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Driven by the collection of enormous amounts of streaming data from sensors, and with the emergence of the internet of things, the need for developing robust detection techniques to identify data anomalies has increased recently. The algorithms for anomaly detection are required to be selected based on the type of data. In this study, we propose a predictive anomaly detection technique, DeepSense, which is applied to soil gas concentration data acquired from sensors being used for environmental characterization at a prospective CO2 storage site in Queensland, Australia. DeepSense takes advantage of deep-learning algorithms as its predictor module and uses a process-based soil gas method as the basis of its anomaly detector module. The proposed predictor framework leverages the power of convolutional neural network algorithms for feature extraction and simultaneously captures the long-term temporal dependency through long short-term memory algorithms. The proposed process-based anomaly detection method is a cost-effective alternative to the conventional concentration-based soil gas methodologies which rely on long-term baseline surveys for defining the threshold level. The results indicate that the proposed framework performs well in diagnosing anomalous data in soil gas concentration data streams. The robustness and efficacy of the DeepSense were verified against data sets acquired from different monitoring stations of the storage site.

Radon and progeny concentrations in indoor air, radon exhalation rates and radon concentrations in soil–gas were measured at various locations in a test village at Tehri Garhwal, India. The aim of this study is to understand inter-correlations of radon species in different media. Indoor radon and its progeny concentrations were observed higher in winter and lower in summer season. The annual average values of radon and thoron equilibrium factors were calculated to be 0.33 and 0.07, respectively. Radon and its progeny were found to contribute 66% of the total annual inhalation dose. Soil-gas and indoor radon concentrations, and radon exhalation rates were found to be positively correlated with each other.

Soil microbes vigorously produce and consume gases that reflect active soil biogeochemical processes. Soil gas measurements are therefore a powerful tool to monitor microbial activity. Yet, the majority of soil gases lack non-disruptive subsurface measurement methods at spatiotemporal scales relevant to microbial processes and soil structure. To address this need, we developed a soil gas sampling system that uses novel diffusive soil probes and sample transfer approaches for high-resolution sampling from discrete subsurface regions. Probe sampling requires transferring soil gas samples to above-ground gas analyzers where concentrations and isotopologues are measured. Obtaining representative soil gas samples has historically required balancing disruption to soil gas composition with measurement frequency and analyzer volume demand. These considerations have limited attempts to quantify trace gas spatial concentration gradients and heterogeneity at scales relevant to the soil microbiome. Here, we describe our new flexible diffusive probe sampling system integrated with a modified, reduced volume trace gas analyzer and demonstrate its application for subsurface monitoring of biogeochemical cycling of nitrous oxide (N2O) and its site-specific isotopologues, methane, carbon dioxide, and nitric oxide in controlled soil columns. The sampling system observed reproducible responses of soil gas concentrations to manipulations of soil nutrients and redox state, providing a new window into the microbial response to these key environmental forcings. Using site-specific N2O isotopologues as indicators of microbial processes, we constrain the dynamics of in situ microbial activity. Unlocking trace gas messengers of microbial activity will complement -omics approaches, challenge subsurface models, and improve understanding of soil heterogeneity to disentangle interactive processes in the subsurface biome.

European Union Council Directive 2013/51/EURATOM recently sets out so-called indicator parameters for: radon, tritium and indicative dose of water intended for human consumption. The aim of this research was to elaborate an effective procedure for determination of radon and radium 226,228Ra isotopes (which are potentially the main contributors to the internal dose from drinking and cooking water) and to find the possible relationships between these radionuclides in underground water reservoirs and 222Rn concentration in the soil gas in their vicinity. The research was performed by applying a non-volatile and water-immiscible scintillation cocktail based on a pure diisopropylnaphthalene (Ultima Gold F: UGF), which allow for efficient radon extraction from 0.5 dm3 of water samples to 20 cm3 of scintillation phase and its direct determination with a detection limit of 5 × 10–3 Bq dm−3. The further preliminary concentration of 3 dm3 of crude water samples by evaporation to 0.5 dm3 samples led to the removal of all unsupported 222Rn activity and allowed the 226Ra determination via equivalent 222Rn detection after one-month samples storage using a low-background Triathler liquid scintillation counter in the α/β separation counting mode. Together with determination of 226Ra isotope in water samples, the simultaneous measurements of 228Ra and 222Rn radionuclides concentrations in water as well as 222Rn activity in the soil gas around the water supply sites were performed. The achieved limit of 226Ra detection was at a very low level of 10–3 Bq dm−3. The measured values of 226Ra concentration in 50 public underground water supply units for the Kalisz district of Poland were relatively low and ranged from below detection limit to 28.5 × 10–3 Bq dm−3 with arithmetic mean and median values of 12.9 and 12.2 × 10–3 Bq dm−3, respectively. Weak correlations were observed between activity concentrations of 226Ra and 222Rn in the crude water samples (R2 = 0.31) and 222Rn in water and its concentration in the nearby soil gas (R2 = 0.48).

Solid-gas-water phase partitioning of mercury (Hg) and the processes governing its diffusivity within soils are poorly studied. In this study, landscape and forest species dependences of gaseous elemental Hg (Hg(0)) in soil profiles (0-50 cm) were investigated over four seasons in eight subtropical (130 days) and temperate (96 days) forest plots. The vertical soil pore Hg(0) concentrations differed between subtropical (Masson pine, broad-leaved forest, and open field) and temperate (Chinese pine, larch, mixed broad-leaf forests, and open field) catchments, with annual averages ranging from 6.73 to 15.8 and 0.95 to 2.08 ng m-3, respectively. The highest Hg(0) concentrations in soil gas consistently occurred in the upper mineral or organic horizons, indicating immobilization of Hg(0) in mineral soils. A strongly positive relationship between pore Hg(0) concentrations and ratios of Hg to organic matter (SOM) in soils suggests that the vertical distribution of Hg(0) is related to soil Hg(0) formation by Hg(II) reduction and sorption to SOM. Temperature was also an important driver of Hg(0) production in soil pores. Based on measurements of soil-air Hg(0) exchange, diffusion coefficients (Ds) of Hg(0) between soil and atmosphere were calculated for field sites, providing a foundation for future development and validation of terrestrial Hg models.

Developing a more mechanistic understanding of soil respiration is hampered by the difficulty in determining the contribution of different organic substrates to respiration and in disentangling autotrophic-versus-heterotrophic and aerobic-versus-anaerobic processes. Here, we use a relatively novel tool for better understanding soil respiration: the apparent respiration quotient (ARQ). The ARQ is the amount of CO2 produced in the soil divided by the amount of O2 consumed, and it changes according to which organic substrates are being consumed and whether oxygen is being used as an electron acceptor. We investigated how the ARQ of soil gas varied seasonally, by soil depth, and by in situ experimental warming (+4 ∘C) in a coniferous-forest whole-soil-profile warming experiment over 2 years. We then compared the patterns in ARQ to those of soil δ13CO2. Our measurements showed strong seasonal variations in ARQ, from ≈0.9 during the late spring and summer to ≈0.7 during the winter. This pattern likely reflected a shift from respiration being fueled by oxidized substrates like sugars and organic acids derived from root and root respiration during the growing season to more reduced substrates such as lipids and proteins derived from microbial necromass during the winter. This interpretation was supported by δ13CO2 values, which were lower, like lipids, in the winter and higher, like sugars, in the summer. Furthermore, experimental warming significantly changed how both ARQ and δ13CO2 responded to soil temperature. Wintertime ARQ and δ13CO2 values were higher in heated than in control plots, probably due to the warming-driven increase in microbial activity that may have utilized oxidized carbon substrates, while growing-season values were lower in heated plots. Experimental warming and phenology change the sources of soil respiration throughout the soil profile. The sensitivity of ARQ to these changes demonstrates its potential as a tool for disentangling the biological sources contributing to soil respiration.

Дослідження складу ґрунтового повітря є надзвичайно важливою задачею, оскільки вміст компонентів газової фази ґрунту, зокрема СО2 та О2, безпосереднім чином відображає показники родючості ґрунту. В роботі проведено огляд щодо компонентного складу ґрунтового повітря, розглянуто існуючі методи визначення дихання ґрунту та показано перспективність використання сенсорного методу, який базується на використанні масиву датчиків, з можливістю проведення онлайн моніторингу без використання реагентів. З метою визначення чутливості синтезованих зразків відносно СО2 методом паро-газового транспорту синтезовано одновимірні наноструктури стануму (IV) оксиду та проведено їх модифікацію ітрієм для використання в чутливих шарах газових сенсорів. Досліджено вольт-амперні характеристики чистих та модифікованих наноструктур SnO2 на повітрі та в атмосфері карбон (IV) оксиду. Investigation of soil air composition is an extremely important task because the content of soil gas phase components, in particular CO2, O2 and NOx , directly reflects soil fertility. The composition of soil air, the so-called "breath of the earth", plays an important role in the nutrition of plants and is an indicator of biochemical and biological processes that occur in the soil. The study of soil gas regime is extremely important for agrochemical and microbiological studies and is a set of all related phenomena: the flow of gases into the soil and their movement along the soil profile; changes in the content and composition of gases in the ground air as a result of the absorption or release of individual gases in biological and biochemical processes, the exchange between soil and atmosphere, solid and liquid phases. Carbon dioxide and oxygen are the most dynamic gases among all gases of ground air. The growth of plants depends on the concentration of CO2, and when it reaches its optimal concentration it is possible to accelerate the growth of the crop. Oxygen of ground air is essential for soil fertility and especially necessary for microbiological processes. It actively participates in chemical reactions of mineral and organic substances and is actively absorbed by the roots of plants and microbes in the process of their breathing. This paper reviews the composition of ground air, considers existing methods of soil breathing determination and shows the prospect of sensor method with online monitoring without reagents usage. In order to determine the sensitivity of synthesized samples towards CO2, one-dimensional nanostructures of the tin (IV) oxide have been synthesized by vapor transport method and their modification by yttrium for use in sensitive layers of gas sensor has been done. The current-voltage characteristics of pure and modified SnO2 nanostructures at ambient and in the atmosphere of carbon (IV) oxide have been investigated. It is shown that yttrium modified onedimensional SnO2 nanostructures have a higher sensory response to carbon dioxide in comparison with the pure tin (IV) oxide sample, that is, they are much more promising for use in sensing systems of soil air composition study

Geological storage of CO2 technologies has become an important and effective way to reduce the greenhouse gas emissions, especially when it is combined with CO2 enhanced oil recovery (EOR), which can not only trap CO2 but also enhance oil recovery. However, the risk of CO2 leakage has always been a prominent issue. In this paper, the mechanisms and pathways of CO2 leakage during geological storage in oil reservoirs were analyzed using fault tree analysis (FTR). Besides, monitoring technologies were discussed and deployed in a CO2 EOR demonstration project. The analysis results showed that the sealing failures of oil producer and CO2 injector wells, like well cement failure and casing failure, are the main reasons for the CO2 leakage, which has been observed in the oil field monitoring project. The monitoring results indicated that there is no large‐scale CO2 leakage, while relatively high and abnormal CO2 concentration in soil gas near some wellbores are observed, which indicates there is some leakage of CO2 through incomplete cement ring and well casing string. FTR results provide guidelines for monitoring and preventing of CO2 leakage during geological storage in oil reservoirs. The near‐surface monitoring methods, especially the soil gas monitoring technologies, can effectively detect the leakage of CO2, and are a proper method for CO2 leakage monitoring. © 2020 Society of Chemical Industry and John Wiley & Sons, Ltd.

The assessment of potential radon-hazardous environments is nowadays a critical issue in planning, monitoring, and developing appropriate mitigation strategies. Although some geological structures (e.g., fault systems) and other geological factors (e.g., radionuclide content, soil organic or rock weathering) can locally affect the radon occurrence, at the basis of a good implementation of radon-safe systems, optimized modelling at territorial scale is required. The use of spatial regression models, adequately combining different types of predictors, represents an invaluable tool to identify the relationships between radon and its controlling factors as well as to construct Geogenic Radon Potential (GRP) maps of an area. In this work, two GRP maps were developed based on field measurements of soil gas radon and thoron concentrations and gamma spectrometry of soil and rock samples of the Euganean Hills (northern Italy) district. A predictive model of radon concentration in soil gas was reconstructed taking into account the relationships among the soil gas radon and seven predictors: terrestrial gamma dose radiation (TGDR), thoron (220Rn), fault density (FD), soil permeability (PERM), digital terrain model (SLOPE), moisture index (TMI), heat load index (HLI). These predictors allowed to elaborate local spatial models by using the Empirical Bayesian Regression Kriging (EBRK) in order to find the best combination and define the GRP of the Euganean Hills area. A second GRP map based on the Neznal approach (GRPNEZ) has been modelled using the TGDR and 220Rn, as predictors of radon concentration, and FD as predictor of soil permeability. Then, the two GRP maps have been compared. Results highlight that the radon potential is mainly driven by the bedrock type but the presence of fault systems and topographic features play a key role in radon migration in the subsoil and its exhalation at the soil/atmosphere boundary.

International audience; Soils and groundwater are often contaminated by complex organic mixtures also called Non Aqueous Phase Liquids (NAPLs). Several techniques such as drilling, monitoring of soil gas or injection of tracers are traditionally used to quantify NAPLs in aquifers but are complex to perform. The use of natural soil gas such as 222Rn could be an easy and cheap alternative. This method requires the knowledge of the radon NAPL-water partitioning coefficients (Kn-w.). Once spilled on soil, NAPL will undergo degradation (evaporation, effects of sun light among others) and this degradation could impact the Kn-w. This study aims at investigating the partitioning coefficients of complex NAPLs such as commercial diesel fuel and gasoline in relation to degradation such as evaporation and UV-degradation. For that purpose, batch experiments and GCMS investigations were carried out. The results show different Kn-w for the commercial diesel fuel (60.7 ± 6.1) and gasoline (37.4 ± 5.6). The results also show different Kn-w behaviors in relation with degradation. Degraded diesel fuel display opposite Kn-w values (74.8 ± 7.5 and 25.1 ± 2.5 for UV degraded and evaporated diesel fuel, respectively), compared to fresh one. Degraded gasoline shows no significant variations of the Kn-w compared to fresh one. The molecular investigation reveals the removal of the most volatile fraction for the evaporation treatment, whereas UV-degradation do not have pronounced effects on the chromatogram pattern. For the gasoline molecular investigation, no difference is observed between the treatments excepted a very slight removal of the lightest compounds under evaporation. These results show that NAPL degradation have effects on the Kn-w for diesel fuel and no significant effects for gasoline, at least with these degradation paths. This Kn-w variation will have in fine effects on 222Rn activity interpretation and NAPL subsurface quantification.

In the last decades radon (Rn) has been widely proposed as a naturally occurring tracer for non-aqueous phase liquids (NAPL) in the soil. This work examines the feasibility of using soil gas data collected at some distance from the source zone for the application of the Rn deficit technique for the identification and quantification of NAPL contamination. To this end, we used a steady-state 1-D analytical solution that is based on a 3-layer model that allows to simulate the transport and distribution of Rn in the source zone, capillary fringe and overlying unsaturated soil. The analytical solution was first validated against a more detailed numerical model available in the literature. Then, a series of simulations were carried out to evaluate the vertical concentration profiles of Rn in soil gas above the source zone and in background location not impacted by NAPL. Simulation results showed that the parameters that most influence the migration and distribution of Rn in the subsurface are the distance of the soil gas probe from the source zone and, to a lower extent, the type of contamination (e.g. diesel or gasoline) and the soil type. On the basis of these results, we developed some easy-to-use nomographs to estimate the residual NAPL phase based on the observed radon deficit in soil gas and on the probe to source distance and soil and NAPL characteristics. According to the obtained results, the radon deficit technique results a feasible method for a qualitative identification of residual NAPL when radon in soil gas is measured at distances lower than 2 m from the contaminated zone. However, for an accurate quantitative estimation of the NAPL phase content, soil gas probes should be preferably located at distances lower than 1 m from the source zone.

A high throughput system for processing and detection of low levels of radioxenon in soil gas samples has been developed. Processing and analysis of sub-soil noble gas samples puts high demands on the gas separation part of the system since the samples might contain high levels of Rn, CO2 as well as other gases. The gas process is optimized to remove all CO2, H2O and Rn with a high recovery yield of the xenon in the sample to ensure a high sensitivity even for small samples. The system is designed to handle multiple samples per day with a high level of automation and sample traceability to be suitable for use in an on-site inspection (OSI) an important component in the verification of the Comprehensive Nuclear Test Ban Treaty. To ensure a rapid deployment the system could be pre-installed in a flight container.

Soils are the largest terrestrial pool of mercury (Hg), a neurotoxic pollutant. Pathways of Hg accumulation and loss in forest soils include throughfall, litterfall, soil gas fluxes, and leaching in soil solution, all of which will likely be altered under changing climate. We took advantage of three ongoing climate-change manipulation experiments at the Hubbard Brook Experimental Forest, New Hampshire, USA: a combined growing-season warming and winter freeze-thaw cycle experiment, a throughfall exclusion to mimic drought, and a simulated ice storm experiment to examine the response of the forest Hg cycle to climatic disturbances. Across these three experiments, we compared Hg inputs in throughfall and leaf litterfall and Hg outputs in soil gas fluxes. Soil solution was measured only in the simulated ice storm experiment. We found that northern forest soils retained consistently less Hg by 16–60% in the three climate manipulations compared to the undisturbed controls (~ 7.4 µg Hg m−2 year−1), although soils across all three experiments still served as a net sink for Hg. Growing-season soil warming and combined soil warming and winter freeze-thaw cycles had little effect on litterfall and throughfall flux, but they increased soil Hg0 evasion by 31 and 35%, respectively, relative to the control plots. The drought plots had 5% lower litterfall Hg flux, 50% lower throughfall Hg flux, and 21% lower soil Hg0 evasion than the control plots. The simulated ice storm had 23% higher litterfall Hg flux, 1% higher throughfall Hg flux, 37% higher soil Hg0 evasion, and 151% higher soil Hg leaching than the control plots. These observations suggest that climate changes such as warmer soils in the growing season or more intense ice storms in winter are likely to exacerbate Hg pollution by releasing Hg sequestered in forest soils via evasion and leaching.

CO2 and CH4 flux measurements over a septic tank soakaway located in a northern maritime climate (Ireland) were conducted for a period of 81 days using a multi-chamber automated soil gas flux chamber system with high spatial and temporal resolution. Overall median CO2 fluxes were 7.28; 6.40 μmol CO2 m−2 s−1 from the soakaway and control soil, respectively. Overall median CH4 fluxes were − 0.28; −0.67 nmol CH4 m−2 s−1 from the soakaway and control soil, respectively. While CO2 fluxes expressed strong diurnal variability driven by soil temperature, CH4 fluxes were less affected by environmental factors and effectively limited to the first few meters from the septic tank. However, localised CH4 degassing events were observed during drying conditions with up to 60-times higher fluxes compared to the overall median. The soakaway was found to be a net emitter of both CO2 and CH4, releasing a total of 7.327 kg CO2 yr−1 and 0.033 kg CO2Eq. yr−1, respectively. The apparent spatio-temporal heterogeneity of observed soil gas fluxes identified in this study emphasises the importance of integrating measurements with both high spatial and temporal resolution from on-site installations as engineered nature-based solutions.

In this study, we investigate the soil gas concentration attenuation with diffusive transport in lateral and vertical transport in cases with surface pavements with a pilot-scale tank. Three scenarios were investigated, one with a completely open soil surface and the other two involving partially paved soil surface. The results, on the one hand, indicate that the soil gas concentration generally decreases linearly and exponentially in the vertical and horizontal transport directions, respectively, generally in accordance with available modeling studies. On the other hand, our experiment shows that low-permeability ground covers can increase shallow soil gas concentrations beneath the pavement by at most 3–4 times, inducing higher subslab concentration than that below open ground surface, even if the latter is obtained at a closer location to vapor source. For cases with uniform soil properties, our study suggests exterior soil gas sample should be taken at a depth below the building foundation by half of the building footprint size, if the vapor source is laterally extensive relative to the building footprint, or by 1 m and 2–3 m for slab-on-grade and basement scenarios, respectively, if the vapor source is located laterally away from the building.

Reducing greenhouse gas emissions from arable soil while maintaining productivity is a major challenge for agriculture. Biochar is known to reduce N₂O emissions from soil, but the underlying mechanisms are unclear. This study examined the impact of green waste biochar (20 Mg ha⁻¹) and lime (CaCO₃; 2 Mg ha⁻¹) application on soil gas transport properties and related changes in these to soil N₂O and CO₂ emissions measured using automated chambers in a field experiment cropped with maize. In situ soil water content monitoring was combined with laboratory measurements of relative soil gas diffusion coefficient (Dₚ/D₀) at different matric potentials, to determine changes in Dₚ/D₀ over time. Cumulative N₂O emissions were similar in the control and lime treatment, but much lower in the biochar treatment. Cumulative CO₂ emissions decreased in the order: lime treatment > biochar treatment > control soil. When N₂O emissions were not driven by excess N supply shortly after fertilisation, they were associated with Dₚ/D₀ changes, whereby decreases in Dₚ/D₀ corresponded to N₂O emissions peaks. No distinct pattern was observed between CO₂ emissions and Dₚ/D₀. Cumulative N₂O emissions were positively related to number of days with Dₚ/D₀ < 0.02, a critical limit for soil aeration. These results indicate that improved soil gas diffusivity, and hence improved soil aeration, may explain the effect of biochar in reducing N₂O emissions. They also suggest that knowledge of Dₚ/D₀ changes may be key to explaining N₂O emissions.

We undertake a sturdy body seismogenic model study along the northern margin of the West Qinling fault zone, China, to address some existing problems of neglecting scientific layout based on certain prediction theory and observation facts surrounding underground fluid monitoring networks across faults. A combination of high-density underground fluid measurements and vertical crustal deformation and seismological observations were used to elucidate the interplay between fluid dynamics, crustal deformation, and seismic activity and to comprehensively analyze the fault segment characteristics along the fault zone. We found correspondence between these parameters along the northern margin of the West Qinling fault zone. All parameters showed higher values in the Wu Shan (WS) segment than in the western Xia He–Huang Xiang Gou–Zhang Xian (XH-HXG-ZX) segment and eastern Tian Shui (TS) area. The 222Rn concentration reached 5.0942 at BZC, and the Hg concentration reached 3.4398 at LJG in WS. Similarly, the vertical crustal deformation and seismic activity in this area were both stronger than those in the western XH–HXG–ZX and TS area. Based on the sturdy body seismogenic model, we found that the ZX and TS segments exhibited weaker activity than the surrounding areas and may be in a deep locked state under the corresponding regional stress. Compared with existing monitoring network for background value detection and comprehensive research results, we propose a technical underground flow monitoring network prototype that includes two grade I and five grade II survey sites along the northern margin of the West Qinling fault zone based on the sturdy body seismogenic model. This prototype will provide a more reliable basis for earthquake prediction, tracking and mitigation, and disaster risk reduction. The presented scheme can be used as a guideline for deploying fault soil gas monitoring networks in China.

Radon, a radioactive gas is a primary source of radioactive pollution and directly influence the humans exposed to it. Radon (Rn222)/thoron (Rn220) exhalation and soil gas radon concentrations were estimated in agricultural soil samples from different locations of Amritsar district of Punjab, India, by using active techniques i.e. Smart RnDuo monitor and RAD7. Rn222 mass and Rn220 surface exhalation rate of 22 locations varied from 21.41 to 43.81 mBq kg−1 h−1 and 64.73 to 717.03 mBq m−2 s−1 with average values of 32.58 ± 1.11 mBq kg−1 h−1 and 195.10 ± 53.02 mBq m−2 s−1, respectively. Mean soil radon concentration of 12 agricultural soils samples varied from 0.1 ± 0.04 to 9.7 ± 0.40 kBq m−3. Potentially toxic metals such as Zn, Cu, Pb, Cr, and Cd were also estimated in agricultural soil samples and soils were found to be drastically suffering from Zn and Cu pollution followed by some Pb contamination. On the basis of average values (in mg kg−1), potentially toxic metal contents in soil samples can be arranged in decreasing order as: Zn (78.93) > Cu (42.32) > Cr (36.92) > Pb (7.49) ≫ Cd. The results indicated the probability of occurrence of potentially toxic metal accumulation in edible parts of crops grown in the study area. Although no direct significant correlation has been observed between soil gas radon and mass/surface exhalation rate in soil samples under investigation but a positive correlation was observed among some toxic metals such as Zn:Cu, Zn:Cr, Cu:Cr, Cu: Pb and Pb:Cr. pH and conductivity were negatively correlated whereas, SOM and mass exhalation showed positive correlation. The investigation demonstrated the dominance of potentially toxic metal contamination by Cu, Zn and Pb over Rn222 emanation rate in agricultural soil towards health risks posed to residents of Amritsar.

The natural radioactivity (238U, 226Ra, 232Th and 40K) and radon emanation coefficient for 57 soil samples belonging to alluvial, red, forest surface, slip-debris, metamorphic and sandy soil of the Ninh Son region in Ninh Thuan province have been determined. The soil gas radon was measured by in-situ with RAD7 radon monitor coupled with a soil gas probe while activity concentrations of 238U, 226Ra, 232Th, and 40K were measured by an HPGe gamma-ray spectrometry system. The 226Ra/238U disequilibrium occurred in the soil samples and a great majority of the 226Ra/238U values lie above 1. Average activity concentrations of 226Ra, 232Th, and 40K are significantly higher than the worldwide average concentrations in soils published by UNSCEAR, 2008. The gamma dose rate ranged from 55 ± 2 to 248 ± 7 nGy h−1 with an average of 130 ± 4 nGy h−1 which is greater than the world value. Strong positive correlations were recorded between 238U and 226Ra, 232Th and 226Ra, 232Th and 238U, and 226Ra and 222Rn. The results of weathering and alteration processes were proposed to be dominated reasons for the 226Ra/238U disequilibrium occurred in the soil samples. Most of the radon in soil gas samples are considered “normal risk” or low radon index. The mean values of the emanation coefficient for alluvial, red, forest surface, slip-debris, metamorphic and sandy soil were found to be 0.51 ± 0.03, 0.40 ± 0.02, 0.36 ± 0.02, 0.30 ± 0.02, 0.26 ± 0.02 and 0.15 ± 0.01, respectively. Radon emanation was found to be an inverse function of grain size for grain sizes larger than 0.1 mm in diameter and independent on the radium content of the soil sample.

Atmospheric radioactive noble gas radon (Rn-222) originates from soil gas exhaled in the atmospheric surface layer. Radon exhalation rates from soil as well as corresponding meteorological and soil parameters were recorded for two subsequent years. Based on long-term field data, a statistical regression model for the radon exhalation and the most important influencing parameters soil water content, temperature of soil and air, air pressure and autocorrelation of the exhalation rate was established. The fitting result showed that the multivariate model can explain up to 61% of the variation of the exhalation rate. First, the exhalation rate increases up to 80 Bq m(-2) h(-1) with increasing soil water content. Later, at water content N10%, increasing soil wetness suppressed the exhalation rate: at values higher than 24% to approximately one third. The air temperature had a distinct positive effectwhile the soil temperature had a strong negative effect on the exhalation rate, indicating their different influencing-mechanisms on the exhalation. The air pressure was negligible. The lagged values of radon exhalation had to be included in the model, as the variable shows strong autocorrelation. (c) 2018 Elsevier B. V. All rights reserved.

The Nirano mud volcano is located in the western sector of the Modena Apennine margin (Italy). It represents one of the most spectacular phenomena of sedimentary volcanism in the entire Italian territory and is among the largest in Europe. Here numerous aligned gryphon clusters and seeping pools constantly burst gas and mud inside a morphological depression. Besides the obvious surface expressions of these emission spots, until now the type and amount of gas released in the rest of the large Nirano caldera zone remained unknown. An extensive geochemical soil gas survey (O2, N2, CO2, CH4, 222Rn, He, H2, and light hydrocarbons) and exhalation fluxes (CO2 and CH4), was carried out inside the mud volcano field with the aim of identifying soil degassing distribution, and to estimate the micro- and macro-seepage budget for both CO2 and CH4. Soil gas data highlight the presence of two zones characterized by high concentrations and flux values. These enhanced seepage zones are located in the SW and NE sectors of the mud volcano suggesting that the enhanced gas emissions present in the peripheral zones, are controlled by caldera collapse structures. The most significant CO2 flux (up to 91 g m−2 d−1) and 222Rn anomalies are located in the central part of the crater in correspondence of a morphological escarpment. Here we infer the presence of a buried tectonic system of collapsed terraces that facilitate fluids degassing. In contrast, CH4 fluxes show a scattered distribution and low values (mean 221 mg m−2 d−1). Overall the CH4 degassing budget is low (27.09 t km−2 y−1) when compared with other Italian mud volcanoes. This could be related to a relative low emission activity during the period of the geochemical survey and to a more homogeneous dilution of surface distribution of the emission point-s. Chemical and isotopical composition of the gas discharged from the active gryphons is methane-dominated and the thermogenic signature (ranging from −41 to −47‰) suggests a deep reservoir source. This conclusion is supported by noble-gas measurements (He, Ne, Ar, Kr, Xe) conducted in the pore water phase of the emitted mud, indicating a secondary gas exchange occurring at a depth of a few kilometers. The geochemical anomalies found in this study, successfully predicted the occurrence of new degassing phenomena towards the NE sector of the caldera. Indeed recently (i.e. after the survey data acquisition) new manifestations of mud and gas emissions appeared in the north-eastern edge of the caldera.

Global methane (CH4) emissions are becoming increasingly important due to the contribution of CH4 to global warming. Leaking oil and gas wells can lead to subsurface CH4 gas migration (GM), which can cause both aquifer contamination and atmospheric emissions. Despite the need to identify and quantify GM at oil and gas well pads, effective and reliable monitoring techniques are lacking. In this field study, we used CH4 and carbon dioxide (CO2) efflux measurements together with soil gas stable carbon isotopic signatures to identify the occurrence and to characterize the spatio-temporal migration of fugitive gas across 17 selected well pads in Northeastern British Columbia, Canada. At 13 of these sites, operators had previously reported the occurrence of GM; however, subsequent inspections based on visual, olfactory or auditory evidence only identified GM at two of these sites. Using the soil gas efflux method, evidence for GM was found at 15 of the 17 well pads with CH4 and CO2 effluxes ranging from 0.017 to 180 μmol m−2 s−1(0.024 to 250 g CH4 m−2 d−1) and 0.50 to 32 μmol m−2 s−1 (1.9 to 122 g CO2 m−2 d−1), respectively. Stable carbon isotopic composition was assessed at 10 of the 17 well pads with 9 well pads showing evidence of GM. The isotopic values indicated that CH4 in soil gas was from the same origin as CH4 in the surface casing vent flow gas. There was no correlation between CH4 effluxes and the distance from the well head; an equal portion of elevated effluxes were detected >10 m from the well head as were detected

The nano forms of the metals molybdenum oxide (MoO3), nickel oxide (NiO) and lithium oxide (Li2O) are finding wide application in advanced technologies including batteries and fuel cells. We evaluated soil responses to nanoMoO3, nanoNiO, and nanoLi2O as some environmental release of the materials, either directly or following the land application of biosolids, is expected. Using Drummer soil (Fine-silty, mixed, superactive, mesic Typic Endoaquolls), we evaluated the impacts of the three nanometals on soil gas (N2O, CH4, and CO2) emissions, enzyme activities (β-glucosidase and urease), and microbial community structure (bacterial, archaeal, and eukaryal) in a 60 day microcosms incubation. Soil treated with nanoLi2O at 474 μg Li/g soil, released 3.45 times more CO2 with respect to the control. Additionally, β-glucosidase activity was decreased while urease activity increased following nanoLi2O treatment. While no clear patterns were observed for gas emissions in soils exposed to nanoMoO3 and nanoNiO, we observed a temporary suppression of β-glucosidase activity in soil treated with either metal. All three domains of microbial community were affected by increasing metal concentrations. This is the first evaluation of soil responses to nanoMoO3, nanoNiO, or nanoLi2O.

Boreal forests store large amounts of organic carbon and are susceptible to climate changes, particularly rising temperature, changed soil water and increased fire frequency. The young post-fire ecosystems might occupy larger proportions of the boreal forests region with the expected increases in fire frequency in the future and change the carbon (C) balance of this region. However, it is unclear how soil C fluxes in the post-fire boreal forest response to the climate changes. Therefore, a two-year field experiment was conducted in a boreal forest to investigate the effects of fire on the soil C (CO2 and CH4) fluxes and the responses of these fluxes to simulated warmer and drier climate conditions. The results showed that the boreal forest recovered form wildfire 7–8 years had higher soil CO2 flux than the mature forest. Furthermore, the treatments of warming, drying and the combination of warming and drying increased growing season cumulative soil CO2 flux in the post-fire forest by 15.8%, 20.4% and 34.2%, respectively. However, the boreal forest soil changed from a weak CH4 source to a weak CH4 sink after fire disturbance. Although CH4 absorption increased by warming and drying treatments, the interaction of warming and drying led to a decrease in soil CH4 uptake. The results indicated that the post-fire soil showed CO2 and CH4 fluxes with a greater global warming potential than before burning and that the global warming potential of the soil gas fluxes further increased by warming and drying. The predictive power of models of C cycle-climate feedbacks could be increased by incorporating the distinct ecosystem following fire with permafrost degradation and climate change across the boreal zone.

A study involving soil radon monitoring using RAD-7 instrument was carried out near Balakot-Bagh (B-B) Fault line hit by a 7.6 magnitude earthquake in October 2005. The study aimed to determine the spatial distribution of soil radon gas levels and the relationship between the soil radon gas and fracture density. Eleven soil samples were collected near the fault line, and 56 more samples (fourteen each from the adjoining district/area). Field measurements were made in the summer season of 2013, as a part of continuous measurement for regular monitoring the area for radon emanation and for observing the anomalies with previous values. The study area is located in Lesser Himalayas, North Pakistan, the Balakot–Bagh (B–B) fault in the Hazara–Kashmir Syntaxis. Soil gas radon concentrations were found higher near the Balakot-Bagh Fault line with an average value of 11.9 $${\text{kBq}}\;{{\text{m}}^{ - 3}}$$ compared to other sites of the study area with an average value of around 6.5 $${\text{kBq}}\;{{\text{m}}^{ - 3}}$$ . The radon value near the fault line is 70% higher as compared to the surrounding area.

The fluctuation of the groundwater table can cause upward and downward advection of soil gas within the vadose zone, just like breathing. In this study, we developed a three-dimensional numerical model and used it to investigate the role of vadose zone breathing in vapor intrusion, through which subsurface volatile chemicals migrate into the concerned building at contaminated sites. The developed model was first applied to a sand tank experiment, followed by examining the influences of fluctuation amplitude and period of water table, soil textures, and groundwater level depth. Our results suggest that the indoor pollutant concentration can be increased by about three times with the oscillatory water table of 0.4 m amplitude and 4 d period. Within one cycle of vadose zone breathing, the indoor pollutant concentration is found to vary by about 7 orders of magnitude. The results also show that, compared to the groundwater level depth, the soil texture plays a significant role in determining vapor intrusion risks. Specifically, when soil particles increase from 0.25 mm to 0.44 mm, the indoor pollutant concentration tends to increase and becomes more sensitive to groundwater table fluctuation.

The contribution of thoron (220Rn) to natural radiation exposure is commonly neglected. However, dry porous surfaces with relatively high 232Th content can pose a thoron radiation hazard to the environment. Therefore, this research aims at establishing a baseline data for 220Rn activity concentration in soil gas and categorise the measured data based on the geology of Johor state, Malaysia. The activity concentration of 220Rn in soil gas was measured using RAD7 alpha detector. The measured 220Rn activity concentration data varied from MDA to 159.07 ± 3.40 Bq/L. Kruskal–Wallis test on the 220Rn concentration data among the geological formations and soil types reveals a statistically significant result, p = 0.006 and p = 0.005, respectively. An isoconcentration map of 220Rn in soil gas is created. The map indicates higher concentration values generally characterised the Districts of Muar and Ledang.

In this study, the role of building pressure cycling (BPC) method in generating a subslab aerobic barrier at petroleum contaminated sites was examined numerically. The numerical model was first validated with field observations and then used to simulate BPC applications in petroleum vapor intrusion scenarios. The results indicated that, after a long-term BPC operation (60 days), a subslab aerobic barrier could be generated with an adequate air injection rate (10 L/min in this study). The effects on hydrocarbon soil gas concentration profiles are expected to last for weeks even after the BPC system is turned off. Moreover, our investigations showed that the performances of the BPC application are virtually independent of hydrocarbon's reaction rate constant. The simulated sub-foundation aerobic conditions expected during BPC were comparable to those observed in a field study where a subsurface pipe system at the same air injection rate was used to create a subslab aerobic barrier. Thus, BPC application can represent an interesting alternative approach to the subsurface delivery systems as it is expected to achieve similar performance but with lower installation costs.

International audience; In order to observe the relationships between the temporal variations of CO2 surface fluxes and the CO2 soil gas transport in soil profile before and during rainfall events, two experiments were conducted in a controlled natural environment at different time periods. These experiments consisted in injecting pure CO2 in a lysimeter at 160 cm depth and simulating heavy rainfall event at its surface for 2 weeks. During the whole experiments, CO2 soil gas concentrations and surface fluxes were continuously monitored. These measurements showed that the flux measured through the flux chamber were consistent with the concentration profiles. During simulated rainfall events, the concentrations and fluxes showed a clear change linked to the presence of water on the top of the water profile. The results clearly show a significant decrease of CO2 flux to atmosphere induced by rainfall infiltration and consequential wash-out of the CO2 present in the soil.

As an inert radioactive gas, 222Rn could be easily transported to the atmosphere via emanation, migration, or exhalation. Research measurements pointed out that 222Rn activity concentration changes during the winter and summer months, as well as during wet and dry season periods. Changes in radon concentration can affect the atmospheric electric field. At the boundary layer near the ground, short-lived daughters of 222Rn can be used as natural tracers in the atmosphere. In this work, factors controlling 222Rn pathways in the environment and its levels in soil gas and outdoor air are summarized. 222Rn has a short half-life of 3.82 days, but the dose rate due to radon and its radioactive progeny could be significant to the living beings. Epidemiological studies on humans pointed out that up to 14% of lung cancers are induced by exposure to low and moderate concentrations of radon. Animals that breed in ground holes have been exposed to the higher doses due to radiation present in soil air. During the years, different dose-effect models are developed for risk assessment on human and non-human biota. In this work are reviewed research results of 222Rn exposure of human and non-human biota. © 2020, ISB.

While radioisotopes of noble gases are known to be indicators of underground nuclear explosions (UNE), McIntyre et al. (2017) was the first to report the presence of 39Ar in shallow soil gas in association with a decades old UNE. While this finding hinted at the potential application of 39Ar to be used as an indicator of a UNE, doing so would also require an understanding of the natural concentrations of 39Ar present in soil gas. Without knowing the expected range and variability of naturally occurring concentrations of 39Ar, it is difficult to determine what measured concentrations would be indicative of an elevated concentration. This paper presents results from 16 soil gas samples and three atmospheric air samples collected from various locations across the western United States. Shallow soil gas samples were collected into self-contained underwater breathing apparatus (SCUBA) tanks using a custom-built soil gas sampling system and then processed and analyzed for 39Ar. The measured concentrations of 39Ar varied from atmospheric air concentrations to about 3.5 times atmospheric air concentrations (58 mBq/m3). The results presented here represent the first measurements of natural background 39Ar concentrations in shallow soil gas. This data will be necessary if 39Ar is to be used as an indicator of UNE.

A novel approach is proposed to detect underground nuclear explosions (UNEs) through the displacement of natural radon isotopes (222Rn and 220Rn). Following an explosion, it is hypothesized that the disturbance and pressurization of the sub-surface would facilitate the movement of radon from the depth of the UNE towards the surface resulting in increased soil gas activity. The resulting signal may be magnified by a factor of 2.0–4.9 by the decay of radon to its short-lived progeny. Increases in background activity may be useful for identifying locations to perform additional measurements, or as a detectable signal at monitoring stations. To validate this hypothesis, radon detection instrumentation was deployed at the Dry Alluvium Geology (DAG) site of the Source Physics Experiment (SPE) at the Nevada National Security Site (NNSS). Natural fluctuations in the soil gas activity due to barometric pumping, and the lower yield of the chemical explosions (1–50 t) made it difficult to confirm a displacement of radon from the explosions, and further study to validate the proposed hypothesis is recommended.

Over 40 soil gas samples were collected both in post-industrial areas as well as in undisturbed areas in the region of Kvarntorp, Sweden. Radioxenon (133Xe) was detected in 15 samples and radioargon was detected in 7 from 10 samples analysed. The concentration of radioxenon and radioargon in soil gas ranged up to 109 mBq/m3 and 19 mBq/m3, respectively. During sample collection other soil gases such as radon, CO2 and O2 were also measured and soil samples were taken along with dose rate measurements. The field experiment presented here shows that it is possible to detect naturally occurring radioxenon and radioargon in soil gas simultaneously.

In recent years, a number of methods have been used to measure the biodegradation of petroleum light non-aqueous phase liquids (LNAPL) at petroleum release sites, a process known as natural source zone depletion (NSZD). Most commonly, NSZD rates have been measured at sites with unconsolidated geology and relatively shallow groundwater (50 ft. bgs,15 m bgs). For this study, we have used two methods (1. carbon dioxide flux measured using carbon traps and 2. heat flux based on subsurface temperature gradients) to measure NSZD rates at a petroleum release site in Hawaii with basalt geology and deep groundwater (300 ft. bgs,100 m bgs). Both methods documented the occurrence of NSZD at the facility and the two methods yield estimates of the NSZD rate that agreed within a factor of 2 (4600 to 7400 gal/yr; 17,000 to 28,000 L/yr for the flux method and 8600 to 13,000 gal/yr; 33,000 to 49,000 L/yr for the temperature method). Soil gas samples collected directly above the water table and at shallower depths within the vadose zone indicated aerobic conditions throughout the vadose zone (oxygen13%) and no detectable methane. These results indicate that NSZD occurs at this site through the direct aerobic biodegradation of LNAPL rather than the two-step process of anaerobic methanogenesis followed by methane oxidation at a shallow depth interval documented at other sites.

In this study, systematic soil methane cycle geochemical monitoring was carried out in a typical gas hydrate region in the Qinghai-Tibet Plateau. Soil gas samples were collected for hydrocarbon components and carbon isotope analysis. Meanwhile, soil-methane fluxes from the upper active layer (20–30 cm) were monitored during six months of one year. The results of this research provide evidence of a new source of methane emission from wetland soils in permafrost regions: gas hydrate release. Sites with large methane emissions were found using flux monitoring, the characteristics of thermogenic methane were identified using carbon isotope tracing, and the relationship between emission by soils and effusion from gas hydrates was determined through correlation analyses of soil-adsorbed hydrocarbons. Seasonal variation of methane emissions are also discussed by considering the emission of bacterial methane, thermogenic methane, and the absorption of methane from the soil active layer. These comprehensive findings provide valuable information for carbon cycle research of wetlands in permafrost regions.

The soil gas concentration attenuation in lateral diffusive transport determines the influence area of a contamination plume in soil vapor intrusion, a major exposure pathway of volatile chemicals at contaminated sites. In this study, we utilize both physical and mathematical models to investigate the roles of soil geology heterogeneities and impermeable surface pavements in determining the attenuation of contaminant soil gas concentration. The results indicate that the attenuation of soil gas concentration with lateral diffusion is observed to be the most significant if with a low-permeability soil layer at the bottom and a high-permeability layer on top, followed by the cases with the uniform soil properties, and the lateral attenuation is the least significant in cases with a high-permeability soil layer at the bottom and a low-permeability soil layer on top, regardless of the surface coverage. Compared to soil heterogeneity, the influences of surface conditions are less significant, and the capping effect of surface cover can only play a role in determining shallow soil gas concentration profiles. At last, the physical experimental results were used to examine a previously developed analytical vapor intrusion model including the influences of layering and surface conditions.

The radioactive gas radon (Rn) is considered as an indoor air pollutant due to its detrimental effects on human health. Radon is known as the second most important cause for lung cancer after tobacco smoking. The dominant source of indoor Rn is the ground beneath the building in most cases. Following the European Basic Safety Standards, all EU Member States are required to delineate Rn priority areas, i.e. areas with increased risk of high indoor radon concentrations. One possibility to this end is using the “geogenic Rn potential” (GRP), which quantifies the availability of geogenic Rn for infiltration into buildings. The GRP is defined as a function of Rn concentration in soil gas and soil gas permeability.In this study we used > 4,000 point measurements across Germany in combination with ~50 environmental co-variables (predictors). We fitted machine learning regression models to the target variables Rn concentration in soil and soil gas permeability. Subsequently, the GRP is calculated from both quantities. We compared the performance of three algorithms: Multivariate Adaptive Regression Splines (MARS), Random Forest (RF) and Support Vector Machines (SVM). Potential candidate predictors are geological, hydrogeological and soil landscape units, soil physical properties, soil chemical properties, soil hydraulic properties, climatic data, tectonic fault data, and geomorphological parameters.The identification of informative predictors, tuning the model hyperparameters and estimation of the model performance was conducted using a spatial 10-fold cross-validation, where the folds were split by spatial blocks of 40*40 km. This procedure counteracts spatial autocorrelation of predictor and response data and is expected to ensure independence of training and test data. MARS, RF and SVM were evaluated in terms of its prediction accuracy and prediction variance. The results revealed that RF provided the most accurate predictions so far. The effect of the selected predictors on the final map was assessed in a quantitative way using partial dependence plots and spatial dependence maps. The RF model included 8 and 14 informative predictors for radon and permeability, respectively. The most important predictors in the RF model were geological and hydrogeological units as well as field capacity for radon and soil landscape, geological and hydrogeological units for soil gas permeability.

Passive sampling (PS) is a method employed to detect volatile organic compounds in groundwater and soil gas. This study attempted to manufacture a polydimethylsiloxane (PDMS) dialysis passive sampler for potential application in detecting trichloroethylene (TCE) in aqueous and gaseous phases. The equilibrium time of the passive sampler was initially determined, followed by multilayer passive sampling in a three-dimensional sandbox to construct a tomography of TCE vapor spatial distribution in the vadose zone above the saturated water level. The results indicated that an equilibrium time period of >10 d was required in the aqueous phase containing TCE concentrations ranging from 3 to 25 mg L-1, while an equilibrium time period of >12 d was necessary for TCE vapor concentrations ranging from 2.6-26 mg L-1. Therefore, a 14 d of equilibrium time was suggested for application of this passive sampler in detecting vapor and aqueous phase TCE. After collection of the passive samples from the three-dimensional sandbox, a three dimensional visualization was created, and it was demonstrated to be a reasonable way to simulate a three dimensional TCE distribution. It was confirmed that the passive sampler developed in this study is effective for assessing TCE contamination in the subsurface.

We present here the first attempt to understand the fast dynamics of an active basaltic volcano, namely Mt. Etna using soil gas radon measured in some sites located in strategic places around the volcano. Data were measured continuously from July 2015 to February 2017 and the raw signals were treated in order to filter out all possible periodic components that are normally due to non-volcanic factors, applying a method that does not require acquisition of other parameters, which are not always available. the residual signals highlighted seven anomalous changes, with radon values reaching levels from 2 to 5 times higher than the normal background. in six out of seven cases, anomalies were almost contemporaneous in all or almost all of the sites, indicating a common source for the observed radon variations. the pattern of anomalies suggests a transient wave-like propagation in the space/time domain, compatible with pressure-induced displacement of the gas. the observed patterns are most probably caused by the rapid upward motion of gas-rich magma into the volcano conduits, as almost all anomalies precede or accompany major volcanic events. in some cases, an alternative explanation could be the strong and sudden strain releases through earthquakes swarms, with consequent variations in the permeability of rocks at a large scale, given the apparent correlation between those anomalies and intense seismicity., Scientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [BIDEB-2219], The authors thank A. Cannata for kindly providing the Matlab codes used in this paper for the time series analysis of radon data, S. Inzerilli for helping us download some of the radon data, R. Grouas and L. Juchler for the initial organization of the database and G. Galli for the calibration of the radon sensors used at sites 1 and 2. the authors also thank the Scientific and Technological Research Council of Turkey (TUBITAK) for supporting the postdoctoral fellowships (BIDEB-2219) of M. Ichedef, under which his work was carried out. S. Conway improved the English.

Near-surface leakage detection is often a crucial part of verifying the success of CO2 sequestration projects, and it cannot be achieved without a detailed description of the natural state of an operational site prior to injection. Without baseline studies, it is difficult to define CO2 anomalies outside natural variation in the subsurface that may be related to leakage. CO2 concentrations and δ13C-CO2 values (of DIC, dissolved gas, and soil gas) were investigated to establish a baseline modelling of natural chemical processes leading to CO2 occurrence and δ13C-CO2 fractionation in the soil-groundwater interface on an example at the Glenhaven site in Queensland, Australia. This was analysed within the context of the hydrogeology and hydrogeochemistry of a shallow aquifer system (

Natural gas pipelines are an important source of fugitive methane emissions in lifecycle greenhouse gas assessments but limited monitoring has taken place of UK pipelines to quantify fugitive emissions. This study investigated methane emissions from the UK high-pressure pipeline system (National Transmission System - NTS) for natural gas pipelines. Mobile surveys of CH4 emissions were conducted across four areas in the UK, with routes bisecting high-pressure pipelines (with a maximum operating pressure of 85 bar) and separate control routes away from the pipelines. A manual survey of soil gas measurements was also conducted along one of the high-pressure pipelines using a tunable diode laser. For the pipeline routes, there were 26 peaks above 2.1 ppmv CH4 at 0.23 peaks/km, compared with 12 peaks at 0.11 peaks/km on control routes. Three distinct thermogenic emissions were identified on the basis of the isotopic signal from these elevated concentrations with a peak rate of 0.03 peaks/km. A further three thermogenic emissions on pipeline routes were associated with pipeline infrastructure. Methane fluxes from control routes were statistically significantly lower than the fluxes measured on pipeline routes, with an overall pipeline flux of 627 (241–1123 interquartile range) tonnes CH4/km/yr. Soil gas CH4 measurements indicated a total flux of 62.6 kt CH4/yr, which equates to 2.9% of total annual greenhouse gas emissions in the UK. We recommend further monitoring of the UK natural gas pipeline network, with assessments of transmission and distribution stations, and distribution pipelines necessary.

The current work is an attempt to illustrate the importance of using passive soil gas as an innovative investigation technique in the assessment of soil and groundwater pollutions that emanates from volatile hydrocarbon activities in newly emerging countries. Bazian Oil Refinery as one of the largest refinery in Iraqi Kurdistan Region produces 40,000 barrels a day and provides a wide range of petroleum products for daily consumption. The types and scale of different process that happen in this industrial site have led to concerns with regard to its impact on both the soil and groundwater the vicinity of the factory. The researcher conducted a combined sampling design with a dual-phased extraction procedure for soil vapor and groundwater samples in order to assess the susceptibility of the subsurface to pollution with hydrocarbon. The aims were to characterize potential source(s), map the areal extent of the site which is at risk to be affected with the identified9 hydrocarbon compounds and vapor. A collection kit from Beacon Environmental Service was used to collect a total number of 50 passive soil vapors in the first step of work. To extrapolate results, five shallow boring for soils and six for water sampling were carefully observed. The selection of the sampling points was based on the results revealed by the PSG survey that showed significant quantities of analyzed organic hydrocarbon for a follow-up investigation. The matrices were analyzed by ALS Laboratory to target more than 40 VOCs and SVOCs. The plan was to make the mass to concentration tie-in for the selected analyzed compounds (Benzene, Toluene, and Total Petroleum Hydrocarbons) from the PSG in mass (nanograms) with both the soil and water samples in concentration. The results revealed that the PSG technique is unique in identifying the source and extent of soil and groundwater pollutions plume.

In this work, we introduce a screening method for the evaluation of the natural attenuation rates in the subsurface at sites contaminated by petroleum hydrocarbons. The method is based on the combination of the data obtained from standard source characterization with dynamic flux chambers measurements. The natural attenuation rates are calculated as difference between the flux of contaminants estimated with a non-reactive diffusive model starting from the concentrations of the contaminants detected in the source (soil and/or groundwater) and the effective emission rate of the contaminants measured using dynamic flux chambers installed at ground level. The reliability of this approach was tested in a contaminated site characterized by the presence of BTEX in soil and groundwater. Namely, the BTEX emission rates from the subsurface were measured in 4 seasonal campaigns using dynamic flux chambers installed in 14 sampling points. The comparison of measured fluxes with those predicted using a non-reactive diffusive model, starting from the source concentrations, showed that, in line with other recent studies, the modelling approach can overestimate the expected outdoor concentration of petroleum hydrocarbons even up to 4 orders of magnitude. On the other hand, by coupling the measured data with the fluxes estimated with the diffusive non-reactive model, it was possible to perform a mass balance to evaluate the natural attenuation loss rates of petroleum hydrocarbons during the migration from the source to ground level. Based on this comparison, the estimated BTEX loss rates in the test site were up to almost 0.5 kg/year/m2. These rates are in line with the values reported in the recent literature for natural source zone depletion. In short, the method presented in this work can represent an easy-to-use and cost-effective option that can provide a further line of evidence of natural attenuation rates expected at contaminated sites.

Remediation of subsurface systems, including groundwater, soil and soil gas, contaminated with light non-aqueous phase liquids (LNAPLs) is challenging. Field-scale pilot trials of multi-phase remediation were undertaken at a site to determine the effectiveness of recovery options. Sequential LNAPL skimming and vacuum-enhanced skimming, with and without water table drawdown were trialled over 78 days; in total extracting over 5 m3 of LNAPL. For the first time, a multi-component simulation framework (including the multi-phase multi-component code TMVOC-MP and processing codes) was developed and applied to simulate the broad range of multi-phase remediation and recovery methods used in the field trials. This framework was validated against the sequential pilot trials by comparing predicted and measured LNAPL mass removal rates and compositional changes. The framework was tested on both a Cray supercomputer and a cluster. Simulations mimicked trends in LNAPL recovery rates (from 0.14 to 3 mL/s) across all remediation techniques each operating over periods of 4–14 days over the 78 day trial. The code also approximated order of magnitude compositional changes of hazardous chemical concentrations in extracted gas during vacuum-enhanced recovery. The verified framework enables longer term prediction of the effectiveness of remediation approaches allowing better determination of remediation endpoints and long-term risks.

The Anninghe fault (ANHF) and the Zemuhe fault (ZMHF) with left-lateral strike-slip, located along the eastern boundary of the Sichuan-Yunnan block (southwestern of China), are some of the most active faults. These faults mainly control the seismicity of southwestern area of China. Measurement of soil gas radon (Rn) emitted from fault along the ANHF and the ZMHF has been carried out for the research of tectonic activity. We obtained the Rn concentrations at 394 sampling points along 15 profiles across the ANHF and the ZMHF in 2016. The measurement results show that the values of Rn in the ANHF are significantly higher than that in the ZMHF. The relative coefficient KQ of Rn activity attained in profiles of the ANHF ranges from 3.3 to 9.1, which are obviously higher than that of 2.1–2.5 in profiles of the ZMHF. The radon flow brings up the deeper and radon-richer gas upward through the high-level cracked strata caused by the tectonic activity accounts for the anomalously high values attained. The spatial variation of Rn in the concentration profile and the relative coefficient KQ calculated indicate that the tectonic activity of the south segment of the ANHF is significantly higher than that of the north segment of the ZMHF.

The CO2 injected into deep formations during implementation of carbon dioxide (CO2) capture and storage (CCS) technology may leak and migrate into shallow aquifers or ground surfaces through a variety of pathways over a long period. The leaked CO2 can threaten shallow environments as well as human health. Therefore, almost all monitoring programs for CCS projects around the world contain near-surface monitoring. This paper presents a U-tube based near-surface monitoring technology focusing on its first application in the Shenhua CCS demonstration project, located in the Ordos Basin, Inner Mongolia, China. First, background information on the site monitoring program of the Shenhua CCS demonstration project was provided. Then, the principle of fluid sampling and the monitoring methods were summarized for the U-tube sampler system, and the monitoring data were analyzed in detail. The U-tube based monitoring results showed that the U-tube sampler system is accurate, flexible, and representative of the subsurface fluid sampling process. The monitoring indicators for the subsurface water and soil gas at the Shenhua CCS site indicate good stratification characteristics. The concentration level of each monitoring indicator decreases with increasing depth. Finally, the significance of this near-surface environmental monitoring technology for CO2 leakage assessments was preliminarily confirmed at the Shenhua CCS site. The application potential of the U-tube based monitoring technology was also demonstrated during the subsurface environmental monitoring of other CCS projects.

Contaminated sites pose ecological and human-health risks through exposure to contaminated soil and groundwater. Whereas we can readily locate, monitor, and track contaminants in groundwater, it is harder to perform these tasks in the vadose zone. In this study, tree-core samples were collected at a Superfund site to determine if the sample-collection location around a particular tree could reveal the subsurface location, or direction, of soil and soil-gas contaminant plumes. Contaminant-centroid vectors were calculated from tree-core data to reveal contaminant distributions in directional tree samples at a higher resolution, and vectors were correlated with soil-gas characterization collected using conventional methods. Results clearly demonstrated that directional tree coring around tree trunks can indicate gradients in soil and soil-gas contaminant plumes, and the strength of the correlations were directly proportionate to the magnitude of tree-core concentration gradients (spearman's coefficient of -0.61 and -0.55 in soil and tree-core gradients, respectively). Linear regression indicates agreement between the concentration-centroid vectors is significantly affected by in planta and soil concentration gradients and when concentration centroids in soil are closer to trees. Given the existing link between soil-gas and vapor intrusion, this study also indicates that directional tree coring might be applicable in vapor intrusion assessment.