Isotopes 2H Research Articles

Temporal variability of precipitation isotopes in Damascus, Syria — implications for regional climate change

Records of stable isotopes (2H and 18O), deuterium excess (d-excess) and tritium (3H) values in precipitation (P) during 1990–2022, together with long-term time series (1919–2022) of air temperature (T) and P-amount values at the Damascus station, were analysed to explore the seasonal and annual variability patterns of those parameters in P and assess the vulnerability to climate change in this area. Variation of the annual average air T values over the period 1919–1969 shows an increase gradient of ≈ + 0.1 °C/decade. However, a remarkable much higher gradient (+ 0.64 °C/decade) is calculated for the period 1990–2022. The average P-amount value calculated for the last three decades (≈185 mm) was lower by ≈28 mm, compared to the value (≈213 mm), relative to the reference period (1919–1969). This significant decline in the annual P-amount value by ≈11–13%, accompanied by an annual heating of 0.2–0.6 °C/decade in the annual air T, is likely the result of the climate change affecting this area. The linear relationships between annual average δ18O and annual average δ2H values versus time over the period 1990–2019 indicate increased gradients in both stable isotopes (≈0.3–0.5‰ and ≈1.1–3.2‰ per decade for δ18O and δ2H, respectively), accompanied with a decrease gradient of ≈0.9–1.1‰ per decade in d-excess values. Variability of annual 3H concentrations towards low levels (< 6 TU) during the later years strongly suggests the return back towards the cosmogenic production of this radioisotope in the upper atmosphere. Information gained from this work would offer new insights to improve the understanding of the temporal variability of P isotopes and assess the risks associated with climate change on the natural water resources in the Eastern Mediterranean region.

Investigating the Potential Impact on Shallow Groundwater Quality of Oily Wastewater Injection in Deep Petroleum Reservoirs: A Multidisciplinary Evaluation at the Val d’Agri Oilfield (Southern Italy)

The increase in oil production from petroleum reservoirs has led to studies examining the effects of these activities on groundwater quality. Oily wastewater associated with oil production is often reinjected through abandoned wells into the unproductive portions of the reservoir to avoid its discharge on the surface. The reinjection process is designed to be environmentally friendly and to exclude direct interactions between injected fluids and the surrounding groundwater; nevertheless, the evaluation of the compatibility between this process and the protection of the surrounding environment is of utmost importance when oilfields are located within sensitive and protected areas. The present work aimed to evaluate the impact of the oily wastewater reinjection into a long-term and high-rate disposal well in the Val d’Agri oilfield (Southern Italy). Previous preliminary investigations carried out at the study site led researchers to hypothesize the possible hydrocarbon contamination of the shallower aquifer caused by reinjection well integrity issues. Our strategy is based on an integrated and multidisciplinary approach involving isotopic (stable isotopes 2H and 18O), chemical, and microbiological (characterization of bacterial and archaeal communities) analyses. After a comprehensive and meticulous examination of the research data, it has been ascertained that significant discrepancies exist between the shallow and reinjection water systems. This allowed us to clarify the area’s complex flow dynamics and exclude hydrocarbon contamination of spring waters caused by the reinjection process.

Study of groundwater recharge using combined unsaturated‐and saturated‐zone chloride mass balance methods

AbstractUnderstanding groundwater recharge mechanisms is essential for reliable groundwater recharge estimation for sustainable groundwater resource assessment and management, especially in arid and semiarid areas. In this study, chloride, together with stable isotopes (18O and 2H), in 1‐year rainfall, soil water from representative profiles, and groundwater samples, collected in the Ordos Plateau, northern China were analysed. Groundwater recharge was estimated using unsaturated‐ and saturated‐zone chloride mass balance (CMB). An equation that describes the relationship between chloride concentrations in saturated zone water (Csz) and soil water residence time (τ) was derived. With the help of the relationship, chloride concentrations in unsaturated zone water (Cuz) and in groundwater (Csz) can be used to uncover water flow and chloride transport in the unsaturated zone. The relationship between Csz and Cuz indicates that, the groundwater was recharged mainly by intense rainfall events. Small rainfall events did not lead to groundwater recharge but contributed to the flux of chloride to soil surface. Stable isotopic compositions of 18O and 2H provided corroborative evidence of the recharge processes. The relationship between Csz and τ indicates further that there is no source of chloride in the groundwater other than that from precipitation. Thus, Csz can give more reliable recharge estimates. Cuz was influenced by heavy rainfall‐induced runoff, run‐on and bypass flow events and cannot give reliable recharge estimates. However, if used jointly with Csz, Cuz can help to gain insights into recharge processes and yield groundwater recharge estimates with higher certainty. The outcomes of this study can assist for groundwater recharge investigation and assessment in regions where the assumptions and boundary conditions necessary for the correct application of the CMB method may not be met.

Intrinsic labelling of common beans with 2H2O to enable estimates of protein digestibility

ABSTRACT Background: The use of plant protein intrinsically labelled with stable isotopes provides an innovative solution to assess the efficiency of protein intake by humans. Here, the incorporation of 2H has been applied to intrinsically labelled plant protein in the common bean. This study aimed to evaluate which is the best phenological phase of seed maturation to incorporate the heavy hydrogen isotope 2H into seed amino acids. Common beans (Phaseolus vulgaris L.) were grown in pots, then, after 50 days sowing, 2H2O dissolved in irrigation water was applied, then again at an interval of either 3, 6, 9, and 12 days. Results: Applications of 2H2O at 6, 9, and 12 days after the first application, in the full-flowering stage, were the best treatments for enriching protein-bound amino acids in the bean seed with 2H. Conclusion: All treatments resulted in enrichment above 500 ppm, so the treatments (quantity and timing of 2H2O addition) were deemed successful for enriching bean seeds. This makes the intrinsically labelled seeds suitable for preparing test meals to assess the digestion and essential amino acid absorption of common bean amino acids in human subjects.

Leaf water δ18O, δ2H and d‐excess isoscapes for Australia using region‐specific plant parameters and non‐equilibrium vapour

AbstractOxygen (δ18O) and hydrogen (δ2H) isotope ratios, and their relationship to one another (d‐excess) are altered as water travels from the atmosphere to the land surface, into soils and plants and back to the atmosphere. Plants return water to the atmosphere through transpiration (evaporation through the stomata), which causes isotopic fractionation concentrating the heavier isotopes (18O and 2H) in the water that remains behind in the leaves. The degree of isotopic fractionation during transpiration is controlled largely by climate, and as a result can be predicted using process‐based models and climate data. The modelled transpirational isotopic fractionation can be applied to plant source water isotopic values to predict leaf water isotope ratios and generate maps of isotopic composition, or isoscapes. This approach of mechanistic modelling has been well demonstrated in the first generation of global leaf water isoscapes (PLoS One, 3(6), e2447, 2008). However, use of leaf water isoscapes in fields such as hydrology, ecology, and forensics requires a new generation of updated region‐specific isoscapes. Here, we generate leaf water isoscapes of δ18O, δ2H and d‐excess for Australia, the driest vegetated continent on Earth, where leaf water represents a critical water resource for ecosystems. These isoscapes represent an improvement over previous global isoscapes due to their higher resolution, region‐specific, empirically derived plant parameters, and non‐equilibrium corrections for water vapour isotopic composition. The new isoscapes for leaf water are evaluated relative to observed isotope ratios of leaf cellulose and cherry juice. The model predictions for annual average leaf water isotope ratios showed strong correlations with these plant tissues that integrate over time. Moreover, inclusion of region‐specific leaf temperature estimates and non‐equilibirum vapour corrections improved prediction accuracy. Regionally based isoscapes provide improved characterisations of average leaf water isotope ratios needed to support research in hydrology, plant ecophysiology, atmospheric science, ecology, and geographic provenancing of biological materials.

Combining stable isotope (2H, 18O, and 87Sr/86Sr) and hydrochemistry to understand hydrogeochemical processes in karst groundwater system, Xin’an, northern China

Combining stable isotope (2H, 18O, and 87Sr/86Sr) and hydrochemistry to understand hydrogeochemical processes in karst groundwater system, Xin’an, northern China

CircBCL11B acts as a ceRNA to facilitate 1,2-dichloroethane-induced astrocyte swelling via miR-29b-3p/AQP4 axis in SVG p12 cells

1,2-Dichloroethane (1,2-DCE) is a pervasive environmental pollutant found in ambient and residential air, as well as ground and drinking water. Brain edema is the primary pathological consequence of 1,2-DCE overexposure. We found that microRNA (miRNA)-29b dysregulation after 1,2-DCE exposure can aggravate brain edema by suppressing aquaporin 4 (AQP4). Moreover, circular RNAs (circRNAs) can regulate the expression of downstream target genes through miRNA, and affect protein function. However, circRNAs’ role in 1,2-DCE-induced brain edema via miR-29b-3p/AQP4 axis remains unclear. To address the mechanism’s bottleneck, we explored the circRNA-miRNA-mRNA network underlying 1,2-DCE-driven astrocyte swelling in SVG p12 cells by circRNA sequencing, electron microscopy and isotope 3H labeling combined with the 3-O-methylglucose uptake method. The results showed that 25 and 50 mM 1,2-DCE motivated astrocyte swelling, characterized by increased water content, enlarged cell vacuoles, and mitochondrial swelling. This was accompanied by miR-29b-3p downregulation and AQP4 upregulation. We verified that AQP4 were negatively regulated by miR-29b-3p in 1,2-DCE-induced astrocyte swelling. Also, circRNA sequencing highlighted that circBCL11B was upregulated by 1,2-DCE. This was manifested as circBCL11B overexpression playing an endogenous competitive role via upregulating AQP4 by binding to miR-29b-3p, thus leading to astrocyte swelling. Conversely, circBCL11B knockdown reversed the 1,2-DCE-motivated AQP4 upregulation and alleviated the cell swelling. Finally, we demonstrated that the circBCL11B was targeted to miR-29b-3p by fluorescence in situ hybridization and dual-luciferase reporter assay. In conclusion, our findings indicate that circBCL11B acts as a competing endogenous RNA to facilitate 1,2-DCE-caused astrocyte swelling via miR-29b-3p/AQP4 axis. These observations provide new insight into the epigenetic mechanisms underlying 1,2-DCE-induced brain edema.

MANIFESTASI PANAS BUMI SERTA REKOMENDASI PEMANFAATANNYA DI DESA KOTO SANI DAN SEKITARNYA, KECAMATAN X KOTO SINGKARAK, KABUPATEN SOLOK, PROVINSI SUMATRA BARAT

The volcanic arc or volcanic arc that extends along the western side of Sumatra Island. Koto Sani Village, Kec. X Koto Singkarak, Solok Regency, West Sumatra Province is one of the areas on Sumatra Island that has geothermal potential. In terms of the developing tectonic order, namely in the form of a geological structure in the form of the Sumani segment of the Sumatra Fault which moves in a strike slip to the right or dextral. This geological structure is one of the main components forming the geothermal system apart from the heat source, reservoir rock, stratigraphic characteristics and the cap layer. This study aims to determine the geological setting, any geothermal manifestations found in the study area and estimate the temperature below the surface for recommendations for its use. The research method used was the interpretation of satellite imagery on the 1:25,000 scale of the Indonesian Rupa Bumi map (RBI), surface geological mapping, measurement of the physical characteristics of geothermal fluids, geochemical analysis of geothermal fluids (anion-cation) and then plotting Giggenbach's triangle diagram (1991). and geothermal geothermal calculations, as well as analysis of 18O and 2H isotopes. The research area generally forms a landscape of elongated hills with quite steep valleys as a result of tectonic activity in the form of geological structures as migration routes of hot fluids from the reservoir to the surface. This is reinforced by the results of the interpretation of river flow patterns, namely meandering or sub-dendritic and elongated or called parallel as an indication of disturbance from faults or faults. Geothermal manifestations found are hot springs, sintered silica and hydrothermal alteration rocks. The estimated temperature below the surface is 407.64°C with a high temperature category and is recommended for direct use, such as the tourism and fisheries sector, as well as indirect use, such as geothermal energy power plants.

Field variation of groundwater recharge and its uncertainty via multiple tracers' method in deep loess vadose zone

Accurate estimation of groundwater recharge is a precondition for assessing its spatial variation at different scales, especially field scale. In the field, the limitations and uncertainties of different methods are first evaluated based on site-specific conditions. In this study, we evaluated field variation in groundwater recharge via multiple tracers in the deep vadose zone on the Chinese Loess Plateau. Five deep soil profiles (approximately 20 m deep) were collected in the field. Soil water content and particle compositions were measured to analyse soil variation, and soil water isotope (3H, 18O, and 2H) and anion (NO3− and Cl−) profiles were used to estimate recharge rates. Distinct peaks in soil water isotope and nitrate profiles indicated a vertical one-dimensional water flow in the vadose zone. Although the soil water content and particle composition were moderately variable, no significant differences were observed in recharge rates among the five sites (p > 0.05) owing to the identical climate and land use. The recharge rates did not show a significant difference (p > 0.05) between different tracers' methods. However, recharge estimates by the chloride mass balance method indicated higher variations (23.5 %) than those by the peak depth method (11.2 % to 18.7 %) among five sites. Moreover, if considering the contribution of immobile water in vadose zone, groundwater recharge would be overestimated (25.4 % to 37.8 %) using the peak depth method. This study provides a favourable reference for accurate groundwater recharge and its variation evaluated using different tracers' methods in deep vadose zone.

Summer-autumn variability of isotopes (2H and 18O) in water at small mountain catchments in South Sikhote-Alin (Pacific Russia)

Summer-autumn variability of isotopes (2H and 18O) in water at small mountain catchments in South Sikhote-Alin (Pacific Russia)

Conceptual model of a semi-arid coastal aquifer using hydrogeochemical seasonal variation and isotopic fingerprints in Tamoios, Rio de Janeiro, Brazil

The present study focuses on the Tamoios aquifer (Rio de Janeiro State, Brazil), which is under pressure due to receivinga significant volume of urban runoff and sewage. The objective was based on a number of hydrogeochemical and isotope data to assess the aquifer functioning and establishing a conceptual model to evaluate the hydrogeochemical processes. The database consisted of groundwater samples (n = 20) and surface water samples (fluvial, lagoon, and seawater) (n = 4), analyzed for major and trace constituents plus 18O and 2H isotopes. Results demonstrate that most of the groundwater samples were classified as sodium-chloride type in the rainy season and magnesium-chloride type in the dry season. Ion ratios indicated the ion sources and chemical behavior. Groundwater remained with a relatively high salt content throughout the seasons, particularly in the samples from the southern portion of the aquifer. PHREEQC software simulations exposed dolomite and calcite inmostly undersaturated condition and halite subsaturated throughout the year. Hydrogeochemical behavior indicated the salt content in the groundwater was not related toa hypotheticalsaltwater intrusionand revealed a steady state condition for the groundwater interface. Groundwater samples have a similar isotopic signature and were likely influenced by evaporative effects, indicating a role for the existingponds in aquifer recharge. Strong free surface evaporation effects, evapotranspiration, and drainage processes in the floodplains probably enhanced the high ionic concentration in the groundwater environment.

Humic Substance Photosensitized Degradation of Phthalate Esters Characterized by 2H and 13C Isotope Fractionation.

The photosensitized transformation of organic chemicals is an important degradation mechanism in natural surface waters, aerosols, and water films on surfaces. Dissolved organic matter including humic-like substances (HS), acting as photosensitizers that participate in electron transfer reactions, can generate a variety of reactive species, such as OH radicals and excited triplet-state HS (3HS*), which promote the degradation of organic compounds. We use phthalate esters, which are important contaminants found in wastewaters, landfills, soils, rivers, lakes, groundwaters, and mine tailings. We use phthalate esters as probes to study the reactivity of HS irradiated with artificial sunlight. Phthalate esters with different side-chain lengths were used as probes for elucidation of reaction mechanisms using 2H and 13C isotope fractionation. Reference experiments with the artificial photosensitizers 4,5,6,7-tetrachloro-2',4',5',7'-tetraiodofluorescein (Rose Bengal), 3-methoxy-acetophenone (3-MAP), and 4-methoxybenzaldehyde (4-MBA) yielded characteristic fractionation factors (-4 ± 1, -4 ± 2, and -4 ± 1‰ for 2H; 0.7 ± 0.2, 1.0 ± 0.4, and 0.8 ± 0.2‰ for 13C), allowing interpretation of reaction mechanisms of humic substances with phthalate esters. The correlation of 2H and 13C fractions can be used diagnostically to determine photosensitized reactions in the environment and to differentiate among biodegradation, hydrolysis, and photosensitized HS reaction.

Impact of the Hydroelectric Dam on Aquifer Recharge Processes in the Krško Field and the Vrbina Area: Evidence from Hydrogen and Oxygen Isotopes

The impact of the damming of the Sava river for the Brežice hydroelectric power plant on the rise of the groundwater level was studied in the intergranular aquifer of the Krško field and the Vrbina area, Slovenia. The study is based on the application of hydrogen and oxygen isotopes (18O, 2H and 3H). Parameters were determined for precipitation, surface water, and groundwater for periods before and after the filling of the accumulation basin, with the aim of evaluating the groundwater–surface water interaction and to elucidate the impact of the hydroelectric dam on aquifer recharge processes. The results show the proportions of the surface water component in groundwater sampled from four wells at high and low water conditions, separately for the period before and after the filling the accumulation basin. After filling the accumulation basin, the proportion of the Sava river component at high water conditions increased from 60% to 80% in the Brege and Drnovo wells (drinking water resources), from 50% to 80% in the Cerklje well and to almost 100% in the near-river NEK well. Combined with previous studies, the results provide important information about the direction of groundwater flow in the aquifer and improve the conceptual model of the study site.

The Spatiotemporal Variability of Snowpack and Snowmelt Water 18O and 2H Isotopes in a Subarctic Catchment

AbstractThis study provides a detailed characterization of spatiotemporal variations of stable water 18O and 2H isotopes in both snowpack and meltwater in a subarctic catchment. We performed extensive sampling and analysis of snowpack and meltwater isotopic compositions at 11 locations in 2019 and 2020 across three different landscape features: (a) forest hillslope, (b) mixed forest, and (c) open mires. The vertical isotope profiles in the snowpack's layered stratigraphy presented a consistent pattern in all locations before snowmelt, and isotope profiles homogenized during the peak melt period; represented by a 1–2‰ higher 18O value than prior to melting. Our data indicated that the liquid‐ice fractionation was the prime reason that caused the depletion of heavy isotopes in initial meltwater samples prior to the peak melt period. The liquid‐ice fractionation was influenced by snowmelt rate, with higher fractionation during slow melt. The kinetic liquid‐ice fractionation was evident only in close examination of meltwater lc‐excess values, not 18O values alone. Meltwater was isotopically heavier and more variable than the depth‐integrated snowpack; the weighted mean of meltwater isotope values was higher by 0.62–1.33‰ 18O than the weighted mean of snowpack isotope values in forest hillslope and mixed forest areas, and 1.51–6.37‰ 18O in open mires. Our results reveal close to 3.1‰ 18O disparity between the meltwater and depth‐integrated snowpack isotope values prior to the peak melt period, suggesting that proper characterization of meltwater 18O and 2H values is vital for tracer‐based ecohydrological studies and models.

Insights into moisture sources and evolution from groundwater isotopes (2H, 18O, and 14C) in Northeastern Qaidam Basin, Northeast Tibetan Plateau, China

Knowledge of moisture sources is of great significance for the understanding of groundwater recharge and hydrological cycle. However, it is often difficult to identify the moisture sources and evolution especially in the areas with complex climate system. Isotopes in groundwater that acts as a climate archive provide a unique perspective on the moisture sources and evolution. In this study, the stable isotopes (2H, 18O) of precipitation and groundwater, radioactive isotope (14C) of groundwater, water vapor trajectory modeling (HYSPLIT models) and d-excess based on mass balance model were employed to reveal the groundwater origin, moisture source and evolution in the northeastern Qaidam Basin, northeast Tibetan Plateau, China. The stable isotopic compositions indicate that the precipitation in the mountainous areas is the main origin of groundwater. The spatiotemporal variation of groundwater d-excess together with HYSPLIT modeling suggest that the moisture sources in the northeastern Qaidam Basin have been controlled by the Westerlies and did not alter obviously with time, whereas Delingha with relatively low elevation is influenced by both the Westerlies and local recycled moisture. More than 80 % water vapor derives from the northwest of study area for the plain and mountainous area, except for the mountainous area of Delingha, where approximately 23 % water vapor originates from the surface water evaporation in the plain area. The water vapor with high d-excess formed in the plain area is transported to the mountainous area and mixed with advected water vapor, resulting in the large d-excess of groundwater in Delingha. The moisture recycling fraction in precipitation for the mountainous area of Delingha is estimated to be about 2.0 % by using d-excess-based mass balance model. The results of the study could be helpful to the understanding of hydrological cycle of the area and elsewhere.

Quantitative partitioning of temporal origin of transpiration into pre- and post-plantation under deep-rooted vegetation on the Loess Plateau of China

Deep-rooted vegetation transpires a considerable amount of deep soil water with different ages in the unsaturated zone. However, the tradeoffs between new water of transpiration (temporally originating from post-planting precipitation) and old water of transpiration (temporally originating from pre-planting precipitation) across the vegetation lifespan are poorly understood. In this study, we collected soil samples from beyond 28 m soil depth on the Loess Plateau of China to investigate the influence of deep-rooted vegetation on the age of soil water and analyze the proportion of new and old water of transpiration in the unsaturated zone under grassland, 22-year-old apple orchard, and 17-year-old peach orchard. Water isotopes (2H, 18O, and 3H), solutes (chloride, nitrate, sulfate), and soil water content were used to identify the critical water ages in the unsaturated zone (one-year water age, water age corresponding to stand age, and the maximum water age of transpiration), and to determine soil water deficit, soil evaporation loss fraction, and potential groundwater recharge. The results showed that soil water mainly moved as piston flow in these soil profiles, and deep soil water largely came from heavy precipitation. Deep-rooted vegetation restrained new pore water velocity and potential groundwater recharge. New pore water velocity declined from 0.40 m yr−1 to 0.14 m yr−1 and 0.34 m yr−1 for apple and peach, respectively. Deep-rooted vegetation decreased groundwater recharge by 9.46 % for apple and 7.04 % for peach, compared to grassland. Over the vegetation lifespan, annual average transpiration was 500.56 mm yr−1 and 468.89 mm yr−1 with maximum water age of 63 years and 45 years for apple and peach, respectively. The transpiration of deep-rooted vegetation mainly used new water—94.97 % for apple and 97.47 % for peach. The total old water of transpiration was 553 mm for apple and 209 mm for peach. Our results identify the temporal sources of vegetation water use, offering new insights into the transpiration process of deep-rooted vegetation.

Application of isotopic tools to understand the hydrological processes and groundwater dynamics of Mianwali area-Punjab, Pakistan

AbstractThe study was conducted to investigate the hydrological system of ‘Mianwali’ area, which comprises an alluvium aquifer. Groundwater dynamics including groundwater direction, velocity and recharge mechanism were investigated to assess the groundwater sources conservation in the area. Hydrological samples were collected and analyzed for stable isotopes (18O and 2H); radioisotopes (3H), chloroflourocarbons (CFCs) and groundwater real and filtration velocities measured to understand the groundwater dynamics. Isotopic data suggested a variant recharge mechanism due to localize impacts of canals, lake and river. Groundwater residence time, using Tracer Lump Parameter Model (LPM), and CFCs data suggest a very young water in the range of 14–59 years old. The real and filtration velocities of groundwater found to be 22.2 cm/day and 10.94 cm/day, respectively, in south-west direction and in-situ effective porosity of the aquifer was 49.3%. The hydraulic conductivity of the aquifer was estimated using grain size analysis that varies from 48 to 278 m/day with average value of 139 m/day.

Genesis Mechanisms of Geothermal Resources in Mangkang Geothermal Field, Tibet, China: Evidence from Hydrochemical Characteristics of Geothermal Water

The Mangkang geothermal field, distributed in the Mediterranean–Himalayas geothermal belt, hosts abundant hot springs whose geneses remain unclear. To determine the hydrochemical characteristics, reservoir temperature, circulation and recharge depths, and water–rock interactions of the geothermal water in the geothermal field, this study analyzed hydrochemical compositions and isotopes (2H, 3H, and 18O), conducted a PHREEQC simulation, and established a conceptual model to illustrate the genesis of geothermal resources in the Mangkang field. Based on the study of hot springs in Meipu, Qvzika, and Zulongpu villages and Rumei town, the following results are reported: The orifice temperatures of these hot springs vary between 18 °C and 67.5 °C. The hydrochemical composition analysis results indicate that the geothermal water in the hot springs is of hydrochemical type HCO3-Ca·Mg. Moreover, the geothermal water has high HBO2 and Na+ concentrations, suggesting protracted water runoff and strong water–rock interactions during its evolution. According to the mineral–water solubility equilibrium and silica geothermometers, it is estimated that the reservoir temperature of the Zulongpu hot spring is 47 °C and other hot springs have much higher reservoir temperatures of 116–130 °C. As indicated by geothermal gradients, annual temperatures, and reservoir temperatures, the geothermal water in Meipu and Qvzika villages has the greatest circulation depth, up to 3600–4300 m, followed by that in Rumei town (3700–4000 m) and Zulongpu village (~1500 m). The 2H-18O isotopic analysis of the geothermal surface water revealed that the geothermal water originates from meteoric water. The recharge elevation was inferred to be ~4700–4900 m. Moreover, the low 3H values (&lt;1 Tu) suggest that the geothermal water is older than 40 years. The PHREEQC inverse simulation results indicated that the variation in the hydrochemical composition of the geothermal water results from the precipitation of chalcedony and dolomite, the absorption of NaX, and the loss of CaX2 during migration and storage.

Aromatic ring flips in differently packed ubiquitin protein crystals from MAS NMR and MD

Probing the dynamics of aromatic side chains provides important insights into the behavior of a protein because flips of aromatic rings in a protein’s hydrophobic core report on breathing motion involving a large part of the protein. Inherently invisible to crystallography, aromatic motions have been primarily studied by solution NMR. The question how packing of proteins in crystals affects ring flips has, thus, remained largely unexplored. Here we apply magic-angle spinning NMR, advanced phenylalanine 1H-13C/2H isotope labeling and MD simulation to a protein in three different crystal packing environments to shed light onto possible impact of packing on ring flips. The flips of the two Phe residues in ubiquitin, both surface exposed, appear remarkably conserved in the different crystal forms, even though the intermolecular packing is quite different: Phe4 flips on a ca. 10–20 ns time scale, and Phe45 are broadened in all crystals, presumably due to µs motion. Our findings suggest that intramolecular influences are more important for ring flips than intermolecular (packing) effects.

Stable isotope modeling of the groundwater discharge in complex watersheds of the state of São Paulo, Brazil

The increasing pressure on water resources demands integrated and multidisciplinary approaches to address environmental, scientific, and social issues related to water availability in watersheds. In large watersheds, many factors control hydrologic processes, requiring the application of a methodology able to describe water dynamics in complex situations. This study uses stable isotope (2H and 18O) modeling to characterize the groundwater contribution in an area of heterogeneous hydrogeological framework and advanced anthropization, located in the Piracicaba-Capivari-Jundiaí (PCJ) and Tietê-Jacaré (TJ) water management units – central-eastern portion of the state of São Paulo, Brazil. Groundwater dynamics are controlled by the direct interaction of the rainfall regime with hydrogeological domains. The modeling in this study indicates that some 60–80% of the total streamflow volume comes from groundwater. However, in the crystalline domain, the aquifer capacity for surplus water storage is smaller, increasing the importance of rainfall for generating direct runoff and maintaining the streamflow. For this characteristic, the PCJ unit is more dependent on surface water and vulnerable to prolonged droughts. On the other hand, in the sedimentary areas, the contribution of groundwater discharge is around 80%, showing that the aquifer storage capacity guarantees homogenization of the discharge throughout the year, and ensures water security in drought periods. It is concluded that the successful application of stable isotope modeling in large basins. The method, combined with others already established, can add a more dynamic and sensitive set of information for understanding hydrological processes in complex hydrographic basins, with heterogeneous hydrogeological structures and the effects of anthropic action.