Here we present digitization and analysis of the thermal springs of the world dataset compiled by Gerald Ashley Waring in 1965 into a collection of analog maps. We obtain the geographic coordinates ...of ~6,000 geothermal spring areas, including complementary data (e.g., temperature, total dissolved solids, flow rate), making them available in electronic format. Using temperature and flow rate, we derive the heat discharged from 1483 thermal spring areas (between ~10
and ~10
MW, with a median value of ~0.5 MW and ~8300 MW in total). We integrate this data set with other global data sets to study the relationship between thermalism and endogenous and exogenous factors with a supervised machine learning algorithm. This analysis confirms a dominant role of the terrestrial heat flow, topography, volcanism and extensional tectonics. This data set offers new insights and will boost future studies in geothermal energy exploration.
The processes leading to high levels of arsenic (As), iron (Fe), and manganese (Mn) in groundwater, in a naturally reducing aquifer at a controlled municipal landfill site, are investigated. The ...challenge is to distinguish the natural water-rock interaction processes, that allow these substances to dissolve in groundwater, from direct pollution or enhanced dissolution of hydroxides as undesired consequences of the anthropic activities above. Ordinary groundwater monitoring of physical-chemical parameters and inorganic compounds (major and trace elements) was complemented by environmental isotopes of groundwater (tritium, deuterium, oxygen-18 and carbon-13) and dissolved gases (carbon-13 of methane and carbon dioxide and carbon-14 of methane). Pearson/Spearman correlation indices, as well as Principal Component Analysis (PCA), were used to determine the main correlations among variables. The concurrent presence of As, Fe and CH4, as reported in similar anoxic environments, suggests that anaerobic oxidation of methane could drive the reductive dissolution of As-rich Fe(III)(hydro)oxides. Manganese is more sensitive to carbon dioxide, possibly due to a decrease in pH which accelerates the dissolution of Mn-oxides. Finally, we found that tritium and deuterium, which have been used for decades as leachate tracer in groundwater, may be subject to false positives due to the reuse of water recovered from leachate treatment (which has the same isotopic signature of leachate) within the plants, to comply with the requirements of the circular economy. The integration of the environmental isotope analysis into the traditional monitoring approach can effectively support the comprehension of processes. However, this strategy needs to be complemented by a good conceptual hydrogeological model and expert evaluation to avoid misinterpretations.
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•A co-occurrence of As, Fe and CH4 was observed in anaerobic groundwater.•Reductive dissolution of As-rich Fe(III)(hydro)oxides with CH4 as electron donor.•Mn correlates with CO2 suggesting Mn-oxides dissolution in acidic environment.•Isotopes, methane, CO2 provides new insights in groundwater monitoring at landfills.•Tritium as leachate tracer might be confused by false positives due to water reuse.
Numerous soil gas measurements of four gaseous species with very different geochemical behaviors were performed in the Fucino Basin, an area characterized by known and inferred structural ...discontinuities. A comprehensive statistical and geostatistical treatment of these data followed in order to provide insight into the spatial influence of tectonic discontinuities and geology on deep‐seated gas migration toward the surface. The results yielded anomalies with different features, reflecting the different gas‐bearing properties of the eastern seismogenic faults related to the 1915 earthquake (Mb = 7.0) and the hidden structural features occurring in the western side of the plain. In particular, this approach demonstrates that soil gas concentration (i.e., Rn and CO2) can identify the simpler normal faults of the eastern sector of the plain. In contrast, the more pervasive fracturing and faulting, as well as the occurrence of coarser deposits, on the western side of the area, make the location of faults less clear. The results show that gases migrate preferentially through zones of brittle deformation by advective processes, as suggested by the relatively high rate of migration needed to obtain anomalies of short‐lived 222Rn in the soil pores. Furthermore, a geostatistical study of soil gas data was conducted to quantify the spatial domain of correlation and the gas‐bearing properties of faults on the basis of shallow soil gas distribution (i.e., anisotropic behavior). The results provide a clear correlation between the shape and orientation of the anomalies and the different geometry of the faults recognized in the plain.
Purpose
The environmental quality standards (EQSs) were defined by the Water Framework Directive (
2000/60/EC
) and daughter directives for hindering the chemical pollution of surface water bodies. ...For substances with poor solubility in water and/or the tendency to bioaccumulate along the food chain, member states could choose to define the EQSs on sediments and marine organisms if they guarantee the same level of protection of the EQSs derived for water. Also, Italy defined them on sediments without considering harbors because of their role as pressure sources. Considering the available environmental information, this study focused on verifying the applicability and possible limits of the EQSs in sediments from different Italian harbors.
Materials and methods
A dataset with concentrations of metals and trace elements (MTEs) and organic compounds (OCs) from the sediments of 34 Italian harbors was assessed. Grain size parameters were also included for complete information on sediment characteristics. Data were processed through univariate statistics to identify the position of the EQSs within the whole distribution of concentration values. Moreover, a logistic model was applied to verify the probability of exceeding the EQSs for at least one parameter (susceptibility) in the harbor areas.
Results and discussion
The EQSs of all MTEs were found close to the overall medians, demonstrating that they are suitable values for highlighting widespread metal contamination, also recognizable in the output of the logistic model, where wide areas with a homogeneous susceptibility were highlighted. The EQSs of most OCs resulted considerably higher than the overall medians, but a minor part of the data exceeded them by far, demonstrating that the contamination was characterized by patchy distribution, as also shown by the susceptibility maps.
Conclusions
Applying a statistical approach, this study tried to compare the distribution of concentration data with the EQSs of sediments based on a specific dataset containing many records from many Italian harbors. The logistic model applied in this study, based on the excess of the EQSs for at least one parameter, represented a robust tool to define areas at high susceptibility in the harbors and confirmed their adaptability also in these highly impacted areas.
In many countries, assessment programmes are carried out to identify areas where people may be exposed to high radon levels. These programmes often involve detailed mapping, followed by spatial ...interpolation and extrapolation of the results based on the correlation of indoor radon values with other parameters (e.g., lithology, permeability and airborne total gamma radiation) to optimise the radon hazard maps at the municipal and/or regional scale. In the present work, Geographical Weighted Regression and geostatistics are used to estimate the Geogenic Radon Potential (GRP) of the Lazio Region, assuming that the radon risk only depends on the geological and environmental characteristics of the study area. A wide geodatabase has been organised including about 8000 samples of soil-gas radon, as well as other proxy variables, such as radium and uranium content of homogeneous geological units, rock permeability, and faults and topography often associated with radon production/migration in the shallow environment. All these data have been processed in a Geographic Information System (GIS) using geospatial analysis and geostatistics to produce base thematic maps in a 1000 m × 1000 m grid format. Global Ordinary Least Squared (OLS) regression and local Geographical Weighted Regression (GWR) have been applied and compared assuming that the relationships between radon activities and the environmental variables are not spatially stationary, but vary locally according to the GRP. The spatial regression model has been elaborated considering soil-gas radon concentrations as the response variable and developing proxy variables as predictors through the use of a training dataset. Then a validation procedure was used to predict soil-gas radon values using a test dataset. Finally, the predicted values were interpolated using the kriging algorithm to obtain the GRP map of the Lazio region. The map shows some high GRP areas corresponding to the volcanic terrains (central-northern sector of Lazio region) and to faulted and fractured carbonate rocks (central-southern and eastern sectors of the Lazio region). This typical local variability of autocorrelated phenomena can only be taken into account by using local methods for spatial data analysis. The constructed GRP map can be a useful tool to implement radon policies at both the national and local levels, providing critical data for land use and planning purposes.
•Geogenic Radon Potential (GRP) measures what Earth delivers in term of radon.•The estimation of the Geogenic Radon Potential map of the Lazio region is proposed.•Geological and geochemical data are used as proxies and response variables.•Geographically Weighted Regression and geostatistics are applied to construct GRP map.
Due to its potential use as a carbon-free energy resource with minimal environmental and climate impacts, natural hydrogen (H2) produced by subsurface geochemical processes is today the target of ...intensive research. In H2 exploration practices, bacteria are thought to swiftly consume H2 and, therefore, small near-surface concentrations of H2, even orders of 102 ppmv in soils, are considered a signal of active migration of geological gas, potentially revealing underground resources. Here, we document an extraordinary case of a widespread occurrence of H2 (up to 1 vol%), together with elevated concentrations of CH4 and CO2 (up to 51 and 27 vol%, respectively), in aerated meadow soils along Italian Alps valleys. Based on current literature, this finding would be classified as a discovery of pervasive and massive geological H2 seepage. Nevertheless, an ensemble of gas geochemical and soil microbiological analyses, including bulk and clumped CH4 isotopes, radiocarbon of CH4 and CO2, and DNA and mcrA gene quantitative polymerase chain reaction analyses, revealed that H2 was only coupled to modern microbial gas. The H2-CO2-CH4-H2S association, wet soil proximity, and the absence of other geogenic gases in soils and springs suggest that H2 derives from near-surface fermentation, rather than geological degassing. H2 concentrations up to 1 vol% in soils are not conclusive evidence of deep gas seepage. This study provides a new reference for the potential of microbial H2, CH4 and CO2 in soils, to be considered in H2 exploration guidelines and soil carbon and greenhouse-gas cycle research.
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•High concentrations of H2, CH4 and CO2 in soil resembling geological seepage•Modern microbial CH4 and CO2 origin revealed by multiple isotopic analyses•The highest concentrations of microbial CH4 and CO2 ever reported in aerated soils•H2 up to 1 vol% in aerated soil may not necessarily be related to geological degassing.•Re-evaluation of the interpretation of H2 in soils for natural hydrogen exploration
Ongoing studies conducted in northern polar regions reveal that permafrost stability plays a key role in the modern carbon cycle as it potentially stores considerable quantities of greenhouse gases. ...Rapid and recent warming of the Arctic permafrost is resulting in significant greenhouse gas emissions, both from physical and microbial processes. The potential impact of greenhouse gas release from the Antarctic region has not, to date, been investigated. In Antarctica, the McMurdo Dry Valleys comprise 10 % of the ice-free soil surface areas in Antarctica and like the northern polar regions are also warming albeit at a slower rate.
The work presented herein examines a comprehensive sample suite of soil gas (e.g., CO2, CH4 and He) concentrations and CO2 flux measurements conducted in Taylor Valley during austral summer 2019/2020. Analytical results reveal the presence of significant concentrations of CO2, CH4 and He (up to 3.44 vol%, 18,447 ppmv and 6.49 ppmv, respectively) at the base of the active layer. When compared with the few previously obtained measurements, we observe increased CO2 flux rates (estimated CO2 emissions in the study area of 21.6 km2 ≈ 15 tons day−1). We suggest that the gas source is connected with the deep brines migrating from inland (potentially from beneath the Antarctic Ice Sheet) towards the coast beneath the permafrost layer. These data provide a baseline for future investigations aimed at monitoring the changing rate of greenhouse gas emissions from Antarctic permafrost, and the potential origin of gases, as the southern polar region warms.
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•First extensive soil gas and flux survey in Antarctica•Discovered zones of multigas (CO2, CH4, He, H2) anomalies•CO2 emissions estimation in Lower Taylor Valley•Gas rising from deep brines
Italian sinkholes, which are mainly related to karst phenomena (i.e., solution sinkholes, collapse sinkholes, etc.), are widespread along the Apennine ridge and in pedemontane areas where there are ...carbonatic bedrock outcrops. However, other collapses, which seem unrelated to karst dissolution, have been identified in plain areas with a thick sedimentary cover over buried bedrock. The main goal of this work is to study the geological, geomorphological, and structural setting of these areas to identify the possible mechanism of the generation and evolution of these collapses. About 750 cases were identified by research based on historical archives, specific geological literature, and information from local administrations. Geological, geomorphological, and hydro-geochemical surveys were conducted in 300 cases, supported by literature, borehole, and seismic data. A few examples were discarded because they could be ascribed to karst dissolution, volcanic origin (i.e., maar), or anthropogenic causes. Field studies regarding the other 450 cases are in progress. These cases occur along the Tyrrhenian margin (Latium, Abruzzo, Campania, Tuscany) in tectonic, coastal, and alluvial plains close to carbonate ridges. These plains are characterized by the presence of pressurized aquifers in the buried bedrock, overlaid by unconsolidated sediments (i.e., clay, sands, pyroclastic deposits, etc.). The majority of these collapses are aligned along regional master and seismogenetic faults. About 50% of the studied cases host small lakes or ponds, often characterized by highly mineralized springs enriched with CO
2
and H
2
S. The Periadriatic margin does not seem to be affected by these phenomena, and only a few cases have been found in Sicily, Sardinia, and Liguria. The obtained scenarios suggests that this type of collapse could be related to upward erosion through vertical conduits (i.e., deep faults) caused by deep piping processes whose erosive strength is increased by the presence of acidic fluids. In order to distinguish these collapses from typical karst dissolution phenomena, they are defined as deep piping sinkholes (DPS).
Recent research into CO2 geological storage has shown that it has potential to be a safe and effective way to rapidly decrease short-term anthropogenic CO2 emissions. Despite this progress, ...stakeholders must be convinced that the scientific community has studied all possible scenarios, including a potential leak into the biosphere. To better understand the potential impact of such an event, a detailed geochemical and biological study was conducted during two different seasons on a naturally occurring gas vent located within a Mediterranean pasture ecosystem (Latera geothermal field, central Italy). Results from botanical, soil gas, and gas flux surveys, and from chemical and biological analyses of shallow soil samples (0-20 cm depth), show that a significant impact is only observed in the 6 m wide centre of the vent, where CO2 flux rates exceed 2000-3000 g m−2 d−1. In this "vent core" there is no vegetation, pH is low (minimum 3.5), and small changes are observed in mineralogy and bulk chemistry. In addition, microbial activities and populations are regulated in this interval by near-anoxic conditions, and by elevated soil gas CO2 (>95%) and trace reduced gases (CH4, H2S, and H2). An approximately 20 m wide halo surrounding the core forms a transition zone, over which there is a gradual decrease in CO2 concentrations, a rapid decrease in CO2 fluxes, and the absence of reactive gas species. In this transition zone grasses dominate near the vent core, but these are progressively replaced by clover and a greater plant diversity moving away from the vent centre. Physical parameters (e.g. pH, bulk chemistry, mineralogy) and microbial systems also gradually return to background values across this transition zone. Results indicate that, even at this anomalous high-flux site, the effects of the gas vent are spatially limited and that the ecosystem appears to have adapted to the different conditions through species substitution or adaptation.
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