical and geological setting

The spa town of Aix-les-Bains (Savoie, France)lies on the shores of Lake Bourget between theMontagne du Chat, the Montagne de la Chambotteand the Revard ridge. The town has two spa estab-lishments: the Thermes Nationaux in the town cen-tre and the Thermes de Marlioz, a few kilometres tothe south (Fig. 1). The Thermes Nationaux havetwo natural springs, the Alun spring and the Soufrespring, and two boreholes, the 1100-m deep ReineHortense borehole and the 2200-m deep Chevalleyborehole. The Thermes de Marlioz have three natu-ral springs, the Esculape, Bonjean and Adelaıde

Fig. 1. Location plan of the study area.

Fig. 2. Circulation diagram for Aix-les-Bains’ thermal waters.

S. Gallino et al. / Applied Geochemistry 23 (2008) 1367–1382 1369

1370 S. Gallino et al. / Applied Geochemistry 23 (2008) 1367–1382

springs, and a borehole, the 230-m deep Arianaborehole. However, the two spas do not use thewater from the springs; the Thermes Nationaux taketheir water from the Reine Hortense and Chevalley

0

1

2

3

4

5

6

Ca Mg Na+K C

conc

entra

tion

(meq

.L-1

)

Alun spring Chevalley borehole

Fig. 3. Schoeller Berkalloff diagram for th

0

1

2

3

4

5

6

7

Ca Mg Na+K

conc

entra

tion

(meq

•L-1

)

Adélaïde spring Ariana borehole

Fig. 4. Schoeller Berkalloff diagram for th

boreholes and the Thermes de Marlioz draw theirwater from the Ariana borehole.

Geologically, the study site is situated at the mostsoutherly point of the Jura Range (Fig. 2), in an

l SO4 HCO3+CO3 NO3

Reine Hortense borehole Soufre spring

e waters of the Thermes Nationaux.

Cl SO4 HCO3+CO3 NO3

Bonjean spring Esculape spring

e waters of the Thermes de Marlioz.

Table 1Monthly sulphate concentrations at Reine Hortense borehole

Month SO2�4 concentrations (mg L�1)

August 2005 152.3September 2005 136.2October 2005 160.4November 2005 171.8December 2005 173January 2006 175.8February 2006 170March 2006 171April 2006 170.5May 2006 161.5June 2006 162.4July 2006 159.1August 2006 161.6Mean value 163.5Standard deviation 10.7

Table 2Total reduced sulphur and sulphide concentrations obtainedusing three different methods of analysis

Spring orborehole

Iodometric totalreduced sulphur(mg L�1)

Colorimetricsulphides(mg L�1)

Potentiometricsulphides(mg L�1)

Esculape 164 16 37Ariana 104 5 26Adelaıde 875 130 136Alun 174 – 41Soufre 97 – 10R. Hort. 705 – 129Esculape 172 27 48Ariana 117 8 24Adelaıde 861 130 168Alun 249 31 43Soufre 134 14 29R. Hort. 754 88 137Esculape 168 22 42Ariana 111 15 20Adelaıde 817 125 124Alun 221 17 39Soufre 126 15 22R. Hort. 723 108 124

S. Gallino et al. / Applied Geochemistry 23 (2008) 1367–1382 1371

area where faults injected with evaporitic rocks havethrust anticlines over synclines for a distance of sev-eral kilometres. The direction of these structures isglobally west. Lake Bourget lies in a mollassic syn-cline bounded by two anticlines, the Montagne de laCharvaz anticline to the west and the Aix-les-Bainsanticline to the east.

The infiltration zone is on the Upper Kimmerid-gian to Valanginian limestones of the Montagne dela Charvaz, to the west of Lake Bourget. Thepresence of the underlying Hauterivian marls forcesthe water to percolate down to a depth of 2200 m inthe Lake Bourget syncline and it is during this des-cent that it acquires its thermal properties. Themean geothermal gradient is thought to be around1 �C/33 m. The second part of the water circulationsystem is less well understood. It is thought that thewater follows the fault plane along which the Aix-les-Bains anticlinal dome has been thrust over theLake Bourget syncline. It is during this phase thatthe water becomes mineralised with Cl, SO4, Naand K ions. Below Aix-les-Bains the waters entera series of vertical fractures that traverse all the bedsof the Aix-les-Bains Dome (from Upper Kimmerid-gian to Urgonian). The water passes through thesefractures too fast for it to achieve thermal equilib-rium with the surrounding rock. As the water rises,the dissolved sulphates are reduced to sulphides bybacterial action (Carfantan, 1994).

As they approach the surface, the thermal waterstraverse the Urgonian karst that forms the mostrecent layer of the Aix-les-Bains anticlinal dome.The karst network disperses the flow of the thermalwaters, causing them to mix with surface karstwaters. As a result, the natural thermal springs area mixture of deep thermal waters and cold surfacewaters, with the proportions of the mixture depend-ing on the hydrostatic pressures within the twoaquifers.

The chemical facies of the water are conditionedby two factors: contact with the evaporitic rocks ofthe thrust zone and dilution by the surface waters ofthe Urgonian karst. Thus, as the Chevalley boreholedraws its water from below the thrust zone (Fig. 2),it is of HCO3-calcareous type, whereas the ReineHortense borehole water, which is drawn from justabove the thrust zone, is of HCO3–SO4-calcareoustype (Fig. 3) (Fig. 3 represents mean values of avail-able data during the last 25 a and standard devia-tions for each element). The natural spring watersof the Thermes Nationaux (Alun and Soufresprings) and of the Thermes de Marlioz (Adelaıde,

Bonjean and Esculape springs) are of almost identi-cal physicochemical facies due to dilution of thethermal water by the cold waters of the surface karst(Fig. 4). As the Thermes de Marlioz borehole drawsits water from the bottom of the Urgonian layer, ithas characteristics similar to those of the springwaters.

In terms of physical parameters, such as flowrate, temperature and conductivity, the springs canbe divided into two groups:

–The Alun and Soufre springs of the ThermesNationaux are hyperthermal springs with mean

Table 3Summary of the concentrations of total reduced sulphur and of sulphides during the monitoring weeks

Iodometry (�SF) Reine Hortense Alun Soufre Adelaide Esculape Ariana

24/04/2006 Monday 103.4 20.3 4.5 110 22 13.225/04/2006 Tuesday 93.6 17 3 101 22.1 12.726/04/2006 Wednesday 93.6 14.7 3.1 95 22 12.927/04/2006 Thursday 94.6 14.3 2.8 96.3 21.8 12.228/04/2006 Friday 93.4 14.9 3.2 95 22.4 13

22/05/2006 Monday 95.5 23.9 13 105.6 14 22.923/05/2006 Tuesday 97.5 20.5 10.8 96 15.1 22.624/05/2006 Wednesday 98 19.2 9.8 102.9 15.6 23.425/05/2006 Thursday 92.8 15 4.4 95.1 13.8 22.326/05/2006 Friday 97.3 19 10.7 102.6 13.9 21.627/05/2006 Saturday 91.8 19.2 8.8 103.3 12.5 22.128/05/2006 Sunday 109.6 27.3 17.3 108.6 14.2 21.8

21/08/2006 Monday 94.5 28.7 17.9 115.6 20.1 13.422/08/2006 Tuesday 95.6 25.5 16.5 107.1 22 15.623/08/2006 Wednesday 92.5 22.8 14.7 110.5 21.9 14.524/08/2006 Thursday 93.7 19.6 13.1 106.8 20.4 13.425/08/2006 Friday 87.1 19 14 103.6 20.7 14.126/08/2006 Saturday 88.6 19.6 13.6 107.3 22.5 1527/08/2006 Sunday 101.9 21.4 16.3 112.5 21.3 14.4

Potentiometry (mg L�1) Reine Hortense Adelaıde Soufre Alun Esculape Ariana21/08/2006 Monday 80.0 98.8 19.1 30.3 38.5 22,222/08/2006 Tuesday 107.9 119.9 – 23.4 38.0 18.923/08/2006 Wednesday 114.7 129.6 19.8 33.9 44.4 27.124/08/2006 Thursday 119.9 119.2 13.4 28.4 43.9 25.225/08/2006 Friday 96.6 102.1 11.9 22.6 27.7 18.526/08/2006 Saturday 64.4 92.4 10.6 – – –27/08/2006 Sunday 101.0 114.1 10.6 19.2 21.7 10.3

Fig. 5. Results of monitoring of total reduced S concentrations for the Reine Hortense borehole.

1372 S. Gallino et al. / Applied Geochemistry 23 (2008) 1367–1382

S. Gallino et al. / Applied Geochemistry 23 (2008) 1367–1382 1373

discharge temperatures of 42 �C and 39 �C,respectively. Their flow rates are quite high ataround 20 L s�1 for the Alun spring and17 L s�1 for the Soufre spring and they havesimilar conductivities of around 900 lS cm�1.The temperature and conductivity of the Cheval-ley borehole water are around 70 �C and450 lS cm�1, respectively. The Reine Hortenseborehole water is cooler because it is drawn fromcloser to the surface. Its temperature is about37 �C and its conductivity is around800 lS cm�1.–The Adelaıde, Esculape and Bonjean springs ofthe Thermes de Marlioz are hypothermal waterswith discharge temperatures of around 12–13 �C. The flow rates for the Adelaıde, Esculapeand Bonjean springs are approximately 0.0027,0.012 and 0.021 L s�1, respectively, thus theyare much lower than those of the Alun and Sou-fre springs. Their conductivities, which areinversely proportional to their flow rates, areof the order of 900 lS cm�1 for the Adelaıdespring, 770 lS cm�1 for the Esculape springand 450 lS cm�1 for the Bonjean spring.

3. Methodology

Several methods can be used to determinereduced S species, three of which were tested for thisstudy. Here, the different methods are explained in

0

5

10

15

20

25

30

01/01/1996 1/01/1998 1/01/2000

Tota

l red

uced

sul

phur

con

cent

ratio

ns (°

SF)

Alun spring

Fig. 6. Results of monitoring of total reduced S co

general. Detailed methodology is presented inAppendix 1:

–Iodometric method: this method involves react-ing I with the total reduced S species (sulphides,thiosulfate, sulfite. . .). Results are expressed inS hydrometric degrees. They can be convertedinto mg L�1 by multiplying the result by 7.93.–Colorimetric method: sulphides react with thenitrogen oxalate N-dimethyl-p-phenylenediamineto form methylene blue. The concentration of themethylene blue formed is determined byspectrophotometry.–Potentiometric method: this method is based onmeasuring the activity of the sulphide ions with aspecific electrode.

4. Results

Total reduced S concentrations were monitoredin all the water sources except for the Chevalleyborehole at the Thermes Nationaux and the Bon-jean spring at the Thermes de Marlioz (Table 3).The decision not to sample these two waters wasbased on the following reasons. (1) The Chevalleyborehole draws its water from below the thrust zoneand therefore does not contain sulphates. (2) TheBonjean spring water, like the other thermal waters,is a mixture of deep thermal water and the cold sur-face waters of the karst. In the latter case, the cold

1/01/2005 1/01/2007

Soufre spring

4800

Dai

ly e

xtra

ctio

n ra

tes

at T

herm

es N

atio

naux

bor

ehol

es (m

3 )

ncentrations for the Alun and Soufre springs.

1374 S. Gallino et al. / Applied Geochemistry 23 (2008) 1367–1382

surface water dominates the mixture and thusmasks the total reduced S content of the deepsource.

It should be noted that the extraction rate fromthe Ariana borehole is kept constant over long peri-ods of time (several months) with flow rates set at

40

60

80

100

120

140

160

may-05 sept.-05 dec.-05 ma

Tota

l red

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sul

phur

con

cent

ratio

ns (°

SF)

Fig. 8. Results of monitoring of total reduced

0

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30

0 2 4

Extraction rates (m3. h-1

Tota

l red

uced

con

cent

ratio

ns (°

SF)

0

500

1000

1500

2000

2500

june aug.-05 -05 oct.-05 dec.-05 feb.-06

Mon

thly

ext

ract

ion

volu

mes

(m3)

Fig. 7. Results of monitoring of total reduced

values between 2 and 3 m3 h�1. It is never turnedoff, except for maintenance operations. On the otherhand, the extraction rates for the Thermes Nation-aux boreholes are regulated to meet the needs ofthermal water, which depend on the number ofspa patients.

rch-06 july-06 oct.-06

1600

Dai

ly e

xtra

ctio

n ra

tes

at T

herm

es N

atio

naux

bor

ehol

es (m

3 )

S concentrations for the Adelaıde spring.

6 8

)

apr. -06 june-06 aug.-06 oct.-0610

11

12

13

14

15

16

17

18

Tota

l red

uced

sul

phur

con

cent

ratio

ns

(°S

F)

S concentrations for the Ariana borehole.

S. Gallino et al. / Applied Geochemistry 23 (2008) 1367–1382 1375

4.1. Monthly monitoring

Averaged over one year, the SO4 concentrationsof all the springs and boreholes, except the Alunand Soufre springs, have been found to be stable(the deviation from the mean is never greater than10%). Total reduced S concentrations of all thesprings and boreholes are determined once a month.This monthly monitoring has shown three types ofrelationship between extraction rate and sulphideconcentration:

Reine Hortense's extraction volume

Chevalley's extraction volume

Alun spring (LG)

Soufre spring (LG)

0

200

400

600

800

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1400

1600

23/4/06 25/4/06 27/4/06 29/4/06

Extra

ctio

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(m3 )

Extra

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Extra

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Extra

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tract

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(m3 )

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ulph

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(°SF

)To

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educ

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ulph

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tions

(°SF

)

20

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22/5/06 24/5/06 26/5/06 28/5/060

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20

22

24

26

28

30

Tota

lred

uced

sulp

hurc

once

ntra

tion

(°S

F)

A

B

C

Fig. 9. Results of daily monitoring of total reduced S concentrations of the2006 ; (B) 22nd–28th May 2006 ; (C) 21st–27th August 2006.

–1st type of relationship: An inverse correlationbetween flow rate and total reduced S concentra-tion, i.e., total reduced S concentrations are highduring periods when extraction rates are low(when the thermal baths are closed). This typeof relationship applies to the Reine Hortenseborehole (Fig. 5).–2nd type of relationship: A direct correlationbetween total reduced S concentration andextraction rate, i.e. total reduced S concentra-tions are low when flow rates from the aquifer

Ariana borehol e(LG)

Reine Hortense borehole (RG) Adélaïde spring (RG)

Tota

l red

uced

sul

phur

co

ncen

tratio

ns (°

SF)

Tota

l red

uced

sul

phur

co

ncen

tratio

ns (°

SF)

Tota

l red

uced

sul

phur

co

ncen

tratio

ns (°

SF)

0

0

0

0

0

0

0

0

0

3/4/06 25/4/06 27/4/06 29/4/0680

85

90

95

100

105

110

115

120

0

0

0

0

0

0

0

0

0

2/5/06 24/5/06 26/5/06 28/5/0690

92

94

96

98

100

102

104

106

108

110

112

0

0

0

0

0

0

0

0

0

0/08/06 22/08/06 24/08/06 26/08/06 28/08/0680

85

90

95

100

105

110

115

120

different spring waters during the week of (A) 23rd–28th April

Table 4Summary of extraction rates during the monitoring weeks.(RH = Reine Hortense Borehole, CH = Chevalley borehole)

Volume extracted (m3/j) RH CH

23/04/2006 Sunday 223.8 386.824/04/2006 Monday 304.2 1086.425/04/2006 Tuesday 483.8 1513.226/04/2006 Wednesday 321.9 1358.427/04/2006 Thursday 303.1 1055.828/04/2006 Friday 443.9 1325.629/04/2006 Saturday 619.7 1244.4

22/5/06 Monday 435.71 1194.4523/5/06 Tuesday 706.39 1504.4824/5/06 Wednesday 558.39 1495.8925/5/06 Thursday 525.80 1105.5626/5/06 Friday 648.46 1481.6027/5/06 Saturday 413.67 959.1628/5/06 Sunday 406.36 750.16

20/08/2006 Sunday 307 67521/08/2006 Monday 563 129222/08/2006 Tuesday 682 140323/08/2006 Wednesday 557 143324/08/2006 Thursday 453 131925/08/2006 Friday 640 134726/08/2006 Saturday 581 101727/08/2006 Sunday 311 63328/08/2006 Monday 816 311

1376 S. Gallino et al. / Applied Geochemistry 23 (2008) 1367–1382

are low. The Alun and Soufre springs show thistype of relationship. Past records and the datafor 2006 (Fig. 6) show that the lowest concentra-tions are recorded in February and March, andthe highest concentrations in June, July, Augustand September.The Ariana borehole appears to function in anidentical way, in that the reduction in boreholeextraction rates over the years has led to a reduc-tion in total reduced S concentrations (Fig. 7).Similarly, an increase in the borehole flow rateduring 2006 was immediately followed by anincrease in the concentration of total reduced S(Fig. 7).The Adelaıde spring also appears to function inthis way; however, past records only give yearlymean values, which are not sufficient for deduc-ing behaviour; analyses at reduced time intervalsare only available for 1998–2001.–3rd type of relationship: No correlation betweensulphur concentration and extraction rate.The total reduced S concentrations recorded forthe Esculape spring were quite stable at around20�SF (158 mg L�1).The samples collected at Adelaıde spring betweenSeptember 2005 and August 2006 do not showany relationship (Fig. 8).

4.2. Daily monitoring

4.2.1. Variations in total reduced sulphur

concentrations

Monitoring was carried out over a period of fivedays during April 2006 (Fig. 9A), and then overperiods of seven days in May 2006 (Fig. 9B) andin August 2006 (Fig. 9C). Total reduced S concen-trations and the volumes extracted are shown inTables 3 and 4.

For the week 23/04/06 to 28/04/06, the variationsin total reduced S concentrations in the Reine Hor-tense borehole and the Adelaıde spring waters wereinversely correlated with extraction rates (Fig. 9A).The concentrations of total reduced S in the Alunand Soufre springs gradually decreased from Mon-day 24/04 to Thursday 27/04. However, totalreduced S concentrations increased rapidly at theend of the week when extraction volumes werereduced. Similar remarks can be made for the evolu-tion of total reduced S concentrations during theweek of 21st–27th August (Fig. 9C). The totalreduced S concentrations of the Esculape spring

were almost completely stable during both the Apriland August monitoring periods.

For the week from 22/05 to 28/05, the inversecorrelation was less obvious for all springs andboreholes, (Fig. 9B). Total reduced S concentra-tions were inversely correlated with flow rates on22/05 and 24/05. However, from 24/05 to 28/05,the inverse correlation only functioned when thetotal reduced S concentrations for one day werecompared with the extraction rates of the daybefore. This may be due to the fact that, unlikethe other two monitoring weeks, there was noreduction in flow rate on the Wednesday andThursday.

4.2.2. Variations in sulphide concentrations

During the August monitoring week sulphideconcentrations were determined (Fig. 10) along withtotal reduced S concentrations. The changes insulphide concentrations and in sulphide/totalreduced S ratios did not appear to follow the samepattern as the changes in total reduced S concentra-tions (Fig. 11). The sulphide/total reduced S ratiowas not constant throughout the week and theinverse correlation was not as clear as for the totalreduced S concentration. Nevertheless, the springs

0

200

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800

1000

1200

1400

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20/08/2006 22/08/2006 24/08/2006 26/08/2006 28/08/2006

Extra

ctio

n vo

lum

e (m

3 )

60

70

80

90

100

110

120

130

140

Sul

phid

eco

ncen

tratio

ns(m

g.L-

1 )

Chevalley's extraction volume Reine Hortense,s extraction volumeReine Hortense borehole Adélaïde spring

0

200

400

600

800

1000

1200

1400

1600

20/08/2006 22/08/2006 24/08/2006 26/08/2006 28/08/2006

Extra

ctio

n vo

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e (m

3 )

0

5

10

15

20

25

30

35

40

45

50

Sulp

hide

con

cent

ratio

ns (m

g.L-1

)

Chevalley's extraction volume Reine Hortense's extraction volumeSoufre spring Alun springEsculape spring Ariana borehole

Fig. 10. Results of daily monitoring of sulphide concentrations of the different spring waters during the week of 21st– 27th August 2006.

S. Gallino et al. / Applied Geochemistry 23 (2008) 1367–1382 1377

can be divided into two groups according to theirbehaviour:

–The ratios for the Adelaıde spring and for theReine Hortense borehole increased from Mon-day to Thursday, and then decreased until Satur-day, before increasing again on Sunday. Thesewere the sources with the highest concentrationsof sulphides.–The ratios for the Esculape, Soufre and Alunsprings and for the Ariana borehole were muchmore variable over the week. Most of the time,

the ratios were inversely correlated with the vol-umes extracted.

For the moment, there are no proven scientificexplanations. However, it seems that the phenome-non could be linked to mixing with surface watersthat is greater for Esculape, Alun and Soufre springs.

4.3. Hourly monitoring

The springs and boreholes of the ThermesNationaux and the Thermes de Marlioz were sam-

0.05

0.10

0.15

0.20

0.25

0.30

21/08/2006 22/08/2006 23/08/2006 24/08/2006 25/08/2006 26/08/2006 27/08/2006Rat

io o

f sul

phid

e co

ncen

tratio

n to

tota

l red

uced

sul

phur

conc

entra

tion

Reine Hortense borehole Adélaïde spring Soufre springAlun spring Esculape spring Ariana borehole

Fig. 11. Variations in the sulphide to total reduced S ratio of the different spring waters during the week of 21st–27th August 2006.

1378 S. Gallino et al. / Applied Geochemistry 23 (2008) 1367–1382

pled hourly, on Thursday 1st June 2006 between8.30 a.m. and 5.30 p.m. (Fig. 12).

The total reduced S concentrations of the ReineHortense borehole water were inversely correlatedwith the extraction rates with a 1-h time lag, therebyindicating a certain amount of inertia in the system.The total reduced S concentrations in the Alun andSoufre spring waters seemed to correlate withextraction rates. In general, the concentrationsdecreased during the day, except for the periodbetween 1.30 and 3.30 p.m. when the Reine Hor-tense borehole was operating again. The springs atthe Thermes de Marlioz did not appear to be influ-enced by the extraction rates of the ThermesNationaux boreholes, although the reduced S con-centrations for the Adelaıde spring were highlyvariable.

5. Discussion and conclusions

Variations in total reduced S concentrations wererelated to extraction rates and to the hydrostatichead conditions of the Urgonian surface aquifer.

Two cases can be distinguished for the ThermesNationaux springs:

–On the one hand, the total reduced S concentra-tion of the Reine Hortense borehole water, whichis drawn directly from the reservoir layer, isinversely correlated with extraction volumes overthe monthly, daily and hourly sampling periodsi.e., total reduced S concentrations are higher

during low flow rates. On the other hand, themonitoring of the monthly SO4 concentrationvariations over 1-a reveals small variations(Table 1) (less than 6.5% for 12 values), but theyseem to be higher during low flow rates (Decem-ber and January) and lower during high flowrates (July and August).Sulphate and total reduced S concentrations arealso inversely correlated with extraction rates.Nevertheless, the variability is different. Indeed,SO4 concentration evolution is less than 7% oftotal SO4 concentrations when total reduced Sconcentrations comprise more than 20% of totalreduced S concentrations. The increase in theflow rates seems to induce an increase in thespeed at which the water circulates and adecrease in the mineralization time. The lowestSO4 concentration variations could be due tothe almost instantaneous gypsum dissolution.The pumping extracts an outflow of total reducedS species greater than the production of such spe-cies available from the kinetics of bacterial reduc-tion. Hence, extraction rate can be concluded todirectly influence the concentration of reducedS species.–On an annual scale, the total reduced S concen-trations of the Alun and Soufre spring waters,which are a mixture of hot deep waters and coldsurface waters in variable proportions, are corre-lated with extraction rates. However, long-termsampling records show that periods of lowextraction correspond to periods of high precipi-

0

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7:30 8:30 9:30 10:30 11:30 12:30 13:30 14:30 15:30 16:30 17:30 18:3080

85

90

95

100

105

110

115

120

Tota

l red

uced

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phur

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cent

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SF)

Chevalley's extraction rates Reine Hortense's extraction ratesReine Hortense borehole Adélaïde spring

0

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7:30 8:30 9:30 10:30 11:30 12:30 13:30 14:30 15:30 16:30 17:30 18:30

Extra

ctio

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tes

(m3 .h

-1)

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ctio

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tes

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-1)

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18

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24

26

28

Tota

l red

uced

sul

phur

con

cent

ratio

n (°

SF)

Chevalley extraction rates Reine Hortense extraction ratesAriana borehole Esculape springSoufre spring Alun spring

Fig. 12. Results of hourly monitoring of total reduced S concentrations of the different spring waters on 1st June 2006.

S. Gallino et al. / Applied Geochemistry 23 (2008) 1367–1382 1379

tation and that periods with high concentrations,which are also periods of high extraction, corre-spond to phreatic lows in the surface aquifer.Therefore, seasonal variations in precipitationand therefore in additions of cold water have adirect influence on the concentration of reducedS species. During the three sampling weeks, thesprings’ total reduced S concentrations wereinversely correlated with extraction rates, or, atleast, the highest concentrations were found dur-ing the weekend when extraction was lowest.There was no precipitation during the monitor-ing weeks; therefore the hydrostatic head of theUrgonian surface aquifer was constant. Under

such conditions, variations in total reduced Sconcentrations follow an identical pattern to thatof the boreholes.

For the Thermes de Marlioz:

–On an annual scale, the total reduced S con-centration of the Ariana borehole water is corre-lated with its own extraction rate. This boreholedraws its water from the base of the Urgonianlayer; therefore the head balance between theUrgonian aquifer and the thermal aquifer isidentical to that of the Alun and Soufre springs.On the other hand, the proportions of the

1380 S. Gallino et al. / Applied Geochemistry 23 (2008) 1367–1382

mixture in the Ariana borehole are not governedby seasonal variations in the hydrostatic head ofthe surface aquifer, but by the borehole extrac-tion rate, which determines the size of the coneof depression formed in the surface aquifer.Variations in day-to-day and hourly totalreduced S concentrations are almost non-exis-tent because of the stability of the extractionrate.–The total reduced S concentration of the Escul-ape spring water was stable over all the monitor-ing periods. A system has been installed to drainsurface water from the area above this spring,thereby limiting the inflow of surface water.Thus, the stability of the borehole extraction rateand the drainage of the surface water favour thetemporal stability of the concentration ofreduced S species.–In general, the total reduced S concentrations ofthe Adelaıde spring water are very variable.There is little monthly data, so it is difficult todraw any definite conclusions. The hourlymonitoring showed large variations in totalreduced S concentration, although there was nocorrelation with extraction rate. On the otherhand, the daily variations appeared to be inver-sely correlated with the extraction rate of theThermes Nationaux. This is surprising, as thetwo establishments are approximately 1700 mapart. In addition, the variations in the sulphideconcentrations of the Reine Hortense boreholeat the Thermes Nationaux and of the Adelaıdespring at the Thermes de Marlioz show identicalpatterns.

In general, total reduced S species and sulphideconcentrations clearly fluctuate, with values depend-ing on the time of year (high or low water periods inthe surface aquifer), day of the week, time of dayand, almost certainly, on the amount of precipita-tion, although this final parameter was not investi-gated. Nevertheless, the mean variation observedover a year remains almost constant. The simulta-neous monitoring of total reduced S species andsulphides showed that these two forms behavedifferently.

From an administrative point of view, Aix-les-Bains’ thermal waters do not conform to Frenchstandard specifications established for a thermalwater. Indeed, the concentrations of the differentelements present in the water are fixed by a singlereference analysis carried out at the beginning of a

spa’s operational life or when the waters are recog-nised to have curative properties. This analysis fixesthe concentrations, which are required for furtheranalyses because according to French law, chemicalproperties of such waters are considered to be stableover time.

The different monitoring programmes carried outin this study show that variations of total reduced Sconcentrations can naturally occur and that a singlereference value, measured at random time that canbe unrepresentative of the average values, is inade-quate. In fact, several analyses over different timescales are needed to provide a mean value and astandard deviation that can serve as a reference fig-ure. In addition, it is essential, for the referenceanalysis, to report the precision of the analyticalmethodology and which substances are being deter-mined. The monitoring analysis will require thesame methodology.

Acknowledgement

The authors would like to thank the personnel ofthe Environmental Molecular Chemistry Labora-tory of the University of Savoie for providing uswith access to the equipment we needed.

Appendix 1

A.1. Iodometric method

This method involves reacting I with the reducedS species present in a water sample. The reactionsare as follows:

�H2Sþ I2 ! I� þ 2Hþ þ S

� S2�n þ I2 ! nSþ 2I�

� 2S2O2�3 þ I2 ! 2I� þ S4O2�

6

�HSO�3 þ I2 þH2O! SO2�4 þ 2I� þ 3Hþ

An excess volume of I of known concentration is re-acted with the thermal water containing sulphides.The reaction between the I and the sulphides decol-ours the solution. The concentration of the remain-ing I is determined using spectrophotometry(350 nm). Results are expressed in S hydrometric de-grees, with a degree corresponding to the number ofmg I absorbed by 1 L of thermal water. Sulphurhydrometric degrees can be converted into mg L�1

by multiplying the result by 7.93 (the ratio of themolar masses of I and S).

S. Gallino et al. / Applied Geochemistry 23 (2008) 1367–1382 1381

A.2. Colorimetric method

When combined with an oxidizing agent, suchas iron chloride, and placed in a very acid medium,sulphides react with the nitrogen oxalateN-dimethyl-p-phenylenediamine to form methyleneblue. The concentration of the methylene blueformed is determined by spectrophotometry.

Concentrated NaOH is added to the sample toincrease its pH to above 8. The reduced S, whichthen is mostly in the form S2�, is converted to amore stable precipitate of ZnS by adding Zn ace-tate. Adding an oxidizing agent, such as iron chlo-ride, then catalyzes the reaction of sulphide withnitrogen oxalate N-dimethyl-p-phenylenediamine,forming a deep-pink precipitate that disappearsimmediately. Ammonium phosphate is added toremove the remaining colour due to the iron chlo-ride. The methylene white precipitate that forms isrendered soluble again by adding H2SO4, resultingin the formation of methylene blue. The concentra-tion of methylene blue is measured using a spectro-photometer (664 nm). The sulphide concentrationof the sample is obtained from a calibration curve,drawn up using sulphide solutions whose concentra-tions are determined using K dichromate. In thepresent study, the 4 control solutions used to drawup the calibration curve (0, 10, 50, 100 mg L�1)had a correlation coefficient of R2 = 0.994 (Bulloz,2006).

A.3. Potentiometric method

This method is based on measuring the activity ofthe sulphide ions. The analysis was carried out usinga specific electrode for sulphide ions combined witha KNO3double-junction reference electrode. Sul-phide ion concentrations were determined from acalibration curve, drawn up using 8 standard Na2Ssolutions (5, 10, 15, 20, 50, 100, 140, 190 mg L�1).A basic buffer was added to the sample flasks, withidentical quantities of the buffer solution being usedfor the samples and for the standards in order tomaintain the same ionic strength. The calibrationcurve had a correlation coefficient of R2 = 0.9659(Bulloz, 2006).

A.4. Advantages and disadvantages of these methods

Over a period of three days, simultaneous sam-ples were taken for analysis using each of the threemethods (Table 2). The iodometric method, with

which total reduced S is determined, gave highervalues than the other two methods. Although thesame species is determined by the two other meth-ods, the values obtained using the colorimetricmethod were about 30% lower than those obtainedusing the potentiometric method, for the sampleswith the lowest sulphide concentrations. It wouldseem that the ZnS precipitate formed during thesampling (the sampling flask contained Zn acetateto ensure that the reaction took place as soon asthe sample was collected) dissolved during the reac-tion with the nitrogen oxalate N-dimethyl-p-phenyl-enediamine. In addition, this method is relativelytime consuming. Therefore, the subsequent moni-toring was carried out using the iodometric andpotentiometric methods.

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