Atmospheric and Soil Methane Concentrations Integrating a New Gas Detection Technology

Cities are major contributors to greenhouse gas emissions (GHG) due to the high density of urbanization, numerous industrial centers, and intensive agricultural activities. This study focused on soil methane and radon gas measurements in the subsurface, as well as in the atmosphere. Measurements were conducted using new gas detection instrumentation and as low-cost devices for methane gas concentrations. Maximum soil radon gas concentration was observed to be approximately 1770 ± 582 Bq/m3 at a depth of 1 m below the ground surface. The soil comprised of 64.31% sand, 20.75% silt, and 14.94% clay, and 0.526 ppm of uranium. The maximum concentration of methane was about 0.06%, at a depth of 1 m into the soil, characterized by 83% sand, 8.96% silt, and 7.89% clay. Moreover, this study focused on a better understanding of the advantages and disadvantages of new soil gas detection technology. The results and findings of environmental data obtained from the soil gas survey were shared with the community, whose involvement was critical in the data acquisition process.

Soil gas geochemical behaviour across buried and exposed faults during the 24 august 2016 central Italy earthquake

<p>Following the earthquake (M_L=6.0) of 24 August 2016 that affected large part of the central Apennine between the municipalities of Norcia (PG) and Amatrice (RI) (central Italy), two soil gas profiles (i.e., ²²²Rn, ²²⁰Rn, CO₂ and CO₂ flux) were carried out across buried and exposed coseismic fault rupture of the Mt. Vettore fault during the seismic sequence. The objective of the survey was to explore the mechanisms of migration and the spatial behaviour of different gas species near still-degassing active fault. Results provide higher gas and CO₂ flux values (about twice for ²²²Rn and CO₂ flux) in correspondence of the buried sector of the fault than those measured across the exposed coseismic rupture. Anomalous peaks due to advective migration are clearly visible on both side of the buried fault (profile 1), whereas the lower soil gas concentrations measured across the exposed coseimic rupture (profile 2) are mainly caused by shallow and still acting diffusive degassing associated to faulting during the seismic sequence. These results confirm the usefulness of the soil gas survey to spatially recognise the shallow geometry of hidden faults, and to discriminate the geochemical migration mechanisms occurring at buried and exposed faults related to seismic activity.</p>

Investigation and Remedial Approach Development for a TCE Spill Site: A Case Study

A trichloroethene (TCE) plume has been discovered inside an industrial park located in Taiwan. The objectives of this study were to characterize the solvent spill site and prepare a corrective action plan (CAP) for site remediation. The following tasks have been performed under Taiwan Soil and Groundwater Remediation Act corrective action: (1) geophysical survey to verify the existence and fate of all potential contaminant sources in the vicinity of the avionics repair shop; (2) soil-gas survey and soil/groundwater analyses to delineate the lateral and vertical extent of contaminants in the subsurface; (3) application of field screening techniques to determine the presence of dense, non-aqueous-phase liquids (DNAPLs); (4) contaminant transport modeling; (5) evaluation of the remedial options, conduction of cost analysis, and selection of the optimal treatment system. Results from the site characterization indicate that an extended TCE plume existed in site groundwater, which needs to be contained and remediated. A two-phase remedial approach has been developed. Phase I was to contain the existing dissolved groundwater plume in the surficial aquifer and initiate mass removal of DNAPLs. Phase II was to conduct feasibility studies and possibly test surfactant washing and biobarrier techniques.

Rn and CO₂ geochemistry of soil gas across the active fault zones in the capital area of China

The present work is proposed to investigate the spatiotemporal variations of soil gas Rn and CO2 across the active faults in the capital area of China, for the understanding of fault activities and the assessment of seismic hazard. A total of 342 soil gas sampling sites were measured twice in 2011 and 2012 along seven profiles across four faults. The results of soil gas surveys show that in each profile, due to the variation of gas emission rate, the concentrations of Rn and CO2 changed in the vicinity of faults. Spatial distributions of Rn and CO2 in the study areas were different from each other, which was attributed to soil types affecting the existence of Rn and CO2. Compared with 2011 soil gas survey, the increases of Rn and CO2 concentrations in 2012 were related to the enhancement of seismic activities in the capital area of China. Our results indicate that special attention for seismic monitoring should be paid to Xinbaoan-Shacheng Fault and the north east segment of Tangshan Fault in the future.

Soil-gas survey of liquefaction and collapsed caves during the Emilia seismic sequence

<p>The epicentral area of the Emilia seismic sequence is located in the Emilia-Romagna Region (northern Italy), 45 km from the city of Modena (Figure 1). This area is sited within thrust-related folds of the Ferrara Arc, which represent the most external part of the northern Apennines. This sector is considered as having been active during late Pliocene to early Pleistocene times [Scrocca et al. 2007] and encompasses also the Mirandola and Ferrara seismogenic sources [e.g., Burrato et al. 2003, Boccaletti et al. 2004, Basili et al. 2008]. The main sedimentary infilling of the Po Plain is represented by Pliocene–Pleistocene alluvial deposits (alternating fluvial sands and clays) that overlie a foredeep clastic sequence, with a total average thickness of 2 km to 4 km [e.g., Carminati et al. 2010]. Soon after the mainshock, several liquefaction phenomena coupled to ground fractures were observed in the epicentral area (e.g., San Carlo, Ferrara). Soil liquefaction is a phenomenon in which the strength and stiffness of a soil is reduced by earthquake shaking or other rapid loading. […] Collapsed caves reported in the literature and/or local press [e.g., Febo 1999, Martelli 2002] in the epicentral area were previously investigated by our research group in 2008, with several soil measurements of CO2 and CH4 fluxes. Immediately after the May 20, 2012, mainshock and during the Emilia seismic sequence, the collapsed caves were sampled again to determine any variations in these CO2 and CH4 fluxes. In this survey, newly formed collapsed caves were also found and measured (especially in the northern part of investigated area). […]</p>

Comparison of perchloroethylene extraction techniques in soil gas survey quantification

Subsurface pollution by volatile organic compounds has emerged as a widespread problem in industrialized countries. This study compares static headspace technique and methanol extraction/purge-and-trap analysis followed by thermal desorption/gas chromatography in attempts for quantification of gas survey results in the determination of these chemicals in soil. Several soils were contaminated with aqueous solution of perchloroethylene (PCE) (140 mg L−1) using a vapor treatment method. Soil spiking took place up to 24 h in desiccator by exposing individual soil samples contained in open 40 mL glass vials to PCE evaporated from the solution. After exposure the samples were stored and analyzed within 2 days. The achieved results strongly suggest that gas extraction can provide quantitative results, regarding PCE concentration in soils, which are not significantly different from liquid based extraction analysis.

The Southern Extension and Reactivations of the Clarendon-Linden Fault System

ABSTRACT Gas seeps located near Pike, New York, on the inferred location of the central fault of the Clarendon-Linden Fault System (CLF), were initiated during, or slightly after, the Saguenay earthquake, 1988. Analyses of the gas show that the gas seeps have a Devonian shale source, and a nearby well suggests that the source may be as deep as 330 m. Thus, CLF fractures extending to depths possibly as great as 300+ m were probably opened as a local response to the Saguenay event, allowing the gas to be vented. Published data show that the CLF extends from Lake Ontario to slightly south of Pike. Previously, there were insufficient data available to enable investigators to determine if the fault system continued farther south. Our soil gas survey and analyses of well logs indicate the CLF continues south into Allegany County, which borders the state of Pennsylvania. Closely-spaced wells suggest that the central fault of the CLF is probably a series of step faults, even in units above the Silurian evaporite section, although a monocline cannot be ruled out. Growth-fault geometries of the CLF suggest that the CLF experienced motion during the Taconic and Acadian orogenies. Isopach maps, coupled with the proposed southward extrapolation of the CLF, suggest that in Late Devonian times the CLF motion history recorded the passage of the Appalachian foreland basin axis across the CLF.