Subsurface Samples Research Articles

Carbon mobilization in response to the 2021 Mw 7.4 Maduo earthquake: Constraints from carbon isotope systematics of subsurface fluids

Active fault zones provide favorable channels for the discharge of carbon-bearing fluids from Earth’s interior. Earthquakes, as a common fault-related dynamic process, can disturb the circulation of subsurface fluids and their interactions with country rocks and sediments on short timescales, which may cause changes in carbon mobilization processes and carbon sources of the discharged fluids. However, quantitative research on earthquake-induced changes in carbon mobilization at deep and shallow levels remains lacking. Here, we present a quantitative study on stable carbon isotopes (δ13C) and radiocarbon values (Δ14C) of dissolved inorganic carbon (DIC) in subsurface fluid samples from the surface rupture zone formed by the Mw 7.4 Maduo earthquake (22 May 2021) and the East Kunlun fault, NE Tibetan Plateau. Our results show that δ13CDIC values vary from –11.6‰ to 0.1‰, while Δ13CDIC values have a range of –980‰ to –46‰. Using a mass balance model based on δ13CDIC and DIC concentrations, we calculated the proportions of source components involved in DIC, including organic carbon, carbonates, and deeply-sourced carbon. On average, waters discharging from the surface rupture zone have higher inputs from organic carbon (28.1%) than those from the East Kunlun fault (18.6%), with the latter showing higher deeply-sourced carbon contributions (45.7% vs. 30.7%). This is consistent with the lower average Δ14CDIC value (–544‰) observed from the East Kunlun fault, suggesting more inputs from carbon source components that are devoid of 14C (i.e., deeply-sourced carbon and carbonates). These findings indicate that seismic events can significantly affect the carbon mobilization processes at variable depths, especially the shallow soil organic carbon in the case of the 2021 Maduo earthquake. The potential effects of earthquake-induced changes in carbon mobilization processes should be taken into account in the modeling of tectonic carbon dioxide degassing and carbon cycle on longer timescales.

Evaluating uncertainty in empirically derived unconfined compressive strength (UCS) estimates and implications for drilling applications; a case study from the Cooper Basin

Accurate estimates of Unconfined Compressive Strength (UCS) are essential for a range of subsurface applications, including drilling wells for subsurface fluid extraction or injection. However, measuring UCS of subsurface rock samples through laboratory-based uniaxial and triaxial testing is time consuming, expensive, and potentially subject to individual sample variance. P-wave velocity logs are routinely obtained in petroleum basins and are commonly used to estimate UCS using empirically-derived correlations. In this study we analysed P-wave velocity data from 43 wells in the Cooper Basin, Australia and created mean ranges of expected UCS through the Tirrawarra, Toolachee, Patchawarra, Murteree Shale and Epsilon formations, using literature-derived P-wave velocity-UCS correlations, and also estimated UCS based on selected available laboratory-determined P-wave velocity measurements. These two suites of P-wave velocity-derived estimates of UCS are then compared to available results from laboratory uniaxial testing of core samples. Our analysis indicates that P-wave velocities, and subsequent derived estimates of UCS from P-wave wireline logs, are typically lower than those from laboratory-analysed samples. This may reflect a sampling bias towards the selection of strong rocks for laboratory UCS testing or lower estimates of UCS due to wellbore damage and pore space content (air or liquids) from P-wave log derived velocities. However, the laboratory-derived P-wave velocities generally agree with laboratory-derived UCS data from the Patchawarra, Murteree Shale and Epsilon formations when using published empirical velocity-strength correlations. A retrospective case study presents the impacts of different UCS estimates on mud weight required to produce observed borehole breakouts in the Epsilon Formation. Breakouts were observed 90 degrees to the orientation of SHmax (117° N) with a mean width of 51°, the breakouts were produced during drilling using a 9.7 ppg mud weight. The back-calculated estimate of UCS from the observed breakout widths at 9.7 ppg is 154 MPa. This sits between the UCS estimate of 171 MPa from uniaxial testing and 145 MPa from the mean of laboratory sample-derived P-wave velocities. Estimates of UCS from empirical correlations based solely on p-wave log-derived are far lower and vary between 87.3 and 114.4 MPa.

Study on reservoir characteristics, pore-throat structure, and origin of tight oolitic reservoirs: A case study of Triassic Feixianguan Formation, NE Sichuan Basin, SW China

The origin and pore-throat structure of different lithofacies are key issues in exploration and development of tight oolitic reservoirs. Based on core and thin section observation, four types of lithofacies can be recognized in the Feixianguan Formation oolitic reservoir: 1) oolitic limestone with intergranular pores (Lithofacies A), 2) oolitic limestone with mold pores (Lithofacies B), 3) oolitic dolostone (Lithofacies C), and 4) silty crystalline dolomite and fine crystalline dolostone (Lithofacies D). The subsurface core samples from the different lithofacies were studied using mercury injection, 3D CT scanning, and nuclear magnetic resonance, indicating that Lithofacies D possesses the best pore-throat structure and reservoir connectivity. The pore-throat structure of Lithofacies C is very similar to that of D, but the heterogeneity is much stronger. By comparison, the pore-throat structure of Lithofacies A and B is relatively poor. Although the pore heterogeneity of Lithofacies B is weaker than that of Lithofacies A, there is no effective throat connection in Lithofacies B. On the basis of oolitic shoal deposition, the factors controlling the origin of different lithofacies are meteoric freshwater leaching and then dolomitization. Meteoric freshwater leaching dominates the origin of Lithofacies B but does not affect the origin of Lithofacies C. Lithofacies C is jointly controlled by seepage-reflux and hydrothermal dolomitization fluids. The origin of Lithofacies D is only controlled by seepage-reflux dolomitization. Some other diagenesis effects may also have an impact on petrophysical properties of different lithofacies, but they do not play a decisive role in the origin of different lithofacies.

Design and Verification of a Novel Sampling System for Lunar Water Ice Exploration

Aiming at the problem that it is difficult to collect the subsurface lunar water ice samples quickly due to the cementation-hardening of ice and soil at extremely low temperature in the permanent shadow regions, a novel lunar water ice sampling system is proposed, which uses kinetic energy penetration to efficiently expose the subsurface lunar water ice and uses manipulator to accurately collect and transfer the lunar soil samples. Based on the analysis of the working strategy of the sampling system, an engineering prototype of penetrating modular was designed and developed, and its penetration efficiency was tested based on the principle that the mechanical characteristics are equivalent. The test results show that the penetrating modular can penetrate into the target whose uniaxial compressive strength(UCS) is about 30Mpa (equivalent to the UCS of the simulated lunar water ice) with low power consumption and high efficiency, the penetration depth can reach 234mm, and the penetration time is less than 1s.

A Survey of Aquatic Macrophytes in the Akassa Axis of the River Nun, Niger Delta, Nigeria

An ecological study was conducted to measure the diversity of aquatic macrophytes and nutrient levels of the River Nun estuary around Akassa, Niger Delta, Nigeria. This was done to ascertain the current ecological status of the estuary and gauge the ecological health of the water body as a result of anthropogenic additions into the water body. Macrophye and Subsurface samples were collected from three sampling points on the estuary. Macrophyte samples were identified using standard keys while water samples were investigated for pH, Salinity, Nitrates, Phosphates, and Sulphates. Result from the study reveals the presence of 17 species of aquatic macrophytes from 8 families. All nutrient parameters were within the permissible levels. There is no significant difference (P>0.05) in pH, salinity and sulphate between stations. There is a significant difference (P<0.05) in nitrate and phosphate between stations. The diversity of macrophytes was also uniformly high in all stations. The preponderance of macrophytes in this study agrees with the aphorism that marine ecosystems contain a high diversity of living organisms. The River Nun is therefore not under any immediate ecological threat.

Using Digital Rock Physics to Evaluate Novel Percussion Core Quality

This paper details a benchmarking and validation workflow using digital rock physics (DRP) to evaluate the effectiveness of various percussion sidewall core (PSWC) acquisition methods. The workflow consists of obtaining digital rock properties and images of reference material to compare with material obtained from laboratory percussion sidewall acquisition, including novel designs. This workflow allows insight into the acquisition processes and potential sources of damage in the PSWC technique, and potentially other rock sampling techniques, and offers an opportunity to evaluate its appropriateness as a subsurface rock sample acquisition method. Sample cubes from six outcrop sandstone formations of known properties were used in the testing program to cover a wide range of particularly low and medium unconfined compressive strengths (UCS). Multiple control rotary plug samples were cut from each sandstone formation. The sample cubes were then used as the parent material in laboratory testing of various designs of PSWC bullets. The PSWC bullets, including novel designs, were shot in simulated downhole environments. Both control rotary plug samples and PSWC test core samples were imaged with high-resolution X-ray micro-computed tomography (micro-CT) at resolutions between 2 and 11 μm, and digital rock analysis was conducted on all samples. Using pre- and post-test images, the damage could be identified, and petrophysical properties, including porosity and permeability, could be determined and directly compared with DRP results from control samples and available routine core analysis (RCA) results. DRP provides unique insight to evaluate and quantify changes (or lack of changes) to the sample material subjected to the PSWC acquisition. Damage encountered in the test samples includes grain crushing and compaction that degrades storage and transport properties and dilatant zones that locally enhance transport properties. The presence, frequency, and distribution of these zones are dependent on experimental parameters. In all cases, undisturbed rock fabric could be identified in each sample, and intact texture was verified by comparison with reference material. A novel and efficient method for acquiring and evaluating subsurface samples was developed and benchmarked. Lab results indicate this method may be equally applicable to low- and mid-range UCS rocks. This approach enables a cost-effective reservoir characterization strategy. By optimizing PSWC bullet design and coupling this with mature, image-based digital rock technology, this work demonstrated that the samples and results obtained by this method are representative and that the controls on storage and transport properties are well understood.

Depth wide distribution and metabolic potential of chemolithoautotrophic microorganisms reactivated from deep continental granitic crust underneath the Deccan Traps at Koyna, India.

Characterization of inorganic carbon (C) utilizing microorganisms from deep crystalline rocks is of major scientific interest owing to their crucial role in global carbon and other elemental cycles. In this study we investigate the microbial populations from the deep [up to 2,908 meters below surface (mbs)] granitic rocks within the Koyna seismogenic zone, reactivated (enriched) under anaerobic, high temperature (50°C), chemolithoautotrophic conditions. Subsurface rock samples from six different depths (1,679-2,908 mbs) are incubated (180 days) with CO2 (+H2) or HCO3 - as the sole C source. Estimation of total protein, ATP, utilization of NO3 - and SO4 2- and 16S rRNA gene qPCR suggests considerable microbial growth within the chemolithotrophic conditions. We note a better response of rock hosted community towards CO2 (+H2) over HCO3 -. 16S rRNA gene amplicon sequencing shows a depth-wide distribution of diverse chemolithotrophic (and a few fermentative) Bacteria and Archaea. Comamonas, Burkholderia-Caballeronia-Paraburkholderia, Ralstonia, Klebsiella, unclassified Burkholderiaceae and Enterobacteriaceae are reactivated as dominant organisms from the enrichments of the deeper rocks (2335-2,908 mbs) with both CO2 and HCO3 -. For the rock samples from shallower depths, organisms of varied taxa are enriched under CO2 (+H2) and HCO3 -. Pseudomonas, Rhodanobacter, Methyloversatilis, and Thaumarchaeota are major CO2 (+H2) utilizers, while Nocardioides, Sphingomonas, Aeromonas, respond towards HCO3 -. H2 oxidizing Cupriavidus, Hydrogenophilus, Hydrogenophaga, CO2 fixing Cyanobacteria Rhodobacter, Clostridium, Desulfovibrio and methanogenic archaea are also enriched. Enriched chemolithoautotrophic members show good correlation with CO2, CH4 and H2 concentrations of the native rock environments, while the organisms from upper horizons correlate more to NO3 -, SO4 2- , Fe and TIC levels of the rocks. Co-occurrence networks suggest close interaction between chemolithoautotrophic and chemoorganotrophic/fermentative organisms. Carbon fixing 3-HP and DC/HB cycles, hydrogen, sulfur oxidation, CH4 and acetate metabolisms are predicted in the enriched communities. Our study elucidates the presence of live, C and H2 utilizing Bacteria and Archaea in deep subsurface granitic rocks, which are enriched successfully. Significant impact of depth and geochemical controls on relative distribution of various chemolithotrophic species enriched and their C and H2 metabolism are highlighted. These endolithic microorganisms show great potential for answering the fundamental questions of deep life and their exploitation in CO2 capture and conversion to useful products.

Combining voltammetric and mass spectrometric data to evaluate iron organic speciation in subsurface coastal seawater samples of the Ross sea (Antarctica)

Iron (Fe) is the most important trace element in the ocean, as it is required by phytoplankton for photosynthesis and nitrate assimilation. Iron speciation is important to better understand the biogeochemical cycle and availability of this micronutrient, in particular in the Southern Ocean. Dissolved Fe (dFe) concentration and speciation were determined in 24 coastal subsurface seawater samples collected in the western Ross sea (Antarctica) during the austral summer 2017 as part of the CELEBeR (CDW Effects on glacial mElting and on Bulk of Fe in the Western Ross sea) project. ICP-DRC-MS was used for dFe determination, whereas CLE-AdSV was used to obtain the concentration of complexed and free dFe, of the ligands, and the values of the stability constants of the complexes. Dissolved Fe values ranged from 0.4 to 2.5 nM and conditional stability constant (logK’Fe’L) from 13.0 to 15.0, highlighting the presence of Fe-binding organic complexes of different stabilities. Principal component analysis (PCA) allowed us to point out that Terra Nova Bay and the neighboring area of Aviator and Mariner Glaciers were different in terms of chemical, physical, and biological parameters. A qualitative investigation on the nature of the organic ligands was carried out by HPLC–ESI–MS/MS. Results showed that siderophores represented a heterogeneous class of organic ligands pool.

Dynamics, distribution, and transformations of mercury species from pyrenean high-altitude lakes

While mercury (Hg) is a major concern in all aquatic environments because of its methylation and biomagnification pathways, very few studies consider Hg cycling in remote alpine lakes which are sensitive ecosystems. Nineteen high-altitude pristine lakes from Western/Central Pyrenees were investigated on both northern (France) and southern (Spain) slopes (1620–2600 m asl.). Subsurface water samples were collected in June 2017/2018/2019 and October 2017/2018 for Hg speciation analysis of inorganic mercury (iHg(II)), monomethylmercury (MMHg), and dissolved gaseous mercury (DGM) to investigate spatial and seasonal variations. In June 2018/2019 and October 2018, more comprehensive studies were performed in four lakes by taking water column depth profiles. Besides, in-situ incubation experiments using isotopically enriched Hg species (199iHg(II), 201MMHg) were conducted to investigate Hg transformation mechanisms in the water column. While iHg(II) (0.08–1.10 ng L−1 in filtered samples; 0.11–1.19 ng L−1 in unfiltered samples) did not show significant seasonal variations in the subsurface water samples, MMHg (<0.03–0.035 ng L−1 in filtered samples; <0.03–0.062 ng L−1 in unfiltered samples) was significantly higher in October 2018, mainly because of in-situ methylation. DGM (0.02–0.68 ng L−1) varies strongly and can exhibit higher levels in comparison with other pristine areas. Depth profiles and incubation experiments highlighted the importance of in-situ biotic methylation triggered by anoxic conditions in bottom waters. In-situ incubations confirm that significant methylation, demethylation and photoreduction extents are taking place in the water columns. Overall, drastic environmental changes occurring daily and seasonally in alpine lakes are providing conditions that can both promote Hg methylation (stratified anoxic waters) and MMHg photodemethylation (intense UV light). In addition, light induced photoreduction is a major pathway controlling significant gaseous Hg evasion. Global warming and potential eutrophication may thus have direct implications on Hg turnover and MMHg burden in those remote ecosystems.

Adsorption comparison of Cu(II) on riverbank soil from north of Sichuan and Chongqing, China

Riverbank soil is the final barrier to prevent pollutants from migrating into the river. Surface and subsurface soil samples of Cangxi, Nanbu, Jialing, Hechuan, Santai, Chuanshan, Quxian, and Guangan were collected from the three rivers in the north of Sichuan and Chongqing, China to explore the effects of riverbank soils on Cu(II) adsorption. Basic physicochemical characteristics of the riverbank soils were analyzed. The isothermal and thermodynamic characteristics of each soil sample on Cu(II) adsorption were studied by batch method, and the adsorption differences under various pH, temperature, and ionic strength were compared. Meanwhile, the adsorption form of Cu(II) on different riverbank soils was analyzed. Results show the following: (1) the adsorption isotherms of Cu(II) on different soil samples were all L-shaped and consistent with Langmuir model. The maximum adsorption capacity (qm) of Cu(II) on the test samples was between 83.63 and 247.24 mmol/kg, and the adsorption capacity of Cu(II) in Jialing soil was the highest under the same equilibrium concentration. (2) The adsorption amount of Cu(II) on different soil samples increased with the increase in temperature, showing a positive temperature effect. The adsorption amount of Cu(II) increased with the increase in pH; it initially increased and then decreased with the increase in ionic strength. Cu(II) adsorption on soil samples was a spontaneous, endothermic, and entropy-increasing process. (3) The adsorbed Cu(II) on banksoils was mainly in the form of carbonate bound and iron manganese oxidation, accounting for more than 60% of the total adsorbed Cu(II). Cu(II) in exchangeable form was the second, and the organic matter form was the lowest. (4) CEC and SBET of soil samples are the key factors affecting the adsorption capacity of Cu(II), and pH and CEC are the key factors determining the adsorption form of Cu(II) on riverbank soil.

Metagenomics diversity analysis of sulfate-reducing bacteria and their impact on biocorrosion and mitigation approach using an organometallic inhibitor

Sulfate-reducing bacteria (SRB) have impacted the biocorrosion process for various industrial sectors, especially in the oil and gas industry. The higher stability over extreme conditions is the key parameter for their survival in such environments. So far, many materials have been tried to minimize or control the growth of SRB. In the present study, an organo-metallic compound of the zinc sorbate (ZS) was successfully synthesized by the simple co-precipitation method and its improved antibacterial activity against SRB. The SRB consortia are enriched from the sub-surface soil sample and identified by 16s rDNA sequencing by targeting the V3-V4 region. The most dominating genera identified with sulfate-reducing capability are Sulfurospirillum (42 %), Shewanella (19 %) Bacteroides (14 %), and Desulfovibrio (8 %). Further biocorrosion experiments are conducted by weight loss methods. Higher corrosion current density (Icorr) and less charge transfer resistance (Rct) are observed for the SRB consortia. Concurrently, higher Rct is kept for the inhibitor-included systems. The slowest release of the sorbate into the medium suppressed the growth of the SRB bacterial cells with 86 ± 3 % corrosion inhibition efficiency and prevented further corrosion reactions by forming a protective layer over the surface of the carbon steel API 5LX. The surface analysis strongly confirmed that SRB caused pitting corrosion, which has been suppressed in the inhibitor-included systems.

Carbonate fractures from conventional well log data, Kometan Formation, Northern Iraq case study

The Borehole Acoustic Televiewer, Formation Micro scanner (FMS), Formation Micro-Imager (FMI), and Electric Micro Imaging (EMI) are the most qualified approaches to fracture identification. Still, they are more expensive and only give images at specific intervals. Conventional well log tools can be identified without interval limitations. This study aimed to demonstrate the ability of the Conventional well logging tools to identify fractures in the Upper Cretaceous Kometan Formation in the Northern part of Iraq. The study area is located at latitudes 3,922,836.34 N to 3,930,557 N and longitudes 448,350.78E to 417772E for the well of Kirkuk 216 (K216) and Khabbaz 40 (Kz40), respectively. Quantitative interpretations like secondary porosity index and qualitative are the total porosity-sonic porosity cross-plot, caliper log, total gamma-ray log, and porosity logs (neutron, sonic, and density log) have been used to identify fractures in the studied formation. Some subsurface rock samples (spectral gamma ray) and outcrop observations were also used to validate well log data results. Good secondary porosity (fractures) has been Identified from the Secondary Porosity Index (SPI), which is reached a maximum value of 17%, and the average is 4% for Kz40. The maximum value is 30%, and the average is 8% for K216. Based on the qualitative interpretations of the available log data, which were validated by subsurface rock samples and observed outcrop sections of the studied formation, it has been concluded that the reservoir quality of the Kometan formation was enhanced due to high fractures in the studied wells.

Soil tungsten contamination and health risk assessment of an abandoned tungsten mine site

The mining and beneficiation of tungsten ores, including waste treatment and tailings disposal, may cause soil contamination in the mining area and environments. Few studies have addressed soil contamination in tungsten mine sites. The current research quantitated the leachates in the surface and subsurface soil samples from mining and beneficiation areas, peripheral area, sand-making area, dumping area, and tailings pond of an abandoned tungsten mine site in Ganzhou City, Jiangxi Province of China. We further evaluated the degree of soil tungsten pollution and the risk to human health. The results showed that soil tungsten contamination mainly occurred in the sand-making area where tailings were used to make sand. The highest tungsten content in the surface and subsurface soils of the sand-making area was 1250 and 3020 mg/kg, respectively, exceeding the EPA's Regional Screening Level of tungsten (930 mg/kg) for industrial land use. The leaching concentrations of soil tungsten had similar distribution patterns to that of total soil tungsten, with the highest leaching concentration (0.860 mg/L) found in the sand-making area. The geo-accumulation index evaluation indicated heavy tungsten contamination at the sand-making area and tailings pond. The hazard quotient (HQ = 1.34) of tungsten contamination in the surface soils of the sand-making area exceeded the acceptable level (HQ = 1), implying a significant risk to human health. The present study provided valuable information for pollution control and risk management of soil contamination in tungsten mine sites. CapsuleWe studied the degree of soil tungsten pollution and health risk assessment in an abandoned tungsten mining area to provide helpful information for soil pollution control and risk management in China's tungsten mining areas.

Site selection for the Hayabusa2 artificial cratering and subsurface material sampling on Ryugu

Hayabusa2 took on the challenge of collecting fresh subsurface samples from asteroid (162173) Ryugu during its second touchdown operation. For this ambitious goal, the spacecraft conducted artificial cratering by using a small carry-on impactor (SCI), leading to the exposure of subsurface materials. The key to mission success lies in the target site selection for the SCI and landing operations, which is the focus of this paper. On the one hand, the science goal of collecting subsurface materials required us to land on one of the areas with a large amount of impact ejecta excavated by SCI, where boulder abundance is not necessarily low. On the other hand, spacecraft safety demanded that we avoid landing on hazardous areas with large boulders. These two conditions often conflicted with each other. In order to resolve this dilemma, we developed a scheme to select a target site that secures the chance of retrieving a significant amount of subsurface samples without posing serious safety risks. Although the basic selection scheme was similar to that for the first touchdown, the second landing site selection involved additional analyses of artificial cratering and subsurface sampling. Consequently, the site selection campaign, including various types of spacecraft operations, contributed to the successful retrieval of Ryugu samples, which presumably contain materials excavated from subsurface layers. The present study provides the framework to access internal asteroid materials, pushing the envelope of space exploration. • Hayabusa2 aimed to collect subsurface samples from Ryugu excavated by an impactor. • Hayabusa2 completed landing and sampling on a target site with a diameter of 3.5 ​m. • The estimated thickness of the impact ejecta at the landing site was 1–3 ​cm. • No hazardous boulders larger than 65 ​cm existed within the landing site.

Boron in the strata and waters of the Eocene Green River and Uinta Formations, Uinta Basin, Utah

Boron is a naturally occurring element that can be found in the strata and water of the Eocene Green River and Uinta Formations of the Uinta Basin of Utah. Whereas boron is suspected to be a necessary trace nutrient for proper plant and animal growth and development, higher concentrations of boron can be detrimental to living things, but the element is not known to be carcinogenic. Utah has no limit on boron content in drinking water; however, for irrigation purposes a limit of 750 μg B/L (0.75 mg/L) has been established. The Green River Formation (GRF), deposited in ancient lakes in Wyoming, Colorado, and Utah, is well known for its oil shale and saline mineral deposits, particularly the thick, economic trona beds in Wyoming. Such evaporitic mineral deposits are characteristic of a saline lake environment that existed at the end stages of Eocene lacustrine deposition. In Utah they are found in the upper GRF, and to a minor extent in the lower Uinta Formation, where elevated boron is evident. Boron-bearing minerals are present in the Parachute Creek Member of the GRF in Utah, and they occur as secondary silicate minerals in at least 12 wells across Utah’s Uinta Basin. These minerals were first reported by the U.S. Geological Survey in the 1950s. This study determined that the boron mineral occurrences correlate stratigraphically and coincide with the areas delineated for the hypersaline events in the Parachute Creek Member of the GRF. This argues that boron was concentrated with other saline constituents in Lake Uinta and is an indicator of hypersaline conditions. Water quality analyses reporting boron content from surface and subsurface samples were compiled from public databases from the Utah Department of Environmental Quality, the U.S. Geological Survey, and the Utah Geological Survey. This new database consists of 155 samples from 38 sites from the upper part (Parachute Creek Member) of the GRF, and 58 samples from 26 sites from the lower part (Douglas Creek Member) of the GRF. The boron concentration was found to be different for the two GRF parts. The average boron content of the 58 lower GRF aquifer water analyses is 6338 μg/L, while the mean boron content for the 26 individual sites varies from 15 to 205,000 μg/L. The upper GRF aquifer contains at least twice the boron content of the lower GRF, and the average boron content of the 155 analyses of upper GRF groundwater is 18,172 μg/L. The mean boron content for the 38 individual sites varies 40 to 480,000 μg/L. Areas of highboron concentration in groundwater of the GRF tend to coincide with the location of GRF hypersaline paleodepocenters. Groundwater boron content in the Uinta Formation comes from 40 analyses from 36 sites. The average of the 40 Uinta Formation analyses is 3251 μg B/L, while the mean boron content for the 36 individual sites varies from 40 to 24,000 μg/L. For each interval studied, less boron tends to be found in analyses from sites near the outcrop and boron content tends to increase in the studied formations as they are more deeply buried. Additionally, boron content was compiled for surface waters and springs for 3955 analyses from 374 sites in the Uinta Basin. When the mean boron content of these surface water sites was examined by hydrologic drainage unit subareas, it was found that the tributaries in the northern Uinta Basin, north of the Duchesne and White Rivers, contain the lowest mean boron contents, whereas higher mean boron contents are common for the tributaries in southern part of the basin. The boron content of surface water from the southern Uinta Basin drainages also tends to increase northward toward the demarking water courses. The tributaries in the southern part of the Uinta Basin have higher boron contents due to their waters having contact with the boron-bearing, shallow-inclined strata of the upper GRF or member B of the Uinta Formation. The tributaries in northern part of the basin have lower boron contents because they are not in contact with the GRF, have less contact with the member B of the Uinta Formation, and are diluted by greater snow-melt runoff from the Uinta Mountains which bound the basin to the north.

Radium radioactivity in soil profiles following long term irrigation with high radioactivity fossil groundwater

High radioactivity in a relatively saline confined aquifer water in different locations of the Disi area (South East of Jordan) was reported by some authors who recommended further investigation on the impact of that water on irrigated soils. Five well water samples (jointly used for irrigation and drinking) and 28 surface and subsurface soil samples from five profiles were collected from that area for the purpose of this study. Selected mineralogical, chemical, and physical properties of the soil samples were determined. Mineralogical compositions of the 28 soil samples were identified using x-ray diffraction, x-ray fluorescence, and ICP-MS techniques. Determination of activity concentrations of 238U, 226Ra and 228Ra in the five well waters and 22 soil samples from 4 sites (including a native soil) were determined using γ-ray spectroscopy. The results showed low salinity levels of both soil and water samples and low clay and organic matter contents in all soil samples. Kaolinite and mica were the dominant clay minerals with Fe substituting Al in the octahedral layer of these minerals. The average activity concentration of 226Ra and 228Ra in the well-water samples were 0.31 ± 0.09 and 1.74 ± 0.12 BqL−1, respectively. Such a high specific activity could be ascribed to the water enrichment with 228Ra diffusing from 232Th-rich sandstone geologic strata. Average concentrations of 238U and 232Th in the soil samples (0–120 cm depth) were 1.48 ± 0.38 mg kg−1 and 4.78 ± 1.55 mg kg−1, respectively. High correlation between these two radionuclides (R2 = 0.90) indicated no specific enhancement of these two metals from external sources, especially through chemical precipitation from irrigation water. Average activity concentration of 238U, 226Ra, and 228Ra in the soil samples were substantially low (20.8 ± 5.6, 16.94 ± 4.48, and 20.7 ± 6.2 Bq kg−1, respectively). No particular changes were observed when comparing concentration or radioactivity of these radionuclides with depth of a given soil or between irrigated and native soil samples at comparable depths. This could lead to the conclusion that there was no appreciable precipitation or adsorption of these radioactive metals from the percolating irrigation water onto the sandy soil complex.

Spatial and temporal distributions of glycerol dialkyl glycerol tetraethers in suspended materials in the northern East China Sea: Applicability as a paleotemperature proxy

The spatial and temporal distributions of the glycerol dialkyl glycerol tetraether (GDGT) concentrations in suspended materials were investigated to determine whether the GDGT-based TEX86 can be used as a proxy for annual mean sea surface temperature in the northern East China Sea (ECS). Seawater samples were collected seasonally at three-month intervals from the surface and subsurface of the northern ECS. GDGT in the surface seawater was detected consistently across all seasons. However, the TEX86 temperatures of the surface seawater samples differed significantly from the in situ temperatures over the entire study area; in particular, TEX86 temperatures were higher (4–7 °C) than in situ temperatures in winter, and lower (9–12 °C) than in situ temperatures in summer. The occurrence of a high concentration of GDGTs near the bottom, with marked differences between TEX86 and in situ temperatures in the shallow water (~30 m) supports the possibility of sediment resuspension near the bottom in the western part and subsequent transportation eastward. GDGTs may have been resuspended owing to vertical mixing by strong winds, such as those from the monsoon (winter) and typhoons (summer), and increased turbulence near the bottom caused by tides across all seasons in the shallow waters (30–50 m). In contrast, the vertical distribution of GDGT concentration in the eastern part of the study area deeper than 100 m indicated that maximum GDGT concentrations occurred at depths of between 20 m and 50 m in all seasons. The TEX86 temperatures of the subsurface samples were similar to or warmer than in situ temperatures between 20 m and 50 m, suggesting that the main depth at which GDGT was produced in the eastern area could be the subsurface in that same depth range. A new local calibration equation was established based on the subsurface samples from the east. Our results indicate that sediment resuspension and subsurface production of GDGTs can have a significant impact on the use of GDGT-based TEX86 as a SST proxy in continental shelf area.

A Multivariable Empirical Algorithm for Estimating Particulate Organic Carbon Concentration in Marine Environments From Optical Backscattering and Chlorophyll-a Measurements

Accurate estimates of the oceanic particulate organic carbon concentration (POC) from optical measurements have remained challenging because interactions between light and natural assemblages of marine particles are complex, depending on particle concentration, composition, and size distribution. In particular, the applicability of a single relationship between POC and the spectral particulate backscattering coefficient bbp(λ) across diverse oceanic environments is subject to high uncertainties because of the variable nature of particulate assemblages. These relationships have nevertheless been widely used to estimate oceanic POC using, for example, in situ measurements of bbp from Biogeochemical (BGC)-Argo floats. Despite these challenges, such an in situbased approach to estimate POC remains scientifically attractive in view of the expanding global-scale observations with the BGC-Argo array of profiling floats equipped with optical sensors. In the current study, we describe an improved empirical approach to estimate POC which takes advantage of simultaneous measurements of bbp and chlorophyll-a fluorescence to better account for the effects of variable particle composition on the relationship between POC and bbp. We formulated multivariable regression models using a dataset of field measurements of POC, bbp, and chlorophyll-a concentration (Chla), including surface and subsurface water samples from the Atlantic, Pacific, Arctic, and Southern Oceans. The analysis of this dataset of diverse seawater samples demonstrates that the use of bbp and an additional independent variable related to particle composition involving both bbp and Chla leads to notable improvements in POC estimations compared with a typical univariate regression model based on bbp alone. These multivariable algorithms are expected to be particularly useful for estimating POC with measurements from autonomous BGC-Argo floats operating in diverse oceanic environments. We demonstrate example results from the multivariable algorithm applied to depth-resolved vertical measurements from BGC-Argo floats surveying the Labrador Sea.

Evaluation of subsurface transport processes of delayed gas signatures applicable to underground nuclear explosions

Radioactive gas signatures from underground nuclear explosions (UNEs) result from gas-migration processes occurring in the subsurface. The processes considered in this study either drive or retard upward migration of gases from the detonation cavity. The relative importance of these processes is evaluated by simulating subsurface transport in a dual-permeability medium for the multi-tracer Noble Gas Migration Experiment (NGME) originally intended to study some aspects of transport from a UNE. For this experiment, relevant driving processes include weak two-phase convection driven by the geothermal gradient, over pressuring of the detonation cavity, and barometric pumping while gas sorption, dissolution, radioactive decay, and usually diffusion represent retarding processes. From deterministic simulations we found that over-pressuring of the post-detonation chimney coupled with barometric pumping produced a synergistic effect amplifying the tracer-gas reaching the surface. Bounding simulations indicated that the sorption and dissolution of gases, tending to retard transport, were much smaller than anticipated by earlier laboratory studies. The NGME observations themselves show that differences in gas diffusivity have a larger effect on influencing upward transport than do the combined effects of tracer-gas sorption and dissolution, which is consistent with a Sobol’ sensitivity analysis. Both deterministic simulations and those considering parametric uncertainties of transport-related properties predict that the excess in concentration of SF_6 compared to ^{127}Xe as might be captured in small volumetric samples should be much smaller than the order-of-magnitude contrast found in the large-volume gas samples taken at the site. While extraction of large-volume subsurface gas samples is shown to be capable of distorting in situ gas compositions, the highly variable injection rate of SF_6 into the detonation cavity relative to that of ^{127}Xe at the start of the field experiment is the most likely explanation for the large difference in observed concentrations.

Icy Moon Penetrator Organic Analyzer Post-Impact Component Analysis

Europa is an established high-priority astrobiology target where identifying chemical signatures of life is one of NASA’s highest-priority goals. Remote sensing techniques are powerful tools for extraterrestrial exploration, but in situ data through analyses of subsurface materials is necessary for ground-truthing these habitability investigations. Instrument designs fitting small volume, mass, and power consumption envelopes have a high potential for enabling efficient, low-cost missions. The Ice Shell Impact Penetrator (IceShIP) is a state-of-the-art miniaturized payload design dedicated to lower-cost extraterrestrial impact-penetrator missions. It houses the Icy Moon Penetrator Organic Analyzer (IMPOA), a first-of-its-kind payload housing miniaturized analytical instrumentation employing laser-induced fluorescence for the detection of low concentration organic species pervasive in the solar system. IMPOA is capable of sustaining high g-loads, avoiding the need for soft landing platforms, and facilitating crustal penetration for subsurface sample analyses. Three IMPOA test articles with varying material choices, construction designs, and internal components were modeled using COMSOL Multiphysics and then tested at 12 k-g, 25 k-g, and 50 k-g accelerations in an air gun assembly. The internal components consisted of linear piezoelectric micro-actuators, microcontroller board, mock microfluidic glass wafers, collimating lens, optical filters, and laser diodes. This work focuses on an extensive analysis of the impact-tested components. All components physically survived the impact tests except the mock microfluidic disk. Functionality tests of the individual components confirm their survival post-impact. All components used in this design are commercially available or easily machinable, which will simplify technology transfer for further technology elevation. Impact-resistance, miniaturization, energy efficiency, and cost-effectiveness are pivotal for impact-penetrator space-flight missions. This work satisfies these key aspects and demonstrates technology of a novel design for astrobiological in situ instrumentation.