Effect of CO2 on biogeochemical reactions and microbial community composition in bioreactors with deep groundwater and basalt.

Changes in subsurface microbiology following CO2 injection have the potential to impact carbon trapping in CO2 storage reservoirs. However, much remains to be learned about responses of natural microbial consortia to elevated CO2 in basaltic systems. This study asks: how will microbes from deep (700 m) groundwater change along a gradient in CO2 (0-20 psi) in batch reactor systems containing basalt chips and groundwater amended with lactate? Reactors incubated for 87 days at 23 °C. Results for reactors with low CO2 (0 and 3 psi) differed considerably from those with high CO2 (10 and 20 psi). In reactors with low CO2, pH was >6.5 and lactate started to be used within 24 days. By 40 days, lactate was completely consumed and acetate increased to ~4 mM. As lactate was consumed, sulfate decreased from 0.16 to 0 mM after 40 days. In contrast, in reactors with high CO2, pH was <6.5, lactate and sulfate concentrations varied little and acetate was not produced. Biogeochemical modeling and community analyses indicate that differences between reactors with low and high CO2 reflect tolerances of reactor microbes to CO2 exposure. Communities in the low CO2 reactors carried out syntrophic lactate oxidation coupled with methanogenesis and sulfate reduction. Bacteroidota and Firmicutes became dominant phyla after 24 days and groups capable of sulfate reduction and methanogenesis were detected. In reactors with high CO2, however, biogeochemical activity was insignificant, no groups capable of sulfate reducion or methanogenesis were observed, and the community became less diverse during the incubation. These findings show that the response of microbial consortia can vary sharply along a CO2 gradient, creating significant differences in community composition and biogeochemistry, and that the timescale of basalt weathering is likely not rapid enough to prevent significant stress following a rapid increase in CO2 abundance.

Recent pollution and source identification of metal(loid)s in a sediment core from Gunsan Reservoir, South Korea.

We assessed the contributions of Cu smelting and Asian dust influx to metal(loid) pollution over the last century based on metal(loid) concentrations, Pb isotope ratios, and 210Pb dating of sediments from Gunsan Reservoir, South Korea. During the pre-industrial period (1827-1936), heavy metal pollutants were predominantly geogenic. Local smelting activity was dominant between 1936 and 2008. Between 1936 and 1971, Cu and Pb contamination was not significant, with contributions from smelting activities accounting for < 6.2% of the measured concentrations. In contrast, anthropogenic Cu and Pb inputs increased between 1971 and 2008 due to intense smelting activity. Based on the similar 206Pb/207Pb ratios of the reservoir sediments and smelter bottom ash, anthropogenic contributions reached 95% during 1987-1995. In comparison, the sediments deposited between 2008 and 2018 were characterized by a higher Zn and Cd geoaccumulation index and enrichment factor values and less-radiogenic Pb signals than the regional geogenic Pb signal. These trends are attributed to the long-range transport of pollutants from China, the contribution of which gradually increased from 11.0% in 2008 to 19.2% in 2018. Our results show that reservoir sediments are valuable archives for reconstructing metal(loid) contamination histories and changes in pollution sources over time.

Compositional data analysis and geochemical modeling of CO2-water-rock interactions in three provinces of Korea.

The CO2-rich spring water (CSW) occurring naturally in three provinces, Kangwon (KW), Chungbuk (CB), and Gyeongbuk (GB) of South Korea was classified based on its hydrochemical properties using compositional data analysis. Additionally, the geochemical evolution pathways of various CSW were simulated via equilibrium phase modeling (EPM) incorporated in the PHREEQC code. Most of the CSW in the study areas grouped into the Ca-HCO3 water type, but some samples from the KW area were classified as Na-HCO3 water. Interaction with anorthite is likely to be more important than interaction with carbonate minerals for the hydrochemical properties of the CSW in the three areas, indicating that the CSW originated from interactions among magmatic CO2, deep groundwater, and bedrock-forming minerals. Based on the simulation results of PHREEQC EPM, the formation temperatures of the CSW within each area were estimated as 77.8 and 150 °C for the Ca-HCO3 and Na-HCO3 types of CSW, respectively, in the KW area; 138.9 °C for the CB CSW; and 93.0 °C for the GB CSW. Additionally, the mixing ratios between simulated carbonate water and shallow groundwater were adjusted to 1:9-9:1 for the CSW of the GB area and the Ca-HCO3-type CSW of the KW area, indicating that these CSWs were more affected by carbonate water than by shallow groundwater. On the other hand, mixing ratios of 1:9-5:5 and 1:9-3:7 were found for the Na-HCO3-type CSW of the KW area and for the CSW of the CB area, respectively, suggesting a relatively small contribution of carbonate water to these CSWs. This study proposes a systematic, but relatively simple, methodology to simulate the formation of carbonate water in deep environments and the geochemical evolution of CSW. Moreover, the proposed methodology could be applied to predict the behavior of CO2 after its geological storage and to estimate the stability and security of geologically stored CO2.

Geochemical Influence on Microbial Communities at CO2-Leakage Analog Sites.

Microorganisms influence the chemical and physical properties of subsurface environments and thus represent an important control on the fate and environmental impact of CO2 that leaks into aquifers from deep storage reservoirs. How leakage will influence microbial populations over long time scales is largely unknown. This study uses natural analog sites to investigate the long-term impact of CO2 leakage from underground storage sites on subsurface biogeochemistry. We considered two sites with elevated CO2 levels (sample groups I and II) and one control site with low CO2 content (group III). Samples from sites with elevated CO2 had pH ranging from 6.2 to 4.5 and samples from the low-CO2 control group had pH ranging from 7.3 to 6.2. Solute concentrations were relatively low for samples from the control group and group I but high for samples from group II, reflecting varying degrees of water-rock interaction. Microbial communities were analyzed through clone library and MiSeq sequencing. Each 16S rRNA analysis identified various bacteria, methane-producing archaea, and ammonia-oxidizing archaea. Both bacterial and archaeal diversities were low in groundwater with high CO2 content and community compositions between the groups were also clearly different. In group II samples, sequences classified in groups capable of methanogenesis, metal reduction, and nitrate reduction had higher relative abundance in samples with relative high methane, iron, and manganese concentrations and low nitrate levels. Sequences close to Comamonadaceae were abundant in group I, while the taxa related to methanogens, Nitrospirae, and Anaerolineaceae were predominant in group II. Our findings provide insight into subsurface biogeochemical reactions that influence the carbon budget of the system including carbon fixation, carbon trapping, and CO2 conversion to methane. The results also suggest that monitoring groundwater microbial community can be a potential tool for tracking CO2 leakage from geologic storage sites.

Role of oxbow lakes in controlling redox geochemistry of shallow groundwater under a heterogeneous fluvial sedimentary environment in an agricultural field: Coexistence of iron and sulfate reduction.

This study aimed to extend the knowledge of the vertical distribution of redox conditions of shallow groundwater in heterogeneous fluvial sediments near oxbow lakes. For this study, we revisited the study area of Kim et al. (2009) to examine the redox zoning in details. Three multi-level samplers were installed along a flow path near two oxbow lakes to obtain vertical profiles of the subsurface geology and hydrochemical and isotopic data (δ(18)O and δD of water, δ(15)N and δ(18)O of nitrate, and δ(34)S of sulfate) of groundwater. Geologic logging showed that characteristics of the heterogeneous subsurface geology are closely related to the pattern of vertical redox zoning. Hydrochemical data in conjunction with nitrogen and sulfur isotope data show that the redox status of groundwater near oxbow lakes is controlled by denitrification, iron reduction, and sulfate reduction. The oxidizing condition of groundwater occurs in the sand-dominant alluvium located in the up-gradient of oxbow lakes, whereas the reducing condition accompanying denitrification, iron reduction, and local sulfate reduction is developed in silt-rich alluvium in and the downgradient of oxbow lakes. The occurrence of sulfate reduction was newly found in this study. However, the vertical profiles of redox-sensitive parameters show that iron reduction and sulfate reduction occur concurrently near oxbow lakes, although the measured redox potentials suggest that thermodynamic conditions are controlled by the stability of Fe(2+)/Fe-oxides. Therefore, this study shows that the redox condition of groundwater in the iron-rich zone should be carefully interpreted. For this purpose, depth-specific sampling and careful examination of sulfur isotope data will be very useful for identifying the redox processes occurring in the zone with overlapping iron reduction and sulfate reduction in heterogeneous fluvial sediments.

Types of subtalar joint facets.

Articular facets of the clinical subtalar joint (CSTJ) were analyzed using a total of 118 (right 57, left 61) dry, paired calcanei and tali from 68 Korean adult cadavers. The CSTJ facets were classified into the following three types depending on their continuity: type A, all three facets are separated; type B, the anterior and middle facets are partially connected; and type C, the anterior and middle facets are fused to form a single facet. The continuity between the anterior and middle facets was represented by the degree of separation (DS), which ranged between 2.00 (type A) and 1.00 (type C). Type A was most common (39.0 %) in calcanei and rarest (11.0 %) in tali. Matching of calcaneus-talus pairs yielded five combined types: A-A (11.0 %), A-B (28.0 %), B-B (18.6 %), B-C (13.6 %), and C-C (28.8 %). The mean DS was slightly greater in calcanei (1.53) than in tali (1.32), and decreased in the order of types A-A, A-B, B-B, B-C, and C-C. The intersecting angles between the anterior and middle facets, which are related to the mobility of the CSTJ, were inversely related to the DS. These findings indicate that the anterior and middle facets are fused more frequently in tali than in calcanei, and combinations of different CSTJ facet types (A-B, B-C) exist over 40 % of feet. Our results indicate that types with a smaller DS (such as B-C and C-C) are relatively mobile but less stable compared to those with a greater DS (such as A-A and A-B).

Assessment of mobility and bio-availability of heavy metals in dry depositions of Asian dust and implications for environmental risk.

We assess the potential mobility and bio-availability of selected metals (As, Cd, Co, Cr, Cu, Ni, Mo, Pb, S, Zn, and Zr) in the dry depositions of Asian and non-Asian dust from the city of Daejeon, Korea. For this study, we applied Pb isotopes, total extraction and chemical sequential extraction methods to the dry depositions. In addition, microscopic analysis was performed using X-ray diffraction (XRD) and focused ion beam (FIB)-scanning electron microscopy (SEM-EDS). FIB-SEM cross-section observations and Pb isotope data showed a black carbon is an important carrier of associated heavy metals originating from China. A five-step sequential extraction performed on the dry depositions showed that S and Cd are the most abundant elements in the water-soluble and cation-exchangeable fraction. In addition, Zn and Pb appeared predominantly in the carbonate and reducible fractions. On the other hand, Cu, Mo and, to a lesser degree, As were significantly associated with the organic fraction, while Co, Ni, Cr and Zr were bound to the residual fraction. These results showed that S, Cd, Zn and Pb, which were highly concentrated in potentially mobile fractions, have potential environmental risk because potential changes in redox state and pH may remobilize these metals. In addition, the estimated remobilization concentrations of these metals were significant. Thus, this study shows that frequent and careful monitoring of S, Cd, Z, Pb and, to a lesser degree, Cu, Mo and As is very important for assessing environmental risk in Korea.

Morphology of the mentalis muscle and its relationship with the orbicularis oris and incisivus labii inferioris muscles.

The mentalis muscle (MT) is the only elevator of the lower lip and the chin, and it provides the major vertical support for the lower lip. However, there are few reports on the relationship between the MT and its surrounding muscles. The aim of this study was to clarify the morphology of the MT, especially in relation to the orbicularis oris muscle and the incisivus labii inferioris muscle (ILI), thereby providing data to understand the function of the MT in relation to the surrounding muscles. The MT was examined in 40 specimens of embalmed adult Korean cadavers. The medial fibers of both MTs descended anteromedially and crossed together, forming a dome-shaped chin prominence in all specimens. The lateral fibers of the MT descended inferomedially in 38 specimens (95%) and inferolaterally in 2 specimens (5%). The upper fibers of the MT were short and ran horizontally, whereas the lower fibers were long and descended inferomedially or vertically. The upper fibers of the MT were intermingled with the inferior margin of the orbicularis oris muscle in all specimens. The originating muscle fibers of the ILI were intermingled with the upper lateral MT in all specimens. Some of the ILI fibers extended inferomedially to the middle or lower portion of the MT in 22 specimens (55%). The results of this study constitute new anatomical knowledge regarding the MT and will be useful to surgeons performing various surgical procedures of the chin area.

An anatomic study of the quadratus plantae in relation to tendinous slips of the flexor hallucis longus for gait analysis.

The aim of this study was to demonstrate the morphology of the quadratus plantae (QP) in relation to the tendinous slips of the flexor hallucis longus (FHL) and their surrounding structures, thereby providing data to understand function of the QP during gait, and for analyzing the movements of the foot and designing postoperative rehabilitation programs. The QP was investigated in 50 specimens of embalmed adult cadavers. The QP inserted into the tendon of the flexor digitorum longus (FDL) and the tendinous slips of the FHL in 96%, and only to the tendon of the FDL in 4%. The tendinous slip of the FHL targeted the tendon for the second toe in 4 of the 50 specimens (8%). The tendinous slip divided into two separate slips to the tendons for the second and third toes in 32 specimens (64%), and for the second, third, and fourth toes in 14 specimens (28%). Thus, the tendon and tendinous slips of the FHL may distribute the load of the great toe to the second toe to the third or fourth toe in the forefoot, especially during toe-off. In addition, the main attachment of the QP to the tendinous slips of the FHL may provide more efficient control of the long flexor tendons in comparison with that of the QP to the tendon of the FDL.

Mapping atomic contact between pentacene and a Au surface using scanning tunneling spectroscopy.

We mapped spatially varying intramolecular electronic structures on a pentacene-gold interface using scanning tunneling spectroscopy. Along with ab initio calculations based on density functional theory, we found that the directional nature of the d orbitals of Au atoms plays an important role in the interaction at the pentacene-gold contact. The gold-induced interface states are broadened and shifted by various pentacene-gold distances determined by the various registries of a pentacene molecule on a gold substrate.

Hydrochemical and multivariate statistical interpretations of spatial controls of nitrate concentrations in a shallow alluvial aquifer around oxbow lakes (Osong area, central Korea).

Hydrochemical and multivariate statistical interpretations of 16 physicochemical parameters of 45 groundwater samples from a riverside alluvial aquifer underneath an agricultural area in Osong, central Korea, were performed in this study to understand the spatial controls of nitrate concentrations in terms of biogeochemical processes occurring near oxbow lakes within a fluvial plain. Nitrate concentrations in groundwater showed a large variability from 0.1 to 190.6 mg/L (mean=35.0 mg/L) with significantly lower values near oxbow lakes. The evaluation of hydrochemical data indicated that the groundwater chemistry (especially, degree of nitrate contamination) is mainly controlled by two competing processes: 1) agricultural contamination and 2) redox processes. In addition, results of factorial kriging, consisting of two steps (i.e., co-regionalization and factor analysis), reliably showed a spatial control of the concentrations of nitrate and other redox-sensitive species; in particular, significant denitrification was observed restrictedly near oxbow lakes. The results of this study indicate that sub-oxic conditions in an alluvial groundwater system are developed geologically and geochemically in and near oxbow lakes, which can effectively enhance the natural attenuation of nitrate before the groundwater discharges to nearby streams. This study also demonstrates the usefulness of multivariate statistical analysis in groundwater study as a supplementary tool for interpretation of complex hydrochemical data sets.

Hydrochemistry of urban groundwater, Seoul, Korea: the impact of subway tunnels on groundwater quality.

Hydrogeologic and hydrochemical data for subway tunnel seepage waters in Seoul (Republic of Korea) were examined to understand the effect of underground tunnels on the degradation of urban groundwater. A very large quantity of groundwater (up to 63 million m3 year(-1)) is discharged into subway tunnels with a total length of 287 km, resulting in a significant drop of the local groundwater table and the abandonment of groundwater wells. For the tunnel seepage water samples (n = 72) collected from 43 subway stations, at least one parameter among pathogenic microbes (total coliform, heterotrophic bacteria), dissolved Mn and Fe, NH4+, NO3(-), turbidity, and color exceeded the Korean Drinking Water Standards. Locally, tunnel seepage water was enriched in dissolved Mn (avg. 0.70 mg L(-1), max. 5.58 mg L(-1)), in addition to dissolved Fe, NH4+, and pathogenic microbes, likely due to significant inflow of sewage water from broken or leaking sewer pipes. Geochemical modeling of redox reactions was conducted to simulate the characteristic hydrochemistry of subway tunnel seepage. The results show that variations in the reducing conditions occur in urban groundwater, dependent upon the amount of organic matter-rich municipal sewage contaminating the aquifer. The organic matter facilitates the reduction and dissolution of Mn- and Fe-bearing solids in aquifers and/or tunnel construction materials, resulting in the successive increase of dissolved Mn and Fe. The present study clearly demonstrates that locally significant deterioration of urban groundwater is caused by a series of interlinked hydrogeologic and hydrochemical changes induced by underground tunnels.

Horizontal angular asymmetry of the face in korean young adults with reference to the eye and mouth.

PURPOSE: Organs and structures develop symmetrically, but various degrees of asymmetry can also develop because of the effects of function and disease. The human face is often asymmetrical, but faces can be perceived as beautiful even if they are asymmetrical. The purpose of the present study was to investigate horizontal angular asymmetry of the face. MATERIALS AND METHODS: The angle between the horizontal line through the bilateral exocanthions and the line though the bilateral mouth corners of the face was measured on standardized frontal facial photographs of 1,282 volunteers (18 to 29 years of age; 761 males, 521 females). RESULTS: The magnitude of the angle was 0.2 +/- 1.4 and 0.3 +/- 1.3 degrees (mean +/- SD) in males and females, respectively. Faces were classified into 3 types relative to the parallel type. The incidence of the parallel type, the right-dominant type (>/=1 degree), and the left-dominant type (

Conformational molecular switch of the azobenzene molecule: a scanning tunneling microscopy study.

We propose to utilize azobenzene as a nanomolecular switch which can be triggered by transmitting electrons above threshold biases. The effect is explained by an electron impact trans-cis conformational change of the isolated azobenzene molecules. The molecular electronic states of both isomers have been measured with spatially resolved scanning tunneling microscopy or spectroscopy, leading to suggested transition pathways of the electron-induced isomerization.

Paired gap states in a semiconducting carbon nanotube: deep and shallow levels.

Several paired, localized gap states were observed in semiconducting single-wall carbon nanotubes using spatially resolved scanning tunneling spectroscopy. A pair of gap states is found far from the band edges, forming deep levels, while the other pair is located near the band edges, forming shallow levels. With the help of a first-principles study, the former is explained by a vacancy-adatom complex while the latter is explained by a pentagon-heptagon structure. Our experimental observation indicates that the presence of the gap states provides a means to perform local band-gap engineering as well as doping without impurity substitution.

Upregulated and prolonged differentiation potential of the ependymal cells lining the ventriculus terminalis in human fetuses.

The ventriculus terminalis (VT) is a dilated cavity within the conus medullaris of the spinal cord. Although the VT was discovered in the mid-nineteenth century, little is known about its characteristics during development in human fetuses. Ependymal cells lining the cavities within the CNS retain high differentiation potential, and are believed to be responsible for the postnatal neurogenesis. To evaluate the differentiation capacity of the ependymal cells lining the VT during development, we examined glial fibrillary acidic protein (GFAP) and proliferating cell nuclear antigen (PCNA) expression in the spinal cord of 18-24-week-old human fetuses. GFAP is a marker for the degree of ependymal cell differentiation in the human fetus, and PCNA is a well-known marker for cell division. Morphological characteristics of the VT were also examined. At the lower portion of the conus medullaris, the central canal abruptly expands dorsally to become the VT. Then the VT widens bilaterally while its anteroposterior diameter reduces gradually in a caudal direction. Finally, the VT becomes a narrow, transverse slit at the level of the lowermost conus medullaris. Compared with those lining the central canal, more numerous ependymal cells lining the VT showed more intensive GFAP and PCNA expression throughout all gestational ages examined. This suggests that, in the developing human spinal cord, ependymal cells lining the VT retain their differentiation potential, including a higher proliferative capacity, until a later stage of development than those lining the central canal.

Hydrogeochemistry of alluvial groundwaters in an agricultural area: an implication for groundwater contamination susceptibility.

Alluvial groundwaters in the area where intensive agricultural activity takes place were geochemically investigated to evaluate factors regulating groundwater quality of alluvial aquifers. For this study, 55 groundwater samples were taken from the uniformly distributed irrigation wells and were classified into three distinct groups according to their geochemical characteristics. This study reveals that the groundwater quality and the geochemical characteristics of the clustered groups are consistent with the geology of the area. The samples collected from the area where a thick silt bed overlies the sand aquifer are clustered into Group II and show water quality that is only slightly affected by the contaminants originating from the land surface. However, groundwaters of this group are very high in Fe and Mn levels due to strong anoxic condition caused by the thick silt bed. In contrast, Group I shows water quality largely influenced by agricultural activities (i.e., fertilization, liming) and occurs in the area adjacent to the river where the silt bed is not observed and the sand aquifer is covered with sandy soils. Group III mostly occurs in the upgradient of Group I where a thin, silty soil covers the sand aquifer. In overall, the results show that the clustered groups closely reflect the groundwater susceptibility to the contaminants originated from the land surface. This suggests that groundwater clustering based on water chemistry could be applied to the contamination susceptibility assessment for groundwaters in the agricultural area.

Atmospheric versus lithogenic contribution to the composition of first- and second-order stream waters in Seoul and its vicinity.

The spatial variations in the chemistry of first- and second-order stream waters (N = 65) were investigated in the easterly bound of Seoul in order to assess the effects of urban air pollution on surface water chemistry. The sulfate (SO4(2-)) was high (range 3.9-17.8 mg l(-1), mean 11.8 mg l(-1)) within 30 km away from the center of Seoul, compared to the levels (range 1.1-7.7 mg l(-1), mean 4.3 mg l(-1)) observed in remote areas (30-70 km away). Both graphical examination and statistical evaluation (variogram) of sulfate concentration data consistently showed the decrease of sulfate concentration with increasing distance. The results of mass balance modeling also indicate that the concentrations of SO4(2-), Cl- and Na+ may be affected mainly by dry/wet deposition. However, the spatial variations of major cations such as Ca2+ and Na+ are well explained by the reaction of rainwater with diverse rocks in the watercourse. The water type was found to change from Ca(-Na)-SO4) type to Ca(-a)-HCO3 type with the increasing distance. It is thus inferred that the pollutants like SO2 emitted from strong man-made source areas of Seoul are transported to the considerable distance (at least 30 km away) by westerlies and that such mechanism may lead to the changes of the anion composition in surface water. In the remote area (> 30 km away from Seoul), the stream water chemistry appears to be influenced more effectively by the weathering of rock-forming minerals.