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.

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.

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.

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.

In September 2021, the La Fossa crater at Vulcano, in Italy, entered a new phase of unrest. We discuss a set of monitoring parameters included in the INGV surveillance network, which closely tracked the sequence of effects related to the crisis. The low-frequency local seismicity sharply increased, while the GPS and tiltmeter networks recorded the inflation of the cone, as an effect of fluid expansion in the hydrothermal system. Gravity variations were probably the effects of fast processes within shallow sources. The anomalies in soil CO2 flux, fumarole temperature, and in plume SO2 flux marked the strong increase in the vapor output from crater fumaroles. The signs of the impending crisis had been evident in the chemical and isotopic composition of fumarole gases since July 2021. These geochemical anomalies were clearly indicative of the enhanced input of gases from a magmatic source. In October, the massive degassing also influenced the areas at the base of the cone. In some areas, soil CO2 degassing and the thermal aquifer recorded strong anomalies. By early November, the crisis reached its acme. Afterward, the monitored parameters started a slow and discontinuous decreasing trend although remaining, some of them, sensibly above the background for several months. The multidisciplinary approach proved decisive for the interpretation of the underlying processes acting in the different phases of the unrest, thus allowing a consistent evaluation of the multiple hazards.

The INGV monitoring system operating in the volcano Island since three decades, recorded a new phase of unrest at the La Fossa volcano since September 2021. The main set of the crisis was the central hydrothermal system, deeply affected by the input of heat and chemicals from the magmatic source. The Levante Bay, located northwest of the La Fossa edifice, is a thermal area, where the vapor, coming from a local hydrothermal aquifer, is emitted from several low temperature (100°C) fumaroles along the beach and in the near off shore. The composition of the gas is typical of hydrothermal systems, and indicates equilibrium at temperature close to 200°C. By the onset of the crisis, in September 2021, the composition of the gas emitted from these fumaroles showed a smooth trend of increasing contribution of the magmatic gas. In May 2022, a sudden release of gas occurred in the Levante Bay, which was testified by the whitening of the seawater in the bay, due the formation of sulfur flakes, and by the appearance of typical pockmark structures on the seafloor. The drastic increase of the gas flux from the underwater gas vents, coupled to the presence of the pockmarks, suggested that an explosive emission of gas occurred in May 2022. The chemical and isotopic composition (He and C isotopes) of the gas emitted from the fumaroles revealed the prevailing presence of the magmatic component, closely approaching the composition of the gas emitted from crater fumaroles. This episode drove the attention of the scientific community to this area, currently affected by a significant input of the magmatic vapor, because of the risk related to the huge gas emission and the eventual overpressurization of the local hydrothermal aquifer.

In September 2021, the La Fossa volcano entered a new phase of unrest. The monitoring system, operating in the island since late ‘80s, recorded a sudden variation in seismicity, ground deformation, fumarole temperatures, soil and plume degassing. These variations were interpreted as due to the fast vaporization and expansion of the hydrothermal system (Federico et al., submitted), hypothesized at depth > 1.5 km bsl. At the same time, fumarole chemistry showed clear-cut variations, related to the dominant contribution of the magmatic gas over the hydrothermal one. The CO2 content and the helium isotope composition of the magmatic source revealed the appearance of a more primitive magma, compared to that feeding the fumaroles in the previous period, during the climax of the unrest. The signs of the enhanced contribution of magmatic gases in the fumarolic gases was already evident since 2018, so the 2021 unrest appears to have been the outcome of a long lasting preparatory phase. The systematics of gas species together with C and He isotopes, emitted from fumaroles after the first months of the unrest, revealed the appearance of a different magmatic component, poorer in N2, 3He and richer in He, S and 13C. The magmatic contribution is persistently overwhelming the hydrothermal one by the time of this communication.

Karst hydrosystems represent one of the largest global drinking water resources, but they are extremely vulnerable to pollution. Climate change, high population density, intensive industrial, and agricultural activities are the principal causes of deterioration, both in terms of quality and quantity, of these resources. Samples from 172 natural karst springs were collected in the whole territory of Greece. To identify any geogenic contamination and/or anthropogenic pollution, analyses of their chemical compositions, in terms of major ions and trace elements, were performed and compared to the EU limits for drinking water. Based on chloride content, the collected karst springs were divided into two groups: low-chloride (< 100 mg L-1) and high-chloride content (> 100 mg L-1). An additional group of springs with calcium-sulfate composition was recognised. Nitrate concentrations were always below the EU limit (50 mg L-1), although some springs presented elevated concentrations. High contents in terms of trace elements, such as B, Sr, As, and Pb, sometimes exceeding the limits, were rarely found. The Greek karst waters can still be considered a good quality resource both for human consumption and for agriculture. The main issues derive from seawater intrusion in the aquifers along the coasts. Moreover, the main anthropogenic pollutant is nitrate, found in higher concentrations mostly in the same coastal areas where human activities are concentrated. Finally, high levels of potentially harmful trace elements (e.g. As, Se) are very limited and of natural origin (geothermal activity, ore deposits, etc.).

Decades of geochemical monitoring at active crater lakes worldwide have confirmed that variations in major elements and physico-chemical parameters are useful to detect changes in volcanic activity. However, it is still arduous to identify precursors of single phreatic eruptions. During the unrest phase of 2009–2016, at least 679 phreatic eruptions occurred at the hyperacid and hypersaline crater lake Laguna Caliente of Poás volcano (Costa Rica). In this study, we investigate the temporal variations of Rare Earth Elements (REE) dissolved in Laguna Caliente in order to 1) scrutinize if they can be used as a new geochemical tool to monitor changes of phreatic activity at hyperacid crater lakes and 2) identify the geochemical processes responsible for the variations of REE concentrations in the lake. The total concentration of REE varies from 950 to 2,773 μg kg −1 . (La/Pr) N-local rock ratios range from 0.93 to 1.35, and Light REE over Heavy REE (LREE/HREE) N-local rock ratios vary from 0.71 to 0.95. These same parameters vary in relation to significant changes in phreatic activity; in particular, the (La/Pr) N-local rock ratio increases as phreatic activity increases, while that of (LREE/HREE) N-local rock decreases when phreatic activity increases. REE concentrations and their ratios were compared with the variations of major elements and physico-chemical parameters of the lake. Calcium versus (La/Pr) N-local rock and versus (LREE/HREE) N-local rock ratios show different trends compared to the other major elements (Na, K, Mg, Al, Fe, SO 4 , and Cl). Moreover, a higher loss of Ca (up to 2,835 ppm) in lake water was found with respect to the loss of Al, K, and Na. This loss of Ca is argued to be due to gypsum precipitation, a process corroborated by the mass balance calculation simulating the precipitation of gypsum and the contemporaneous removal of REE from the lake water. The observed relations between REE, changes in phreatic activity, and the parameters commonly used for the monitoring of hyperacid volcanic lakes encourage investigating more on the temporal and cause-effect relationship between REE dynamics and changes in phreatic activity at crater lake-bearing volcanoes.

We report on original geochemical data, which combine the rainfall trace metal contents from three different areas of Mt. Etna, variably fumigated by the volcanic plume, and those from soils, collected over the whole volcano. Trace element contents in rainfall appear mostly related to acidic ash leaching, while only for the most volatile elements (Cu, Zn, Cd, Pb, As, Sb, Tl, Se) we suggest a derivation from magmatic degassing. We analyzed separately the labile fraction of soil samples, considered the fraction bioavailable to plants and soil organisms living in. The complexing medium used to extract the bioavailable fraction simulates the growth environment of plant roots. The contents of trace elements in the bioavailable fraction from soil samples showed peculiar patterns, apparently unrelated to the plume fumigation. The transition metal contents in the bioavailable fraction account for less than 15 % of the pseudo-total fraction and the highest contents were measured in the less acidic soil samples and farthest from the summit craters. In particular, high Fe, Mn, Co, Ni, Pb, Zn, Cd contents were paralleled by high soil organic carbon concentrations, which increased in the samples collected downwind the summit vents. Concerning immobile elements, their abundance in the bioavailable fraction was related to the degree of alteration of soils. Two elements, Se and Tl, were enriched in soil samples collected at closer distance from the summit vents. Their origin is probably related to the plume deposition. The study highlighted that the accessibility of plants to potentially harmful trace elements present in the soil is not simply related to the exposure to pollutants, but also to their fate in the pedogenetic environment.

The eruption of Mt. Etna which occurred on December 24th 2018 was characterized by strombolian activity and fire fountains, emitted by the New South-East Crater and along a fissure that propagated towards the SE. The influence of volcanic emissions on atmospheric deposition was clearly detectable at several kilometres from the source. Wet and dry (bulk) deposition samples were collected each month, through a network of eleven collectors, in the areas of Milazzo, and Priolo between June 2018 and June 2019. They were analysed for major ions and trace elements concentrations. The pH values range from 3.9 to 8.3, while the EC values range from 7 to 396 mu S cm(-1). An extensive neutralization of the acidity has been recognised mainly due to the suspended alkaline dust particles, which have a buffering role in rainwater. A high load of Na+ and was observed at all sites, related to the closeness of the study areas to the coast, showing a high positive correlation (R-2 = 0.989) along the line of Na+/Cl- ratio in seawater. During the eruption, the volcanic plume was carried by the winds for long distance (more than 300 km) affecting the area of Priolo but not that of Milazzo, which was upwind with respect to Mt. Etna. The impact of volcanic HF was clearly recognised in the samples collected after the eruption. Volcanic SO2 and HCl had a lower impact due to the overwhelming input of anthropogenic sulfate and marine chloride. On the contrary, the signature of the Mt. Etna eruption can be well recognised in the high concentrations of certain trace elements in the samples collected immediately after the eruption. The strongest contrast between affected and non-affected samples was recognised in Al, Cd, and especially in the volatile elements Tl and Te, which are typically enriched in volcanic emissions. The results showed that volcanic eruptions might have a relevant effect on the atmospheric chemistry and on the composition of rainwater up to distances of 80 km from the emission vents.

Samples of efflorescences and encrustations of hydrothermal origin were collected at Sousaki (Greece) and analysed for their mineralogical (XRD) and chemical composition. Solutions obtained both from mineralization with HNO3 and from leaching with deionised water were analysed for major (ICP-OES), minor and trace metals (ICP-MS) and sulfate contents (IC). Results evidence the dependence of the chemical and mineralogical composition on micro-environmental conditions i.e. humidity, oxygen-rich or -poor environment, exposed or sheltered from meteoric agents. In fact, the presence of highly soluble sulfate minerals with elevated contents of many metals (e.g. Mg, Al, Fe, Mn, Cr, Ni, etc.) further underscores the important influence of hydrothermal activity on elements' mobility, whilst the sometimes very high concentrations in toxic elements like Al, Cr, Ni suggest also possible environmental impacts.

Nisyros Island (Greece) is an active volcano hosting a high-enthalpy geothermal system. During June 2013, an extensive survey on Hg concentrations in different matrices (fumarolic fluids, atmosphere, soils, and plants) was carried out at the Lakki Plain, an intracaldera area affected by widespread soil and fumarolic degassing. Concentrations of gaseous elemental mercury (GEM), together with H2S and CO2, were simultaneously measured in both the fumarolic emissions and the atmosphere around them. At the same time, 130 samples of top soils and 31 samples of plants (Cistus creticus and salvifolius and Erica arborea and manipuliflora) were collected for Hg analysis. Mercury concentrations in fumarolic gases ranged from 10,500 to 46,300 ng/m3, while Hg concentrations in the air ranged from high background values in the Lakki Plain caldera (10-36 ng/m3) up to 7100 ng/m3 in the fumarolic areas. Outside the caldera, the concentrations were relatively low (2-5 ng/m3). The positive correlation with both CO2 and H2S in air highlighted the importance of hydrothermal gases as carrier for GEM. On the other hand, soil Hg concentrations (0.023-13.7 μg/g) showed no significant correlations with CO2 and H2S in the soil gases, whereas it showed a positive correlation with total S content and an inverse one with the soil pH, evidencing the complexity of the processes involving Hg carried by hydrothermal gases while passing through the soil. Total Hg concentrations in plant leaves (0.010-0.112 μg/g) had no direct correlation with soil Hg, with Cistus leaves containing higher values of Hg with respect to Erica. Even though GEM concentrations in the air within the caldera are sometimes orders of magnitude above the global background, they should not be considered dangerous to human health. Values exceeding the WHO guideline value of 1000 ng/m3 are very rare (<0.1%) and only found very close to the main fumarolic vents, where the access to tourists is prohibited.