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The study of higher-order statistics, particularly three-point statistics, of the Large Scale Structure (LSS) of the Universe provides us with unique information on the biasing relation between luminous and dark matter and on deviations from primordial Gaussianity. As a result, much effort has been put into improving measurement techniques as well as theoretical modelling, especially in Fourier space. Comparatively, little progress has been made, instead, in configuration space analyses. This work represents a first step towards filling this gap by proposing a new strategy for modelling 3-point statistics at higher perturbative orders in configuration space. Starting from the next-to-leading order model for the matter bispectrum, we use 2D- FFTLog to generate its counterpart in configuration space. We calibrate the procedure using the leading order predictions for which an analytic model for the three-point correlation function (3PCF) already exists. Then we assess the goodness of the 3PCF model by comparing its predictions with measurements performed on the matter distribution in collisionless cosmological N-body experiments. We focus on two redshifts (z = 0.49 and z = 1.05) in the range spanned by current and future galaxy redshift surveys. The chi-square analysis reveals that the next-to-leading order 3PCF models significantly improve over the leading order one for all triangle configurations in both redshifts, increasing the number of matched configurations at redshift z = 1.05 and z = 0.49, respectively. In particular, a significant improvement is also seen on the Baryonic Acoustic Oscillations (BAO) scale for triangle configurations whose smallest side length is well into the nonlinear regime. The computational cost of the model proposed here is high but not prohibitively - five hours for 48 cores - large and represents the first step towards a complete 3PC model for the galaxies.

The trace-element geochemistry of speleothems is becoming increasingly used for reconstructing palaeoclimate, with a particular emphasis on elements whose concentrations vary according to hydrological conditions at the cave site (e.g. Mg, Sr, Ba and U). An important step in interpreting trace-element abundances is understanding the underlying processes of their incorporation. This includes quantifying the fractionation between the solution and speleothem carbonate via partition coefficients (where the partitioning (D) of element X (D-X) is the molar ratio [X/Ca] in the calcite divided by the molar ratio [X/Ca] in the parent water) and evaluating the degree of spatial variability across time-constant speleothem layers. Previous studies of how these elements are incorporated into speleothems have focused primarily on stalagmites and their source waters in natural cave settings, or have used synthetic solutions under cave-analogue laboratory conditions to produce similar dripstones. However, dripstones are not the only speleothem types capable of yielding useful palaeoclimate information. In this study, we investigate the incorporation of Mg, Sr, Ba and U into a subaqueous calcite speleothem (CD3) growing in a natural cave pool in Italy. Pool-water measurements extending back 15 years reveal a remarkably stable geochemical environment owing to the deep cave setting, enabling the calculation of precise solution [X/Ca]. We determine the trace element variability of 'modern' subaqueous calcite from a drill core taken through CD3 to derive D-Mg, D-Sr, D-Ba and D-U then compare these with published cave, cave-analogue and seawater-analogue studies. The D-Mg for CD3 is anomalously high (0.042 +/- 0.002) compared to previous estimates at similar temperatures (similar to 8 degrees C). The D-Sr (0.100 +/- 0.007) is similar to previously reported values, but data from this study as well as those from Tremaine and Froelich (2013) and Day and Henderson (2013) suggest that [ Na/Sr] might play an important role in Sr incorporation through the potential for Na to outcompete Sr for calcite non-lattice sites. DBa in CD3 (0.086 +/- 0.008) is similar to values derived by Day and Henderson (2013) under cave-analogue conditions, whilst DU (0.013 +/- 0.002) is almost an order of magnitude lower, possibly due to the unusually slow speleothem growth rates (

In this study, we performed leaching experiments for timescales of hours-to-months in deionized water on fresh volcanic ash from Mt. Etna (Italy) and Popocatépetl (Mexico) volcanos to monitor Fe release as a function of ash mineral chemistry and size, with the aim of clarifying Fe release mechanisms and eventually evaluating the impact of volcanic ash on marine and lacustrine environments. To define sample mineralogy and Fe speciation, inclusive characterization was obtained by means of XRF, SEM, XRPD, EELS and Mössbauer spectroscopies. For Etna and Popocatépetl samples, glass proportions were quantified at 73 and 40%, Fe2O3 total contents at 11.6-13.2 and 5.8 wt%, and Fe3+/FeTot ratios at 0.33 and 0.23, respectively. Leaching experiments showed that significant amounts of iron, ~ 30 to 150 and ~ 750 nmol g-1 l-1 for pristine Etna and Popocatépetl samples, respectively, are released within the first 30 min as a function of decreasing particle size (from 1 to 0.125 mm). The Popocatépetl sample showed a very sustained Fe release (up to 10 times Etna samples) all along the first week, with lowest values never below 400 nmol g-1 l-1 and a maximum of 1672 nmol g-1 l-1 recorded after 5 days. This sample, being composed of very small particles (average particle size 0.125 mm) with large surface area, likely accumulated large quantities of Fe-bearing sublimates that quickly dissolved during leaching tests, determining high Fe release and local pH decrease (that contributed to release more Fe from the glass) at short timescale (hours-to-days). The fractional Fe solubility (FeS) was 0.004-0.011 and 0.23% for Etna and Popocatépetl samples, respectively, but no correlation was found between Fe released in solution and either ash Fe content, glass/mineral ratio or mineral assemblage. Results obtained suggest that volcanic ash chemistry, mineralogy and particle size assume a relevant role on Fe release mostly in the medium-to-long timescale, while Fe release in the short timescale is dominated by dissolution of surface sublimates (formed by physicochemical processes occurring within the eruption plume and volcanic cloud) and the effects of such a dissolution on the local pH conditions. For all samples, a moderate to sustained Fe release occurred for leaching times comparable with their residence time within the euphotic zone of marine and lacustrine environments (variable from few minutes to few hours), revealing their possible contribution to increase Fe bioavailability.

In 2017 we established the first Earth Critical Zone Observatory in Italy, at the high-altitude Nivolet plain in the Gran Paradiso National Park, between about 2500 and 2700 meters asl (CZO@Nivolet). The Observatory is currently equipped with an eddy-covariance tower for CO2 and H2O fluxes; a portable accumulation chamber to measure H2O, CO2, CH4 and H2S fluxes; a double rain gauge for rainfall isotopic studies; soil moisture and hydrometric gauges. Regular samplings of the physical and chemical properties of soil as well as surface and groundwater are performed. The in-situ instruments are complemented by analyses in a suite of geochemical and isotopic laboratories at CNR IGG in Pisa and by analysis of high-resolution satellite images. While the CZO@Nivolet has multiple goals and the instrument pool is continuously upgraded, a specific question we have considered during the first year of activity is whether and how the geological setting and the geological substratum of soils affect carbon fluxes in a mountain prairie above the tree line. To this end, we have identified four plots, each having an average area of about 200 square meters, characterized by different geological substratum: (1) soil on gneiss (the dominant rock type of the Gran Paradiso massif), (2) soil on carbonate rocks, (3) soil over glacial deposits (common to most alpine areas), and (4) alluvial soil near the main stream of the Nivolet plain (Dora del Nivolet). In each plot, we performed on average 30 randomly-positioned flux measurements with the accumulation chamber method, approximately every two weeks from June to October 2017 and measuring both the sum of photosynthesis and respiration (using a transparent chamber) and pure respiration (using an opaque chamber). The preliminary results of the statistical analyses indicate that the carbonate soils behave quite differently from the other three types. A full discussion of the findings and their implications will be given.

Lake Albano was stratified at the time of our survey, in December 1997, in agreement with previous observations [Martini et al., Geochem. J. 28 (1994) 173–184; Cioni et al., Report for the Civil Protection Department (1995); Pedreschi, Accad. Lucch. Sci. Lett. Arti (1995) 39]. In the absence of phenomena induced by seismic activity, either local or regional, lake stratification may be perturbed by cooling of shallow waters below ∼8.5°C. Circulation is expected to homogenize lake waters and eventually to trigger gas exsolution when total gas pressure exceeds hydrostatic pressure. In December 1997, total gas pressure in lake water was very close to atmospheric pressure (0.9–1.3 bar) at all depths, possibly due to the occurrence of a recent episode of circulation and presumed gas exsolution. The state of saturation of Lake Albano waters and the similarity of the relative concentrations of Na, K, Mg, and Ca in lake waters, local groundwaters, and local volcanic rocks indicate that Na, K, Mg, and Ca concentrations in Lake Albano waters are mainly governed by incongruent dissolution of local volcanic rocks, coupled with minor calcite precipitation at shallow depths.

Individual and monthly precipitation samples from the polluted atmosphere of Bologna (Emilia-Romagna province) were collected during March 1996 to May 1997 and analyzed for major ions in solution and S isotopes in dissolved SO4. Weighted mean enrichment factors relative to seawater are found to be 1.0 for Na, 15.2 for K, 105 for Ca, 3.3 for Mg, 17.3 for SO4 and 663 for HCO−3. Very good positive correlations are observed for the Ca2+–Mg2+–HCO−3–SO2−4–NO−3 system, indicating that dissolution of Ca (±Mg)-carbonate particles by H2SO4 and HNO3 from combustion of oil and gas is a major process controlling the chemical composition of rain and snow. Na+ and Cl− in monthly precipitation derive essentially from sea spray, but the contribution of Na+ from continental sources is appreciable in a number of individual rains. NH+4 appears to be on average more abundant in spring and summer precipitation, its main sources being microbial activity in soils and application of fertilizers. K+ is probably of continental origin from soil dust. The S isotopic composition of SO4 is systematically positive, with mean δ34S values of +3.2±1.6‰ (n=40) in individual precipitation and +2.8±1.4‰ (n=12) in monthly precipitation. These isotopic compositions are interpreted in terms of a dominant contribution of S from anthropogenic emissions and subordinate contributions from biogenic and marine sources. Pollutant SO4 is estimated to have a δ34S value in the range +2.5 to +4.5‰, whereas a distinctive δ34S of −4.5‰ or lower indicates SO4 from oxidation of biogenic gases. The isotopic and chemical compositions of SO4 do not depend on wind direction, thus testifying to a mostly local source for pollutant S in the Bologna atmosphere.

A geochemical survey carried out in November 1993 revealed that Lake Quilotoa was composed by a thin (,14 m) oxic epilimnion overlying a ,200 m-thick anoxic hypolimnion. Dissolved CO2 concentrations reached 1000 mg/kg in the lower stratum. Loss of CO2 from epilimnetic waters, followed by calcite precipitation and a consequent lowering in density, was the apparent cause of the stratification. The Cl, SO4 and HCO3 contents of Lake Quilotoa are intermediate between those of acid‐SO4‐Cl Crater lakes and those of neutral-HCO3 Crater lakes, indicating that Lake Quilotoa has a ‘memory’ of the inflow and absorption of HC1- and S-bearing volcanic (magmatic) gases. The Mg/Ca ratios of the lake waters are governed by dissolution of local volcanic rocks or magmas, but K/Na ratios were likely modified by precipitation of alunite, a typical mineral in acid‐SO 4‐Cl Crater lakes. The constant concentrations of several conservative chemical species from lake surface to lake bottom suggest that physical, chemical and biological processes did not have enough time, after the last overturn, to cause significant changes in the contents of these chemical species. This lapse of time might be relatively large, but it cannot be established on the basis of available data. Besides, the lake may not be close to steady state. Mixing of Lake Quilotoa waters could presently be triggered by either cooling epilimnetic waters by ,48C or providing heat to hypolimnetic waters or by seismic activity. Although Quilotoa lake contains a huge amount of dissolved CO2O,3 £ 10 11 gU; at present the risk of a dangerous limnic eruption seems to be nil even though some gas exsolution might occur if deep lake waters were brought to the surface. Carbon dioxide could build up to higher levels in deep waters than at present without any volcanic re-awakening, due to either a large inflow of relatively cool CO 2-rich gases, or possibly a long interval between overturns. Periodical geochemical surveys of Lake Quilotoa are, therefore, recommended. q 2000 Elsevier Science B.V. All rights reserved.

The accumulation chamber methodology allows one to obtain reliable values of the soil CO2 flux, ϕsoil CO2, in the range 0.2 to over 10 000 g m−2 d−1, as proven by both laboratory tests and field surveys in geothermal and volcanic areas. A strong negative correlation is observed between Δϕsoil CO2/Δt and ΔPatm/Δt. Maps of classes of log ϕsoil CO2 for the northern sector of Vulcano Island, Solfatara of Pozzuoli, Nea Kameni Islet and Yanbajain geothermal field evidence that active faults and fractures act as uprising channels of deep, CO2-rich geothermal or magmatic gases. The total diffuse CO2 output was evaluated for each surveyed area.

Two well-equilibrated NaCl geothermal liquids are recognizable in the San Marcos area. Both have the same Cl concentration (540 mg/kg) and the same isotopic composition (δD of −66.5‰ and δ18O of −9‰) under reservoir conditions, but they come from two distinct aquifers with different temperatures, i.e. 240°C below La Cimarrona and 185°C below La Castalia. The numerous thermal NaCl to NaClHCO3 springs located in the San Marcos area originate through dilution and boiling of these two geothermal liquids and different degrees of re-equilibration at lower temperatures. Silica and K contents are useful in discriminating between dilution, boiling and re-equilibration phenomena. Thermal NaHCO3 waters, generated through conductive heat transfer or input of geothermal vapor or gases from below, delineate the extent of the geothermal reservoir(s) at depth.

Obtaining meaningful redox potential determinations is questionable in disequilibrium solutions, like surface waters and groundwater. However, identifying redox processes in a natural ecosystem is a key factor to characterize the chemical quality and, consequently, the sustainability of that environment. To do that, the determination of an exact redox potential is not needed and on many cases it is more important to describe how and if the redox state of a system changes. In particular, the redox status of aqueous systems is assigned based on analysis of samples for redox-sensitive compounds. In general, these analyses do not include measurements of gases dissolved in the waters. Here, we present an innovative method to underline in an easy way changes in redox state of a system using the elemental composition (C, H, S) measured in the headspace gas after the equilibration with water phase. The results allow defining the empirical formula of the gas, the mean number of oxidation of the carbon and the molar ratio between C:H:S. The method is applied to investigate the redox condition in a stratified lake, San Rocchino (Northern Tuscany, Italy) using an instrument (Thermo Scientific FlashEA 1112) equipped for headspace gas analysis. Samples of waters and dissolved gases were collected at five different depths along a vertical profile. Such analytical system is used to determine the mean oxidation number of the carbon gaseous phase in the headspace, which allows distinguishing relatively oxidizing from relatively reducing condition. Further information on the redox state is reached considering the molar ratio C/H and C/S. This innovative method is simple and rapid, and the instrument is robust and it needs low maintenance. Moreover, it could be applied to other research and exploratory fields, such as geothermic and volcanic monitoring, polluted aquifer and contaminated sites.

This paper describes a method for computing: (1) the chemical composition of the first drop of condensate which forms at dew-point temperature through expansion of superheated steam, and (2) the saturation index of the drop with respect to relevant solid phases, such as halite, amorphous silica, boric acid, borax and sal ammoniac. Boiling-point elevation is taken into account in these calculations. Preliminary application to some wells in the Larderello geothermal field indicate that: (1) the high concentration of HCl in the steam causes both the low pH and very high TDS of the first drop; (2) the lower the dew-point temperature, the higher the TDS of the first drop; (3) for a given chemical composition, the lower the steam pressure, the higher the risk of corrosion and scaling in the steam path.

The Monte Corchia Cave is one of the most promising sites for studying the paleoclimate of the Mediterranean basin, but its hydrology and hydrogeochemistry are still poorly known. In this paper, we report some meteoclimatic and hydrochemical data for different parts of the cave. Conductivity and water level data from La Gronda channel show that this system reacts rapidly to external meteoric events, indicating the presence of a conductive epikarst. Data on two different drips indicate that the physicochemical parameters, suchas conductivity, pH, δ 13 C DIC and drip rate depend on the local structural setting and water pathlength. The data presented show that Galleria delle Stalattiti (the focus of the paleoclimate research) has the most stable conditions in terms of temperature, and the dripwaters show constant pH, electrical conductivity, alkalinity, calcium and magnesium content and δ 18 O. Drip rate is not affected by rain events and displays long-term trends that require a longer period of monitoring for elucidating their nature. The preliminary data presented here corroborate the hypotheses suggesting Galleria delle Stalattiti as a good example of a “deep” hypogean system of Fairchild et al. (2007).

International audience; The South Poroto-Rungwe geothermal field, in the northern part of the Malawi rift, Tanzania divides in two main areas. The relatively high altitude northern area around the main Ngozi, Rungwe, Tukuyu and Kyejo volcanoes, is characterised by cold and gas-rich springs. In contrast, hot springs occur in the southern and low-altitude area between the Kyela and Livingstone faults. The isotopic signature of the almost stagnant, cold springs of the Northern district is clearly influenced by H2O-CO2(g) exchange as evidenced from negative oxygen-shifts in the order of few deltas permil. In contrast, the isotopic signature of waters discharged from the hot springs of the Southern district is markedly less affected by the H2O-CO2(g) interaction. This evidence is interpreted as an effect of the large, permanent outflow of these springs, which supports the hypothesis of a regional-scale recharge of the major thermal springs. Measurements of carbon isotope variations of the dissolved inorganic carbon of waters and CO2(g) from the Northern and Southern springs support a model of CO2(g)-driven reactivity all over the investigated area. Our combined chemical and isotopic results show that the composition of hot springs is consistent with a mixing between (i) cold surface fresh (SFW) and (ii) Deep Hot Mineralised (DHMW) Water, indicating that the deep-originated fluids also supply most of the aqueous species dissolved in the surface waters used as local potable water. Based on geothermometric approaches, the temperature of the deep hydrothermal system has been estimated to be higher than 110 degrees C up to 185 degrees C, in agreement with the geological and thermal setting of the Malawi rift basin. Geochemical data point to (i) a major upflow zone of geothermal fluids mixed with shallow meteoric waters in the Southern part of the province, and (ii) gas absorption phenomena in the small, perched aquifers of the Northern volcanic highlands. (C) 2010 Elsevier B.V. All rights reserved.

Many boiling springs and fumaroles are present along the shores of Lake Bogoria, which is a closed-basin alkaline saline lake typical of African Rifts. Two different geothermal waters, both of Na-HCO3 type have been recognized. The first, discharged by the boiling springs located along the western shores of the lake, comes from a shallow steam-heated thermal aquifer. Its temperature is close to 100°C, as indicated by chalcedony solubility, while the chloride content of these waters is slightly higher than 200 mg L−1. The second, recognizable in the southernmost boiling springs, is representative of a deeper and hotter geothermal reservoir. The occurrence of mixing and boiling processes complicates the interpretation of geochemical data. Nevertheless, a chloride content of about 660 mg L−1, an equilibrium temperature close to 170°C and a high carbon dioxide partial pressure, at least 10–20 bar, have been estimated for the deep geothermal reservoir.

The theoretical compositions of an aqueous solution in equilibrium with a mineral assemblage made up of low-albite, K-feldspar, either a Ca-Al-silicate or calcite, clinochlore, muscovite, quartz, anhydrite, and fluorite, under varying T-PCO2-mcl conditions of geothermal interest, indicate that 1. 1) the total SO4 content as well as the Na K , K 2 Mg , and SO 4 F 2 ratios are potential geothermometers; 2. 2) the total HCO3 content as well as the K 2 Ca , Ca Mg , HCO 3 F , and (HCO 3 ) 2 SO 4 ratios are potential PCO2 indicators; 3. 3) the Na, K, Ca, and Mg total contents as well as the Na 2 Mg and Na 2 Ca ratios are mainly controlled by the total ionic salinity and are therefore hardly suitable as geoindicators. A preliminary test of the equations involving total HCO3 content as well as K 2 Ca and HCO 3 F ratios as PCO2 indicators have provided satisfactory results.

The densely populated metropolitan area of Quito is located on the slopes of the active Guagua Pichincha volcano at only 10 km from the crater. Recently, the Italian Ministry of Foreign Affairs sponsored a project for the mitigation of volcanic hazard in this area. The geochemical study carried out as part of this project was aimed at constructing a geochemical model of the zone for use in volcanic surveillance. According to this geochemical model, a hydrothermal aquifer (T = 200–240°C), fed both by meteoric waters and by fluids released by a magma body, lies at shallow levels beneath Guagua Pichincha crater. The crater fumaroles are essentially fed by steam boiled off from the hydrothermal aquifer. The high flow rate fumaroles located in the dome area show significant SO2 contents, which suggest a relatively high contribution of magmatic fluids in the zone of the aquifer feeding them. The absence of SO2 in the fumarolic discharges near the southern crater wall indicates instead that the magmatic fluids dissolve entirely into the aquifer here. The hot springs located at the western end of the crater represent the lateral discharge of the hydrothermal aquifer. On the basis of this model, it is likely that an increment in the flux of both the magmatic fluids and the heat from a magma body produces an increase, albeit small, of the pressure-temperature conditions of the hydrothermal system and consequent changes in flow rate and fluid chemistry of the fumarolic vents. In particular, total sulphur and possibly hydrochloric acid may increase in all the vents and sulphur dioxide may appear in other fumarolic discharges. The varying thermodynamic conditions in the hydrothermal aquifer can be evaluated on the basis of the equilibria among carbon species and hydrogen. Only minor delayed changes are expected in the physical-chemical characteristics of the springs located at the western end of the crater.

Target of this paper is to draw the relationship between environmental factors and some impacts due to human activity, in order to outline environmental quality restoring strategies for water bodies, which include among result indicators also biological parameters expected for Italian regulation and European directives. Morphologic equilibrium and correct knowledge of processes regulating fluvial dynamic, as basic factor of ecosystem functionality condition, are highlighted. Statistic evaluation processes of water quality data and implementation and validation of mathematical models are described.

The main geothermal reservoir of Acqui Terme-Visone hosts Na–Cl waters, which are in chemical equilibrium at 120–130°C with typical hydrothermal minerals including quartz, albite, K-feldspar, illite, chlorite (or smectite), anhydrite, calcite and an unspecified Ca-Al-silicate. In the Acqui Terme-Visone area, these geothermal waters ascend along zones of high vertical permeability and discharge at the surface almost undiluted or mixed with cold, shallow waters. To the SW of Acqui Terme, other ascending geothermal waters, either undiluted or mixed with low-salinity waters, enter relatively shallow secondary reservoirs, where they reequilibrate at 65–70°C. Both chemical and isotopic data indicate that bacterial SO4 reduction affects all these waters, especially those discharged by the secondary reservoirs. Therefore, geothermal waters must get in contact with oil, acquiring the relatively oxidized organic substances needed by SO4-reducing bacteria. This oil–water interaction process deserves further investigations, for potential economic implications.

Both geochemical and geophysical evidence indicates that the activity of the fumarolic system of the Fossa crater can be divided into two periods. From 1978 to 1983, such activity has been mainly controlled by two competing processes which affect the permeability of the fumarolic system at deep levels: (1) rock fracturing induced by faulting and (2) mineral deposition-alteration. The latter, which causes a slow decrease of the permeability at deep levels through clogging of fractures and voids, prevailed at the end of this period, determining a fluid pressure increment in the deep parts of the system. From 1984 to 1989, fluid pressure at deep levels remained persistently high, triggering local microseismic swarms. Furthermore, PT conditions much higher than before were attained in the zones where hydrothermal fluids seep into the conduits from lateral aquifers, owing to an uprising of the isotherms, a deepening of these seeping zones, or both.

Two geochemical surveys carried out in March 1991 and September 1992 revealed the existence of a hydrothermal system in the southern portion of Montserrat Island, below Soufriere Hills Volcano. This conclusion is supported by the presence of: (a) the thermal springs of Plymouth which are fed by deep Na–Cl waters (Cl concentration ∼25 000 mg/kg, temperature ca. 250 °C) mixed with shallow steam-heated waters; (b) the four fumarolic fields of Galway's Soufriere, Gages Upper Soufriere, Gages Lower Soufriere, and Tar River Soufriere, where acid to neutral, steam-heated waters are present together with several fumarolic vents, discharging vapors formed through boiling of hydrothermal aqueous solutions. Involvement of magmatic fluids in the recharge of the hydrothermal aquifers is suggested by: (a) the high 3He/4He ratios of fumarolic fluids, i.e., 8.2 RA at Galway's Soufriere and 5.9 RA at Gages Lower Soufriere; (b) the δD and δ18O values of Na–Cl thermal springs and steam condensates, indicating the involvement of arc-type magmatic water in the formation of deep geothermal liquids; and (c) the CH4/CO2 ratios of fumarolic fluids, which are lower than expected for equilibrium with the FeO–FeO1.5 hydrothermal rock buffer, but being shifted towards the SO2–H2S magmatic gas buffer.

The Massaciuccoli palustrine marsh is amongst the most important wetlands in Tuscany. It is a coastal lagoon of fresh to brackish water, which drains a total basin area of about 112 km2 and opens to the sea by way of an artificial channel, known as Burlamacca.In the palustrine area there are old quarries (30 m max depth and 2.5 km2 total area) which have been left by the previous sand extraction activity. Sewage, wastewaters of reclamation lands and wastewaters of cattle-breeding and of a food-industry are the main polluting sources. Within the basin, there are two landfills and several agricultural farming activities.This research, attempts to study 1) the anthropogenic impact on water chemistry; 2) the seawater inflow, the groundwater infiltration and the evaporation rate; 3) the role of the excavation area and 4) the function of the biotic processes, by applying geochemical techniques and chemical (Br, B, Cl and nutrients) and isotopic (δ18O, δ11B, δ2H, δ13C, δ34SSO4 and δ18OSO4) tracers.This study highlighted some important methodological aspects concerning:1-the role of biotic processes to regulate the contents of several dissolved chemical compounds2-the application of isotopes to trace the chemical-physical processes, taking place at the interface between the different compartments, to establish the origin of the elements and to get dating.In particular we point out:i. the distribution in the system of trace elements depends on the presence and intensity of biotic activityii. the importance of isotope geochemistry to trace the origin of water and active, chemical-physical processesiii. the increase in the radiocarbon activity of the sedimentary organic matter, corresponding to the atomic experiments carried out during the 60's, at different depths in the sediments from different sites in the lake.We can conclude that geochemical research allowed us to underline the influence of agricultural activity on the chemical composition of lake water, the hydrodynamic equilibrium and superficial sediment composition.The quarries, because of their high water volume, represent a hydraulic barrier for seawater intrusion into the lake. They act also as a sink for nutrients and they have a positive hydraulic function to prevent lake contamination. However, in future, they will become a serious problem if the stratification (chiefly due to chemical stability) disappears or if they are filled up.iv, Le marais de Massaciuccoli est la plus importante zone humide de la Toscane septentrionale. C'est une lagune côtière qui draine un bassin d'environ 112 km2 de surface totale et qui est caractérisée par des eaux à salinité très variable. Cette zone est reliée à la mer par un canal artificiel, appelé « Burlamacca ».Dans cette zone palustre, on retrouve de vieilles carrières (profondeur maximum : 30 m., superficie totale : 2,5 km2 ), témoignage d'une ancienne activité d'extraction de sable siliceux. Les principales sources polluantes sont représentées par les déchets urbains et industriels et par les eaux de drainage agricole ; au sein du bassin, il y a en effet 2 décharges et plusieurs entreprises agricoles.Ce projet de recherche se propose d'étudier : 1) l'impact anthropique sur la chimie des eaux du bassin du lac de Massaciuccoli ; 2) l'apport de l'eau de mer, l'infiltration des eaux souterraines et le taux d'évaporation du lac ; 3) le rôle exercé par les anciennes carrières, et 4) le rôle des processus biologiques.Les résultats ont été obtenus en appliquant des techniques géochimiques et en utilisant des traceurs chimiques (Br, B, Cl et des éléments nutritifs) et isotopiques (δ18O, δ11B, δ2H, δ13C, δ34SSO4 et δ18OSO4).L'étude a mis en évidence des aspects méthodologiques importants, concernant :1. l'influence des processus biologiques sur le contenu des composés chimiques dissous dans les eaux2. l'application des techniques isotopiques qui, non seulement, a permis de suivre les processus chimiques et physiques qui se développent à l'interface entre les différents compartiments, mais qui a permis aussi d'établir l'origine des divers éléments et d'effectuer des datations.Notamment, on a mis en évidence les points suivants:a. la distribution des éléments dans le système étudié est fonction de la présence et de l'intensité de l'activité biologiqueb. la géochimie est importante pour tracer l'origine des eaux et des processus chimiques et physiques.c. Les datations effectuées sur la matière organique des sédiments avec le 14C mettent en évidence la présence d'un pic de l'activité radioactive, qui correspond aux essais atomiques effectués dans les années '60. La profondeur, à laquelle on peut trouver ces évidences, varie selon les différents sites échantillonnés.En conclusion, ce travail a permis de mettre en évidence l'influence de l'activité agricole sur la composition chimique de l'eau du lac, sur l'équilibre hydrodynamique et sur la composition du sédiment superficiel. En outre, les carrières, en relation à leur extension et profondeur, représentent une barrière hydraulique à l'intrusion de l'eau marine dans le lac ; la disparition de la stratification des eaux des carrières ou un éventuel remplissage de ces dernières pourrait devenir un problème très sérieux pour l'équilibre de l'écosystème palustre.vi