Hélène Celle-Jeanton

Frédéric Huneau
email: f.huneau@ghymac.u-bordeaux1.fr

Yves Travi

W M Edmunds

Twenty years of groundwater evolution in the Triassic sandstone aquifer of Lorraine: Impacts on baseline water quality

) provides new inorganic geochemical data (including trace elements) that allow improving the knowledge of baseline conditions and hydrochemical functioning of a major sandstone aquifer. The good correlation between 14 C activities, temperature and depth along the main flow line indicate regular downgradient trends and possible water stratification. Unreactive tracers, mainly stable isotope ratios 18 O and 2 H, as well as C isotopes are used to define a timescale for the aquifer, showing two groups of groundwater, namely of modern and Holocene age, and late Pleistocene age, with a mixing zone. Baseline quality is then represented by a wide range of concentrations, mainly the result of time-dependent water-rock interaction, as already observed elsewhere in Triassic sandstone aquifers. Some trace elements such as Li, Rb, Cs, which are not limited by solubility constraints, show linear trends. During saturated flow downgradient, the chemistry is also specifically characterised by a regular increase in Na and Cl (and locally SO 4 ) as a result of evaporite dissolution related to overlying or basement limits. The aquifer is mostly oxidising with a redox boundary marked by U decrease, some 40 km from outcrop.

Groundwater abstraction since the 1970s has created a strong lowering (10-150 m) of the water table, especially from 1970 to 1980. Based on nine boreholes, previously sampled in 1979, a decreasing evolution in radiocarbon content of the TDIC, together with significant evolution of 18 O content, indicate that old groundwater has moved upgradient. The major difference in terms of baseline evolution is observed using Cl and Na concentration and, locally, SO 4 , indicating an increasing influence of water circulation involving overlying or basement formations, or of mixing with Permian waters. From the point of view of aquifer management, the perceptible NO 3 increase could provide information on the progress of any contamination under the aerobic conditions. In addition, the few key elements, indicators of disequilibrium, related to overlying or deep waters, should be included in regular monitoring programmes.

Introduction

Understanding the natural baseline quality of groundwaters requires knowledge of the aquifer mineralogy, flow paths, residence time and geochemical controls [START_REF] Shand | The baseline inorganic chemistry of European groundwaters[END_REF]. Baseline geochemistry is an essential prerequisite for understanding pollution, for identifying over-exploitation and for imposing regulatory limits, as suggested in the European Water Framework Directive 2000/60/EC. However, groundwater exploitation, by means of drilling, may penetrate water of different ages and/or quality with increasing depth and then disturb hydrogeological conditions. The younger waters may include some anthropogenic component affecting water quality and can thus badly influence deeper parts of the aquifer.

Investigations using a combination of geochemical and isotopic methods were carried out on the Lorraine Triassic Sandstone Aquifer (LTSA) in 1979 [START_REF] Blavoux | Radiocarbon dating of groundwater of the aquifer confined in the lower Triassic sandstones of the Lorraine region, France[END_REF] and interpreted in terms of residence time of groundwater within the aquifer. Another study carried out by [START_REF] Marty | Geochemical evidence for efficient aquifer isolation over geological timeframes[END_REF] focused on the isolating properties of aquitards. As part of studies of representative European aquifers -BaSeLiNe [START_REF] Shand | The baseline inorganic chemistry of European groundwaters[END_REF] completed under the European Union Framework VI programme, the LTSA was selected for a comparison of modern analysis with those carried out 20 a previously. The red-bed sandstones of the Lorraine aquifer are also typical of similar aquifers in Europe used for water supply (in the UK and Germany as well as France). These aquifers are also of importance in many other regions, in North Africa and the Middle East as well as North America [START_REF] Lloyd | The hydrogeology and groundwater resources development of the Cambro-Ordovician sandstone aquifer in Saudi Arabia and Jordan[END_REF][START_REF] Edmunds | Groundwater evolution in the Continental Intercalaire aquifer of southern Algeria and Tunisia: trace element and isotopic indicators[END_REF][START_REF] Gossel | A very large scale GIS based groundwater flow model for the Nubian sandstone aquifer in Eastern Sahara (Egypt, northern Sudan and eastern Libya)[END_REF][START_REF] Nastiv | Developing conceptual hydrogeological model for Potsdam sandstones in southwestern Quebec, Canada[END_REF]. A similar study was carried out for the East Midlands Triassic aquifer (UK) and the present paper compares the groundwater chemistry of these two aquifers. Both are characterised by groundwaters of similar age and have large sections of aerobic groundwaters which persist, due to the absence of any significant amount of organic material. The LTSA aquifer can be viewed as being important for the study of hydrogeological trends (mainly conducted using isotopic studies) as well as defining baseline characteristics within a typical sandstone aquifer.

This paper presents the results obtained from a new field campaign realised in 2001 on the LTSA, in order to highlight the modifications of the water quality in relation to the modifications of the potentiometric levels and the circulation flow path that have occurred after the large scale pumping that has taken place over the 20 a period. In addition, the identification of major groundwater geochemical characteristics and the determination of controlling processes responsible for downgradient changes in water chemistry lead to an improvement of the knowledge of the LTSA baseline and hydrogeological functioning in terms of dynamics of groundwater flow.

Geological and hydrogeological setting

The LTSA forms an important aquifer on the eastern limb of the Paris Basin, in eastern France. It provides water supply to a number of large towns in the Lorraine region, where it is the most important reservoir. The LTSA is used as a water supply (drinking water and farming and industrial uses), for underground gas storage, for the thermal water industry and geothermal energy production. It has been intensely exploited by large scale pumping which began in the 1970s and created a significant decrease in head level. In the Sarre area groundwater flow is greatly influenced by coal mine exploitation (natural outlet and water pumped out of coal mines). Land use is dominated by farming (arable and livestock), although industrial areas are present around some large towns. The western and northwestern portions of the aquifer suffer from naturallypoor water quality and there is less abstraction than in the more easterly areas. Most of the area is covered by Mesozoic deposits (upper Trias and Lias) with low permeability. The recharge of the LTSA only occurs through the outcropping zones, so the Mesozoic cover provides groundwater with protection from anthropogenic inputs. The current impact could be from diffuse or wide-spread pollution sources from agricultural or industrial activities in the areas of outcrop.

Geological features

In eastern France, the lower Triassic is mainly represented by sandstones and conglomerates which crop out along the western border of the Vosges Mountains. Being 500 m thick in the outcropping areas, they become gradually deeper lying and thinner towards the centre of the Paris Basin (Fig. 1). The lower Triassic sandstones comprise with decreasing age (Fig. 2): (1) Annweiler sandstones, red or grey-red fine grained quartzitic and feldspathic sandstones up to 60 m thick that often contain dolomitic nodules and Mn coatings, (2) Vosges sandstones, 300-400 m thick pink sandstones, locally feldspathic, Fe-cemented, with an uppermost conglomerate facies, (3) intermediate layers that alternate between coarse feldspathic sandstones (locally called Main Conglomerate), red or green clay beds and compact dolomites, (4) Voltzia sandstones, fine grained micaceous and feldspathic sandstones up to 20 m thick that often contain pyrite. These permeable formations are covered by about 600 m of deposits: (i) succession of shell sandstones, dolomites, marls and calcareous units up to 285 m thick from the Muschelkalk, (ii) marls and clays that contain evaporitic beds from the Keuper and the lower Lias up to 270 m thick. Finally, Triassic formations are covered by Dogger deposits, oolitic limestone interbedded with marls. The Triassic usually overlies Permian formations consisting of argillaceous cemented sandstone and volcanic flows. Locally, evaporitic deposits, and particularly halite, have been recognised in the Permian formations [START_REF] Salado | Nappes des Grès du Trias Inférieur, Etude de la salinité des eaux dans le département de la Moselle[END_REF].

During at least the latter half of the Tertiary, the Vosges Massif has been uplifted by Alpine deformation while the central part of the Paris Basin has been affected by subsidence. This deformation is characterised by anticlinal and synclinal folds arranged in the direction of the Variscan orogeny (SW-NE) and is cut by SSE-NNW major faults.

The aquifer mineralogy is dominated by silica with coatings of carbonated Fe cement (7% on average; [START_REF] El-Ghali | Diagenetic alterations related to marine transgression and regression in fluvial and shallow marine sandstones of the Triassic Buntsandstein and Keuper sequence, the Paris Basin, France[END_REF], and locally clay-enriched, mainly illite and some kaolinite [START_REF] Tournier | Accordance between the K-Ar ages of authigenetic illites and the ages of magnetic overprinting, the case of Triassic sandstones in Alsace (eastern France)[END_REF]. Some muscovite can also be found [START_REF] Surma | Porosity microstructure of a sandstone affected by a normal fault[END_REF]. Diagenetic feldspar is present in some layers (up to 1%) as K-feldspar and albite [START_REF] El-Ghali | Diagenetic alterations related to marine transgression and regression in fluvial and shallow marine sandstones of the Triassic Buntsandstein and Keuper sequence, the Paris Basin, France[END_REF]. The principal conglomerate levels are mainly quartzitic, sometimes covered by fine clayey sandstones including dolomite nodules and local beds of quartz and calcite. The chemical composition of the different kinds of Lorraine sandstones is presented in Table 1.

Hydrogeological features

The LTSA extends from the eastern outcrop zone for about 150 km westward, where it progressively disappears under Jurassic and Cretaceous cover. South of a line running from Vittel to Epinal, crystalline rocks form the substratum. North of this line sandstones usually overlie Permian formations, with the exception of the Sarre-Lorraine anticline crest where they lie over Carboniferous rocks. The crystalline, Carboniferous rocks act as an aquitard, but local connections can exist between Permian and Triassic groundwater. Moreover, the SSE-NNW faults could play a major hydrogeological role by connecting the LTSA with the overlying Muschelkalk shelly sandstones and Dogger oolitic limestone aquifers. On the whole, confined LTSA water losses by upward leakage towards and through the Muschelkalk/Keuper interface are estimated to be only a few mm/a [START_REF] Vaute | Scénarios d'exploitation de la nappe des grès du Trias inférieur dans le département de la Moselle[END_REF]. In the high pumping areas, where drawdown is important, downward leakage can occur which entails a risk of contamination of pristine waters of the LTSA by highly mineralized waters from the overlying formations. For this reason, LTSA water quality cannot be considered as homogeneous. In addition, it must also be pointed out that the high anisotropy of the reservoir could give rise to natural groundwater quality stratification.

The LTSA represents a huge reservoir thanks to its large extent and thickness and to its well developed permeability of mostly interstitial type. A few compact sandstone layers show, in addition, quite important fracture porosity [START_REF] Surma | Porosity microstructure of a sandstone affected by a normal fault[END_REF]. The LTSA area is around 3000 km 2 for the unconfined and 25,000 km 2 for the confined part from which only 6500 km 2 are exploitable, the rest being too heavily mineralized to be used for both drinking and industrial water supplies. The renewal rate was about 0.05% and the abstraction was estimated at about 110 Mm 3 a À1 in 2000. The total volumes of the different kinds of groundwater uses for the year 2000 are summarized in Table 2. It must be noted that more than 90% of the volume abstracted comes from the northern part of the LTSA both in France (79%) and Germany (11.5%). The first boreholes tapping the LTSA were constructed at the beginning of the 19th century; 30 boreholes were designed in the unconfined and confined LTSA between 1900 and 1930. In the north Lorraine Region, from the 1930s, a series of boreholes were drilled to ensure the water supply of the Maginot Line. But it was mainly after 1948, with the development of the coal extraction industry, that the number of boreholes really began to increase rapidly. In the south of the Lorraine Region boreholes were created in the 1960s, around Vittel and Contrexéville, to ensure the development of the mineral and thermal water industry. In addition, numerous boreholes were constructed for drinking water supply [START_REF] Vaute | Scénarios d'exploitation de la nappe des grès du Trias inférieur dans le département de la Moselle[END_REF].

The aquifer storage coefficient varies from 4 Â 10 À4 to 8 Â 10 À5 in the confined part of the aquifer to 5 Â 10 À2 to 5 Â 10 À3 in the outcropping area. The associated transmissivity varies from 0.1 to 10 À3 m 2 /s [START_REF] Maïaux | Aquifères de Lorraine[END_REF]. The permeability is on average between 1 and 5 Â 10 À5 m/s [START_REF] Vaute | Scénarios d'exploitation de la nappe des grès du Trias inférieur dans le département de la Moselle[END_REF] and the effective porosity of the LTSA is around 10-15%. Since the beginning of the 20th century, potentiometric heads have been strongly modified by the dewatering of coal mines close to the German border and by the development of many drinking water supply boreholes. The initial non-modified conditions of the potentiometric surface of the LTSA are not documented because of the rapid development of pumping in the early 1900s. In addition, most of the boreholes tapping the LTSA are designed for pumping and the measurements of the potentiometric levels are not synchronous. As a result, the potentiometric map (Fig. 1) of the LTSA is only schematic. The general direction of groundwater flow is from the south to north (from the Vosges Mountains to the Sarre Region), and from the SW to the NE (from the Meuse River to the Moselle River). The hydraulic gradient varies strongly from 2 Â 10 À2 to 5 Â 10 À3 in the unconfined aquifer (according to the influence of the river drainage and the pumping rate) and from 10 À4 to 1 Â 10 À3 in the confined aquifer.

The main recharge of the LTSA is provided by the precipitation that occurs in the outcropping zone (Vosges and Sarre regions). Rainfall provides the primary input of solutes and should be considered as representative of the minimum baseline concentration.

In the forested zone, throughfall can also be considered as it locally represents water reaching the soil. Table 3 gives the average chemistry of rainfall and throughfall collected in the period from 1986 to 1989 in the Vosges Massif close to the aquifer recharge zone. Bulk precipitation is acidic with dominant ions being SO 2À 4 and NO À 3 that demonstrates anthropogenic aerosol influence during dissolution of atmospheric gases/aerosols [START_REF] Celle-Jeanton | Rainwater chemistry at a Mediterranean inland station (Avignon, France): local contribution versus long range supply[END_REF]. Throughfall water shows the same characteristics although it contains about five times greater concentrations of major ions.

Methodology

In 1979, the first field campaign was carried out by [START_REF] Blavoux | Radiocarbon dating of groundwater of the aquifer confined in the lower Triassic sandstones of the Lorraine region, France[END_REF]. Using a detailed dataset of chemical (major ions) and isotopic measurements ( 3 H, radiocarbon, 13 C, 18 O and 2 H), the authors evaluated the palaeohydrological regime of the LTSA.

The new campaign conducted in 2001 aimed at highlighting the chemical and isotopic variations related to the modification of potentiometric levels and circulation flow paths that occurred after large scale pumping. Detailed chemical (major ions and trace elements) and isotopic ( 3 H, radiocarbon, 13 C, 18 O and 2 H) analysis were performed on 17 regularly pumped boreholes (Fig. 1, Table 4). Field parameters included temperature (T °C), specific electrical conductance (SEC), alkalinity, pH, dissolved O 2 (DO), and Eh were measured as far as possible in anaerobic conditions. Samples were filtered through 0.45 lm membranes and were collected for major and trace element analysis in polyethylene bottles. The aliquot for cation and trace element analysis were acidified to pH < 2 with 1% v/v HNO 3 . Additional samples were collected in glass bottles for stable isotopes and polyethylene bottles for 3 H and 14 C (precipitation method).

Major anions and cations were determined by ion chromatography and atomic absorption spectrometry (Hydrogeology Depart-ment of the University of Avignon); trace elements by ICPMS (British Geological Survey); stable isotope and 14 C analyses were completed both in the Hydrogeology Department of the University of Avignon and the Geochemistry and Isotope Hydrology Laboratory of the University of Paris XI, by mass spectrometry and conventional counting.

Results and discussion

Results of the current sampling are shown in Tables 5 and6. Groundwater well-head temperatures range between 10.6 °C and 32.1 °C. There is good correlation between temperature and well depth (Fig. 3), which indicates that the water is derived from the main horizon of the aquifer without rapid leakage from overlying formations. Therefore in the present study temperature is used as a proxy for depth and also age (see following discussion). This procedure is the same as that adopted for the UK East Midlands aquifer [START_REF] Edmunds | Hydrochemical evolution of the East Midlands Triassic sandstone aquifer, England[END_REF].

SEC varies from 175 to 1289 lScm À1 (Table 5) with a median value of 735 lScm À1 . The reported pH values measured at well head are generally between 6.7 and 8.5. With the exception of two points (Langatte and Moussey with pH of 8.5 and 8.0, respectively), the waters are relatively well buffered at circumneutral pH b Distance from recharge area along the flowlines.

Table 5

Field parameters and water chemistry data.

Well ID [START_REF] Gat | Comments on the stable isotope method in the regional groundwater investigation[END_REF]. Consequently, they provide information on the recharge processes of groundwater and help to resolve questions relating to residence times and origins. The residence time of groundwater in actively circulating systems may range from tens to thousands of years and changing climate should be recorded in palaeogroundwaters. Such climate changes are manifested by a shift in the stable isotope content of precipitation; the use of the isotopic method is then an important tool to distinguish Holocene waters and Pleistocene waters that could circulate in the deeper confined parts of the aquifer [START_REF] Darling | Isotopic evidence for palaeowaters in the British Isles[END_REF]. Late Pleistocene palaeogroundwaters from temperate regions will be isotopically depleted with respect to modern waters and shifted along the Global Meteoric Water Line (GMWL) towards negative values.

Location T (°C) SEC (lS/ cm) Eh (mV) pH HCO À 3 (mg/L) SO 2À 4 (mg/L) Cl À (mg/L) NO À 3 (mg/L) Ca 2+ (mg/L) Mg 2+ (mg/L) Na + (mg/L) K + (mg/l) SiO 2 (mg/l) IB (%) 1 Gélacourt
The nearest relevant IAEA/WMO GNIP station is Karlsruhe for which there is a continuous temporal record of monthly means of 7), all the groundwaters are situated along the GMWL defined by [START_REF] Craig | Isotopic variations in meteoric waters[END_REF]

Carbonate system evolution and carbon isotopes

The total dissolved inorganic C (TDIC) is equivalent to the groundwater HCO À 3 content for the observed pH range. Most samples are close to calcite saturation or clearly oversaturated, with saturation indices SI calcite = À1.47 to 0.22 (Table 8). Guerting and Gélacourt are strongly undersaturated. There is little variation in TDIC although some increase is observed for the most evolved waters (Fig. 5). The slightly higher concentration in HCO À 3 for evolved waters may be caused by carbonate dissolution driven by cation exchange or by incongruent reaction of the carbonate matrix. Since d 13 C content becomes more enriched along the flow line (Fig. 5), alkalinity is more likely to result from carbonate dissolution [START_REF] Elliot | Hydrochemical trends, palaeorecharge and groundwater ages in the fissured Chalk aquifer of the London and Berkshire basins[END_REF].

Ion exchange-induced dissolution of primary marine carbonate of the matrix is also likely to be of limited extent in the aquifer, reflected only in a slight increase in pH for the most evolved waters. Adjustment of HCO À 3 at equilibrium due to incongruent dissolution may be the explanation. Least evolved groundwaters have d 13 C values close to À13‰, in good agreement with simple congruent reaction between dissolved soil CO 2 and the carbonate matrix. Groundwater evolution then takes place generally under closedsystem conditions with respect to atmospheric CO 2 . The enrichment in d 13 C content is then linked to incongruent dissolution reactions of the aquifer matrix under closed-system conditions. Downgradient trends in the C isotopic contents of TDIC show heavier d 13 C values corresponding with diminishing values of 14 C activities towards the centre of the aquifer. Groundwater with more than 50% of modern C after congruent dissolution must be of recent origin and some of these may also contain an input of 14 C from thermonuclear weapon tests. Under closed-system conditions, decay of radiocarbon from an activity of 50% would evolve according to an exponential law. The more evolved waters have clearly undergone incongruent dissolution exchange and/or mixing with an evolved d 13 C-rich TDIC source. Their 14 C specific activities decrease toward insignificant values as d 13 C increases (Fig. 3). Mixed signatures may occur where high 14 C-content waters mix directly with more evolved waters, possibly due to admixing of a rapid flow path from recharge into the aquifer or as a result of a faulty borehole lining giving rise to bypass flow (Blamont). However the site (Saint-Louis) showing this behaviour is an unconfined site and may simply reflect open system evolution (Table 7).

Age calculation

Groundwater residence times based on 14 C activity of TDIC can be estimated provided that dilution of the 14 C by inactive C of the matrix can be evaluated. Many correction models have been proposed which are based on chemical evolution and/or isotope dilution of 13 C/ 12 C derived from soil CO 2 through interactions with aquifer carbonates. The results of age calculation with several models described in the literature are given in Table 9. Ages proposed by [START_REF] Fontes | Determination of the initial activity of the total dissolved carbon. A review of the existing models and a new approach[END_REF], [START_REF] Evans | Some problems in the interpretation of isotope measurements in United Kingdom aquifers[END_REF], [START_REF] Ingerson | Estimation of age and rate of motion of groundwater by 14 C-method[END_REF] and [START_REF] Eichinger | A contribution to the interpretation of 14 C groundwater ages considering the example of a partially confined sandstone aquifer[END_REF] are all in good agreement and provide very similar solutions. The models of [START_REF] Tamers | Validity of radiocarbon dates on groundwater[END_REF], IAEA [START_REF] Salem | Groundwater flow patterns in the western Lybian Arab Jamahiriaya[END_REF] and [START_REF] Mook | Carbon-14 in hydrogeological studies[END_REF] tend to give rise to over-estimations of groundwater residence times.

In this paper, 14 C activities results (Table 7) were corrected using the [START_REF] Fontes | Determination of the initial activity of the total dissolved carbon. A review of the existing models and a new approach[END_REF] model. This model provides an adequate age estimation taking into account the timing of the Last Glacial Maximum (around 18 ka ago) and well adapted to the geochemical reactions experienced by groundwater within the aquifer. Corrections used measured d 13 C values for TDIC and values for soil CO 2 and the mineral phase of À22‰ [START_REF] Fleyfel | Etude géochimique et isotopique du carbone minéral dans un aquifère karstique[END_REF][START_REF] Dever | Approches chimiques et isotopiques des interactions fluides matrice en zone non saturée carbonatée[END_REF][START_REF] Eichinger | Isotopic and geochemical studies investigating the genesis of carbon dioxide content in young ground water resources development[END_REF][START_REF] Merlot | pCO 2 et minéralisation du carbone dans la zone non saturée du site des eaux minérales de Thonon-lesbains[END_REF], and 0‰, respectively. The [START_REF] Fontes | Determination of the initial activity of the total dissolved carbon. A review of the existing models and a new approach[END_REF] model assumes closed-system carbonate reaction, dilution of the aquifer matrix and continued isotopic disequilibrium between dissolved and solid carbonate.

Groundwaters have been sub-divided into unevolved and evolved groundwaters using both a 14 C and d 13 C criteria, which corresponds also to the subdivision into groups with stable isotopes of the water molecule (Table 9). All applied correction models (which are essentially based on isotope dilution) suggest Holocene or modern ages for unevolved waters (with predominantly light d 13 C); their ages range from modern to approximately 8 ka. All of the evolved groundwaters (mostly heavy d 13 C) have modelled ages which suggest Late Pleistocene recharge (Table 10). The oldest modelled ages range from 25 to 30 ka. Fig. 7 shows a good correlation between 14 C model ages and groundwater temperatures. Groundwaters increase in age (Fig. 7) and temperature (Fig. 5) along the main flow line. So temperature appears to be a good index to separate waters according to their maturity and residence time in the aquifer.

The 14 C modelling results match well with d 18 O and d 2 H data, which show a palaeorecharge effect (Fig. 8). Prior to the Last Glacial Maximum, enriched stable isotope values can be observed and indicate warmer climatic conditions corresponding to the interstadial age [START_REF] Jiráková | Palaeorecharge conditions of the deep aquifers of the Northern Aquitaine region (France)[END_REF]. Comparison with d 18 O and d 2 H substantiate the radiocarbon ages. The lighter d 18 O and d 2 H isotopic conditions indicate groundwater recharge at a lower temperature during the late Pleistocene compared with the Holocene and confirm information provided by noble gases on this aquifer [START_REF] Rudolph | Noble gases and stable isotopes in 14 Cdated paleowaters from central Europe and the Sahara[END_REF][START_REF] Rudolph | Utilisation des gaz rares pour la détermination des conditions climatiques lors de la recharge des nappes aquifères profondes. Cas des grès triasiques de Lorraine[END_REF]. The absence of any ages of between 17 and 24 ka BP may provide evidence for the absence of recharge during or around the glacial maximum [START_REF] Darling | Hydrological factors in the interpretation of stable isotopic proxy data present and past: a European perspective[END_REF]), but it is noted that there is also a smaller number of sampling points compared to the whole aquifer area. The depletion in 18 O and 2 H is about 2d and 10d, respectively, which is consistent with other palaeogroundwater studies in Europe [START_REF] Rozanski | Deuterium and oxygen-18 in European groundwaters. Links to atmospheric circulation in the past[END_REF]Huneau, 2000, etc.).

Groundwater characteristics from major ions and statistical information 4.2.1. Major chemical characteristics

Datasets for major, minor and trace elements are presented using cumulative probability plots [START_REF] Shand | The baseline inorganic chemistry of European groundwaters[END_REF]i n order to consider statistical distributions and to help discriminate geological and geochemical controls on the groundwater compositions (Fig. 9). It appears that the baseline quality of the groundwater in the LTSA is represented by a wide range of concentrations mainly dominated by water-rock interactions. Moreover Fig. 9 shows that Ca 2+ and HCO À 3 are the major constituents for 40% of the groundwater samples characterised by low mineralization (TDS). For the highest TDS, contributions of SO 2À 4 ,C l À and Na + increase; they become the major constituents in association with HCO À 3 . This is confirmed by major element distributions shown on the Piper diagram (Fig. 10); the groundwaters in the LTSA vary from Ca-HCO 3 and Ca-Mg-HCO 3 to Na-Cl types. Kirschnaumen is the exception with a Ca-SO 4 -HCO 3 type.

A principal component analysis (PCA) was carried out to support the relationships between chemical and isotopic variables and distance to recharge area. The two principal axes of PCA explain 69% of the sampling variance. Axis 1 (39%) opposes Na + , Cl À ,K + , distance to recharge area and temperature to d 18 O‰. Axis 2 is defined by Ca 2+ ,S O 2À 4 ; HCO À 3 and Mg 2+ . Two groups of water can be discriminated. Group I is characterised by the highest NO À 3 content, which suggests a short residence time within the aquifers. Group I also has the highest Ca 2+ ,S O 2À 4 ; HCO À 3 . The Kirschnaumen borehole is characterised by the highest value of NO À 3 (14 mg/L) and SO 2À 4 (314 mg/L) that could define an anthropogenic origin for both SO 2À 4 and NO À 3 . However the increase in both Ca 2+ and SO 2À 4 as well as Sr 2+ (Fig. 5) could be due to gypsum dissolution with a possible downward leakage from the Middle Triassic marls and clays. Conversely, Group II shows the greatest distances to recharge area, which suggests a long residence time within the aquifer. These waters also have the highest Na + and Cl À contents that are closely associated with halite dissolution. So the groups discriminated with PCA show different chemical facies according to increasing distance to the recharge area.

Evolution along the main flow direction

According to the results obtained with the PCA, sites have been projected onto a single line following the flow direction from the recharge area in the Vosges Mountains to the Luxembourg border (Fig. 1). The well depths or rather the intervals from which the water is derived are between 120 m in the recharge area to over 800 m in the deepest western part of the study area, close to the Nancy-Metz line.

Groundwater well-head temperatures increase from around 10 °C in the recharge area to greater than 30 °C at depth (Fig. 3). Groundwater chemistry also evolves along a flow path as shown in Fig. 5. Shallow and intermediate depth groundwater in the south has low mineralization (TDS). At greater depth, in the northern part Table 9 A 0 activity of 14 C calculated according to different correction models: [START_REF] Tamers | Validity of radiocarbon dates on groundwater[END_REF], [START_REF] Ingerson | Estimation of age and rate of motion of groundwater by 14 C-method[END_REF], [START_REF] Mook | Carbon-14 in hydrogeological studies[END_REF], [START_REF] Fontes | Determination of the initial activity of the total dissolved carbon. A review of the existing models and a new approach[END_REF], IAEA [START_REF] Salem | Groundwater flow patterns in the western Lybian Arab Jamahiriaya[END_REF], [START_REF] Evans | Some problems in the interpretation of isotope measurements in United Kingdom aquifers[END_REF], [START_REF] Eichinger | A contribution to the interpretation of 14 C groundwater ages considering the example of a partially confined sandstone aquifer[END_REF] of the area, groundwater mineralization increases and as it becomes enriched in Na + and Cl À . Chloride can be regarded as geochemically inert and its concentration and variation should be source-related: atmospheric inputs, anthropogenic inputs or mixing with formation waters or evaporites within the aquifer may give rise to changing Cl concentrations which should indicate significant recharge/mixing boundaries in the aquifer. Close to the outcrop area of the LTSA, Cl À concentrations represent input concentrations from atmospheric sources after allowing for evaporative concentration with values between 2.5 and 18.8 mg L À1 in good agreement with the results observed by [START_REF] Edmunds | Residence time indicators in groundwater: the East Midlands Triassic sandstone aquifer[END_REF] for the East Midlands Triassic Sandstones. It must be noted that the recharge area of the LTSA is covered by the Vosges forest composed of about 70% evergreen trees providing perennial canopy. This kind of land cover is known to collect aerosols during dry periods [START_REF] Appelo | Geochemistry, Groundwater and Pollution[END_REF] and to increase Cl inputs as clearly shown in Table 3 by the throughfall input compared to rainfall input.

The Na + and Cl À concentrations range from 1.6 to 302 mg/L and from 2.6 to 522 mg/L, respectively (Table 5). The strong correlation between these two elements (R = 0.98, Fig. 3) suggests dissolution of halite in the confined part of the LTSA which is supported by Fig. 5. Sources include evaporite deposits, mainly composed of anhydrite and gypsum but also of halite, from the overlying formations and Permian formations that contain local deposits of halite (Fig. 2). A strong correlation exists between depth of boreholes and concentrations of Cl À and Na + (Fig. 3). Tomblaine and Hellimer, two of the deeper boreholes of the study area (708 m and 800 m, respectively, Table 4), have the highest concentrations in Na + (301 mg/L and 170 mg/L, respectively, Table 5) and Cl À (522 mg/L and 330 mg/L, respectively, Table 5) and moderate concentrations in SO 2À 4 and Ca 2+ (Table 5). Their content of Cl À and Na + seems to be influenced by waters circulating within Permian formations [START_REF] Salado | Nappes des Grès du Trias Inférieur, Etude de la salinité des eaux dans le département de la Moselle[END_REF].

Although relatively inert, Br À may be slightly enriched or depleted relative to its ratio to Cl À in sea water as a result of various physical or geochemical processes and the Br/Cl ratio may be used to determine likely origins and evolution of groundwater and to constrain the interpretation of Cl À contents [START_REF] Edmunds | Bromine geochemistry of British groundwaters[END_REF]. In the case of LTSA, a strong depletion of Br/Cl ratios below 0.001 con-firms the dissolution or addition of Cl À from evaporite sources (Table 5).

Sulphate concentrations are variable (Fig. 5), an increase from 1 to around 313 mg/L occurs from the recharge area to Luxembourg. Close to the LTSA outcrop area, the Kirschnaumen and Dalem boreholes have high SO 2À 4 concentrations correlated with high Ca 2+ (Fig. 3), indicating preferential gypsum or anhydrite dissolution. This gypsum or anhydrite dissolution could also occur along the flow line (Rodalbe, Bathélémont). This process concerns mainly shallow and intermediate depth groundwater and so seems directly related with waters circulating at the contact with overlying formations (Muschelkalk and Keuper evaporitic deposits).

The downgradient evolution of silica concentrations is shown in Fig. 5. Silica is rapidly released by water-rock interaction with silicate minerals but the upper concentrations are controlled by slower equilibration with silica polymorphs. Groundwaters are all above quartz saturation and exhibit Si concentration from about 14 to 24 mg/L quite well correlated with distance from the recharge area and thus with residence time. Calculations using PHREEQ-C [START_REF] Parkhurst | User's guide to PHREEQC (version 2). A computer program for speciation, batch-reaction, one dimensional transport, and inverse geochemical calculations[END_REF] indicate that all groundwaters are clearly oversaturated with quartz and slightly undersaturated or at equilibrium with chalcedony, which is the likely main control. The good correlation with temperature indicates that silica could be used as a geothermometer.

The systematic increase of Li (Fig. 5) across the aquifer could be due to the diagenesis of clay minerals [START_REF] Edmunds | Residence time indicators in groundwater: the East Midlands Triassic sandstone aquifer[END_REF]. However, the high concentration ([Li+] = 600 lgL À1 )o f Tomblaine (not shown on the graph), can be linked with the dissolution of evaporites. Rubidium/K and Cs/Rb ratios are relatively constant along the flow path attesting to a similar pathway downgradient for the three elements suggesting an increase of groundwater residence time within the aquifer. Potassium concentrations are dominated by reactions between groundwater and K-bearing mineral phases such as K-feldspar and clays. Increases of Rb and Cs are considered to be linked primarily to the alteration of the K-feldspar with the trace cations being retained in the groundwater.

Sources of Ba also include K-rich minerals such as K-feldspar, biotite and barite. Solubility is controlled by saturation with respect to barite. Barium concentrations in the LTSA remain low and are at or close to saturation throughout the aquifer (Table 8), the smooth increase along the flow line is only a reflection of the adjustment of the equilibrium to the concentrations of SO 2À 4 . The reactions of carbonate minerals may be followed by means of pH, HCO À 3 ,C a 2+ and Mg 2+ as well as some trace elements (Sr 2+ ) and the stable isotope ratio d 13 C. Calcium, Mg 2+ and HCO À 3 concentrations are variable (Fig. 5, Table 5). The positive correlation between HCO À 3 and Ca 2+ (R = 0.88) indicates the occurrence of calcite dissolution in the aquifer. So the dissolution of calcite and dolomite provides the initial dominant control. Most groundwaters are at or above calcite and dolomite saturation (Table 8). This may be an effect of the well-head pH measurements not reflecting an equilibrium condition; a decrease of 0.5 pH units balancing a loss of CO 2 would bring values closer to saturation. The dissolution of gypsum in these waters should also tend to maintain saturation or over-saturation with respect to carbonate minerals. The Mg/Ca ratio is around 0.5 over much of the aquifer with an equilibrium control slightly lower than that expected if both calcite and dolomite are the controls (0.8: [START_REF] Smedley | Redox patterns and trace-element behaviour in the East Midlands Triassic sandstone aquifer[END_REF]. The d 13 C evolution confirms these observations as d 13 C becomes more positive along the flow direction as the calcite reaction is superseded by that of dolomite [START_REF] Kloppmann | Residence time of chalk groundwaters in the Paris Basin and the North German Basin: a geochemical approach[END_REF][START_REF] Edmunds | Residence time indicators in groundwater: the East Midlands Triassic sandstone aquifer[END_REF]. Strontium is typically derived from water-rock interactions mainly from Ca-rich minerals such as calcite, Ca-rich feldspars or gypsum/anhydrite. The increase along the flow line, as Ca 2+ [START_REF] Hem | Study and interpretation of the chemical characteristics of natural water[END_REF], is due initially to the incongruent reactions of carbonate minerals, but then at depth possibly some of the Sr 2+ may be added by the dissolution of anhydrite or gypsum.

Profiles of major chemical markers of redox processes (Eh, NO À 3 , Fe, U) in the LTSA are put together in Fig. 4. Evolution of these redox sensitive parameters does not show any clear redox boundary but a tendency is however observed. The global evolution of NO À 3 follows Eh variations: NO À 3 concentrations decreases from the outcrop area to below detection <0.1 mg L À1 for the deepest boreholes. A few points show little NO À 3 concentrations probably due to mixing with middle and upper Triassic levels thanks to low quality well casing (Kirschnaumen). Concentrations <5 mg L À1 may reflect both the development of redox conditions able to contribute to the lowering of NO À 3 concentrations and the influence of vegetation able to using up the N in the recharge area. The anthropogenic origin of NO À 3 is not then demonstrated because the throughfall content in the recharge area is slightly less than 5 mg L À1 (Table 3). Dissolved P concentrations in groundwater, data not shown, are closely related to NO À 3 concentrations; anthropogenic sources in-clude inorganic and organic fertilisers, water treatment works and farmyard slurry.

Iron and Mn concentrations are low (Table 6) and originate from primary minerals or secondary oxides and oxy-hydroxides present in most rock types. Primary sources of Fe and Mn include carbonates and silicates. Both Fe and Mn are redox sensitive elements in groundwater, being soluble in their reduced form but forming insoluble oxy-hydroxides under oxidising conditions. The Guerting sample with high Fe concentration, high SO 4 and low Ca (Tables 5 and6) shows that pyrite oxidation could be occurring. The relatively low pH strengthens this hypothesis.

Uranium shows a residence-time-dependant increase in the aerobic ground water, reaching 7 lgL À1 (Table 6). In the deeper part of aquifer, about 40 km from the recharge area, there is a residence time control over the increase and downgradient progress. Concentrations of U are very low due to lower solubility of uranous minerals and to the adsorption of ions onto Fe oxides [START_REF] Smedley | Redox patterns and trace-element behaviour in the East Midlands Triassic sandstone aquifer[END_REF]. This evolution suggests the existence of a redox boundary at about 40 km from the recharge area that is clearly translated in the evolution of U exactly as it is in the case of the East Middlands Triassic aquifer [START_REF] Smedley | Redox patterns and trace-element behaviour in the East Midlands Triassic sandstone aquifer[END_REF].

According to this, boreholes Bathélémont, Tomblaine, Puttigny, Morhange, Rodalbe, Holacourt and Hellimer would show reducing conditions. Arsenic (Table 6) does not show any significant evolution from the recharge area. Concentrations are in excess of the European Water Standards (>10 lg/L) in some places (Tomblaine, Langatte, Hellimer). These concentrations do not seem to be due to waterrock interaction processes within the LTSA; mixing with deeper waters enriched in As may be suggested since many boreholes reach the granitic basement where the Permian beds are missing. It must be noted that high concentrations of As are not correlated with high concentrations of Fe or Mn and that no relationship is observed with residence time.

Groundwater evolution since the 1970s

Evolution in groundwater quantity from 1970 to present and prospective

In 2000, the balance between recharge processes and abstraction for the LTSA was in equilibrium. That was not the situation from 1970 to 1980 when a shortage of 19 Mm 3 a À1 was recorded. Between 1977 and 2000, the total volume of groundwater abstracted from the LTSA has decreased by about 30%. In 2013, after the complete cessation of coal mine pumping, this volume would reach 46% [START_REF] Vaute | Scénarios d'exploitation de la nappe des grès du Trias inférieur dans le département de la Moselle[END_REF]. The evolution of the volume abstracted with time is shown on Fig. 11. The total volume of abstracted groundwater is greater than the natural recharge rate of the aquifer as substantiated by the regular decrease of potentiometric levels, of about 0.5 m/a on average since 1950 in the most affected areas. As a consequence, the lowering of the water table has been estimated as follows: 7-8 m in 10 a close to the Sarre region, 18-20 m in 30 a close to Vittel, more than 40 m in 75 a close to Nancy, 50-150 m close to the German border (Fig. 1). The general groundwater flow varied from a north-eastward direction in 1979 [START_REF] Blavoux | Radiocarbon dating of groundwater of the aquifer confined in the lower Triassic sandstones of the Lorraine region, France[END_REF] to a more uniform northward direction in 1997 [START_REF] Burgeap | Réalisation d'une carte piézométrique de la nappe des grès vosgiens en Lorraine[END_REF]. Such a decrease of the water table is responsible for a strong modification of hydraulic gradients and may entail strong modifications in the origin and age of groundwater [START_REF] Huneau | Differences between hydraulic and radiometric velocities of groundwaters in a deep aquifer: example of the Valréas Miocene aquifer (southeastern France)[END_REF].

Evolution of the residence time indicators from 1979 to 2001

Nine out of the 17 sampled boreholes (Hellimer, Tomblaine, Puttigny, Dieuze, Langatte, Moussey, Saint-Clément, Gélacourt, Morhange) were previously sampled by Blavoux andOlive in 1979 (Blavoux and[START_REF] Blavoux | Radiocarbon dating of groundwater of the aquifer confined in the lower Triassic sandstones of the Lorraine region, France[END_REF] and give the opportunity to compare the evolution in chemical and isotopic content of LTSA groundwater (Table 11).

Stable isotopes of the water molecule and particularly 18 O content show significant evolution between 1979 and 2001 in places where strong evolution of radiocarbon content is observed. This evolution corresponds to decreasing values that can be explained by the participation of more 18 O depleted waters originating from palaeogroundwaters (Pleistocene origin) confined within the LTSA. This evolution can be observed at Puttigny, Dieuze and Moussey. Theoretically a similar evolution should be observed in the 2 H content. However, d 2 H results are more difficult to interpret and this indicator does not seem to be suitable for such a comparison. It must also be pointed out that the method used to evaluate the concentrations in 2 H in 1979 and 2001 are not the same and could lead to some small differences of about 2d maximum. Eight out of the nine boreholes involved in the survey show decreasing radiocarbon content of the TDIC (Table 11) which is the translation of a longer residence time of groundwater within the aquifer probably meaning that older groundwater has moved upgradient under the influence of over-abstraction of the aquifer. This evolution is particularly strong for Morhange, Moussey, Langatte, Dieuze, Puttigny and Tomblaine with a lowering of the radiocarbon activity of about 7-34 pmc. A decrease of about 2 pmc is observed at Hellimer. The borehole of Saint-Clément is the only one in the survey to show stable radiocarbon content from 1979 to 2001. All the boreholes from the central part of the aquifer tend to show strong radiocarbon content evolution in contrast with the boreholes from the unconfined aquifer and from the coalfield of the north of the region.

No clear tendency between potentiometric level evolution and evolution of radiocarbon content of groundwater is found between 1979 and 2001 (Fig. 12). For Morhange, Dieuze, Tomblaine, Puttigny and Moussey, the large decrease in groundwater level, that can reach more than 35 m, is accompanied by significant evolution in groundwater 14 C activity of about 12-34 pmc. This illustrates the participation of old deep confined groundwaters to the flow, enhanced by the lowering of the water table. In other words, the higher the pumping rate, the more the abstraction of old groundwater is encouraged. It is evidence of a progressive decrease in the resource volume. In other sectors (Rodhalbe, Holacourt and Hellimer) the strong lowering of the water table can reach 25-35 m and is not accompanied by a strong evolution in groundwater 14 C activity (slight decrease of 3 pmc maximum). This may reflect more stable conditions of flow within the aquifer, with a better productivity of the aquifer and good recharge conditions. The situ- ation of Langatte borehole is intermediate, with a small decrease of potentiometric level (about 7 m) and a decrease in radiocarbon content of about 7 pmc. Anisotropy of the hydraulic parameters of the reservoir could entail bad conditions of groundwater flow around the borehole or a poor connection of this sector to the rest of the confined aquifer.

In terms of water composition, the baseline is confirmed with a variation from Ca-HCO 3 and Ca-Mg-HCO 3 to Na-Cl types. Variations in the natural chemistry of the two periods follow the same trend: the main control on the baseline quality is the geochemistry of the LTSA and downgradient evolution of chemical parameters is observed with increasing residence time. However concentrations of specific chemical parameters have evolved between 1979 and 2001 (Table 11). An increase in components associated with the dissolution of evaporites (Na + and Cl À ) is evident (cf. Section 4.2). This phenomenon appears to have been accentuated in areas of high pumping, where the drawdown is important, close to Mohrange, Saint-Clément, Puttigny, Tomblaine and could be explained by an increase in the residence time. A few places (Dieuze, Langatte, Moussey) show relative stability of these major indicators.

Very low NO À 3 concentrations are found in a few cases at boreholes where previously it was undetected. Thus Hellimer, Puttigny, Langatte, Moussey, Saint-Clément, Gélacourt show NO À 3 concentrations from 1.2 to 4.7 mg/L. Limited mixing between deep groundwater and surface waters is thus suspected in many places and could potentially represent a threat for the long term quality of groundwater.

Only one borehole (Gélacourt) displays a global decrease in dissolved content (HCO À 3 ; SO 2À 4 ,C l À ,C a 2+ ,M g 2+ ,K + ). This could reflect the influence of strong mixing between deep groundwater and superficial waters characterised by low mineralization. As the concentration of NO À 3 measured in this point is low, the mixing implies sub-surface waters instead of surface waters. The poor condition of the well casing may account for the infiltration of these sub-surface waters towards the deeper parts of the borehole and the screen.

Conclusions

The Triassic Sandstone Aquifer of Lorraine represents a huge reservoir, mostly confined, overlying Permian formations and locally Carboniferous and crystalline rocks. Baseline quality of the groundwater is represented by a wide range of concentration, mainly dominated by water-rock interaction. Based both on chemistry and isotopes, two groups varying from Ca-HCO 3 and Ca-Mg-HCO 3 to Na-Cl types and from Holocene to late Pleistocene age, are clearly identified, according to depth and distance to recharge areas. Along the flow path, from unconfined to confined aquifer, an increase in most of the chemical parameters is observed (Ca, K, Sr, Li, Rb, Cs, ...). This general trend is correlated with the evolution of groundwater residence time and is very close to the conceptual model developed for the East Midlands Aquifer, UK, which shows similar geological and hydrogeological patterns compared to the LTSA. However some differences occur. Thus, concentration of several ions, namely Na + and Cl À (and locally SO 2À 4 ), increase downgradient as a result of dissolution of evaporites, related to water circulating along overlying or basement formations, or by mixing with slowly moving Permian waters. Moreover, young groundwater in the unconfined area of the East Midlands Aquifer has suffered from the effects of pollution, while water farther downdip predates pollution inputs [START_REF] Smedley | Redox patterns and trace-element behaviour in the East Midlands Triassic sandstone aquifer[END_REF]. In the LTSA, only limited contamination is noted for NO À 3 with values varying from 1.2 to 14.3 mg L À1 .

Groundwater evolution since the 1970s has created a strong lowering of the water table in some places, especially in the con-fined section of the aquifer, which is accompanied by a significant evolution in groundwater age. The major difference in terms of baseline evolution is observed on Cl À and Na + concentrations, which tend to increase in the LTSA. This evolution can reach and even exceed the upper limit of the drinking water standards for the two latter parameters close to the town of Nancy (increase of 216 mg L À1 in Cl À and 70 mg L À1 in Na + ). From the contaminant point of view, the occurrence of increasing NO À 3 should be mentioned in the unconfined part of the aquifer. Even if the concentrations are very low, NO À 3 contamination should be closely monitored. Thus, since the aerobic sections are extensive, NO À 3 could provide information on progress of any contamination.

The over-exploitation of the aquifer has led to the design of a new management tool, which includes the creation of an accurate database of all boreholes tapping the LTSA, including the description of the well characteristics, the history of the potentiometric head and main hydrogeochemical information. A transient mathematical model of groundwater flow has been set up and updated in 2004 [START_REF] Vaute | Scénarios d'exploitation de la nappe des grès du Trias inférieur dans le département de la Moselle[END_REF], based on hydrogeological data of 2000. Considering application of regulations, different scenarios provide a basis for estimating the recovery of the equilibrium between recharge and pumping.

The Water Framework Directive (2000/60/EC) set out requirements for the European Commission to propose further laws to protect against water pollution. A 'daughter directive' aimed at protecting groundwater has recently been adopted at European level. The Water Framework Directive sets objectives for groundwater quality, including an objective to meet ''good chemical status" by 2015, an objective on pollution trends, and an objective to prevent or limit the input of pollutants to groundwater. Clarification of the objectives, however, is left to the daughter directive. A groundwater directive was proposed by the European Commission in September 2003. It focused on the objectives mentioned above but required further development to ensure that it was practical, effective, risk-based and proportionate. Co-decision on the text for the new directive was reached in October 2006 and the directive was adopted on 12 December 2006 (2006/118/EC). Member States have until January 2009 to bring into force laws, regulations and administrative provisions to implement the new Directive.

In this text, the obligation to member states to develop monitoring tools to identify ''significant and sustained upward trend" is clearly expressed in Article 5. Identification of any statistically and environmentally significant increase of concentration of pollutant, group of pollutants or indicator of pollution in groundwater for which trend reversal is identified as being necessary in accordance with Article 5. The results of the present study show that some chemical or isotopic measurements can be of benefit in such monitoring programmes. Once the overall geochemistry of the aquifer is understood, only a few key elements, namely Na + , SO 2À 4 ,C l À , 18 O, indicators of disequilibrium with increasing or decreasing proportion of overlying or deep water, require to be measured.

Fig. 1 .

 1 Fig. 1. (a). Geological cross-section of the Lorraine Triassic Sandstones and associated formations. Selected boreholes are also indicated, showing their respective depth of penetration in the LTSA. The section runs west to east and sampled boreholes are projected onto the line of section. (b) Location map of the LTSA study area showing the outcrop area and the equipotential lines for 1979 and 1997. Numbered sample sites refer to sample numbers in Tables.

Fig. 2 .

 2 Fig. 2. Lithologic column of the Trias formations of the Lorraine Basin.

  d 18 O and d 2 H for rainfall covering the period 1981-2001 (IAEA/WMO, 2006). The d 18 O and d 2 H compositions of groundwater range from À8.19‰ to À10.81‰ and from À57.1‰ to À72.9‰, respectively. In the d 2 H versus d 18 O diagram (Fig. 6, Table

  and along the Karlsruhe Local Water Line. A mixing line could be observed between two extreme values ([À8.5 d 18 O‰, À57 d 2 H‰]; [À10.4 d 18 O‰, À67 d 2 H‰]). The more enriched isotopic compositions correspond to modern waters that are sampled near the recharge zone (615 km). These values are close to the weighted mean values for modern rainfall in Karlsruhe (d 18 O=À8.11‰, n = 245, r = 2.48 /d 2 H=À57.17, n = 245, r = 19.39). The more impoverished waters are about À2 d 18 O‰ and À10 d 2 H‰ lighter than modern rainfall and must represent a cooler regime. Intermediate d 18 O and d 2 H values (Hellimer, Langatte, Saint-Clément and Gélacourt) can be explained by a mixing between Pleistocene and Holocene waters. Corresponding low 14 C activities and low NO À 3 concentrations in these boreholes reinforce this hypothesis.

Fig. 3 .

 3 Fig.3. Plots of groundwater T °C, Na + and Cl À against depth for the LTSA. Relationship between d 13 C/a 14 C, Ca 2+ /HCO À 3 ,M g 2+ /Ca 2+ ,C a 2+ /SO 2À 4 ,N a + /Cl À .

Fig. 4 .

 4 Fig. 4. Downgradient trends for redox parameters NO À 3 , Fe, U, Eh.

Fig. 5 .

 5 Fig. 5. Downgradient trends for HCO À 3 ,C a 2+ , d 13 C, SiO 2 ,L i + ,T°C, TDS, SO 2À 4 ,C l À and ratios Sr/Ca, Rb/K, Cs/Rb.

Fig. 6 .

 6 Fig. 6. d 18 O versus d 2 H for the LTSA. World meteoric water line (Craig, 1961) and Karlsruhe meteoric water line have been plotted (IAEA/WMO, 2006), weighted mean isotopic content of Karlsruhe precipitation is represented by a triangle.

Fig. 7 .

 7 Fig. 7. (a) Temperature versus 14 C model age in the LTSA. (b) 14 C model (Fontes and Garnier, 1979) age (a) versus distance to recharge area (km).

Fig. 8 .

 8 Fig. 8. Plots of d 18 O and d 2 H against 14 C model (Fontes and Garnier, 1979) age (a).

Fig. 9 .

 9 Fig. 9. Cumulative probability plots for major ions and trace elements in the LTSA.

Fig. 10 .

 10 Fig. 10. Piper diagram for the selected boreholes of the LTSA. Numbered sample sites refer to sample numbers in Tables.

Fig. 11 .

 11 Fig. 11. Evolution of drinking water and industrial water supplies and dewatering volumes of coal mines since 1968 (after Vaute, 2004).

Table 1

 1 Chemical compositions of different Vosges sandstones: (I) siliceous sandstone, (II) conglomerate, (III) clay-enriched sandstone (after[START_REF] Probst | Evidence of spring water acidification in the Vosges Mountains (North-east of France). Influence of bedrock buffering capacity[END_REF].

	%	SiO 2	Al 2 O 3	Fe 2 O 3	FeO	MnO	MgO	CaO		Na 2 O		K 2 O		Tio 2	P 2 O 5	L.I.
	I	94.90	3.64	1.00	-	<0.01	0.07	<0.01		0.02		2.45		0.05	-	0.69
	II	91.19	3.75	0.69	0.53	0.02	0.66	-		0.20		1.30		0.16	0.02	1.33
	III	81.30	7.06	1.60	-	0.01	0.30	0.87		0.21		4.40		O.41	-	3.20
	Table 2							Table 3
	Volume of the different kinds of groundwater uses and their locality for the year 2000	Mean rainfall and throughfall compositions (after Probst et al., 1992).
	(after Vaute, 2004).		Region		Mm 3 a À1	%	mg L À1 Rainfall	pH 4.5	Na + 0.29	K + 0.11	Ca 2+ 0.33	Mg 2+ 0.06	Cl À 0.49	SO 2À 4 2.06	NO À 3 1.81	NH þ 4 0.45
	Drinking water -industrial water	Sarre (Germany)	10.43	9.4	Throughfall	4.1	0.96	1.93	1.26	0.22	2.03	7.46	4.36	0.58
				Moselle		49.68	44.9
				Meurthe-et-Moselle	4.26	3.9
				Vosges		6.24	5.6
	Dewatering of coal mines		Sarre (Germany)	2.29	2.1
				Moselle		37.67	34.1
	Total					110.57	100

Table 4

 4 Well locations.

	Well ID	Location	Date of sampling	X a (km)	Y a (km)	Z a (m)	Depth (m)	Distance b (km)
	1	Gélacourt	03/07/2001	924,775	2,395,919	279	225	10
	2	Saint-Clément	03/07/2001	915,444	2,401,152	250	319	20
	3	Blamont	05/07/2001	933,229	2,408,812	267	243	11
	4	Moussey	04/07/2001	927,209	2,417,931	240	340	22
	5	Bathélémont	05/07/2001	906,622	2,418,790	256	550	43
	6	Tomblaine	05/07/2001	885,353	2,416,786	204	708	49
	7	Saint-Louis	03/07/2001	959,107	2,423,302	227	122	0
	8	Langatte	02/07/2001	940,278	2,427,163	255	360	16
	9	Dieuze	29/06/2001	922,541	2,431,899	210	820	34
		Puttigny	29/06/2001	909,753	2,435,881	210	850	47
		Morhange	29/06/2001	914,936	2,444,424	245	800	48
		Rodalbe	29/06/2001	919,194	2,444,064	268	428	44
		Holacourt	28/06/2001	906,091	2,449,258	232	759	57
		Hellimer	28/06/2001	928,717	2,453,347	228	800	43
		Guerting	27/06/2001	913,525	2,474,150	230	143	0
		Dalem	27/06/2001	910,476	2,479,963	238	120	0
		Kirschnaumen	26/06/2001	896,415	2,498,723	320	290	0
	nd: Not determined.

a Lambert II ''étendu" coordinates.

Table 6

 6 Selected trace element data (lg/L).

	Well ID Location	P	Al As B	Ba	Br (mg/L) Cs	Cu Fe (mg/L) Li	Mn (mg/L) Mo Pb Rb	Sc	Se Sn	Sr	U	Zn	Br/Cl
	1	Gélacourt	35 1 <20	48.31 0.078	3.81 0.5 0.352	25 0.056	<.1 0.4 12.95 3.25 <.5 0.43	38.38 0.24	8.8 0.0042
	2	Saint-Clément <20 <1 <20	97.04 0.103	5.12 2.1 0.022	37 0.003	<.1 0.9 19.21 3.54 0.6 0.33 392.52 4.84 10.3 0.0009
	3	Blamont	22 10 <20	64.92 0.027	0.71 2.5 0.034	15 <0.002	0.1 0.8 5.19 4.04 <.5 0.51	63.84 0.58	6.3 0.0060
	4	Moussey	<20 4 <20 222.85 0.150	1.29 0.3 0.010	12 <0.002	0.2 <.1 5.38 3.32 0.7 0.57	62.83 7.00	2.4 0.0037
	5	Bathélémont	<20 13 <20 114.01 0.100	4.29 0.6 0.332	51 0.005	0.2 <.1 15.01 4.65 1.0 0.48 514.20 <.05	3.9 0.0006
	6	Tomblaine	<20 20 204 72.81 0.348	8.65 1.6 0.663	600 0.042	4.1 <.1 45.44 5.70 9.7 0.46 2533.42 0.08	3.7 0.0007
	7	Saint-Louis	114 10 <20	43.11 0.015	0.35 3.6 <0.005	13 <0.002	<.1 0.9 3.73 3.37 <.5 0.19	19.27 1.04 12.9 0.0059
	8	Langatte	67 18 <20 125.01 0.243	1.12 1.7 0.057	13 0.003	0.4 0.5 4.37 4.12 <.5 1.10	40.27 2.68 77.3 0.0011
	9	Dieuze	<20 8 <20	81.95 0.080	1.63 4.4 0.005	23 <0.002

0.2 0.2 7.74 3.95 0.8 0.21 119.15 4.03 13.6 0.0006 10 Puttigny <20 6 26 73.30 0.214 1.85 1.0 0.038 88 0.016 1.0 0.1 13.94 5.92 0.5 0.17 421.32 <.05 4.0 0.0011 11 Morhange <20 2 <20 93.08 0.051 1.93 1.6 0.008 46 <0.002 0.4 1.0 12.78 4.67 <.5 0.31 242.75 <.05 7.5 0.0005 12 Rodalbe <20 4 <20 95.89 0.142 2.45 1.2 0.074 31 0.009 0.4 1.2 9.58 5.75 <.5 0.21 326.44 <.05 5.9 0.0008 13 Holacourt 28 5 24 62.69 0.134 2.32 1.0 0.272 93 0.009 0.5 <.1 18.46 5.47 1.1 0.42 785.17 <.05 11.2 0.0007 14 Hellimer <20 14 <20 181.74 0.300 3.13 3.3 0.011 45 0.016 0.5 <.1 12.5 6.28 0.6 0.14 667.50 <.05 4.5 0.0009 15 Guerting 31 6 <20 71.17 0.030 0.68 0.4 5.480 8 0.223 <.1 0.2 6.09 4.62 <.5 0.55 51.79 <.05 256.3 0.0042 16 Dalem 29 1 33 85.96 0.031 1.32 1.3 0.053 20 0.038 0.5 8.5 9.66 4.26 <.5 0.31 606.20 1.50 470.2 0.0034 17 Kirschnaumen <20 <1 54 25.12 0.086 3.55 2.5 0.059 35 0.003 1.2 0.1 15.01 5.48 0.5 0.26 1081.72 1.21 34.3 0.0057

Table 8

 8 Saturation indexes for commonly occurring minerals calculated using PHREEQ-C for groundwaters in the LTSA.

	Well ID	Location	Barite	Celestite	Gypsum	Quartz	Chalcedony	Calcite	Dolomite
	1	Gélacourt	À0.39	À3.79	À2.92	0.44	À0.02	À1.47	À2.93
	2	Saint-Clément	0.12	À2.48	À1.95	0.40	À0.05	À0.08	0.11
	3	Blamont	À0.95	À4.26	À3.34	0.44	À0.02	À0.46	À1.02
	4	Moussey	0.01	À3.77	À2.97	0.36	À0.09	0.00	0.15
	5	Bathélémont	0.02	À2.37	À2.01	0.35	À0.07	0.22	0.52
	6	Tomblaine	0.00	À1.47	À1.65	0.06	À0.35	0.04	À0.11
	7	Saint-Louis	À1.50	À5.22	À3.88	0.48	0.01	À0.95	À2.03
	8	Langatte	À0.01	À3.80	À3.21	0.36	À0.08	0.05	0.06
	9	Dieuze	À0.22	À3.17	À2.49	0.36	À0.06	À0.05	0.03
	10	Puttigny	0.15	À2.10	À1.81	0.36	À0.05	0.16	0.28
	11	Morhange	À0.04	À2.69	À2.22	0.38	À0.03	À0.13	À0.15
	12	Rodalbe	0.03	À2.54	À2.23	0.39	À0.04	0.03	0.17
	13	Holacourt	0.11	À1.87	À1.71	0.37	À0.05	0.11	0.12
	14	Hellimer	0.24	À2.21	À2.03	0.35	À0.06	0.21	0.55
	15	Guerting	0.21	À3.31	À2.22	0.54	0.06	À1.19	À2.63
	16	Dalem	0.49	À2.00	À1.48	0.45	À0.02	À0.48	À1.40
	17	Kirschnaumen	0.21	À1.42	À0.88	0.53	0.07	À0.07	À0.61

  .

			Tamers	Pearson	Mook	F&G	IAEA	Evans	Eichinger
	Unevolved groundwater
	3	Blamont	53.8	66.8	105.9	75.5	112.0	66.0	64.7
	7	Saint-Louis	56.3	63.6	100.7	69.0	109.9	63.1	61.2
	15	Guerting	64.6	56.3	79.4	56.2	99.4	55.9	50.4
	16	Dalem	67.2	56.1	75.5	56.0	98.1	55.6	48.8
	17	Kirschnaumen	62.9	58.5	84.1	58.4	100.3	57.8	53.8
	Evolved groundwater
	2	Saint-Clément	55.9	46.5	73.1	46.2	75.3	44.8	42.5
	4	Moussey	51.1	59.5	96.0	64.7	96.6	58.2	57.1
	5	Bathélémont	53.1	46.9	73.9	46.5	70.7	44.0	43.4
	6	Tomblaine	56.4	38.5	61.1	37.5	57.2	34.9	32.6
	8	Langatte	50.3	50.5	84.6	50.7	82.2	49.0	48.0
	9	Dieuze	51.6	54.6	86.1	56.2	84.8	52.6	52.1
	10	Puttigny	51.6	42.5	69.9	42.0	64.1	39.4	39.1
	11	Morhange	53.1	35.6	60.4	34.7	54.3	32.3	31.1
	12	Rodalbe	51.5	39.7	67.2	39.1	61.5	36.9	36.3
	13	Holacourt	52.9	47.8	76.2	47.5	74.0	45.4	44.6
	14	Hellimer	51.4	54.1	83.6	55.5	80.8	51.5	51.7

Table 10

 10 Groundwater age calculation. Modern recharge. Uncertainty: |Dt| = 8267 Á (|DA 0 /F 0 |+|DA t /A t |) year.

			Tamers	±	Pearson	±	Mook	±	F&G	±	IAEA	±	Evans	±	Eichinger	±	nc	±
	Unevolved groundwater
	3	Blamont	5500	230	7300	220	11,100	190	8300	210	11,600	190	7200	220	7000	220	10,600	200
	7	Saint-Louis	6300	230	7300	230	11,100	200	8000	220	11,800	200	7200	230	6900	230	11,000	200
	15	Guerting	2600	220	1400	230	4200	210	1400	230	6100	200	1400	240	500	240	6200	200
	16	Dalem	Modern	140	Mod.	150	Mod.	130	Mod.	150	1700	120	Mod.	150	Mod.	160	1900	120
	17	Kirschnaumen	100	150	Mod.	150	2500	130	Mod.	150	4000	130	Mod.	160	Mod.	160	4000	130
	Evolved groundwater
	2	Saint-Clément	17,200	430	15,700	450	19,400	420	15,600	450	19,700	410	15,300	450	14,900	460	22,000	400
	4	Moussey	15,000	970	16,200	1000	20,100	930	16,900	950	20,200	1000	16,000	960	15,900	960	20,500	930
	5	Bathélémont	30,700	1990	29,700	2000	33,400	1970	29,600	2000	33,000	1970	29,100	2010	29,000	2003	35,900	1950
	6	Tomblaine	30,600	1260	27,400	1290	31,200	1250	27,200	1300	30,700	1260	26,600	1300	26,000	1310	35,300	1230
	8	Langatte	15,300	390	15,200	400	19,500	360	15,300	400	19,300	360	15,000	400	14,800	400	20,900	360
	9	Dieuze	23,600	910	24,000	910	27,800	880	24,200	900	27,600	880	23,700	910	23,600	910	29,000	870
	10	Puttigny	29,900	1260	28,200	1280	32,300	1240	28,100	1280	31,600	1250	27,600	1290	27,500	1290	35,300	1230
	11	Morhange	34,700	2150	31,400	2190	35,800	2140	31,200	2190	34,900	2150	30,600	2200	30,300	2200	39,900	2110
	12	Rodalbe	26,500	1260	24,300	1290	28,700	1250	24,200	1290	27,900	1250	23,700	1300	23,600	1300	31,900	1230
	13	Holacourt	33,700	2840	32,900	2850	36,700	2810	32,800	2850	36,500	2820	32,400	2850	32,300	2850	38,900	2800
	14	Hellimer	26,900	910	27,300	910	30,900	880	27,500	910	30,600	880	26,900	1000	26,900	910	32,300	870
	nc: Not corrected.
	Mod.:

Table 11

 11 Evolution of selected parameters between 1979 and 2001 field campaigns.

	Well ID	Location	d 18 O( ‰)		C l À (mg/L)		Na + (mg/L)		NO À 3 (mg/L)		a 14 C (pmc)
			1978	2001	1978	2001	1978	2001	1978	2001	1978	2001
	4	Hellimer	À10.0	À9.3	313.8	330.0	179.0	170.1	0	2.45	3.9	2.0
	6	Morhange	À10.0	nd	91.0	95.2	18.1	54.3	0	0	15.2	0.8
	8	Puttigny	À9.9	À10.2	193.5	201.2	145.0	151.6	0	1.21	25.4	1.4
	9	Dieuze	À9.9	À10.2	140.2	128.6	82.0	80.2	0	0	17.9	3.0
	10	Langatte	À10.0	À10.0	331.3	223.6	264.0	184.1	0	1.6	15.1	8 .0
	12	Moussey	À10.4	À10.8	57.2	40.8	31.5	31.6	0	1.4	42.4	8.4
	13	Tomblaine	À9.8	À9.8	305.6	522.0	232.0	301.7	0	0	22.8	1.4
	14	Saint-Clément	À9.8	À10.1	112.5	118.0	47.5	58.5	0	4.7	6.9	7.0
	15	Gélacourt	À9.8	À9.8	33.0	18.8	20.2	36.7	0	3.6	11	nd

Fig. 12. Comparison between groundwater potentiometric (H) surface evolution (net drawdown in m) and 14 C content (decrease in pmc).


Benjamin Matuszewski
email: benjamin.matuszewski@ircam.fr

Soundworks A Framework for Networked Music Systems on the Web State of Affairs and New Developments

This paper presents a novel major version of soundworks, a framework dedicated at developing distributed multimedia applications on the web and entirely written in javascript. Since its first release in 2015, the framework has served as a basis for numerous artistic and research projects such as concerts, installations, workshops, teaching or experimental setups. These diverse use cases and situations permitted to validate numerous aspects of the framework but also showed some limitations-particularly in terms of inclusion of non-expert developers such as artists and researchersleading to the novel version presented here.

The paper first presents some applications developed in the last year and show that, despite their idiosyncrasies, recurring problems have emerged during their elaboration and development (e.g. statemanagement). Second, we present new design and implementation aspects of the framework developed to overcome these issues. Finally we describe a simple testbed application-designed to summarize a number of recurring features and constraints encountered in Network Music Systems-and some elements of its implementation within soundworks.

We believe that this novel version will provide solid foundations for the design and implementation of higher-level tools dedicated to non-expert developers, and thereby, foster new artistic, technological and epistemic areas.

INTRODUCTION

The recent specification and development of the WebAudio API-together with other APIs such as WebSockets [START_REF] Wyse | The viability of the web browser as a computer music platform[END_REF] and the developments of ubiquitous computing [START_REF] Weiser | The Computer for the 21 st Century[END_REF] with smartphones and nano-computers-enabled novel possibilities in the area of Networked Music Systems. These novel tools, alongside with the possibilities offered by a full-featured and interactivity-centered language such as javascript permit to envision these technologies from several points of view. First, they can be considered as a new development and a natural extension in the long history of multi-source electro-acoustic music. [START_REF] Taylor | A History of the Audience as a Speaker Array[END_REF] Second, they can provide a novel platform for composition and performance. [START_REF] Bischoff | Music for an Interactive Network of Microcomputers[END_REF] Third, they enable a wide range of possibilities in the creation of new interfaces for musical expression. [START_REF] Poupyrev | New Interfaces for Musical Expression[END_REF] In all cases, these trends tends to show that these technologies-with their simplicity, ubiquity and inherent networked nature-can play a central role in the evolution of Networked Music Systems. [START_REF] Barbosa | Displaced Soundscapes: A Survey of Network Systems for Music and Sonic Art Creation[END_REF][START_REF] Weinberg | Interconnected Musical Networks: Toward a Theoretical Framework[END_REF] In this context, the development of a dedicated framework, adapted to and designed for the specificities of the web platform is essential. In the last years, a number of such frameworks have been proposed by the community. [START_REF] Allison | NEXUS: Collaborative Performance for the Masses, Handling Instrument Interface Distribution through the Web[END_REF][START_REF]Rhizome[END_REF] For now, however, these solutions are far from the maturity of environments such as Max/MSP or PureData. While these environment have developed a number of key concepts along the years, [START_REF] Puckette | The Patcher[END_REF][START_REF] Puckette | Combining Event and Signal Processing in the MAX Graphical Programming Environment[END_REF] we think however that adapting these concepts directly to the web 1, 2 tends to neglect the main specificity of the platform (and the novel possibilities it unfolds): the network. soundworks 3,4 is a framework dedicated to the development of distributed multimedia applications on the web. The initial version of the framework, released in 2015, has been written by S. Robaszkiewicz and N. Schnell. [START_REF] Robaszkiewicz | Soundworks -a playground for artists and developers to create collaborative mobile web performances[END_REF] Since then, the framework has known two major revisions (in 2016 and 2017) and has served as a basis for numerous artistic and research projects (e.g. concerts, installations, workshops, pedagogical or experimental setups). Thereby, soundworks has permitted to explore Network Music Systems in many directions such as: participative performances, use of smartphones as speaker array or as new instruments, measures of movements in collective settings. While these achievements tends to prove the efficacy of the framework considered as an experimental platform, [START_REF] Schwab | Experimental Systems: Future Knowledge in Artistic Research[END_REF] they also permitted to highlight some inherent and recurring difficulties. soundworks#v3 aims to address some of these difficulties as well as to provide solid foundations upon which environments that facilitate the inclusion and agency of non-expert developers can be built.

In Section 2, we review three recent soundworks applications implemented in close collaboration with multiple stakeholders, and present of some of their similarities despite their different aims and goals. In Section 3, we present the main conceptual and technical aspects of soundworks#v3, designed to provide a better support to the recurring needs described in 2. Finally, in Section 4, we describe a simple, yet not trivial, application that we consider representative of recurring aspects of Networked Music Systems, and shortly present elements of its implementation using soundworks.

ACHIEVEMENTS AND RATIONALES

In this section we shortly present three applications that has been designed and used in several contexts (e.g. workshops, performances, installations, scientific experiments) in the last year. These descriptions focus on the features and strategies implemented to support the needs, agency and workflows of non-expert developer users (e.g. artist, researcher, performers) in working situations. We conclude with a formalization of these recurring patterns, leading to the developments presented in section 3.

Elements

Elements5 is an application that has been specifically designed to conceive and prototype movement-based distributed Interactive Machine Learning scenarios. [START_REF] Matuszewski | Designing Movement Driven Audio Applications Using a Web-Based Interactive Machine Learning Toolkit[END_REF] The application has been iteratively tested and developed in several contexts such as workshops, artworks and performances 6 or scientific experiments. 7The key aspects for the appropriation of the application by nonexpert developer users stand in two complementary elements:

• A JSON file dedicated at configuring the different clients in terms of interface, type of synthesis or mapping. • A controller (see Figure 1, left) that allows for both remote monitoring (e.g. plot sensors, decoding of the ML algorithm) and remote control of each client (e.g. mute, volume).

Future Perfect

Future Perfect is an immersive 3D audio visual performance and installation work developed by Garth Paine during a residency that took place in 2018 between Ircam and ZKM. 8 The application allows the composer to perform on the audience smartphone's speakers using several dedicated interfaces. Figure 2 shows the composer in performance situation with three iPads as well as screenshots of the different interfaces designed and used for composing and performing.

In this application, many strategies have been implemented to provide the composer a dynamic environment in which he could test sonic material (i.e. dynamic update of sound files, creation of presets), simply configure many aspect of the synthesis (e.g. granular synthesis parameters, fade times), but also have useful feedback on the state of audience's smartphones (e.g. loading states, position in concert hall). Again, the key elements here were the remote monitoring and control interfaces that enabled a rapid feedback loop in both composition and performance situations.

Biotope

Biotope is an generative and interactive installation composed by Jean-Luc Hervé, realized at Ircam and exposed at the Centre Georges Pompidou, Paris in the context of the exhibition "La fabrique du vivant". 9,10 The installation is composed of 27 Raspberry Pi nano-computers (see Figure 3, left) running soundworks clients written using NodeJs. [START_REF] Matuszewski | Toward a Web of Audio Things[END_REF] The audio synthesis is achieved using a NodeJs wrapper on top of libpd. In this system, many strategies have been implemented to provide a dynamic and testable environment to the composer and to the computer music designer. Among them, the more important ones are: a mean to easily update audio content, and a centralized controller dedicated at both monitoring the state of the application (for example, each square in Figure 3 right, represents a musical agent in its relative position in the exhibition space, the different colors give an overview of their state in real-time) and at controlling the state and parameters of each client in real-time.

Recurring Patterns

We can see that these different examples-which span across a wide range of applications (from experimental system to performance or installation)-share common strategies. First, they all provide a dedicated client that allows to monitor and take control over every client of the system in a simple way. This point stands to be of primary importance to maintain the agency of the user working in a complex setup composed of many devices. Second, they all allow-at different levels of maturity and usability-to update content, mappings and synthesis parameters dynamically or from configuration files. Indeed, these applications implement a similar architectural pattern where the state of each client is synchronized in some way with the server, allowing to update every part of the distributed application from a centralized point.

This pattern-that appeared very effective for implementing versatile and adaptable tools fostering creativity-provide insights on the functionalities our framework must facilitate. More precisely, it shows the necessity of a robust and versatile distributed state management system, aimed at simplifying remote monitoring and control in an environment composed of many devices.

While the presented examples showed the feasibility of creating such systems using the current version of soundworks, the experience showed that these aspects were not properly supported by the framework, leading to overly complicated and redundant architectures. This is these drawbacks that the novel version of soundworks presented in the next section propose to overcome.

DESIGN AND IMPLEMENTATION

In this section, we present some design and implementation aspects of the third version of the soundworks framework. First, we present the scope and high-level aspects of the framework. Second, we describe in more depth the novel state management component that have been introduced to support recurring patterns described in Section 2. We briefly conclude by presenting the motivations and expected benefits of the novel packaging and distribution strategy.

Architecture Overview

Since its inception, soundworks is dedicated at simplifying the development of web-based and distributed real-time musical systems. Figure 4 presents a bird's-eye view of a typical soundworks application. Applications created using soundworks follow a star network architecture centered around a NodeJs server. [START_REF] Matuszewski | Interaction Topologies in Mobile-Based Situated Networked Music Systems[END_REF] Clients can have multiple responsibilities (e.g. audio rendering, visual rendering, control) and be of different kinds (e.g. mobile, desktop, nano-computers). Until now, the framework has mainly focused on mobile applications and has therefore privileged certain caracterictics of these platforms (e.g. graphical user interface, usability). While these aspects remain important, it appears now that-to preserve its efficiency as an experimental platform and to support more and more complex applications and use-cases-the framework must evolve toward more modularity and extensibility, considering both software (e.g. integration of third party components and libraries) and hardware (e.g. integration of IoT elements).

In this objective, the scope of the framework has been refined and narrowed down to focus on three key aspects, namely: communications, service management and state management. As a consequence, some features such as templating, have been removed from the framework and are now delegated to external and specialized libraries. These developments also permitted to reduce the API surface area of the framework.

Communications and Services

While similar in their principles, the communication and service management components have evolved toward more simplicity and efficiency. Figure 5 Indeed, while this approach has already been tested and deployed in a production setting (cf. 2.3), the complete rewriting of the framework permitted to properly integrate it by making most of the code compatible to both platforms. This novel feature should simplify the creation of applications composed of multiple kind of clients (e.g. smartphones and nano-computers), and thus allow to generalize and democratize the concept of web of audio things described in [START_REF] Matuszewski | Toward a Web of Audio Things[END_REF] (note that similar ideas has been proposed in [START_REF] Turchet | Internet of Musical Things: Vision and Challenges[END_REF]).

State Management

An important novel feature of soundworks is the integration of a state management system.

Indeed, since the introduction of the Flux pattern proposed by Facebook, 12 a number of state management libraries 13 have been proposed. The usage of this pattern is nowadays widespread and considered a good practice among the javascript community. However, existing libraries are not firstly designed for distributed applications and are difficult to adapt to our context for two main reasons. First, they do not formalize nor integrate the notion of discrete and volatile events very common in our applications (e.g. triggering a sound). Second, they do not provide out-of-the-box a simple way of synchronizing states across several nodes in the network. 14To tackle these issues, we created a novel protocol and implemented a novel component, inspired by the Flux pattern and adapted to the particular requirements of our applications.

Concepts and Requirements

In the context of real-time, audio-centered and distributed applications, the application of such circular pattern presents certain particularities schematized in Figure 6. The Figure particularly highlights two important requirements and implications for the implementation of this pattern. First, it shows that the state of every client has to be kept synchronized server-side. The rationale for this design strategy (see Section 2 for details) stands in the need to remotely monitor and control any client of the system from a centralized point. Indeed the possibility to dynamically interact with any node of the network, and the rapid feedback loop it enables, is of primary importance in working situations. Furthermore, it appears to be crucial in exploratory contexts (such as artistic and research activities) where the final application cannot be specified beforehand and emerges from a iterative process.

Second, the Figure highlights the need of a certain granularity in the definition and synchronization of the states. Indeed, while some variables and parameters (named globals in the Figure ) needs to be accessible to every client (e.g. master volume, mute), the particular state a client (clients [START_REF] Barbosa | Displaced Soundscapes: A Survey of Network Systems for Music and Sonic Art Creation[END_REF] in the Figure ) should not be shared with all its peers. It only needs to be monitored or controlled by particular types of clients dedicated to authoring and performance situations.

Protocol and API

To fulfill these requirement while preserving the idea of circular flow between actions, data and rendering proposed by the Flux pattern, we designed a simple protocol and implemented a new library. 15 The main principles of the protocol we propose are:

• Allow any node to create a new state from a declared schema.

• Allow to keep the state synchronized with the server.

• Allow any node to observe new states created on the network.

• Allow any node to attach to a state created by another node. A client (we name controller) observes the server and attach to the state created by another client (here, called player). When attached, the controller receives a notification each time the state is updated by its creator (or any other attached node), enabling remote monitoring. The controller can also update values of the attached state, enabling remote control. At any moment, the controller can detach from the state and stop to receive update notifications.

state-management

The protocol is abstracted behind a small and simple API illustrated in the pseudo-code example of Listing 8. This simple example also highlights two interesting aspects of the component:

• The complete abstraction of network communications, allowing users to focus on the application logic rather than routing of network messages. • The possibility to reflect on the schemas' declarations to generate controls and monitoring interfaces, simplifying the implementation of dynamic and complex interfaces.

Distribution: Core and Services

A final aspect that we want to present is the novel approach for the packaging and the distribution of soundworks. The framework is now distributed behind its own npm organization namespace: @soundworks 16 . Furthermore the core of the framework and the different services have been decoupled. 17 As such, services are now imported in the application as plugins that must be registered in the ServiceManager.

We think this modular approach will facilitate future evolutions of the codebase, as well as maintenance of existing applications. Furthermore, this strategy should help to simplify the design and development of new components as well as their testing and documentation.

A TODO(NOISE) APPLICATION FOR DIS-TRIBUTED AUDIO FRAMEWORKS

In this section we describe a simple application, inspired by the TodoMVC project18 , that aims at providing a common basis to test and compare frameworks dedicated at building distributed audio applications. We first present the motivations and features of the application and, second, describe elements of its implementation within soundworks.

User Story

The proposed application purposely privileges the point of view of a user in a working situation (i.e. developer, designer, composer or performer) rather than the point of view of the end user (e.g. participant, audience). Indeed, while the later tends to be very application or artwork specific, we have shown in Section 2 that the former embodies common properties-the need for remote moni-toring and control of the distributed state of the application-that can be reduced to simple features.

To illustrate these features, we have designed a basic application composed of two different clients. The first client, we call player, can be envisioned as the client dedicated to the end users. The application can accept any number of players. Each player has access to the following fonctionalities:

• can trigger a sound • can start and stop a synthesizer • can update a parameter (i.e. volume)

The second client, we call controller, is dedicated to the user in working situation (e.g. design, composition, research, performance). The application can accept any number of controller. A controller can:

• control global parameters of the application (i.e. mute, master volume) • take control over each player (i.e. volume, trigger and state of the synthesizer)

Globals parameters of the application (i.e. mute and master) must stay synchronized across every clients of the application (i.e. player and controller).

We think this minimal set of functionalities provides a good reduction of important and recurring aspects of distributed audio applications. We also believe that it could, after eventual refinements, provide a good basis for testing, demonstrating and compare different frameworks and approaches.

Elements of Implementation

We implemented this application using soundworks (see Figure 9). 19 The experience showed possible to implement all the specified features relying on the state management system described in 3.3, allowing to focus on application logic rather than on network communications and routing. This single fact tends to validate the addition of this component to the core of soundworks. The application is composed of only two schemas:

• The globals schema contains the list of connected player ids, the id of the remote controlled user (if any), the values of the mute and master volume parameters. • The player schema contains the current value of the player's local volume, the state of the synth (started or stopped) and a volatile event dedicated at triggering a sound.

The main logic of the application is implemented in the controller client. Indeed this client (cf. Listing 10), in its subscription to the globals state, observes the value of the remoteControlled parameter and attach to the state of the corresponding player. When attached to the player state, the controller simply instantiate the player's GUI to locally create a remote and synchronized monitor and control interface.

CONCLUSION AND FUTURE WORKS

In this paper, we have presented the motivations, design and implementation of a novel version of soundworks, a framework dedicated at developing distributed multimedia applications on the web. First, we have presented three applications implemented or refined in the last year and discussed some of the recurring difficultiescentered on the point of view of the user in working situation-that the current version of the framework failed to properly address. Second, we have presented the novel architecture as well as a new component dedicated to distributed state management and designed to address these recurring issues. Finally, we have described a simple application-designed on the model of the TodoMVC projectthat summarizes recurring aspects of distributed audio applications, and some elements of its implementation within the new version of soundworks.

While we think this new version provides solid foundations to further explore the possibilities of the web platform for Network Music Systems, it also opens large areas of new developments. First, a cli tool for scaffolding applications would be an important addition. Second, the integration of NodeJs clients in the core of the framework should simplify testing and thus help to stabilize the framework. Third, and more important, it opens many paths for creating a more dynamic working environment, facilitating the inclusion of users with different backgrounds (e.g. artists, researchers) and transdisciplinary approaches.

AKNOWLEDGEMENTS

The presented work has been initiated in the CoSiMa research project funded by the french National Research Agency (ANR, ANR-13-CORD-0010) and further developed in the framework of the Rapid-Mix Project from the European Union'sHorizon 2020 research and innovation programme (H2020-ICT-2014-1, Project ID 644862). It has also been supported by the Ircam project BeCoMe, which is featured in the Constella(c)tions residency of the STARTS program of the European Commission.

We would like to thank our projects partners and our colleagues at IRCAM for their precious contributions to the project.

Figure 1 :

 1 Figure 1: On the left, Elements' controller interface highlighting the different possibilities of monitoring and control. On the right, performance of Cordas composed by Michelle Agnes Magalhaes.

Figure 2 :

 2 Figure 2: On the left, Garth Paine performing Future Perfect. On the right, screenshots of the different interfaces used during composition and performance.

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Figure 3 :

 3 Figure 3: On the left, screenshot of the centralized controller. On the right, photography of the musical agents, running on Raspberry Pi, created for the Biotope installation composed by Jean-Luc Hervé.

Figure 4 :

 4 Figure 4: High-level view of the architecture of a typical soundworks application: clients of various types (e.g. mobile and desktop browsers, embedded hardware running a NodeJs client, external software communicating through OSC or MIDI) connected to a central NodeJs server.

  summarizes the initialization process common to all soundworks clients:• The init step consists in connecting two WebSockets to the server, one dedicated to string (JSON compliant) data and another dedicated to binary data. The API of both sockets is similar and expose a simple publish / subscribe interface. • Once both sockets are connected, soundworks can start the services initialization. As services can depend on each others (for example, the clock synchronization process can rely on a resumed audio context), soundworks takes care of the services' dependency graph and start each service accordingly. • Finally, when all services are in ready state the application specific code (called Experience in soundworks' terminology) can start.

Figure 5 :

 5 Figure 5: Initialization process of a soundworks clients, here a mobile browser and a NodeJs client running in embedded hardware.

Figure 5

 5 Figure5also illustrates a novel feature of the framework that enables the seamless implementation of soundworks clients in any type of javascript environment (i.e. browsers or NodeJs). Indeed, while this approach has already been tested and deployed in a production setting (cf. 2.3), the complete rewriting of the framework permitted to properly integrate it by making most of the code compatible to both platforms. This novel feature should simplify the creation of applications composed of multiple kind of clients (e.g. smartphones and nano-computers), and thus allow to generalize and democratize the concept of web of audio things described in[START_REF] Matuszewski | Toward a Web of Audio Things[END_REF] (note that similar ideas has been proposed in[START_REF] Turchet | Internet of Musical Things: Vision and Challenges[END_REF]).

Figure 6 :

 6 Figure 6: Conceptual overview of a circular and distributed state management system inspired by the Flux pattern. The main addition stands in the necessity to keep states synchronized with the server.

Figure 7 :

 7 Figure 7: Example of the protocol implemented by the StateManager.

Figure 7

 7 Figure7illustrates a generic scenario enabled by this protocol. A client (we name controller) observes the server and attach to the state created by another client (here, called player). When attached, the controller receives a notification each time the state is updated by its creator (or any other attached node), enabling remote monitoring. The controller can also update values of the attached state, enabling remote control. At any moment, the controller can detach from the state and stop to receive update notifications.

Figure 8 :

 8 Figure 8: Pseudo-code example of the main aspects of soundworks state manager API.

Figure 9 :

 9 Figure 9: Interface of the (a.) controller and (b.) player clients of the Todo(Noise) application. Here, the controller duplicates the interface of the player with id 32, allowing for remote monitoring and control of this particular client.

Figure 10 :

 10 Figure 10: Main pseudo-code logic written in the controller to remotely monitor and control any player of the application.

https://github.com/petervdn/webaudiotool

https://github.com/Fr0stbyteR/webaudio-patcher

https://github.com/collective-soundworks/soundworks

https://www.npmjs.com/org/soundworks

https://como.ircam.fr/apps/elements

https://www.youtube.com/watch?v=c6Flruf_Udc

https://www.unige.ch/cisa/emodemos/

https://www.ircam.fr/person/garth-paine/

https://www.ircam.fr/agenda/biotope/detail/

https://youtu.be/RmSujqdT6L0

https://github.com/ircam-jstools/node-libpd

https://facebook.github.io/flux/

For example: https://redux.js.org/ or https://vuex.vuejs.org/

The dop.js (https://distributedobjectprotocol.org/) library propose an interesting approach, however it aims at synchronizing a single state across every node which is not optimal (particularly in terms of bandwidth) in our context.

While the component is for now integrated as a first class citizen in soundworks, it will be abstracted and released as a standalone library in a near future.

https://www.npmjs.com/org/soundworks

https://github.com/collective-soundworks/soundworks

http://todomvc.com/

https://github.com/collective-soundworks/soundworks-todo-noise