Thermogene/hypogean travertine is generally considered as typical terrestrial carbonate deposits associated with Ca-rich hot springs. In the southern range of the Damavand volcano in northeast Tehran occurs a large volume of travertine (usually referred to as the Ab-e Ask travertine). To investigate these, we present a dataset of major and trace element compositions of the Ab-e Ask travertines. Micro-textural and geochemical studies suggested they are deposited mostly under the control of bacterial activity. Six main travertine lithofacies are recognized: coated‑gas bubbles, crystalline crust, raft travertine, reed travertine, laminated boundstone, and shrub travertine. Diagenetic features suggest that the environment varied from meteoric-vadose, meteoric-phreatic to a phreatic-burial type. Positive values of the Langelier Saturation Index (SI) indicated that the Ab-e Ask springs are supersaturated with respect to calcite. On the PAAS-normalized REEs patterns, most of A and B-type travertines indicate MREE enrichment relative to HREE (TbN/YbN>1), strong negative Ce and Eu anomalies, whereas most of the C-type travertines are enriched in heavy rare earth elements (HREE) relative to the LREE (YbN/SmN>1), with a flatter HREE patterns and prominent negative Ce and Eu anomalies. A depletion in LREE relative to MREE and HREE in the Ab-e Ask travertines is considered to be as a result of the difference in geochemical mobility between LREEs and HREEs during deep water–rock interaction, while the MREE enrichment compared to HREE is interpreted to indicate inheritance from reservoir/aquifer rocks. Negative Eu and Ce anomalies indicate that the Ab-e Ask travertines is deposited from low-temperature hydrothermal waters in oxic-anoxic environmental conditions.δ18O values and the calculated values of δ13C(CO2) indicated that these travertines are deposited from hydrothermal fluids with a mixture of mantle and crustal CO2. Geological observations and isotopic analysis obtained in this work are corresponds to a thermogenic origin. This work shows that the depositional environment of the Ab-e Ask travertine is influenced by water-rock interactions.

This study investigates the geochemical behavior and transport mechanisms of Rare Earth Elements (REEs), Yttrium (Y), Zirconium (Zr), and Hafnium (Hf) in three natural water systems under reducing conditions: the Santa Barbara and Occhio dell'Abisso mud volcanoes and a sulphureous spring at Villafranca Sicula. A comprehensive fractionation approach was applied to isolate the truly dissolved fraction (TDF < 10 kDa), the colloidal fraction (10 kDa < CF < 450 nm), the suspended particulate matter (SPM > 450 nm), and the associated bottom sediments. Analytical results reveal that REE distribution is significantly influenced by redox conditions and solid-liquid interface processes. The absence of negative Cerium (Ce) anomalies and the presence of pronounced positive Europium (Eu) anomalies in the Santa Barbara and Occhio dell'Abisso waters suggest strongly reducing environments where Eu2+ stability is enhanced. Shale-normalized patterns indicate that, while SPM and sediment fractions often exhibit Middle REE (MREE) enrichment, linked to Mn-bearing and Fe-oxyhydroxide phases, the dissolved phase reflects dissolution processes governed by a non-CHARAC (CHarge-and-RAdius-Controlled) behavior. Furthermore, the study highlights a significant decoupling in the Zr/Hf and Y/Ho pairs. While these pairs remain coherent during magmatic processes, they undergo mutual fractionation in aqueous systems due to differential reactivity toward colloidal surfaces and organic ligands. Specifically, Zr/Hf ratios in the colloidal and dissolved fractions deviate from chondritic values, driven by the preferential scavenging of Hf onto mineral surfaces. These findings underscore the utility of REE and Zr-Hf systematics as high-resolution tracers for reconstructing water-rock interaction processes and elemental cycling in complex hydrological environments.

This study focuses on the geochemistry of Rare Earth Elements (REE) and Li in the hyperalkaline soda brine of the remnant Rincón de Parangueo (RDP) maar lake, Mexico, a system characterized by the ongoing precipitation of trona, thermonatrite, halite and sylvite. Total REE concentrations in water range between 13.5 and 26.9 μg kg-1, while higher concentrations (688-1,302 μg kg-1) were found in the associated bulk mineral precipitates (trona, thermonatrite, halite and sylvite). Lithium concentrations are higher than REE concentrations, in both RDP waters and bulk minerals. Lithium concentrations in RDP waters and bulk minerals precipitated are quite similar, ranging from 53.8 to 126.5 mg kg-1 and from 51.3 to 149.1 mg kg-1, respectively. Post Archean Australian shale (PAAS) normalized REE patterns in the waters increase from La to Lu. In contrast, PAAS normalized REE patterns of the bulk minerals are different from those of waters, also increasing from La to Lu but with a less pronounced trend. The distribution coefficient (KD) of REE and Li were calculated between the bulk precipitated minerals and the coexisting lake water. KD values of REE decrease from La to Lu and are significantly higher (6-1154), compared to KD values of Li (0.5-0.8). The REE patterns in waters, which increase from La to Lu, can be explained by the KD values, indicating preferential removal of LREE relative to HREE during mineral precipitation. Similar lithium concentration ranges in waters and bulk minerals are consistent with the low KD of Li, indicating a limited removal of Li from the solution during mineral precipitation.

The isotopic compositions of boron (δ11B‰) and strontium (87Sr/86Sr) were measured, for the first time, in 10 rainwater samples from Mt. Etna, Italy. The samples were collected during the paroxysmal sequence of 2021-2022. The chemical composition was determined using an ICP-MS, while the isotopic ratios of B and Sr were measured using a mass spectrometer MC-ICP-MS (Neptune Plus™), after specific pre-concentration procedures in clean rooms (class 100 - 1000). In the analysed rainwater samples, the concentrations of B and Sr were between 4.6 µg L-1 and 42.2 µg L-1, and between 9.7 µg L-1 and 541 µg L-1, respectively. Overall, the isotopic composition of B ranging from +1.29‰ ± 0.30‰ to +42.9‰ ± 0.20‰, with a median value of +22.0‰ ± 0.19‰. The lowest δ11B‰ values were measured in the site closest to the main active craters (3.6 km), with a median value of +11.4‰ ± 0.21‰; the highest was measured in the site close to the Ionian Sea (Zafferana Etnea), with a median value of +38.1‰ ± 0.21‰. Strontium (87Sr/86Sr) ratios were between 0.703728 ± 0.000008 and 0.710363 ± 0.000006, with a median of 0.707328 ± 0.000007. The highest and the lowest 87Sr/86Sr ratios were measured in the sites most and less affected by the contribution of the volcanic emissions, with median values of 0.704339 ± 0.000007 and 0.709583 ± 0.000007, respectively. Although exists few data of isotopic ratios of boron and strontium on fluids in volcanic systems (δ11B‰ between -9.3 to 21.4‰), there are no studies on rainwater influenced by volcanic emissions. Nevertheless, the data available in the literature are sufficient to attribute Etna's volcanic source as the major contributor to B and Sr emissions in the atmospheres of this area. The rainwater chemistry of the Zafferana Etnea site was partly influenced by the volcanic source, but the measured isotopic ratios at this site showed a strong contribution from the marine source. The results provide the first comprehensive study of B and Sr isotopes in Mt. Etna rainwater. Two main sources of atmospheric emissions of B and Sr were recognised: sea-salt aerosols and volcanic gases. This research also adds to the potential for the use of B and Sr isotopes as volcanic emissions contribution tracers.

Active biomonitoring of mercury (Hg) using non-indigenous moss bags was performed for the first time within and around the former Hg mining area of Abbadia San Salvatore (Mt. Amiata, central Italy). The purpose was to discern the Hg spatial distribution, identify the most polluted areas, and evaluate the impacts of dry and wet deposition on mosses. The exposed moss bags consisted of a mixture of Sphagnum fuscum and Sphagnum tenellum from an external uncontaminated area. In each site, two different types of moss bags, one uncovered (to account for the wet + dry deposition) and one covered (to evaluate the dry deposition), were exposed. The behavior of arsenic (As) and antimony (Sb) in the mosses was investigated to assess the potential relationship with Hg. GEM (Gaseous Elemental Mercury) concentrations were also measured at the same sites where the mosses were exposed, although only as a reference in the initial stages of biomonitoring. The results revealed that the main Hg emissions sources were associated with the former mining area of Abbadia San Salvatore, in agreement with the measured GEM concentrations, while arsenic and antimony were related to soil enriched in As-Sb waste material. The three elements registered higher concentrations in uncovered mosses with respect to the covered ones, i.e., wet deposition was the key factor for their accumulation on the uncovered mosses, while dry deposition was especially important for the covered samples in the mining area. Hg was accumulated in the mosses via GEM adsorption, uptake of particulate Hg, and precipitation via raindrops/snowfall, with almost no loss and without post-deposition volatilization. The results testified that the chosen biomonitoring technique was an extremely useful tool for understanding Hg transport and fate in a contaminated area.

Shallow Hydrothermal Vents (SHVs) are fluid emission spots in which water dynamics are characterised by interactions between seawater and free gas due to low hydrostatic pressure. This characteristic marine environment represents a peculiar natural laboratory where the study of geo-biological conditions needs a multidisciplinary approach to better understand the extreme ecosystem dynamics.Although many studies have been already performed on physical-chemical conditions, analysing major chemical species, just a few studies have adopted multidisciplinary approaches, giving a broader and more detailed view of the observed phenomenon.We propose a multidisciplinary study carried out in the period May-August 2022, based on the geophysical, geochemical and biological analysis of Black Point (23m b.s.l.), a hydrothermal spring belonging to the system located at about 2 miles off the coast of Panarea island (Aeolian Archipelago, Italy). Here a multiparametric seafloor observatory is installed (IPANEMA Project funds), equipped with chemical-physical sensors, a hydrophone and a seismometer. The area is periodically monitored by scientific divers performing discrete geochemical sampling, in addition, acoustic radiation studies are regularly conducted close to the emission, to characterise their acoustic signatures and peculiarities in turn. The gained expertise has led to the development of custom algorithms to perform spectral analysis of the acoustic features.Comparing the variation of the flux, investigated through the inversion of acoustic energy (radiated in the band [35 - 55] Hz likely associated with the mass flux variation), with fluctuations related to the environmental seafloor temperature, both series exhibit synchronous relative maxima over the investigated period.Coupling these trends with geochemical and biological variations in terms of Minor, Trace elements and Rare Earth Elements (REEs) concentrations and in the microbial community, simultaneous variations have been highlighted as well.In detail, the highest concentrations of minor elements (Al, Fe, Mn), trace elements (As, V) and REEs correspond to spectral energy and temperature peaks. Moreover, pH is inversely correlated to Fe, Al and Mn, indicating its role in dissolution/precipitation of Fe, Al and Mn oxy-hydroxides; inversely, REEs are positively correlated to Fe, Al and Mn indicating the role of the oxy-hydroxide ligands in fractionation of these elements, as a consequence, REEs patterns shapes show LREE depletion (Lan/Ybn < 1).Furthermore, the composition and diversity of microbial communities were investigated by extracting metagenomic DNA from different matrices (vent fluid, marine sediment near the vent and seawater at a short distance from the vent) and through the next-generation sequencing of a bacterial marker gene (16S rRNA gene). The results show significant differences in the microbial community between the samples and in the two samplings (May and August), especially in the fluid vent. These results are in accordance with the geochemical flux variations and the seafloor temperature, suggesting that each sample carries its specific bacterial fingerprint and the microbial community changes depending on the physicochemical conditions.This study confirms the importance of a multidisciplinary approach as the key to highlight different features of SHVs and how geo-biological fields are strictly linked in extreme environments.

Nyiragongo (D.R. Congo) is an active volcano known for its impressive persistent lava lake within its crater, and it is recognized as one of the most dangerous volcanoes in the world because more than two million people live on its slopes. Suddenly, on 22 May 2021, Nyiragongo produced three different lateral lava flows from the southern lower flanks, and significant amounts of volcanic gas and ash were emitted from the summit crater following the collapse of the crater floor. For a few weeks, the ash fallout impacted the main city of Goma and the numerous villages located in the vicinity of the volcano. 22 samples of volcanic ashes and 135 samples of drinking water (springs, rivers, rainwater, roof runoff) were collected before, during and after the eruption. From the leaching of the ashes and their direct observation through a field emission scanning electron microscope (FE-SEM), large quantities of soluble salts (e.g. sulphates, chlorides) on their surface were identified. The results showed that most of the drinking waters collected in the downwind villages (like Rusayo, Kingi, Sake) were heavily contaminated by volcanic emissions. In fact, fluoride, chloride, sulphur, and many potentially toxic elements (PTEs), including Al, As, Cd, Cr, Cu, Fe, Mn, Mo, Pb, Sb, Se, Te, Tl, and V, exceeded the suggested World Health Organization (WHO) drinking water limits during the eruptive period, exposing the population living in villages downwind of the preferential direction of the volcanic plume, to high health risks.

In Palermo, (Sicily, Italy), a year-long study was conducted to analyse the chemical composition of atmospheric deposition samples. The research was carried out at four urban sites and one semi-rural site. The atmospheric deposition samples were analysed both for major ions and trace elements. Abundances of major ions, on meq L-1 basis, followed the sequence Cl- > HCO3- > NO3- > SO42- > F- > Br- for anions, and Na+ > Ca2+ > NH4+ > Mg2+ > K+ for cations. The statistical technique of Confirmatory Factor Analysis (CFA) was used to identify the main sources of origin of some of the main species and trace elements studied. Ions such as Cl-, Na+, Br and I were attributed to the marine source, whilst NH4+ and NO3- to the anthropogenic source, as well as Mo, Cd, Cu, As, Pb, Sb and V among the trace elements. On the other hand, Ca2+, K+, Li, Fe, Al, and Sr were mainly of crustal origin. The seawater fractions of Mg2+ and SO42- were of marine origin, whereas the non-seawater fractions of the same ions were of crustal and anthropogenic origin, respectively. Anthropogenic sources, such as internal-combustion vehicle, domestic heating, and plant emissions, must be considered for Cu, Cr, Ba, Mo, Sb, Zn, As, Ni, and V. This study produced a previously unpublished dataset on the chemical composition of atmospheric deposition that made it possible to identify the main sources influencing air quality in the metropolitan area of Palermo (Italy).

Volcanoes are an important source of gas and particles into the atmosphere, during the eruptive periods or even during passive degassing activity. The study of volcanic gases is a robust geochemical tool to understand, monitor and predict the behaviour of volcano activity, but it is also important to evaluate the effects of volcanic emission on a local and regional scale. The study of the chemistry of atmospheric deposition can provide important information in this regard. Vulcano Island is a stratovolcano located in the southernmost sector of the Aeolian archipelago (Sicily). Since the last eruption occurred in 1888-1890, volcanic emissions are characterized by intense fumarolic activity localized on the northeastern rim of La Fossa crater. Several episodes of volcanic unrest have occurred over the past 130 years, and the most recent period of crisis was between 2021 and 2022. It was characterised by the increasing fumarole temperatures and gas fluxes, shallow long-period seismicity, and diffuse soil degassing around the main crater. This study reports on the chemical composition of rainwater samples collected from November 2021 to January 2023, during the last unrest period of Vulcano Island. Fifteen rainwater samples were collected through a network of three bulk collectors; two of them were placed inside the fumarolic field, and the last one was located near Vulcano Porto. Rainwater samples were analysed for major and trace element contents, and physicochemical parameters were also measured. The pH of rainwater collected near the summit area reaches very low pH values (min 1.63), with a mean value of 2.29, which is significantly lower respect to the mean value at Vulcano Porto (5.7). The concentrations of dissolved solutes in rainfall (expressed as Total Dissolved Solids) are inversely proportional to pH and reach extremely high values in the most acidic samples (up to 1133 mg/L). The most influenced samples by the volcanic emissions are strongly enriched in sulphate, chlorine and fluorine as a direct result of the dissolution of acid gases in rainwater. In addition to the major species, high concentrations of potentially toxic trace elements (Al, As, B, Cd, Fe, Pb, Sb, Te, Ti, Tl, and REE) were found. At the most distal site (Vulcano Porto) the impact of volcanic emissions on rainfall is much less pronounced and the dominant source is mainly related to marine aerosol. These preliminary results on trace element concentrations in rainfall at Vulcano highlight the importance of these studies to fully evaluate the potential impact of volcanic emissions on rainwater and consequently on other environmental matrices (e.g. soils and plants), especially during a period of intense outgassing.

The system of Domuyo Volcanic Complex is one of the most promising geothermal fields of Patagonia (Argentina). In this paper, we present a geochemical model of the Domuyo geothermal system based on previous studies and integrated with the systematic characterization of trace elements, thus adding a new piece to the puzzle of one of the most impressive geothermal systems in Argentina. A total of 38 water samples were collected from 17 different sampling sites, during three field-campaigns from 2013 to 2016, and analysed for 28 trace elements (Li, Be, B, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Rb, Sr, Y, Zr, Mo, Cd, Sb, Cs, Ba, Tl, Pb, Th and U). Sampling sites included the main river (Varvarco), its tributaries which cross the geothermal area, and thermal and cold springs. The investigation was focused on the origin, behaviour and estimation of mass fluxes of trace elements. Computing mass fluxes of trace elements transported by rivers is an important tool in the estimation of both the impact of potentially toxic elements and the exploitation of economically valuable elements. Among others, the mass fluxes of trace elements originating from the Domuyo geothermal system transported by rivers range from 45 to 278 t y(-1) for As, B, Cs, Li, Sr and Rb; such contributions flow to the Varvarco river, where the concentrations and mass fluxes of these elements increase by one to two orders of magnitude in the site downstream of the geothermal area with respect to that upstream.

This study explores the distribution of 16 trace elements between soluble and insoluble fractions of atmospheric deposition in Sicily, Italy, based on EU protocols for monitoring pollutants. Using a standardised deposimeter, we collected 149 atmospheric deposition samples over two years. Additionally, we analysed the rinse solution of the deposimeter separately. Higher deposition values for elements like Sr, B, Ba, Zn, As, and Cu were found in the soluble fraction, whereas Fe, Ti, Al, Cr, Co, Li, Mn, V, Ni, and Pb were prevalent in the insoluble fraction. The rinse fraction typically accounted for lower deposition values (from 1 % to 19 %), except for Pb and B, which accounted for 42 % and 31 % of the total deposition. We compared trace element distribution during a "dry period" and a "wet period." During the dry period, the insoluble fraction represented up to 97 % for elements like Ti and Fe, while the rinse fraction was notable for B (similar to 51 %) and Pb (similar to 33 %). In the wet period, insoluble contributions were higher for Li, Al, Ti, Cr, Fe, Co, and Pb, and soluble contributions increased for B, V, Mn, Zn, As, Sr, Ba, and Cu. While soluble elements were affected by temporal precipitation distribution, less soluble elements like Ti, Fe, and Al showed no significant differences between periods. Overall, the study highlights varying degrees of solubility among trace elements. Although the rinse fraction was generally negligible for most elements, overlooking it could lead to underestimating total atmospheric deposition for some elements, especially after extended dry periods.

Several researchers recognize the importance of plants as effective tools for environmental biomonitoring. The black poplar (Populus nigra L.) often emerges as a useful bioindicator of air quality in urban environments, where this tree species is widely employed for urban areas. Here, we used ICP-MS analysis to assess the presence and concentration of trace elements, with a special focus on heavy metals (HMs), in black poplar leaves and soil samples from three urbanized sites showing varying degrees of environmental quality. Specifically, the foliar concentrations of Zn (173.3 ppm), Cd (0.7 ppm), Co (1.1 ppm) and As (0.2 ppm) exceeded reference values for unpolluted sites, indicating potential environmental hazards. Additionally, we correlated the foliar concentrations of HMs with those quantified in soil and with air quality data provided by the regional air quality-monitoring network. Subsequently, we estimated the values of foliar fluctuating asymmetry, and evaluated their relationships with HM concentrations in both leaves and soil. Our results suggest that element concentrations in black poplar leaves are related to soil contamination and atmospheric quality, and the extent depends on the proximity to relevant pollution sources. Furthermore, the study species showed a pronounced accumulation capacity for some HMs (i.e., Zn, Cd) commonly found in particulate matter. The extent of foliar fluctuating asymmetry is related to atmospheric quality and HM soil concentration, possibly because of the growth anomalies induced by this kind of environmental contamination. Overall, our data indicate the study species can supply an effective biomonitoring service in urbanized contexts, offering valuable insights into the occurrence and biological implications of heavy metal contamination.

This study presents the first data on REY (Rare Earth Elements plus Yttrium) in the aquifer of Mount Etna (Sicily, Italy). Patterns normalized to chondrites indicate strong water–rock interaction, facilitated by a slightly acidic pH resulting from the dissolution of magma-derived CO2. REY patterns provide insights into the processes of both mineral dissolution and the formation of secondary phases. The relative abundance of light to heavy rare earth elements is compatible with the prevailing dissolution of ferromagnesian minerals (e.g., olivine or clinopyroxenes), reinforced by its strong correlation with other proxies of mineral dissolution (e.g., Mg contents). Pronounced negative Ce anomalies and positive Y anomalies demonstrate an oxidizing environment with continuous formation of secondary iron and/or manganese oxides and hydroxides. The Y/Ho fractionation is strongly influenced by metal complexation with bicarbonate complexes, a common process in C-rich waters. In the studied system, the measured REY contents are always below the limits proposed by Sneller et al. (2000, RIVM report, Issue 601,501, p. 66) for surface water and ensure a very low daily intake from drinking water.

AbstractToday, carbon dioxide removal from the atmosphere is the most ambitious challenge to mitigate climate changes. Basalt rocks are abundant on the Earth’s surface (≈ 10%) and very abundant in the ocean floors and subaerial environments. Glassy matrix and minerals constituting these rocks contain metals (Ca2+, Mg2+, Fe2+) that can react with carbonic acid to form metal carbonates (CaCO3, MgO3 and FeCO3). Here, we present a data compilation of the chemical composition of waters circulating in basalt aquifers worldwide and the results of simple basalt-water-CO2 experiments. Induced or naturally occurring weathering of basalts rocks release elements in waters and elemental concentration is closely dependent on water CO2 concentration (and hence on water pH). We also performed two series of experiments where basaltic rock powder interacts with CO2-charged waters for one month at room temperature. Laboratory experiments evidenced that in the first stages of water-rock interaction, the high content of CO2 dissolved in water accelerates the basalt weathering process, releasing in the water not only elements that can form carbonate minerals but also other elements, which depending on their concentration can be essential or toxic for life. Relative mobility of elements such as Fe and Al, together with rare earth elements, increases at low pH conditions, while it decreases notably at neutral pH conditions. The comparison between experimental findings and natural evidence allowed to better understand the geochemical processes in basaltic aquifers hosted in active and inactive volcanic systems and to discuss these findings in light of the potential environmental impact of CO2 storage in mafic and ultramafic rocks.

Natural thermal and mineral waters are widely distributed along the Hellenic region and are related to the geodynamic regime of the country. The diverse lithological and tectonic settings they are found in reflect the great variability in their chemical and isotopic composition. The current study presents 276 (published and unpublished) trace element water data and discusses the sources and processes affecting the water by taking into consideration the framework of their geographic distribution. The dataset is divided in groups using temperature- and pH-related criteria. Results yield a wide range of concentrations, often related to the solubility properties of the individual elements and the factors impacting them (i.e. temperature, acidity, redox conditions and salinity). Many elements (e.g. alkalis, Ti, Sr, As and Tl) present a good correlation with temperature, which is in cases impacted by water rock interactions, while others (e.g. Be, Al, Cu, Se, Cd) exhibit either no relation or an inverse correlation with T possibly because they become oversaturated at higher temperatures in solid phases. A moderately constant inverse correlation is noticed for the vast majority of trace elements and pH, whereas no relationship between trace element concentrations and Eh was found. Seawater contamination and water-rock interaction seem to be the main natural processes that influence both salinity and elemental content. All in all, Greek thermomineral waters exceed occasionally the accepted limits representing in such cases serious harm to the environment and probably indirectly (through the water cycle) to human health.

The concentrations of trace elements in atmospheric bulk depositions (wet plus dry) were investigated from two highly industrialised areas of Sicily (southern Italy) from June 2018 to July 2019, in order to recognise the main natural and anthropogenic sources. A side objective of this study was to improve the common sampling procedures and analytical methods used for monitoring trace elements in atmospheric deposition. The trace element VWM (Volume-Weighted Mean) concentrations ranged from less than 0.01 μg L−1 for trace elements such as Cs, Tl, and U, up to 24 μg L−1 for minor elements (Al, Zn, Sr), in the filtered aliquot, while they reached concentrations up to 144 μg L−1 for the same elements, in the unfiltered aliquot. Therefore, significant differences in concentrations between these two aliquots were found, particularly for Al, Fe, Ti, Zn, Cr, Pb, Se, Cs, and U. This implies that filtering operations may produce a consistent underestimation of concentrations of certain ‘constituents’ of the atmospheric deposition. Natural (marine spray, local and regional geogenic input, volcanic emanations) and anthropogenic sources (industrial emissions, auto vehicular traffic, and diffuse background pollution) which influence rainwater chemistry were identified. Enrichment factors (EFs), with respect to the upper crust composition, provided clear evidence of the different sources above mentioned: Ti, Fe, Al, Cs, Cr, Rb, and Co have low EFs (<1), and are referable to the (local and/or regional) geogenic input, while Se, Sb, Zn, B, Cd, Cu, Mo, Sr, As, with high EFs (>10), highlight the influence of marine and/or industrial sources. The study produced a novel dataset on the atmospheric deposition rate of several trace elements, which had never been studied in the investigated areas. Finally, a comparison of trace element deposition rates in the studied areas with the atmospheric deposition reported for 53 different sites, belonging to 20 different European nations, was made. The comparison showed that some elements, such as Al, V, Zn, and Mo had higher median deposition fluxes in the Sicilian sites than in European monitoring sites.

The Caviahue-Copahue Volcanic Complex is one of the most studied active volcanic systems in the South American Andean range, and yet little research has focused on trace and rare-earth elements of waters, especially during an eruptive cycle. In this study, we sampled and investigated natural waters from 23 sites (involving the crater lake, hot springs, streams, rivers, and bubbling pools) in two campaigns in 2017 and 2018, using physicochemical parameters, major, trace and rare-earth elements concentrations. With this novel dataset, it was possible to identify, characterize and compare three groups of waters with distinctive hydrofacies. Indeed, the normalization of water compositions against host rock concentrations showed a particular trace element pattern for each group of waters. Although the absolute concentrations of the elements in each sampling site changed from 2017 to 2018, the normalized patterns did not. Boron, As, Cd, Tl, Se, and Te, commonly recognized as volatile, are the main trace elements that magmatic gases supply to the system headwaters, whereas elements such as Ca, K, and Ba are affected by precipitation of secondary minerals (gypsum, anhydrite, barite, jarosite, and alunite). Furthermore, the main river draining the summit volcano shows a steep decrease in As, Cr, and V concentrations correlated to the precipitation of Fe and Al hydroxysulfates (schwertmannite and basaluminite, respectively). Moreover, it is the first time that a comparison between the different water groups is made using the patterns of the rare-earth elements, allowing us to identify and separate depletion patterns due to dilution processes from those due to precipitation processes.

Volcanic lakes are complex natural systems and their chemical composition is related to a myriad of processes. The chemical composition of major, minor, Rare Earth Elements (REE) and physico-chemical parameters at the hyperacid crater lake of Rincón de la Vieja volcano (Costa Rica) are here investigated during February 2013–August 2014. The study of the lake chemical composition allows to identify the main geochemical processes occurring in the lake and to track the changes in the volcanic activity, both important for active volcanoes monitoring. The total REE concentration (∑REE) dissolved in the crater lake varies from 2.7 to 3.6 mg kg −1 during the period of observation. REE in the water lake samples normalized to the average volcanic local rock (REE N-local rock ) are depleted in light REE (LREE). On the contrary REE N-local rock in the solids precipitated (mainly gypsum/anhydrite), from lake water samples in laboratory at 22°C, are enriched in LREE. The low variability of (La/Pr) N-local rock and (LREE/HREE) N-local rock ratios (0.92–1.07 and 0.66–0.81, respectively) in crater lake waters is consistent with the low phreatic activity (less than 10 phreatic eruptions in 2 years) observed during the period of observation. This period of low activity precedes the unrest started in 2015, thus, it could be considered as a pre-unrest, characterized by infrequent phreatic eruptions. No clear changes in the REE chemistry are associated with the phreatic eruption occurred at mid-2013. The results obtained investigating water-rock interaction processes at the Rincón de la Vieja crater lake show that rock dissolution and mineral precipitation/dissolution are the main processes that control the variability of cations composition over time. In particular, precipitation and dissolution of gypsum and alunite are responsible for the variations of REE in the waters. Despite the low variations of (La/Pr) N-local rock and (LREE/HREE) N-local rock ratios, this study allows to suggest that REE can be used, together with major elements, as practical tracers of water-rock interaction processes and mineral precipitation/dissolution at active hyperacid crater lakes over time, also during periods of quiescence and low phreatic activity.