Sergio Calabrese

Mount Etna volcano (Italy) as a major “dust” point source in the Mediterranean area

Volcanic emissions represent one of the most relevant natural sources of trace elements to the troposphere. Due to their potential toxicity, they may have important environmental impacts from local to global scale. They can also severely affect the atmospheric and terrestrial environment at timescales ranging from a few to millions of years. Mt. Etna volcano is known as one of the largest global contributors of magmatic gases (CO2, SO2 and halogens) and particulate matter, including some toxic trace elements. The aim of this study is to characterize the chemical composition and the mineralogical features of the volcanogenic aerosol passively emitted from Mt. Etna. Twenty-five samples were collected by filtration technique from different sites between 2008 and 2014. Chemical and mineralogical analyses allowed to discriminate two main constituents: the first is mainly referable to the silicate component in the volcanic plume, like lithic, juvenile fragments or glass shards and crystals (e.g. plagioclases, pyroxenes, oxides); the second constituent consists of soluble compounds like sulphosalts or halide minerals (sulphates, chlorides and fluorides). Fluxes of major and trace metals emitted in the atmosphere have been estimated. By comparing the Etnean trace elements with those from European anthropic emissions, we conclude that Mt. Etna is the main persistent point source of major and trace metals in the Mediterranean region. Results gathered from this investigation is of fundamental importance due to the exposure and potential impact of harmful chemical compounds for hundred thousand tourist visits each year to the summit of Mt. Etna.

Intense magmatic degassing through the lake of Copahue volcano, 2013-2014

Here we report on the first assessment of volatile fluxes from the hyperacid crater lake hosted within the summit crater of Copahue, a very active volcano on the Argentina-Chile border. Our observations were performed using a variety of in situ and remote sensing techniques during field campaigns in March 2013, when the crater hosted an active fumarole field, and in March 2014, when an acidic volcanic lake covered the fumarole field. In the latter campaign, we found that 566 to 1373 t d−1 of SO2 were being emitted from the lake in a plume that appeared largely invisible. This, combined with our derived bulk plume composition, was converted into flux of other volcanic species (H2O ~ 10989 t d−1, CO2 ~ 638 t d−1, HCl ~ 66 t d−1, H2 ~ 3.3 t d−1, and HBr ~ 0.05 t d−1). These levels of degassing, comparable to those seen at many open-vent degassing arc volcanoes, were surprisingly high for a volcano hosting a crater lake. Copahues unusual degassing regime was also confirmed by the chemical composition of the plume that, although issuing from a hot (65°C) lake, preserves a close-to-magmatic signature. EQ3/6 models of gas-water-rock interaction in the lake were able to match observed compositions and demonstrated that magmatic gases emitted to the atmosphere were virtually unaffected by scrubbing of soluble (S and Cl) species. Finally, the derived large H2O flux (10,988 t d−1) suggested a mechanism in which magmatic gas stripping drove enhanced lake water evaporation, a process likely common to many degassing volcanic lakes worldwide.

Active alkaline traps to determine acidic‐gas ratios in volcanic plumes: Sampling techniques and analytical methods

In situ measurements have been the basis for monitoring volcanic gas emissions for many years and—being complemented by remote sensing techniques—still play an important role to date. Concerning in situ techniques for sampling a dilute plume, an increase in accuracy and a reduction of detection limits are still necessary for most gases (e.g., CO2, SO2, HCl, HF, HBr, HI). In this work, the Raschig-Tube technique (RT) is modified and utilized for application on volcanic plumes. The theoretical and experimental absorption properties of the RT and the Drechsel bottle (DB) setups are characterized and both are applied simultaneously to the well-established Filter packs technique (FP) in the field (on Stromboli Island and Mount Etna). The comparison points out that FPs are the most practical to apply but the results are error-prone compared to RT and DB, whereas the RT results in up to 13 times higher analyte concentrations than the DB in the same sampling time. An optimization of the analytical procedure, including sample pretreatment and analysis by titration, Ion Chromatography, and Inductively Coupled Plasma Mass Spectrometry, led to a comprehensive data set covering a wide range of compounds. In particular, less abundant species were quantified more accurately and iodine was detected for the first time in Strombolis plume. Simultaneously applying Multiaxis Differential Optical Absorption Spectroscopy (MAX-DOAS) the chemical transformation of emitted bromide into bromine monoxide (BrO) from Stromboli and Etna was determined to 3–6% and 7%, respectively, within less than 5 min after the gas release from the active vents.

Characterization of the Etna volcanic emissions through an active biomonitoring technique (moss-bags): Part 1 – Major and trace element composition

Active biomonitoring using moss-bags was applied to an active volcanic environment for the first time. Bioaccumulation originating from atmospheric deposition was evaluated by exposing mixtures of washed and air-dried mosses (Sphagnum species) at 24 sites on Mt. Etna volcano (Italy). Concentrations of major and a large suite of trace elements were analysed by inductively coupled mass and optical spectrometry (ICP-MS and ICP-OES) after total acid digestion. Of the 49 elements analysed those which closely reflect summit volcanic emissions were S, Tl, Bi, Se, Cd, As, Cu, B, Na, Fe, Al. Enrichment factors and cluster analysis allowed clear distinction between volcanogenic, geogenic and anthropogenic inputs that affect the local atmospheric deposition. This study demonstrates that active biomonitoring with moss-bags is a suitable and robust technique for implementing inexpensive monitoring in scarcely accessible and harsh volcanic environments, giving time-averaged quantitative results of the local exposure to volcanic emissions. This task is especially important in the study area because the summit area of Mt. Etna is visited by nearly one hundred thousand tourists each year who are exposed to potentially harmful volcanic emissions.

The sea-air exchange of mercury (Hg) in the marine boundary layer of the Augusta basin (southern Italy): concentrations and evasion flux.

The first attempt to systematically investigate the atmospheric mercury (Hg) in the MBL of the Augusta basin (SE Sicily, Italy) has been undertaken. In the past the basin was the receptor for Hg from an intense industrial activity which contaminated the bottom sediments of the Bay, making this area a potential source of pollution for the surrounding Mediterranean. Three oceanographic cruises have been thus performed in the basin during the winter and summer 2011/2012, where we estimated averaged Hgatm concentrations of about 1.5±0.4 (range 0.9-3.1) and 2.1±0.98 (range 1.1-3.1) ng m(-3) for the two seasons, respectively. These data are somewhat higher than the background Hg atm value measured over the land (range 1.1±0.3 ng m(-3)) at downtown Augusta, while are similar to those detected in other polluted regions elsewhere. Hg evasion fluxes estimated at the sea/air interface over the Bay range from 3.6±0.3 (unpolluted site) to 72±0.1 (polluted site of the basin) ng m(-2) h(-1). By extending these measurements to the entire area of the Augusta basin (~23.5 km(2)), we calculated a total sea-air Hg evasion flux of about 9.7±0.1 g d(-1) (~0.004 tyr(-1)), accounting for ~0.0002% of the global Hg oceanic evasion (2000 tyr(-1)). The new proposed data set offers a unique and original study on the potential outflow of Hg from the sea-air interface at the basin, and it represents an important step for a better comprehension of the processes occurring in the marine biogeochemical cycle of this element.

Geosphere-Biosphere Interactions in Bio-Activity Volcanic Lakes: Evidences from Hule and Rìo Cuarto (Costa Rica)

Hule and Río Cuarto are maar lakes located 11 and 18 km N of Poás volcano along a 27 km long fracture zone, in the Central Volcanic Range of Costa Rica. Both lakes are characterized by a stable thermic and chemical stratification and recently they were affected by fish killing events likely related to the uprising of deep anoxic waters to the surface caused by rollover phenomena. The vertical profiles of temperature, pH, redox potential, chemical and isotopic compositions of water and dissolved gases, as well as prokaryotic diversity estimated by DNA fingerprinting and massive 16S rRNA pyrosequencing along the water column of the two lakes, have highlighted that different bio-geochemical processes occur in these meromictic lakes. Although the two lakes host different bacterial and archaeal phylogenetic groups, water and gas chemistry in both lakes is controlled by the same prokaryotic functions, especially regarding the CO2-CH4 cycle. Addition of hydrothermal CO2 through the bottom of the lakes plays a fundamental priming role in developing a stable water stratification and fuelling anoxic bacterial and archaeal populations. Methanogens and methane oxidizers as well as autotrophic and heterotrophic aerobic bacteria responsible of organic carbon recycling resulted to be stratified with depth and strictly related to the chemical-physical conditions and availability of free oxygen, affecting both the CO2 and CH4 chemical concentrations and their isotopic compositions along the water column. Hule and Río Cuarto lakes were demonstrated to contain a CO2 (CH4, N2)-rich gas reservoir mainly controlled by the interactions occurring between geosphere and biosphere. Thus, we introduced the term of bio-activity volcanic lakes to distinguish these lakes, which have analogues worldwide (e.g. Kivu: D.R.C.-Rwanda; Albano, Monticchio and Averno: Italy; Pavin: France) from volcanic lakes only characterized by geogenic CO2 reservoir such as Nyos and Monoun (Cameroon).

Plume composition and volatile flux of Nyamulagira volcano, Democratic Republic of Congo, during birth and evolution of the lava lake, 2014–2015

Very little is known about the volatile element makeup of the gaseous emissions of Nyamulagira volcano. This paper tries to fill this gap by reporting the first gas composition measurements of Nyamulagira’s volcanic plume since the onset of its lava lake activity at the end of 2014. Two field surveys were carried out on 1 November 2014, and 13–15 October 2015. We applied a broad toolbox of volcanic gas composition measurement techniques in order to geochemically characterize Nyamulagira’s plume. Nyamulagira is a significant emitter of SO2, and our measurements confirm this, as we recorded SO2 emissions of up to ~ 14 kt/d during the studied period. In contrast to neighbouring Nyiragongo volcano, however, Nyamulagira exhibits relatively low CO2/SO2 molar ratios (< 4) and a high H2O content (> 92% of total gas emissions). Strong variations in the volatile composition, in particular for the CO2/SO2 ratio, were measured between 2014 and 2015, which appear to reflect the simultaneous variations in volcanic activity. We also determined the molar ratios for Cl/S, F/S and Br/S in the plume gas, finding values of 0.13 and 0.17, 0.06 and 0.11, and 2.3·10−4 and 1·10−4, in 2014 and 2015, respectively. A total gas emission flux of 48 kt/d was estimated for 2014. The I/S ratio in 2015 was found to be 3.6·10−6. In addition, we were able to distinguish between hydrogen halides and non-hydrogen halides in the volcanic plume. Considerable amounts of bromine (18–35% of total bromine) and iodine (8–18% of total iodine) were found in compounds other than hydrogen halides. However, only a negligible fraction of chlorine was found as compounds other than hydrogen chloride.

Annex 2 to: Trace elements mobility in soils from the hydrothermal area of Nisyros (Greece)

A.1 Analytical Tecniques All soil samples were air dried, thoroughly mixed and split into subsamples for analysis. Particular care was taken using a Riffle-type sample splitter to ensure that representative subsamples were obtained. All analyses were made after sieving the soil samples through a 2-mm sieve and, except for pH determination, ground with an agate mortar. [...]