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OVSICORI, IAMC-CNR We review the state of knowledge on global volcanogenic Hg emissions to the atmosphere and present new data from seven active volcanoes (Poás, Rincón de la Vieja, Turrialba, Aso, Mutnovsky, Gorely and Etna) and two geothermal fields (Las Pailas and Las Hornillas). The variability of Hg contents (c. 4-125 ng m-3) measured in gaseous emissions reflects the dynamic nature of volcanic plumes, where the abundances of volatiles are determined by the physical nature of degassing and variable air dilution. Based on our dataset and previous work, we propose that an average Hg/SO2 plume mass ratio of c. 7.8 × 10-6 (± 1.5 × 10-6; 1 SE, n = 13) is best representative of open-conduit quiescent degassing. Taking into account the uncertainty in global SO2 emissions, we infer a global volcanic Hg flux from persistent degassing of c. 76 ± 30 t a-1. Our data are derived from active volcanoes during non-eruptive periods and we do not have any direct constraint on the Hg flux during periods of elevated SO2 flux associated with large-scale effusive or explosive eruptions. This suggests that the time-averaged Hg flux from these volcanoes is even larger if the eruptive contribution is considered. Conversely, closed-conduit degassing and geothermal emissions contribute modest amounts of Hg. Revisamos el estado del conocimiento sobre las emisiones globales de Hg volcanogénico a la atmósfera y presentamos nuevos datos de siete volcanes activos (Poás, Rincón de la Vieja, Turrialba, Aso, Mutnovsky, Gorely y Etna) y dos campos geotérmicos (Las Pailas y Las Hornillas). ). La variabilidad del contenido de Hg (c. 4-125 ng m-3) medido en emisiones gaseosas refleja la naturaleza dinámica de las columnas volcánicas, donde la abundancia de volátiles está determinada por la naturaleza física de la desgasificación y la dilución variable del aire. Basándonos en nuestro conjunto de datos y trabajos previos, proponemos que una relación promedio de masa de pluma Hg / SO2 de c. 7.8 × 10-6 (± 1.5 × 10-6; 1 SE, n = 13) es el mejor representante de la desgasificación inactiva de conducto abierto. Teniendo en cuenta la incertidumbre en las emisiones globales de SO2, inferimos un flujo de Hg volcánico global a partir de la desgasificación persistente de c. 76 ± 30 t a-1. Nuestros datos se derivan de volcanes activos durante períodos no eruptivos y no tenemos ninguna restricción directa sobre el flujo de Hg durante períodos de flujo elevado de SO2 asociados con erupciones efusivas o explosivas a gran escala. Esto sugiere que el flujo de Hg promediado en el tiempo de estos volcanes es aún mayor si se considera la contribución eruptiva. Por el contrario, la desgasificación de conductos cerrados y las emisiones geotérmicas aportan cantidades modestas de Hg. Revisamos o estado do conhecimento sobre as emissões de Hg vulcanogênicas globais para a atmosfera e apresentamos novos dados de sete vulcões ativos (Poás, Rincón de la Vieja, Turrialba, Aso, Mutnovsky, Gorely e Etna) e dois campos geotérmicos (Las Pailas e Las Hornillas ) A variabilidade dos conteúdos de Hg (c. 4-125 ng m-3) medidos nas emissões gasosas reflete a natureza dinâmica das plumas vulcânicas, onde as abundâncias de voláteis são determinadas pela natureza física da desgaseificação e diluição variável do ar. Com base em nosso conjunto de dados e trabalho anterior, propomos que uma razão média da massa da pluma de Hg / SO2 de c. 7,8 × 10-6 (± 1,5 × 10-6; 1 SE, n = 13) é o melhor representante da desgaseificação quiescente de conduíte aberto. Levando em consideração a incerteza nas emissões globais de SO2, inferimos um fluxo de Hg vulcânico global a partir da desgaseificação persistente de c. 76 ± 30 t a-1. Nossos dados são derivados de vulcões ativos durante períodos não eruptivos e não temos qualquer restrição direta sobre o fluxo de Hg durante os períodos de fluxo elevado de SO2 associado a erupções explosivas ou efusivas em grande escala. Isso sugere que o fluxo médio de Hg desses vulcões é ainda maior se a contribuição eruptiva for considerada. Por outro lado, a desgaseificação por conduíte fechado e as emissões geotérmicas contribuem com quantidades modestas de Hg. University of Palermo, Italy Universidad Nacional, Costa Rica Observatorio Vulcanológico y Sismológico de Costa Rica

Measuring Hg/SO₂ ratios in volcanic emissions is essential for better apportioning the volcanic contribution to the global Hg atmospheric cycle. Here, we report the first real-time simultaneous measurement of Hg and SO₂ in a volcanic plume, based on Lumex and MultiGAS techniques, respectively. We demonstrate that the use of these novel techniques allows the measurements of Hg/SO₂ ratios with a far better time resolution than possible with more conventional methods. The Hg/SO₂ ratio in the plume of FO fumarole on La Fossa Crater, Vulcano Island spanned an order of magnitude over a 30 minute monitoring period, but was on average in qualitative agreement with the Hg/SO₂ ratio directly measured in the fumarole (mean plume and fumarole ratios being 1.09 x 10⁻⁶ and 2.9 x 10⁻⁶, respectively). The factor 2 difference between plume and fumerole compositions provides evidence for fast Hg chemical processing the plume.

We review the state of knowledge on global volcanogenic Hg emissions to the atmosphere and present new data from seven active volcanoes (Poás, Rincón de la Vieja, Turrialba, Aso, Mutnovsky, Gorely and Etna) and two geothermal fields (Las Pailas and Las Hornillas). The variability of Hg contents (c. 4–125 ng m−3) measured in gaseous emissions reflects the dynamic nature of volcanic plumes, where the abundances of volatiles are determined by the physical nature of degassing and variable air dilution. Based on our dataset and previous work, we propose that an average Hg/SO2 plume mass ratio of c. 7.8×10−6 (±1.5×10−6; 1 SE, n=13) is best representative of open-conduit quiescent degassing. Taking into account the uncertainty in global SO2 emissions, we infer a global volcanic Hg flux from persistent degassing of c. 76±30 t a−1. Our data are derived from active volcanoes during non-eruptive periods and we do not have any direct constraint on the Hg flux during periods of elevated SO2 flux associated with large-scale effusive or explosive eruptions. This suggests that the time-averaged Hg flux from these volcanoes is even larger if the eruptive contribution is considered. Conversely, closed-conduit degassing and geothermal emissions contribute modest amounts of Hg.

Mercury (Hg) is emitted in the atmosphere by anthropogenic and natural sources, these last accounting for one third of the total emissions. Since the pre-industrial age, the atmospheric deposition of mercury have increased notably, while ocean emissions have doubled owing to the re-emission of anthropogenic mercury. Exchange between the atmosphere and ocean plays an important role in cycling and transport of mercury. We present the preliminary results from a study on the distribution and evasion flux of mercury at the atmosphere/sea interface in the Augusta basin (SE Sicily, southern Italy), a semi-enclosed marine area affected by a high degree of contamination (heavy metals and PHA) due to the oil refineries placed inside its commercial harbor. It seems that the intense industrial activity of the past have lead to an high Hg pollution in the bottom sediments of the basin, whose concentrations are far from the background mercury value found in most of the Sicily Strait sediments. The release of mercury into the harbor seawater and its dispersion by diffusion from sediments to the surface, make the Augusta basin a potential supplier of mercury both to the Mediterranean Sea and the atmosphere. Based on these considerations, mercury concentration and flux at the air-sea interface of the Bay have been estimated using a real-time atomic adsorption spectrometer (LUMEX-RA 915+) and an home-made accumulation chamber, respectively. Estimated Total Atmospheric Mercury ($TGM$) concentrations during the cruise on the bay were in the range of 1 - 3 ng∙m-3, with a mean value of about 1.4 ng∙m-3. This data well fit with the background Hgatm concentration values detected on the land (1-2 ng∙m-3, this work), and, more in general, with the background atmospheric TGM levels found in the North Hemisphere (1.5 – 1.7 ng∙m-3 ) [a]. Besides, our measurements are in the range of those reported for other important polluted marine areas. The mercury evasion flux at the air-sea interface measured during the first cruise ranges from 110 to 1500 ng m-2 day-1. This range is 1-2 order of magnitude higher than most of marine environments (Pacific Ocean, Mediterranean Sea, Artic Ocean) and some important polluted marine areas, such as the Tokyo Bay (19–259 ng m-2 day-1)[b] and the Yellow Sea (156–722 ng m-2 day-1)[c]. Further estimates on Hg atmospheric deposition flux (wet and dry) and biomonitoring are required for finally assessing a mass balance of Hg in Augusta basin.

The Eyjafjallajökull 2010 eruption was an extraordinary event in that it led to widespread over Europe. Volcanic processes which lead to eruptions can be investigated by monitoring a variety of parameters, including the composition of ash leachates. Fine-grained tephra erupted from active vents, and transported through volcanic plumes, can adsorbs, and therefore rapidly scavenge, volatile elements such as S, halogens, and metal species in the form of soluble salts adhering to ash surfaces. Analysis of such water-soluble phases is a suitable complement for the remote sensing of volcanic gases at inaccessible volcanoes, like Eyjafjallajökull. The 2010 Eyjafjallajökull eruption developed in four main phases, whose difference in gas chemistry and products has been marked in ash-leachates data too. The recurrent ash fallout provided a unique opportunity to characterize the compositional features of ash leachates, and to identify their relation (if any) with the eruptive activity styles of the volcano. By these considerations, we report on the chemical composition of leachates of 20 volcanic ash samples deposited during the most explosive Eyjafjallajökull activities (from 14 April to 8 May) and during the lava fountaining event (on 26th March 2010). We found that ash-leachate solutions are dominated - among cations - by Na and Ca, while they display nearly equal S:Cl:F abundances (mean S/Cl and S/F molar ratios of 0.85 and 0.33, respectively), as characteristic of divergent-plate and within-plate volcanism. The strong correlations between leached Ca-F, Ca-SO4, and Na-Cl (r2=0.7-0.9), suggest that fluorite, anhydrite, and halite are the most likely soluble surface minerals formed in the plume (and therefore leached during our experiments), as also reported at many active volcanoes. Our data bring evidence for variations in S and halogens proportions, with samples from 5-8th May which show the highest S/Cl and lowest Cl/F ratios. By combining the concentration of leached SO4, F and Cl with the mass/area ratio of deposited ash (normalized to 30 min of 5-8 May 2010 volcanic phase), we estimated mean depositional elemental fluxes of about 1.0×10-5, 1.1×10-3 and 1.2×10-3 g m-2 s-1, for the water-soluble SO4, Cl and F, respectively. By integrating these data over the whole sampling area, we estimated a total depositional flux of about 864, 605 and 691 t∙day-1, for SO4, Cl and F, respectively. These data mean that ~15% of Sgas and 29% of Clgas discharged into the plume during the same eruptive phase, may have been scavenged by adsorption processes on ash surfaces within the eruption column.

Volcanic processes which lead to eruptions can be investigated by monitoring a variety of parameters, including the composition of ash leachates. Fine-grained tephra erupted from active vents, and transported through volcanic plumes, can adsorb, and therefore rapidly scavenge, volatile elements such as sulphur, halogens, and metal species in the form of soluble salts adhering to ash surfaces. Analysis of such water-soluble surface materials is a suitable complement for the remote sensing of volcanic gases at inaccessible volcanoes. The April 2010 Eyjafjallajökull eruption has been characterised by several distinct phases, with an initial effusion of alkali basalt on the volcano's northeast flank since March 20th, followed (since April 14th) by a complex summit, sustained, explosive to mixed activity, characterised by trachyandesitic magma The first phase of the summit eruption (14 to 18 April) was initially characterised by interaction between glacial meltwater from the icecap and erupting magma, and by three main pulses during which dark ash plumes were dispersed to the SE and S. Following a decrease in the intensity in explosive activity associated to the emission of a lava flow (from 19 April to 4 May), activity renewed in intensity on 5 May, when an ash-laden plume, up to 10 km in height, was continuously dispersed until May 18. Activity progressively declined and eruption closed on 9 June [1]. Here, we report on the chemical composition of leachates from volcanic ash samples deposited during the Eyjafjallajökull explosive phase (from 14 April to 8 May). Twenty-eight freshly fallen volcanic ash samples were collected at various distances from the eruptive vent, and their leached solutions were analyzed for major and trace elements. We show that ash leachate solutions from Eyjafjallajökull are dominated - among cations - by Na and Ca, while they display nearly equal S:Cl:F abundances (mean S/Cl and S/F molar ratios of 1.04 and 0.76 respectively), as characteristic of divergent-plate and within-plate volcanism. The good correlations between Ca and F (r2=0.8), Ca and SO4 (r2=0.7), and Na and Cl (r2=0.9) in ash leachates suggest that fluorite, anhydrite, and halite were the most likely soluble surface minerals formed in the plume (and therefore leached during our experiments). These correlations in the extracted solutions also indicate that either the sources of cations and anions in ash leachates were the same (e.g. direct condensation of NaCl(g) and CaSO4(g) from the plume) or, more probably, that the highest the condensation of plume acidic compounds (e.g., SO2(g), HCl(g), HF(g)) on ash, the largest the leaching of cations from silicate fragments. Indeed, our data bring evidence for that the extent of gas-ash reaction (likely, a proxy for ash residence time in the plume) was a key casual factor in determining ash leachate composition. Samples from the 4- 8th May eruptive period, showing the most acid pH values (4.5-5.5), consistently have the highest abundances for all elements, and especially Mg, S and F. Large variations in S and halogens proportions are observed in our dataset, with samples from the 4-8th May eruptive period showing the highest S/Cl and lowest Cl/F ratios. To interpret these variations, and particularly to verify whether they reflect changes in plume gas composition, in gas-ash reaction dynamics and rates,2]will require in-depth comparison with direct (FTIR) measurement of the Eyjafjallajökull gas plume[2] . [1] Hoskuldsson, A., et al., 2011. Geophysical Research Abstracts Vol. 13, EGU2011-14165, 2011; [2] Allard, P., et al., 2010. Abstract V53F-07 presented at Fall Meeting, AGU, San Francisco, Calif. 13-17 Dec.

Besides human activities, volcanoes also introduce significant quantities of potentially harmful chemical compounds into the environment, mainly in the forms of gases and particles. High-temperature emissions from persistently degassing volcanoes are a known source of trace metal emissions to the atmosphere which may have important environmental consequences. Among these metals, mercury (Hg) is of particular interest since it is a toxic volatile metal found at elevated concentrations in remote regions of the world. Many natural Hg pathways include a recycled component of anthropogenic material. The anthropogenic contribution to the global atmospheric Hg budget is now well constrained, with most recent estimates ranging from 1484 [AMAP/UNEP, 2008] to 1894 t yr-1 [2005/2006 inventory; Streets et al 2009]. Hg emissions from natural sources are, on the other hand, still poorly characterized, though being likely in the same range [estimates from 500 to 3000 t yr-1; Nriagu 1989] of those reported for anthropogenic release. The poorly constrained Hg speciation in volcanic emissions, and the limited number of studies so far, have hampered accurate estimation of the global Hg flux, with previous estimates ranging from as low as ~1 t yr-1 [Ferrara et al. 2000] to >800 t yr-1 [Varekamp and Buseck 1986]. Besides, historical archives such as ice-cores documented that large eruptions can release quantities of Hg similar to the present anthropogenic burden. The effects, or potential effects, of active volcanoes on the environment and on public health is an important issue, given the large number of communities and populated cities that exist and keep growing around and upon active and dormant volcanoes. Poisonous gases, and in the specific mercury, are also released continuously or semi-continuously into the environment by non-erupting volcanoes causing however regional environmental effects equally severe to the volcanic events of massive proportions. A major uncertainty regarding the impacts of volcanic Hg is the extent to which Hg emitted from a volcano is deposited locally or transported globally. Actually, volcanogenic mercury fluxes are poorly constrained and there is an almost complete absence of data on the factors (magma composition, eruptive temperature, or volcanic gas composition) that influence its degassing rates at different volcanoes. In order to better understand the role of volcanoes in the global mercury budget and to extend the currently limited dataset on volcanogenic Hg emissions, a number of field campaigns were carried out to evaluate Hg flux in volcanic gases by the simultaneously-determined Hg/SO2 ratios and SO2 flux. Measurements were made at the crater edge of a number of quiescently degassing volcanoes (Etna, Stromboli, Asama, Miyakejima, Montserrat, Ambrym, Yasur, Nyiragongo, Masaya). Emissions from open vents were investigated and concentrations of Hg elevated above usual background levels (rural areas far from emitting source, 1-2 ng m-3) were detected. We found that in volcanic plume mercury is mainly found as the relatively inert form of gaseous elemental mercury (GEM) with concentrations ranging from 18 to 373 ng Hg m-3. GEM has a long atmospheric lifetime estimated as 0.5-2 years due to its low solubility and gaseous nature, promoting long-range global transport [Nriagu 1989; Pyle and Mather, 2003]. High variability found in plume Hg concentrations depends on both volcanic (gas flux) and non-volcanic factors (extent of mixing and dilution in the vent; wind speed and direction), hence comparing the concentrations of Hg species between different volcanoes is not necessarily meaningful and it is more useful to compare Hg/SO2 ratios. Using our determined Hg/SO2 mass ratios in tandem with the simultaneously-determined SO2 emission rates, we estimated that the investigated volcanoes have Hg emission rates ranging from 0.2 to 18 t•yr-1 (corresponding to a total Hg flux of ~54 t•yr-1). Based on our dataset and previous works, we propose that a Hg/SO2 plume ratio ~10-5 is best-representative of gas emissions from quiescent degassing volcanoes. Using this ratio, we infer a global volcanic Hg flux from persistent degassing of ~95 t•yr-1. If representative of other volcanoes, these results suggest degassing of basaltic magma plays an important part of the global atmospheric Hg budget. According to both these data and recent observations [Bagnato et al., 2010], volcanism thus would contribute from as little as 12 to as much as 78% of the estimated global natural Hg budget. Volcanic Hg therefore has a greater potential for local and global environmental impact than Hg from the more prodigious but diffuse natural and anthropogenic sources. In particular, Hg released from Mt Etna degassing, the largest active volcano in Europe, represents approximately 5% of the total industrial Hg emissions in the Mediterranean area [~105 t•yr-1, Pirrone et al., 2009] and about 2% of the anthropogenic Hg supplies throughout Europe [~239 t•yr-1, EMEP 2002]. With these new estimates we critically revisit the idea that volcanic activity is a trivial contribution to the atmospheric Hg supply in the Mediterranean area. We shall re-examine the status of the global volcanic mercury emissions budget and its uncertainties, even when only considering quiescent phases of volcanic activity. Besides, large sectors of the planet (SW Pacific) are still un-explored, and thus our global Hg flux value estimated from passive degassing may constitutes a lower limit. However, Hg flux measurements in eruptive gases is a priority for future mercury research at volcanoes.

In this chapter, we review the state-of-the-art of the Campi Flegrei caldera (Naples) hydrothermal system, and its behaviour during the last decades. The Campi Flegrei caldera has been undergoing unrest since 1950, as evidenced by recurrent bradyseismic episodes accompanied by manifest changes in the degassing budget, degassing patterns and in the composition of the fumarolic fluids. In-depth analysis of geochemical and geophysical datasets acquired over decades has allowed identification of the mechanisms driving volcanic unrest at the Campi Flegrei caldera. We propose a conceptual model of the hydrothermal system feeding Solfatara fumaroles, where geochemical information is integrated with Audio Magneto Telluric measurements, which yields a realistic picture of the geometry of the system up to a depth of 2.5km. The model identifies a ~2km elongated vertical high resistivity structure in axis with the Solfatara fumaroles, which represents a relatively high permeability zone allowing hot fluid ascent from depth to the shallower portions of the hydrothermal system. Pulsed injections of hot magmatic fluids (CO2-rich and CH4-poor oxidised fluids) at the bottom of the hydrothermal system is thought to be one of the key processes that has controlled the evolution of the system during the last 40years. The episodes of injection of magmatic fluids changed in frequency and intensity during time, ultimately causing an overall heating and pressurisation of the system since the early 2000s, as reflected by escalating degassing flux, increase in areal extension of the degassing areas, and in the composition of the fumaroles. In particular, the CO2/CH4 and He/CH4 ratios of fumarolic fluids exhibited recurrent peaks, marking the episodes of injection of magmatic fluids. Moreover, the quasi-monotonic increasing trend of the fumarolic CO2/H2O ratio, from 0.15 to 0.18 in 2000 to ~0.4 in 2018–2019, has been interpreted as due to the combined action of partial steam condensation, and CO2 addition from a magmatic source and possibly from de-carbonation of hydrothermal calcite favoured by the heating of the hydrothermal reservoir. These changes strongly suggest that the ongoing (since 2000) unrest is triggered by a degassing magma source, but also that the system’s response is modulated by dynamics and structures of the overlying hydrothermal envelope. This evolution clearly requires careful scientific scrutiny and intensified monitoring in the years to come.

This short communication aims at providing an updated report on degassing activity and ground deformation variations observed during the ongoing (2012–2019) Campi Flegrei caldera unrest, with a particular focus on Pisciarelli, currently its most active fumarolic field. We show that the CO2 flux from the main Pisciarelli fumarolic vent (referred as “Soffione”) has increased by a factor > 3 since 2012, reaching in 2018–2019 levels (>600 tons/day) that are comparable to those typical of a medium-sized erupting arc volcano. A substantial widening of the degassing vents and bubbling pools, and a further increase in CO2 concentrations in ambient air (up to 6000 ppm), have also been detected since mid-2018. We interpret this escalating CO2 degassing activity using a multidisciplinary dataset that includes thermodynamically estimated pressures for the source hydrothermal system, seismic and ground deformation data. From this analysis, we show that degassing, deformation and seismicity have all reached in 2018–2019 levels never observed since the onset of the unrest in 2005, with an overall uplift of ~57 cm and ~448 seismic events in the last year. The calculated pressure of the Campi Flegrei hydrothermal system has reached ~44 bar and is rapidly increasing. Our results raise concern on the possible evolution of the Campi Flegrei unrest and reinforce the need for careful monitoring of the degassing activity at Pisciarelli, hopefully with the deployment of additional permanent gas monitoring units.

Recent geophysical evidence for large-scale regional crustal inflation and localized crustal magma intrusion has made Lastarria volcano (northern Chile) the target of numerous geological, geophysical, and geochemical studies. The chemical composition of volcanic gases sampled during discrete campaigns from Lastarria volcano indicated a well-developed hydrothermal system from direct fumarole samples in A.D. 2006, 2008, and 2009, and shallow magma degassing using measurements from in situ plume sampling techniques in 2012. It is unclear if the differences in measured gas compositions and resulting interpretations were due to artifacts of the different sampling methods employed, short-term excursions from baseline due to localized changes in stress, or a systematic change in Lastarria's magmatic-hydrothermal system between 2009 and 2012. Integrated results from a two-day volcanic gas sampling and measurement campaign during the 2014 International Association of Volcanology and Chemistry of the Earth's Interior (IAVCEI) Commission on the Chemistry of Volcanic Gases (CCVG) 12th Gas Workshop are used here to compare and evaluate current gas sampling and measurement techniques, refine the existing subsurface models for Lastarria volcano, and provide new constraints on its magmatic-hydrothermal system and total degassing budget. While compositional differences among sampling methods are present, distinct compositional changes are observed, which if representative of longterm trends, indicate a change in Lastarria's overall magmatic-hydrothermal system. The composition of volcanic gases measured in 2014 contained high proportions of relatively magma- and water-soluble gases consistent with degassing of shallow magma, and in agreement with the 2012 gas composition. When compared with gas compositions measured in 2006-2009, higher relative H2O/CO2 ratios combined with lower relative CO2/St and H2O/St and stable HCl/St ratios (where St is total S [SO2 + H2S]) are observed in 2012 and 2014. These compositional changes suggest variations in the magmatic-hydrothermal system between 2009 and 2012, with possible scenarios to explain these trends including: (1) decompression-induced degassing due to magma ascent within the shallow crust; (2) crystallization-induced degassing of a stalled magma body; (3) depletion of the hydrothermal system due to heating, changes in local stress, and/or minimal precipitation; and/or (4) acidification of the hydrothermal system. These scenarios are evaluated and compared against the geophysical observations of continuous shallow inflation at ~8 km depth between 1997 and 2016, and near-surface ( < 1 km) inflation between 2000 and 2008, to further refine the existing subsurface models. Higher relative H2O/CO2 observed in 2012 and 2014 is not consistent with the depletion or acidification of a hydrothermal system, while all other observations are consistent with the four proposed models. Based on these observations, we find that scenarios 1 or 2 are the most likely to explain the geochemical and geophysical observations, and propose that targeted shallow interferometric synthetic-aperture radar (InSAR) studies could help discriminate between these two scenarios. Lastly, we use an average SO2 flux of 604 ± 296 t/d measured on 22 November 2014, along with the average gas composition and diffuse soil CO2 flux measurements, to estimate a total volatile flux from Lastarria volcano in 2014 of ~12,400 t/d, which is similar to previous estimates from 2012.

We report measurements of Hg, SO2, and halogens (HCl, HBr, HI) in volcanic gases from Masaya volcano, Nicaragua, and gaseous SO2 and halogens from Telica volcano, Nicaragua. Mercury measurements were made with a Lumex 915+ portable mercury vapor analyzer and gold traps, while halogens, CO2 and S species were monitored with a portable multi gas sensor and filter packs. Lumex Hg concentrations in the plume were consistently above background and ranged up to 350 ng m-3. Hg/SO2 mass ratios measured with the real-time instruments ranged from 1.1 × 10-7 to 3.5 × 10-5 (mean 2 × 10-5). Total gaseous mercury (TGM) concentrations measured by gold trap ranged from 100 to 225 ng m-3. Reactive gaseous mercury accounted for 1% of TGM, while particulate mercury was 5% of the TGM. Field measurements of Masaya's SO2 flux, combined with the Hg/SO2 ratio, indicate a Hg flux from Masaya of 7.2 Mg a-1. At Masaya's low temperature famaroles, Hg/CO2 mass ratios were consistently around 2 × 10-8, lower than observed in the main vent (Hg/C02 ∼ 10-7). Low-temperature fumarole Hg fluxes from Masaya are insignificant (∼150 g a-1). Ratios of S, C and halogen species were also measured at Masaya and Telica volcanoes. CO2/ SO2 ratios at Masaya ranged from 2.8 to 3.9, comparable to previously published values. At Masaya molar Br/SO2 was 3 × 10-4 and I/SO2 was 2 × 10-5, suggesting fluxes of 0.2-0.5 Mg HBr d-1 and 0.02-0.05 Mg HI d-1. At Telica the Br/SO2 ratio was also 3 × 10-4 and the I/SO2 ratio was 5.8 × 10-5, with corresponding fluxes of 0.2 Mg HBr d-1 and 0.06 Mg HI d-1. Gases at both volcanoes are enriched in I relative to Br and Cl, compared to gases from volcanoes elsewhere. Copyright 2008 by the American Geophysical Union.

There have been limited studies to date targeting gaseous elemental mercury (GEM) flux from soil emission in enriched volcanic substrates and its relation with CO 2 release and tectonic structures. In order to evaluate and understand the processes of soil–air exchanges involved at Solfatara of Pozzuoli volcano, the most active zone of Campi Flegrei caldera (Italy), an intensive field measurement survey has been achieved in September 2013 by using high-time resolution techniques. Soil–air exchange fluxes of GEM and CO 2 have been measured simultaneously at 116 points, widely distributed within the crater. Quantification of gas flux has been assessed by using field accumulation chamber method in conjunction with a Lumex®-RA 915 + portable mercury vapor analyzer and a LICOR for CO 2 determination, respectively. The spatial distribution of GEM and CO 2 emissions correlated quite closely with the hydrothermal and geological features of the studied area. The highest GEM fluxes (from 4.04 to 5.9 × 10 − 5 g m − 2 d − 1 ) were encountered close to the southern part of the crater interested by an intense fumarolic activity and along the SE–SW tectonic fracture (1.26 × 10 − 6 –6.91 × 10 − 5 g GEM m − 2 d − 1 ). Conversely, the lowest values have been detected all along the western rim of the crater, characterized by a weak gas flux and a lush vegetation on a very sealed clay soil, which likely inhibited mercury emission (range: 1.5 × 10 − 7 –7.18 × 10 − 6 g GEM m − 2 d − 1 ). Results indicate that the GEM exchange between soil and air inside the Solfatara crater is about 2–3 orders of magnitude stronger than that in the background areas (10 − 8 –10 − 7 g m − 2 d − 1 ). CO 2 soil diffuse degassing exhibited an analogous spatial pattern to the GEM fluxes, with emission rates ranging from about 15 to ~ 20,000 g CO 2 m − 2 d − 1 , from the outermost western zones to the south-eastern sector of the crater. The observed significant correlation between GEM and CO 2 suggested that in volcanic system GEM volatilizes from substrate in a similar manner to the release of CO 2 . The quantitative estimation of the total amount of CO 2 and GEM released from the Solfatara crater gave values of about 304 ± 13 and 3.7 ± 0.2 × 10 − 6 t d − 1 , respectively. Finally, based on our dataset and previous work, we propose that an average GEM/CO 2 molar ratio of ~ 2 × 10 − 8 ( n = 9) is best representative of hydrothermal degassing. Taking into account the uncertainty in global hydrothermal CO 2 emissions from sub-aerial environments (~ 10 12 Mol yr − 1 ), we infer a global volcanic GEM flux from hydrothermal environments of ~ about 8.5 t yr − 1 . Although this value has to be considered as a lower limit for the global emission of GEM from these sources, we suggest that on a local scale hydrothermal activity can be regarded as a significant source of GEM than previously recognized to the atmospheric pool.

The Kamchatka peninsula, in the north-western part of the Pacific ’Ring of Fire’, is one of the most active volcanic realms on Earth, with 29 historically erupting volcanoes along its 700 km-long Eastern Volcanic Belt (EVB). This notwithstanding, volatile input and output fluxes along this arc sector have remained poorly characterised until very recently. We here report on the very first assessment of volatile flux emissions from Gorelyi, a large (25 km3, 1830 m high) and most active shield-like Holocene volcano located on the southern segment of the Kamchatka EVB. By combing results from a variety of in situ and remote sensing techniques (MultiGAS, filter packs, and UV camera), we determine the bulk plume molar concentrations of major (H2O 93.5%, CO2 2.6%, SO2 2.2%, HCl 1.1%, HF 0.3%, H2 0.2%) to trace-halogens (Br, I) and trace-element volatile species, and we estimate a total gas release of 11,000 t/day from Gorelyi during 900°C non-eruptive degassing. Using this observation, we derive new constraints on the abundances and origins of volatiles in the subduction-modified mantle source feeding magmatism in Kamchatka.

Mt. Etna is a major natural source of Hg to the Mediterranean region. Total mercury concentrations, [Hg] tot, in Castanea sativa (sweet chestnut) leaves sampled 7-13km from Etna's vents (during six campaigns in 2005-2011) were determined using atomic absorption spectroscopy. [Hg] tot in C. sativa was greatest on Etna's SE flank reflecting Hg deposition from the typically overhead volcanic plume. [Hg] tot also showed Hg accumulation over the growing season, increasing with leaf age and recent eruptive activity. [Hg] tot in C. sativa was not controlled by [Hg] tot in soils, which instead was greatest on Etna's NW flank, and was correlated with the proportion of organic matter in the soil (% Org). An elevated [Hg] tot/% Org ratio in soils on Etna's SE flank is indicative of increased Hg deposition. This ratio was also found to decrease with local soil pH, suggesting that Hg deposited to the low pH and organic-poor soils on Etna's SE flank may not be retained but will instead be released to groundwater or re-emitted to the atmosphere. These results show that the deposition of volcanic Hg has clear impacts and confirm that Etna is an important source of Hg to the local environment. © 2012 Elsevier B.V.

This study reports on the first quantitative assessment of the geochemical cycling of volcanogenic elements, from their atmospheric release to their deposition back to the ground. Etna’s emissions and atmospheric depositions were characterised for more than 2 years, providing data on major and trace element abundance in both volcanic aerosols and bulk depositions. Volcanic aerosols were collected from 2004 to 2007, at the summit vents by conventional filtration techniques. Precipitation was collected, from 2006 to 2007, in five rain gauges, at various altitudes around the summit craters. Analytical results for volcanic aerosols showed that the dominant anions were S, Cl, and F, and that the most abundant metals were K, Ca, Mg, Al, Fe, and Ti (1.5–50 μg m−3). Minor and trace element concentrations ranged from about 0.001 to 1 μg m−3. From such analysis, we derived an aerosol mass flux ranging from 3000 to 8000 t a−1. Most analysed elements had higher concentrations close to the emission vent, confirming the prevailing volcanic contribution to bulk deposition. Calculated deposition rates were integrated over the whole Etna area, to provide a first estimate of the total deposition fluxes for several major and trace elements. These calculated deposition fluxes ranged from 20 to 80 t a−1 (Al, Fe, Si) to 0.01–0.1 t a−1 (Bi, Cs, Sc, Th, Tl, and U). Comparison between volcanic emissions and atmospheric deposition showed that the amount of trace elements scavenged from the plume in the surrounding of the volcano ranged from 0.1% to 1% for volatile elements such as As, Bi, Cd, Cs, Cu, Tl, and from 1% to 5% for refractory elements such as Al, Ba, Co, Fe, Ti, Th, U, and V. Consequently, more than 90% of volcanogenic trace elements were dispersed further away, and may cause a regional scale impact. Such a large difference between deposition and emission fluxes at Mt. Etna pointed to relatively high stability and long residence time of aerosols in the plume.

Volcanic emissions represent one of the major natural source for several trace metals (Cd, Cu, As, Pb, Hg and Zn) into the atmosphere both as gaseous and aerosol forms. The Mediterranean Sea can be considered a large geochemical sink for these elements whose source are the huge amounts of aerosols of different origin. The industrialized areas located in the northern part of the basin represent a nearly constant source of the anthropogenic-dominated aerosol. By contrast, the arid and desert regions located at the southern and eastern parts of the Mediterranean, are the sources of frequent dust “pulses” perturbing the “steady-state” conditions of the local atmosphere through the input of several millions of tons of desert dust. In this context, Mount Etna, Stromboli and Vulcano represent the biggest volcanic point-sources in the Mediterranean area by introducing several thousands of tons of gases and particles per day in the troposphere, both during eruptive and passive degassing periods. Comparison between estimated annual metal fluxes from the three Italian active volcanoes and the local emissions (Environmental Protection Agency - APAT), evidences the significant contribution of the volcanogenic trace metals (Cu, Se, Cr, As, Hg and Cd) to the metropolitan area of Catania and the whole Sicily. On a regional scale, volcanic degassing plays also an important role accounting for about 1 to 10% for the total European anthropogenic emissions of As, Cd, Cr, Hg, Ni and Pb (European Monitoring and Evaluation Programme - EMEP).

Mercury is a toxic bio-accumulating metal that, due to its volatility has an extended atmospheric lifetime. Understanding Hg sources and sinks is therefore has importance on the global scale. We present new measurements of volcanic Hg from Mount Etna and Vulcano in Italy and Masaya volcano in Nicaragua to improve our estimates of the volcanic Hg flux. In contrast to other metals emitted from volcanoes, volcanic Hg can exist in 3 forms, namely gaseous elemental mercury (GEM), reactive gaseous mercury (RGM) and in the particle phase. These measurements also represent the first fully speciated measurements of volcanic Hg, as well as the first high time resolution measurements of gaseous Hg. Volcanic Hg is primarily emitted as GEM with about 1- 5% present in the particles and about 1% by mass present as RGM. Hg/SO ratios at the 3 2 -5 -6 volcanoes were generally of order 10 to 10 suggesting that global volcanic Hg flux, from -1 degassing basaltic volcanoes, could be of the order of 74 Mg yr . At Masaya Hg/C ratios were also determined at low temperature fumaroles. These low temperature Hg fluxes were found to be insignificant at Masaya; consistent with the dominance of high temperature degassing fluxes for other volatile species at Masaya (e.g. SO , CO ). Much more work remains to be done to 2 2 understand the roles of magma composition, eruptive temperature and volcanic gas composition in determining the SO – Hg – CO systematics of magmatic gases. 2 2