Non-volcanic Areas Research Articles

Analysis of radiative heat flux using ASTER thermal images: Climatological and volcanological factors on Java Island, Indonesia

This study focuses on analysing natural Radiative Heat Flux (RHF) anomalies to map out the heat distribution across the Java Island. Leveraging remote sensing techniques, we calculated natural RHF anomalies using Land Surface Temperature (LST) and Land Surface Emissivity (LSE) data obtained from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) imagery. A key aspect of our approach was distinguishing between natural and anthropogenic heat sources by cross-referencing the LST Map with the Land Use Land Cover (LULC) map of Java Island. The study interprets natural RHF anomalies by examining regional trends in non-volcanic areas and local trends within volcanic regions, considering climatological and volcanological factors. Relation with climatological factors involves assessing soil moisture parameters from Soil Moisture Active Passive (SMAP) data, precipitation from monthly Global Precipitation Measurement (GPM) data, and classifications according to the Köppen-Geiger climate schema. Our regional analysis reveals high natural RHF anomalies in the northern regions of West Java, parts of Central Java, and most of East Java, attributed to low soil moisture and low precipitation in savanna and monsoon climates. On a more localised scale, RHF values are significantly high in volcanic areas, particularly around Central and East Java's volcanoes, such as Mt. Merapi, Mt. Slamet, Mt. Semeru, the Sidoarjo Mud Volcano, and Mt. Ijen. The Natural RHF anomalies at volcanoes in West Java were identified as not being high except at Mt Patuha. These areas exhibit average natural RHF anomalies ranging between 32.22 W/m2 and 115.13 W/m2, indicating strong and intense volcanic activity. The insights obtained from these findings explain the overall thermal characteristics of Java Island and highlight the presence of subsurface thermal zones associated with volcanic activity and geothermal potential.

Effects of volcanic environment on Setaria viridis rhizospheric soil microbial keystone taxa and ecosystem multifunctionality

Keystone taxa are significant within ecosystem multifunctionality, as certain species fulfil essential functions such as recycling soil nutrients, promoting plant growth, influencing biogeochemical processes, and contributing to human health maintenance. However, there are still gaps regarding the relationship between microbial communities in volcanic rhizospheric soil and ecosystem multifunctionality. As a result, in this research, we employed Illumina MiSeq high-throughput sequencing to analyse the microbial community composition of rhizospheric soil from volcanic S. viridis. Compared with non-volcanic areas, volcanic soils have higher fungal alpha diversity and the absolute abundance of bacteria (16S gene copies) showed significant variation between the two successions (P < 0.0001). The network analysis further demonstrated that the microbial diversity in non-volcanic regions surpassed that of the volcanic area. The volcanic fungi network has more nodes and edges, is more complex than non-volcanic areas (Nodes: 425 vs. 770; Edges: 21844 vs. 74532), and more rhizosphere growth-promoting bacteria are enriched. Regression analysis and correlation networks showed that fungal communities were more closely associated with ecosystem multifunctionality than bacteria. This study lays the groundwork for examining the microbial keystone taxa in the rhizosphere of volcanic plants and offers valuable insights into the multifaceted functions of plant rhizospheric soil ecosystems.

Physical and chemical characterization of the Pomici di Avellino ashes (3.9 ka) from Somma-Vesuvius volcano for future health hazard assessment

Volcanic ashes can threaten the human respiratory system through inhalation. In this study we investigated the physical and chemical characteristics of volcanic ashes from the Pomici di Avellino (PdA) eruption, an Early Bronze Age (ca. 3.9 ka) Plinian event from Somma-Vesuvius volcano, southern Italy, whose wide dispersal affected most of the Italian peninsula. In particular, we analysed particle size, shape, composition, and surface reactivity of samples from both proximal and distal locations. Our results indicate that some tephra layers north of Rome have a phonolitic composition and match that of PdA eruption; they reach grain-sizes <2 μm (∼13.5%), thus having the potential to enter the deep respiratory system. Furthermore, the reactivity in free radical generation makes these products potentially able to cause oxidative stress within cells. While commonly no volcanic hazard assessment is made in areas far from active volcanoes, this study highlights that fine ashes from future similar large eruptions, producing high amount of highly fragmented material, can pose a health hazard even in remote, non-volcanic areas, hundreds of km away from the vent, suggesting that further studies on ash toxicity (e.g., in vitro toxicity studies) are required.

Soil gas CO2 emissions from active faults: a case study from the Anninghe—Zemuhe fault, Southeastern Tibetan Plateau, China

Introduction: Carbon dioxide emissions from non-volcanic areas are undervalued in the carbon cycle.Methods: First estimates of diffuse CO2 flux from the Anninghe—Zemuhe fault (AZF), Southeastern Tibetan Plateau, China, which suggests this could equal 15% emissions from all volcanoes in China. Following the accumulation chamber method, CO2 flux was investigated at 1,483 points, and along 67 profiles crossing the AZF. Results and discussion: Total CO2 emissions from the AZF were estimated 1.2 Mt yr-1. The relationship between soil gas CO2 fluxes, earthquakes, and fault activity was discussed. The intense fault activity in the southern part of the Zemuhe fault (ZMHF) and the northern part of the Anninghe fault (ANH) was inferred, which could have enhanced the porosity of the soil, and accelerated the water-rock interactions and soil gas emission within the fault zone. The chemical and isotopic data indicated that biogenic CO2 was the primary source of CO2 from the AZF. Produced by interactions between groundwaters and carbonates, soil gas CO2 could migrate to the near surface through cracks. Spatial variations of CO2 flux in soil gas indicate that seismic activity could be responsible for the jumpy variations of CO2 flux. The diffuse CO2 from deep faults may contribute considerably to the greenhouse gas cycles.

Constraining the geotherm beneath the Japanese islands from Curie point depth analysis and comparison with seismicity and drillhole data in the Kakkonda geothermal field

This paper shows results of Curie point depth (CPD) analysis of the Japanese Islands using magnetic data. The analysis method is Bouligand et al. (2009) based on fractal theory. This analysis result was combined with the cutoff depth of ordinary earthquakes, low frequency earthquakes and drillhole data. CPD by magnetic data (Dcmag) performed in the case of 50 km window size ranges 6–9 km deep in volcanic areas and is deeper than 9 km in non-volcanic areas. The results are concordant with the previous study by Okubo et al. (1989). Cutoff depths calculated by JMA unified catalog are 10 km or shallower in the volcanic area, deeper than 20 km in the forearc side and concordant with Dcmags. Dcmags across the Kakkonda GP gradually become shallower from 6.8 km west Akita-Komagatake toward to 4.6 km near Iwate volcano. The depth-to-temperature curves from drillhole database around the Kakkonda GP show that thermal gradients between Iwate volcano and the Kakkonda GP range 0.157 - 0.222 K/m. Assuming that these thermal gradients continue from the bottom of hole to the deeper part, the depths reaching 580 °C (Dchole) are determined. Dchole is concordant with Dcmag in the west side of the Kakkonda GP and much shallower than Dcmag in the east side. This suggests that Dcmags may miss to delineate a local high temperature area smaller than 50 km square in the east because of the average effect of CPD analysis. Dchole is shallower than 3 km west Iwate volcano and deepens at about 5 km west the Kakkonda GP. Combining the low frequency earthquakes data from the JMA unified earthquake catalog and the drillhole data of the Kakkonda geothermal field, we find the Curie point depths are consistent with those data.

Active degassing of crustal CO2 in areas of tectonic collision: A case study from the Pollino and Calabria sectors (Southern Italy)

Carbon dioxide (CO2) is released from the Earth’s interior into the atmosphere through both volcanic and non-volcanic sources in a variety of tectonic settings. A quantitative understanding of CO2 outgassing fluxes in different geological settings is thus critical for decoding the link between the global carbon budget and different natural processes (e.g., volcanic eruption and earthquake nucleation) and the effects on the climate evolution over geological time. It has recently been proposed that CO2 degassing from non-volcanic areas is a major component of the natural CO2 emission budget, but available data are still sparse and incomplete. Here, we report the results of a geochemical survey aimed at quantifying CO2 emissions through cold and thermal springs of the tectonically active Pollino Massif and Calabrian arc (Southern Italy). The chemical ad isotopic (He and C) composition of fifty-five dissolved gas samples allows to identify two different domains: 1) a shallow system dominated by gas components of atmospheric signature (helium, hereafter He) and biogenic origin (C), and 2) a deeper system in which crustal/deep fluids (CO2 and He) are dominant. The measured He isotope ratios range from 0.03 to 1.1 Ra (where Ra is the He isotopic ratio in the atmosphere) revealing a variable atmospheric contamination. Furthermore, the He isotopic data indicate the presence of traces of mantle He contributions (2%–3%) in the thermal groundwater. The prevailing low R/Ra values reflect the addition of crustal radiogenic 4He during groundwater circulation. Using helium and carbon isotope data, we explore the possible sources of fluids and the secondary processes (dissolution/precipitation) that act to modify the chemistry of pristine volatiles. For the thermal springs, we estimate a deep C output of 2.3 x 107 to 6.1 x 108 mol year−1. These values correspond to deep CO2 fluxes per square km comparable with those estimated in several active and inactive volcanic areas and in continental regions affected by metamorphic CO2 degassing (e.g., the southern margin of the Tibetan Plateau).

Compositional measurement of gas emissions in the Eastern Carpathians (Romania) using the Multi-GAS instrument: Approach for in situ data gathering at non-volcanic areas

The Multi-GAS, a robust and low-cost instrument for real-time in-situ gas measurements, has previously been used mainly for compositional measurements of active volcanic plumes. Here we demonstrate novel use of a specially designed Multi-GAS instrument adapted to low temperature degassing areas. We performed compositional measurements in the Eastern Carpathians on dry and bubbling gas emissions using a sensor kit that allows measurement of CO2, CH4 and H2S (three major components of low-temperature hydrothermal/volcanic manifestations). Our results demonstrate good agreement between Multi-GAS measurements and independently obtained CO2 concentrations from gas chromatography. We also provide some novel H2S information for some anomalous sites, which we relate to possible alteration processes of sulphide minerals. The use of Multi-GAS in such environments could open new possibilities for data collection at non-volcanic areas and exploration of mineral resources. Moreover, it can also be a useful tool in exploration surveys to select the best sampling sites for more detailed laboratory measurements.

Cancer Incidence in Volcanic Areas: A Systematic Review

Background:There are more than 1,000 active volcanoes worldwide with inhabitants within 100 km of them. Volcanoes spill several toxic metals and spew pollution through gasses, causing soil and water contamination. The dangerously active volcanoes place the nearby population at risk for volcanic hazards. This review aimed to determine whether people living in these volcanic areas have higher risk of cancer and more attention should be given to this danger. Methods:A systematic literature search was conducted of PUBMED, Science Direct, SCOPUS, Proquest, and Google Scholar, and from citation searching. We assessed the quality of the studies and extracted the incidence rate of cancer in the volcanic areas compared to non-volcanic areas. Results: The search identified 360 articles, with 11 studies meeting our selection criteria. The results reported the incidence of cancer in children was predominantly in volcanic areas with girls suffering as much as 1.4 per 100,000 per year. The highest cancer age standardized incidence rates for females, males, and overall calculation in volcanic areas were reported as 31.7/100,000/year in Catania, 10.34/100,000/year in Furnas, and 38.3/100,000/year in Catania-Messina-Enna for thyroid cancer. We observed the increasing incidence of carcinoma for some types of cancer in volcanic areas. Conclusion:Cancer incidence in volcanic areas was higher than non-volcanic areas and it is caused by multifactorial conditions. The concentrations of hazardous elements of volcanic products vary among volcanoes and are related to the harmful risk for the inhabitants. The negative effects of volcanic products to human health should be given more consideration.

A comparison of atmospheric geochemistry through lichens from volcanic and non-volcanic areas, north Taiwan

A comparison of atmospheric geochemistry through lichens from volcanic and non-volcanic areas, north Taiwan

KARAKTERISTIK FISIK MATAAIR PANAS DAERAH SAMBOJA, KUTAI KARTANEGARA

Geothermal features can be observed in areas of active volcanism, or areas that have inactive volcanoes. In non-volcanic areas, the temperature of rocks within the Earth also increases with depth. This temperature increase is known as the Geothermal Gradient. If water percolates deeply enough into the crust, it comes into contact with hot rocks and can circulate to the surface to form hot springs. The collection of field hydrothermal data during field study with the help of portable instruments. The different physical parameters of the thermal springs such as temperature, pH, colour, and odour of thermal fluid are noted. The temperature of the thermal springs ranges from 43oC to 48oC. The pH value of the thermal waters shows a neutral (pH 6-6.6) and sulphur odour is discernible particularly. Based on geological, the system geothermal energy that develops is geopressured.

Weathering on volcanic edifices under semiarid climates: insights from a regional assessment of the composition of Fogo Island regoliths (Cape Verde)

Abstract In this study, the geochemistry and mineralogy of regoliths formed on Fogo Island (Cape Verde), a polygenic strato-volcano built during the Quaternary, are used to assess the geomorphological factors that control the early stages of basalt weathering. Fogo Island soils are mainly derived from relatively homogenous silica-undersaturated basaltic rocks. However, a discernible exotic component is recognized in areas most exposed to prevailing winds via ratios of non-mobile elements that are hosted in different amounts by basaltic rocks (e.g. Th, Sc and Ti). The weathering extent is evidenced by a relative depletion in mobile elements (e.g. Na, Ca, Mg) and an enrichment in non-mobile elements (e.g. Ti, Fe, Sc, Al), the decomposition of the most labile minerals (olivines) and the formation of secondary components (phyllosilicates and some Fe-oxides, such as hematite-goethite), along with the enrichment in quartz supplied from non-volcanic areas. Weathering depends on bedrock age and type (pyroclastic deposits v. lava-flows). In particular, soils covering older volcanic units tend to be more affected by chemical alteration than those overlying younger units. In addition, more intense weathering is observed in locations characterized by a combination of moderate elevation, slopes with low gradient and relatively high rainfall. The present investigation shows that even in low humidity environments recently formed basalts are affected by weathering, with the extent of chemical decomposition being mainly determined by the age of surface exposure and local orographic/climatic features.

Heavy Metals in the Environment and Thyroid Cancer.

Simple SummaryEpidemiological observations indicate that the incidence of thyroid cancer is increased in volcanic areas. Indeed, in the volcanic area of Sicily, where residents are biocontaminated by volcano-originated, low-level, multi-elemental metal pollution, the thyroid cancer incidence is double that in non-volcanic areas. The aim of this review is to summarize the evidence suggesting that chronic exposure to heavy metals, even at slightly increased environmental concentrations that cause no harm to mature thyrocytes, may alter the biology of stem/precursor thyroid cells, leading to a predisposition to malignant transformation. Both in vitro and in vivo experiments support this possibility; this phenomenon involves a variety of molecular mechanisms depending on the metal and the target cell involved. The role of the increased and generalized metal pollution in our ecosystem, paralleling the worldwide increase in thyroid cancer in recent decades, requires more attention and further studies.In recent decades, the incidence of thyroid cancer has increased more than most other cancers, paralleling the generalized worldwide increase in metal pollution. This review provides an overview of the evidence supporting a possible causative link between the increase in heavy metals in the environment and thyroid cancer. The major novelty is that human thyroid stem/progenitor cells (thyrospheres) chronically exposed to different metals at slightly increased environmentally relevant concentrations show a biphasic increase in proliferation typical of hormesis. The molecular mechanisms include, for all metals investigated, the activation of the extracellular signal-regulated kinase (ERK1/2) pathway. A metal mixture, at the same concentration of individual metals, was more effective. Under the same conditions, mature thyrocytes were unaffected. Preliminary data with tungsten indicate that, after chronic exposure, additional abnormalities may occur and persist in thyrocytes derived from exposed thyrospheres, leading to a progeny population of transformation-prone thyroid cells. In a rat model predisposed to develop thyroid cancer, long-term exposure to low levels of metals accelerated and worsened histological signs of malignancy in the thyroid. These studies provide new insight on metal toxicity and carcinogenicity occurring in thyroid cells at a low stage of differentiation when chronically exposed to metal concentrations that are slightly increased, albeit still in the “normal” range.

Review: origin, heating process, and groundwater flow system of non-volcanic thermal aquifers in Tunisia

Thermal groundwater is of great economic and social importance. Tunisia is characterized by its hot groundwater spread over several regions. Hydrothermal resources need further investigation and diagnosis to determine their local, Mediterranean, or regional thermal sources and flow regimes. This study aims to differentiate origin and heating process of non-volcanic thermal aquifers. For this, three thermal provinces in Tunisia were reviewed and studied: Cap Bon thermal province (Korbous), Fluorinated Province of Zaghouan (Zriba Hammam), and Southern thermal province (El Hamma). A multidisciplinary approach, integrated with hydrogeological, geochemical, and isotopic data from the various studied provinces, was used. Results reveal that the studied thermal waters are of meteoric origin heated by deep circulation and acquire their thermal energy from the Earth’s heat during long-time residence. The thermal waters of El Hamma are the oldest and the northern waters are younger, influenced by the recent recharge. Thermal groundwater chemistry is influenced by minerals related to rock-water interaction. This study confirms that thermal waters, in non-volcanic areas, are of meteoric origin; their temperature and salinity depend on the residence time and their depth of circulation. This makes it possible to rationalize for their use in the appropriate sectors and ensure sustainable management.

Three‐Dimensional Electrical Resistivity Structure Beneath a Volcanically and Seismically Active Island, Kyushu, Southwest Japan Arc

AbstractTo understand the subduction dynamics around Kyushu Island, Southwest Japan Arc, the distribution of fluids is imaged by resolving three‐dimensional (3‐D) electrical resistivity structure beneath a subregion the island, including volcanic and nonvolcanic areas. The nonvolcanic region in central Kyushu is situated between two regions with numerous Quaternary volcanic structures along a volcanic front aligned N30°E and related to subduction of the Philippine Sea Plate. Two source areas of slow slip events lie at depths of 20–40 km along the eastern coast of Kyushu, whereas earthquakes spread along the subducting Philippine Sea Plate plane over the eastern coast and toward the volcanic front at depths of 20 to &gt;100 km. Our 3‐D resistivity model detects prominent conductors, indicating the presence of fluids, which might control volcanic and seismic activity. The most robust features of the model are three regions of high conductivity. A magma system and a fluid system are imaged as two vertical conductors extending from a depth of ~70 km, both related to slab‐derived fluid and located along the volcanic front, beneath the volcanic and nonvolcanic regions, respectively. The third conductor, which suggests the presence of slab‐derived fluid and hydrated sediments at the plate interface and the presence of serpentinite in the mantle wedge, appears in an area devoid of slow slip events at depths of &lt;~30 km along the southeastern coast.

Sediment Characteristics of Bed Load Transport in Downstream of Progo River, Indonesia

Progo River is one of the rivers that has a sediment supply from volcanic and non-volcanic areas. Sediment transport, especially the bed load transport, it is very influential on the phenomenon of river degradation and aggradation. Therefore, a study to determine the characteristics of bed load transport is needed and important. The research was carried out in the downstream part of Progo River. Sampling locations were taking in four locations, namely Ancol Bridge, Kebon Agung II Bridge, Kebon Agung I Bridge and Bantar Bridge. The bed load transport measurement tool was used Helley Smith (WMO, 1980) equipment. Every river cross section is taken three times. The results showed that the sediment type of bed load transports is silty sand, with specific gravity values of 2.67 to 2.70. The average diameter values (D50) of the bed load transports vary greatly from 0.129 mm to 0.454 mm. The values of bed load transports vary greatly and are influenced by the values of the discharges. The correlation between bed load transport and discharge is linear, with R values are 0.85 to 0.99.

Hydrogeochemistry and geothermometry of the carbonate-evaporite aquifers controlled by deep-seated faults using major ions and environmental isotopes

Carbonate aquifers probably constitute the most important thermal water resources in non-volcanic areas, and are characteristic of great energy potential and easier production as the most ideal targets for development in the future. The thermal waters in the aquifers within Southeast Chongqing (SEC) of China occur in an extensive region with an area of 198,000 km2, which are mainly hosted in the Cambrian and Ordovician carbonate-evaporite rocks. The thermal waters are mainly in pristine conditions and their genesis has not yet been fully understood. The occurrence of thermal waters in SEC is closely related to the presence of deep-seated faults which constitute pathways for the hydrothermal circulation. In this study, an investigation of water major ions and environmental isotopes from 14 hot springs and three drilled wells was carried out to examine their hydrogeochemical evolution and to estimate reservoir temperature. The thermal waters have outflow temperatures from 19 to 54.2 °C. They are divided into two hydrochemical groups with the Yushan Fault as a boundary: Group A, located to the west of the fault, are characterized by facies of chloride sodium waters with higher TDS; Group B, to the east of the fault, are more complicated sulfate-bicarbonate-chloride alkaline-earth waters with lower TDS. The hydrochemical processes such as dissolution of carbonate, gypsum and/or anhydrite, and halite, the common ion effect, and dedolomitization are evident based on the major ions and δ34SSO4 and δ18OSO4. The δ18O and δD compositions of the thermal waters suggest a meteoric recharge in a relatively wetter and colder climatic condition. The silica geothermometers show that the average reservoir temperatures are 63 ± 18 °C for Group A, and 82 ± 15 °C for Group B. The corresponding average reservoir depths are estimated to be 2.5 ± 0.7 km for Group A, and 3.2 ± 0.7 km for Group B. The corrected 14C ages of the thermal waters average at 14.8 ka BP, corresponding to the late Pleistocene. A conceptual circulation model is proposed for the thermal waters. Driven by gravity of topographic gradients, the percolating groundwater circulates at a specific depth, reaching a higher temperature and interacting with the host carbonate with imbedded evaporitic minerals (gypsum and/or anhydrite, and additional halite for Group A) to be saline deep-seated thermal fluids. The fluids rise along faults and emerge at the surface as thermal springs. The slow renewability rate of the thermal aquifers highlights the importance of assessing the resource before groundwater exploitation and extraction.

Distribution of landslides caused by heavy rainfall events and an earthquake in northern Aso Volcano, Japan from 1955 to 2016

A new landslide cannot form until the soil has recovered to the critical depth for the recurrence of a landslide through the weathering of bedrock and soil transportation from adjacent areas. In volcanic areas with tephra deposits, landslides expose tephra and not bedrock. Therefore, the immunity of landslides in volcanic areas may be different from that of landslides in non-volcanic areas. Herein, we developed landslide inventory maps (LIMs) for 6 periods during 1955–2016 using aerial photographs and digital elevation models in northern Aso Volcano. In this area, landslides were found to continuously occur due to rainfall events and a large earthquake. Using the 6 LIMs, we examined the terrain attributes (i.e., slope angle, slope aspect, and normalized distance to ridge) and the overlap of landslides. Among the terrain attributes, slope angle was a dominant factor affecting the occurrence of landslides caused by both rainfall events and an earthquake. The total landslide areal density in 2016 was 50% for a slope angle of 35%–45%. 2 atypical events (a rainfall in July 2012 and an earthquake in April 2016) caused landslides to occur on slopes that were relatively resistant to landslides by typical amounts of rainfall, resulting in high landslide density in 2016. The intensity of rainfall for an event in July 2012 was considerably higher than that for other rainfall events. The type of landslides caused by an earthquake in April 2016 was different from that of landslides caused by rainfall. The depths of some landslides caused by this earthquake were deeper than those of landslides caused by the rainfall in July 2012. The overlap ratio was <2.3% for all combinations of the 6 LIMs. The small overlap ratio in the study area suggests that the immunity of landslides continued during the 60-year period we examined. Further research clarifying the process leading to subsequent landslides would be useful to better understand the immunity of landslide and the associated landslide susceptibility in volcanic areas.

Cryptic dispersal of Cyanidiophytina (Rhodophyta) in non-acidic environments from Turkey.

Cyanidiophytina are a group of polyextremophilic red algae with a worldwide, but discontinuous colonization. They are restricted to widely dispersed hot springs, geothermal habitats, and also some human-altered environments. Cyanidiophytina are predominant where pH is prohibitive for the majority of eukaryotes (pH 0.5-3). Turkey is characterized by areas rich in volcanic activity separated by non-volcanic areas. Here we show that Cyanidiophycean populations are present in thermal baths located around Turkey on neutral/alkaline soils. All known genera and species within Cyanidiophytina were detected in Turkey, including Galdieria phlegrea, recorded up to now only in Italian Phlegrean Fields. By phylogenetic analyses, Turkish G. sulphuraria strains are monophyletic with Italian and Icelandic strains, and with Russian G. daedala strains. G. maxima from Turkey clustered with Icelandic, Kamchatka, and Japanese populations. The discovery of Cyanidiophytina in non-acidic Turkish soils raises new questions about the ecological boundaries of these extremophilic algae. This aids in the understanding of the dispersal abilities and distribution patterns of this ecologically and evolutionarily interesting group of algae.

Hg and CO2 emissions from soil diffuse degassing and fumaroles at Furnas Volcano (São Miguel Island, Azores): Gas flux and thermal energy output

Gaseous elemental mercury (Hg0g or GEM) and CO2 are emitted from active hydrothermal systems in volcanic areas mostly through diffuse degassing. Here, data from about 400 simultaneous measurements of soil GEM and CO2 flux performed within the caldera of Furnas Volcano, São Miguel Island (Azores) are discussed for the first time. This survey aimed at providing a new insight into the origin and magnitude of GEM in the investigated hydrothermal/volcanic environment and its relation with CO2 release. The distribution of GEM and CO2 emissions over an area of about 0.04 km2 are correlated with soil temperature, and measurements have provided total CO2 and GEM output of 39 t d−1 and 1.8 × 10−6 t d−1, respectively. These results are similar to the emission from currently active volcanic/hydrothermal areas elsewhere, as well as from important non-volcanic areas, such as Sulphur Bank Mercury Mine (California, USA) and Idrija Mercury Mine (Slovenia, EU), pointing out the relevance of diffuse degassing processes at Furnas Volcano. Atmospheric spot measurements in the most vigorous fumarole vents of the geothermal field have shown that the fumarolic GEM contribution (9.2 × 10−7 t d−1) represents a minor fraction of the total (fumarolic + diffusive) GEM output (2.7 × 10−6 t d−1) for the study area of this volcano. Basing upon the integration of the hydrothermal CO2 released and the H2O/CO2 ratio in the fumarolic gas, we have also estimated the thermal energy release associated with diffuse degassing at Furnas Volcano. Our estimates are ∼7.8 MW and 9.8 MW, respectively for Furnas Lake and Furnas Village fumaroles.

Exploring uni-element geochemical data under a compositional perspective

Different features of geochemical information were studied by comparing spatial distribution of concentration values and compositional data values. Geochemical data are compositional and should be treated as such to avoid spurious correlations and misleading interpretations. However, geochemists are also interested to discuss in terms of elemental concentrations. In this work the spatial distribution of Fe, Mn, Ti, Co, Cr, Ni and V based on 3535 topsoil samples collected in Campania region (Southern Italy) and analysed by ICP-MS after aqua regia digestion, is studied. Unielement maps and CoDA based maps, namely of ilr-transformed data and of two subcompositions of 3 components have been produced and interpreted. Results show that the ilr maps often show different geochemical patterns from those provided by the maps based on raw concentrations, namely for V, Fe and Co. This is not surprising as each studied ilr is a (log)ratio of an element against the others and account for the compositional variability. Nevertheless, the geochemical patterns of both raw and ilr based maps relate mostly with the geolithological features of the region: (1) (Ti, Ni, Cr)log-ratio variables are the best pathfinder in differentiating between volcanic (relative enrichment in Ti) and non-volcanic (relative enrichment in Ni and Cr) areas. (2) Soil alteration phenomena could locally enhance log-ratios of Ti due its high geochemical stability. (3) The spatial analysis of ilr-Fe and ilr Mn variables amplifies their relative degree of enrichment in correspondence of silici-clastic formations suggesting that Mn-Fe oxides of clay minerals mainly dominate the geochemical composition of the soils of the survey area. (4) Local enrichments of Cr and Ni at the main rivers' mouths and in the metropolitan areas of Naples and Salerno, possibly of anthropogenic origin, are highlighted in the 3-part subcomposition analysis. The developed exploration methodology of uni-element geochemical data under a compositional perspective leads to deeper insight and the gain is a more accurate interpretation of processes controlling soils geochemical variability.