Meteoric Line Research Articles

Estimating Riparian Water Movement in an Incipient Karst Landscape—Minnesota, USA

Understanding rain, ground, and surface water interactions in riparian zones is essential for hydrologic and environmental management. The novelty of this study lies in its revelation of isotopic shifts and consequent evaluation of hydrologic pathways and processes within the forested riparian zones of three distinct streams, valleys, and riparian systems in a carbonate-sandstone incipient karst landscape. We collected water samples from three southeastern Minnesota catchments: Trout Brook, Crystal Creek, and Bridge Creek. A Picarro L2130i was used to measure δ18O for oxygen, and δD for deuterium in units of ‰ (per mil). We estimated the global meteoric line for the study sites, built upon aquifer age dating, and explored aquifer transit time for the study sites using a simple seasonal amplitude model. The results showed small amplitudes for 2020 and 2021, suggesting that bedrock aquifer water was the primary source water with a mean core transit time greater than 10 years. All three catchments were different but had similar bedrock valley types and riparian sediment. The primary driving factor was the seasonal precipitation input mixing with existing water. In a normal to wetter year, the isotopic data showed larger amplitude shifts between seasons with trendlines that adjusted depending on the temperature of the new water additions. The proposed approach is valuable in revealing complex hydrologic processes and pathways and can contribute extensively to the planning and management of karst riparian systems.

Isotopic study of rainfall and definition of local meteoric water lines: Case of the rainfall stations of the city of Bangui in Central African Republic

The study of the isotopic composition of rainwater discussed in this article allows isotopic characterization of rainfall recorded in the Bangui region over 11 years at two stations. It will highlight the relationships between isotopes, climatic parameters, and temporal variation before defining the local meteoric line, which constitutes the reference point for the region. The results obtained after a follow-up of eleven years without interruption showed two major physical effects, the effect of the rainfall influences more strongly the composition in isotopes, the contents in isotopes vary inversely with the precipitation. For example, heavy rainfall in August and September saw a strong depletion of δ¹⁸O and δ²H contents. These values reach up to -4.96‰ for δ¹⁸O and -28.3‰ for δ²H. Similar, although weaker, effects are observed for July and October precipitation. We also note that the isotope contents at the Bangui University station are lower than those measured at the Bangui Sodeca station located at 386 m altitude on the Lower Ubangi Hill, which is similar to a pseudo-altitude effect. The evolution of stable isotope content in water as a function of meteorological parameters (temperature, rainfall, altitude) has allowed us to determine a local meteorological line for the city of Bangui from two measuring stations defined as follows: δ2H = 7.6 × δ18O + 10.4 (R2 = 0.9909) Université de Bangui, δ2H = 8.4 × δ18O + 12.5 (R2 = 0.9909) Bangui-Sodeca and δ2H = 7.9 × δ18O + 11.3 (R2 = 0.9939) Bangui local meteoric water lines.

A multi-tracer approach to quantifying groundwater discharge in flat areas

Identifying of groundwater discharge in surface waters is of outstanding interest in order to complete water balance models, understand the dynamics of surface hydrology, or quantify solute contribution, including nutrients and pollutants. This study aims to evaluate groundwater discharge into two small streams in the Atlantic coastal area of the Argentine Pampa Plain and ascertaining the relationship between groundwater age and 222Rn as a discharge indicator. In August 2017, samples were collected from two streams, La Ballenera and Vivoratá, and 222Rn activities, CFCs concentration, ionic composition, EC, and stable isotopes (δ18O, δ2H) were measured. The chemical composition and EC of the two streams was similar. The isotopic composition showed some difference in the Vivoratá stream among the samples close to the headwaters, which are more depleted and have a deuterium excess value similar to the ordinate of the local meteoric line. This behavior is consistent with the dominance of baseflow, with values most depleted appearing upstream and the most enriched being downstream as a result of slight evaporation from the course. The three samples in La Ballenera stream are closer to the global meteoric line, although greater enrichment is observed upstream. 222Rn concentrations were in the range of 1–2.5 Bq.L−1 in both. In the Vivoratá stream, 222Rn showed a tendency to increase in the downstream direction of the flow, while in the La Ballenera stream this trend was observed in the first two sections. CFCs values were significantly homogeneous at all sites. For most of the samples, the recharge year was set between 1987 and 1990, resulting in transit times in the order of 30 years. Combining field measurements of streamflow and EC, laboratory analyses of stable isotopes, CFCs and 222Rn, provides an efficient method for estimating groundwater discharge rates, which is ascertained by water apparent ages.

Identifying sources of groundwater and recharge zone using stable environmental isotopes in the Erbil basin-northern Iraq

The Dashty-Hewler basin is a groundwater basin located in Erbil in northern Iraq. It comprises three distinct sub-basins (Kapran, Central, and Bashtapa) covering a total basin area of 2,660 ​km2. It is bounded by the greater Zab river to the north and the little Zab to the south. The groundwater in this catchment has never been investigated using modern environmental isotope evidence. Since the groundwater in this basin serves as both drinking water and a source of irrigation, its management is crucial. Recently, due to the increase in population, excessive pumping has taken place, which has led to a decline in the water table. Accordingly, it is necessary to address the issues of where the groundwater will recharge and what the source of the recharge will be. For this purpose, 27 groundwater samples from different wells and two river water samples were analyzed for stable isotopes (δ18O and δ2H). The distribution of δ18O and δ2H over the study area was utilized by inverse distance weighted (IDW) interpolation within ESRI ArcGIS (10.8). The results indicated that the relationship between δ18O and δ2H in the groundwater samples (δ2H ​= ​6.59 δ18O +7.48‰) showed relative shifts of both the slope and the deuterium excess when compared to the Iraq meteoric water line (δ2H ​= ​7.66 δ18O ​+ ​14.19‰). The deviation of data points from the meteoric line can be attributed to high evaporation both during the rainy season and through run-off on the ground surface before infiltration. Most of the groundwater samples had a deuterium excess above 10‰ between 12.14 and 22.72‰, suggesting the precipitation present in the groundwater comes from the Mediterranean sector. Based on local isotopic gradients (δ18O, −0.22/100 ​m), in combination with topographic and geologic criteria, the recharge areas were identified as being between 400 ​m and 1,100 ​m above sea level.

Stable isotopic composition of fog and rainfall in a Macaronesian cloud forest

Stable isotopes of water are commonly used to investigate the role of fog in cloud forests. This first requires the characterization of the isotopic signatures of both fog and local rainfall. The isotopic composition of rain and fog water and their variability were analysed for a Macaronesian cloud forest in Tenerife, Canary Islands, from samples collected over 5 years within the Global Network of Isotopes in Precipitation (GNIP) project. The results showed little differences in the isotopic signature of fog and rain with the former being slightly higher with respect to the latter (differences in absolute value of 1‰ in δ18O, 7‰ in δ2H and 0.7‰ in d-excess, on average) and with a similar statistical variability. Their meteoric lines, LMWL (local meteoric water line for precipitation): δ2H = 6.56 δ18O + 11.56 and FWL (fog water line): δ2H = 5.57 δ18O + 9.98, which are very close to each other and above the GMWL (Global Meteoric Water Line), reveals that rain and fog may originate from water evaporated from the same water sources and under moisture conditions typical of semi-arid regions. Different slopes and interception in LMWL and FWL point to seasonal processes affect fog and rain differently, i.e. summer evaporation of small fog droplets and autumn-winter rainfalls isotopically depleted from frontal or low-pressure systems that are decoupled from fog formation processes. Both isotopic signatures showed low correlation with temperature and total rainfall (R2 <0.3 in all cases). However, the high anticorrelation observed (R2 values >0.6) between the isotopic composition of rain and fog with rainfall totals with values between 100 and 150 mm for both fog and rain, associated with a well-defined synoptic rainfall pattern affecting the Canary Islands, supports the hypothesis that the “amount effect” is related to the moisture source region and transport patterns. Annual variability of the isotopic signatures showed a marked pattern, typical of these latitudes, with enriched values in summer and more depleted in winter for both rainfall and fog. The high amplitude observed in the seasonal pattern of d-excess for both rain and fog, point to the Mediterranean Sea as a potential source of moisture in the winter months or to a mixing process when the moist air mass trajectories pass over North Africa. Despite the similarities observed in these seasonal patterns, some anomalies were found in the summer d-excess, indicating the participation of some local processes to which d-excess is sensitive, such as sub-cloud evaporation or moisture recycling.

Isotope Composition of Natural Water in Lake Onega Basin

In 2009–2018, the isotopic composition of oxygen and hydrogen in the atmospheric precipitation, groundwater and river and lake water of Lake Onega basin was studied. The weighted annual isotope composition of precipitation at Petrozavodsk was δ18O = −11.7‰ and δ2H = −84‰ and varied from −30.9 to −4.1‰ for δ18O and from −23 to −22‰ for δ2H. The isotopic composition of the water in Lake Onega was relatively uniform from −11.5 to −9.3‰ for δ18O and from −85 to −71‰ for δ2H. In the bays, the isotopic composition of the water varied more substantially than in the central part of the lake due to the river runoff during springtime flooding. In late summer, the concentrations of deuterium and oxygen-18 increased in the lake water, and figurative points on the δ2H vs. δ18O diagram shifted above the meteoric line. The absorption of the isotopically heavy summer precipitation and disequilibrium isotope fractionation during evaporation led to the enrichment of the lake water by heavy isotopes. Experiments were conducted to estimate the evaporation influence on the isotope enrichment of the residual water, and a comparison of the obtained isotope data with the experimental function showed that commonly, about 4% and up to 12% of water was lost during the spring and summer, respectively. In the water of the tributaries, the abundance of the deuterium and oxygen-18 varied in a wider scale than in the lakes, from −14.4 to −9.1‰ for δ18O and from −102 to −73‰ for δ2H. An evaporation loss of up to 35% was found for the rivers in late summer, and this value was proportional to the area of lakes and wetlands in the elementary watershed. The initial isotope composition of the water in the tributaries prior to evaporation was estimated to be δ18O ≈ −14.1‰ and δ2H ≈ −103‰ on average and crossed the approximation and meteoric lines. This estimation was close to the average composition of the groundwater, i.e., δ18O ≈ −13.4‰ and δ2H ≈ −94‰ on the Lake Onega catchment. The slightly increased isotope depletion of the calculated composition in the initial river water in comparison with the groundwater was the result of the contribution of the spring snowmelt water, which had a significant influence on the lake water balance.

Geochemical investigation on the implications of fluid origin, subsurface processes and recharge on the Tangkuban Perahu geothermal conceptual model

Tangkuban Perahu and nearby volcano-hosted geothermal prospects are believed to be important for future power generation in West Java, Indonesia. Recharge areas of these prospects and geothermal fluid evolution are not yet fully understood. This study aims to describe the fluid origin, processes, and evolution of geothermal fluids concerning the recharge and the conceptual model of the Tangkuban Perahu Geothermal Systems (TPGS). Sampling and analyses of geothermal waters, rainwater, and gases collected in fumaroles and other manifestations were implemented in this study. Isotopic results of δ18O and δ2H collected from thermal and rainwater indicate deep-circulating meteoric origin, at an infiltration altitude range between 753 and 850 m in low terrain. Meanwhile, the high-standing terrain indicates the recharge zone to be within the wall of the Sunda Caldera and mountain slopes. Chondrite normalized patterns reveal an overall flat trendline that suggests the enrichment of Lower Rare Earth Elements (LREEs) in the central part of Tangkuban Perahu which is derived from the magmatic influx. The non-atmospheric gases origin was diagnosed by the lower N2/Ar (≤ 38) and is characterized by meteoric origin. The positive δ18O shifts from Ciater (CT), Batu Gede (BG), and Domas Crater (KwD) geothermal waters samples comparatively to the local meteoric lines are influenced by the interaction with wall rocks or magmatic influx. In these geothermal systems, the meteoric water infiltrated to the depth is heated, mixed with near-surface water, and followed by partial discharge as thermal springs along the faults. The resultant Tangkuban Perahu conceptual model has six distinct reservoirs with five geothermal systems hosted in the sedimentary (northern parts) and volcanic rock composition in the central and southern parts.

Seasonal and deep groundwater‐surface water interactions in the tropical Middle Magdalena River basin of Colombia

AbstractThis study is an attempt to understand flow patterns in the Middle Magdalena Valley River basin (MMV), a tropical lowland humid forest. For this purpose, we used δ2H and δ18O water stable isotopes measured in different surface and groundwater sources collected in the area both during the dry and the wet seasons. Two hundred and forty‐five water samples were collected in rainfall, springs, rivers, swamps, and wells (from 10 to 350 m depth). Thus, we were able to establish three tendencies that suggest the existence of surface‐groundwater interactions or preferential groundwater fluxes in the MMV: (i) samples with an isotopic enrichment from the wet to the dry season (groundwater samples following the rainfall isotopic variability), (ii) groundwater samples with an isotopic depletion from the wet to the dry season (opposite to the rainfall isotopic signal), and (iii) groundwater samples whose isotopic composition did not change significantly among seasons. However, none of these tendencies could be related to geology or the type of sampled site, which suggests that some not fully understood processes must be taking place in the hydrological system of the MMV. Both, surface, and groundwater samples are grouped close to the Colombian meteoric line, with exception of some swamp samples collected during the dry period, which displayed the expected evaporation trend line tendency. This may be an indicator of the connection/disconnection of swamps with the river during the hydrological year. Finally, this study aims to fulfil the gap in water‐stable isotope data in Colombia and provide insights about the hydrological setup of a lowland tropical basin.

The use of stable isotopes (18O, 2H) and hydrochemistry to determine the type and origin of water for Euphrates Aquifer in Alkhasfa Area –Western of Iraq

Alkhasfa area is located in Al-Anbar Governorate - Western of Iraq. Isotopes and Hydrochemical analysis in groundwater were attempted the study area to learn more about water quality conditions and geochemical evolution. Groundwater in study area is dominated by (Ca+2 and SO4 −2) ions refers to the effect of gypsum that exists in the Fatha Formation and limestone in Euphrates Formation. The type of water according to Piper classification is alkaline water with an increase in alkalinity due to the prevailing of chloride and sulphate ions. Through the relationship between δ 2H and δ 18O, Three group may be distinguished, the first group include the well (W8), the water representing the mixing between groundwater and surface water (Haditha Lake), the second group includes the well (W1) the water representing the more enriched in δ18O, δ2H isotopic values indicate deep water impacts due to the location of the well above a Fault and the third group includes the remaining wells which have more depleted in heavy stable (δ18O, δ2H) values indicates that rainfall recharged to groundwater in these well. All groundwater samples are located right the Local meteoric line and global meteoric waterline. This means that water undergoes evaporates.

USE OF HYDROGEN AND OXYGEN ISOTOPES TO UNDERSTAND EVAPORATION FROM ENCLOSED WATERBODIES

Getting information on evaporation is important for water resource protection and managing regional enclosed waterbodies. Some lake water samples were collected in May and June from a representative enclosed waterbody – the Pearl Lake, Suzhou, China – and the hydrogen and oxygen isotopes determined. Most samples taken in June have higher δ18O and δD values than those in May, indicating that there are differences between the intensity of evaporation of May and June. This was further confirmed by the water samples’ d-excess values, which were below the meteoric line. However, the variations of d-excess value have been shown to be influenced by source moistures or evaporation processes, which were controlled by the local environment, e.g., whether the water was shaded or not. The residual water quantities calculated were 53 to 63% and 49 to 56% for May and June, respectively, relative to the initial water, indicating that about 5% of the water evaporated between 5 May and 5 June.

Oxygen and hydrogen stable isotopes as recharge indicators, Central Nile Delta Quaternary aquifer, Egypt

This work aims to utilize oxygen and hydrogen stable isotopes as tracers for determining the groundwater sources of recharge in the central Nile delta. The analyzed water samples were collected from canals and drains as surface water, soil water and shallow, intermediate and deep zones of the groundwater. The isotopic data indicated that surface water samples have higher isotopic content than recent Nile river water (δ 18O = 2.39‰ and δ2H = 22‰) which reflect the influence of an evaporation process that takes place in surface water bodies during its flow. Soil water samples were affected by evaporation process during water infiltration via soil. It was estimated that soil water samples have higher enrichment isotopic contents than groundwater and less than surface and recent Nile water. Studied groundwater is composed of mixed source from groundwater recharged before and that recharged after High Dam construction. Few groundwater samples have depleted isotopic content which suggested a mixing source between the rainwater and the Nile River water before High Dam construction. The evaporation is indicated in the shallow groundwater by the deviation away from the global meteoric line. In the deep groundwater, more deviation from global meteoric line was noticed which reflects the effect of mixing between freshwater and seawater. The intermediate groundwater samples average line showed an intermediate deviation indicating the effect of both evaporation and seawater intrusion.

Influence of Evaporation on the Hydrogen and Oxygen Stable Isotopes in an Enclosed Water Body: A Case Study

It is of great significance to study the influence of evaporation on the protection and management of regional water resources. In this study, water samples have been collected from a typical enclosed water body, Liuxi, a small brook in the campus of Suzhou University in May and June, and then analyzed for their hydrogen and oxygen stable isotopes. The results indicate that the samples collected in June have higher d18O and dD values relative to the samples collected in May, and both of them have d18O and dD values plotted at the right of the meteoric line, in combination with their lower deuterium excess (d-excess) values relative to the meteoric line, implying that the water has been influenced by evaporation. Moreover, the d-excess values showed decreasing and increasing in different sampling sites, which was demonstrated to be influenced by different extents of evaporation. Based on the calculation, the residual water quantities were 70–75% and 51–70% for May and June relative to the initial water, which indicates that about 10% of the water had evaporated during May and June.

Processes explaining the origin and evolution of groundwater composition in the Andean Precordillera and Altiplano of the Tarapacá Region of northern Chile

In the arid area of northern Chile, groundwater resources in the Andean formations are essential for native populations, ecological services, mining, and other human activities. Validated conceptual hydrogeological models are required for current and future water and land management. This work aims to explain the processes controlling the origin and distribution of recharge and groundwater composition in the Andean Precordillera and Altiplano of the Tarapacá Region of northern Chile, using major solutes in spring, river, and well water, and the stable and radioactive isotopes of water oxygen, hydrogen, and dissolved inorganic carbon. The waters are mainly of the Na-Ca-SO4 type. Processes controlling the chemical evolution of waters are atmospheric dust contribution, evapo-concentration, and enhanced volcanic rock weathering, as well as halite dissolution in some locations. The isotopic composition of Precordillera eastern flank water samples follows an evaporation line, while those in the western flank, in the Altiplano, follow a line that is parallel to the local meteoric line, suggesting unsaturated zone evaporation processes of infiltrated rainfall. δ13CDIC contents (-2 to -27‰) indicate mixing processes, volcanic CO2 in the Altiplano, and calcite dissolution in some sectors. In the western depression, the only recharge is due to water infiltration in creek channels. In the highland areas, 5–25% of precipitation produces recharge. The estimated groundwater renewal time in the Precordillera was 3–14 kyr. The piezometric elevation in the Precordillera due to low-permeability intrusive rocks and local recharge prevents the east-west groundwater transfer from the Altiplano to the western depression and explains why the volcanic CO2 in the Altiplano basins is not observed on the western flank. These results provide new insights for the evolution of water quality in volcanic aquifers in arid environments and provide considerations for estimating groundwater residence times using radiocarbon in areas influenced by volcanic CO2.

Isotopic composition of precipitation and groundwater onshore of the Rio del Rey Basin, southwest Cameroon: local meteoric lines and recharge

The link between rainfall and groundwater recharge in the Rio del Rey Basin, which is of socio-economic importance to Cameroon, is poorly understood. Accordingly, the stable isotopes in monthly rainfall from January to December 2012 (in Lobe and Mundemba) and 52 surface water and groundwater samples were investigated. High values of δ18O and δD were recorded in the dry period (February to March), and the least values of δ18O and δD were observed in the wet period (September). This indicates that different condensation processes primarily influenced stable isotopes in rainfall as a function of the difference in moisture sources. The relationship between δD and δ18O defined the Lobe meteoric water line as δD = 7.97 δ18O + 12.48 and Mundemba water line as δD = 7.75 δ18O + 10.79. The similarity of their slopes to the global meteoric line suggests that the isotopic composition of investigated rains was not significantly affected by evaporation during precipitation. The ranges in deuterium-excess of precipitation from 5.8 to 16.56‰ suggest the source of vapour is from the Atlantic Ocean. The groundwater isotope values (ranging from −3.81 to −2.52‰ for δ18O) plotted close to and along the GMWL, showing that its isotopic composition is of meteoric origin under rapid recharge conditions. The isotopic similarity between groundwater and June–August rains suggests a significant recharge during this period.

Genesis of the Nailenggele Mo-Cu-Pb-Zn polymetallic orefield in the Boluokenu Metallogenic Belt, Western Tianshan, China: Constraints from geochronology, fluid inclusions and isotope geochemistry

The Nailenggele orefield, located in the northwestern Chinese Tianshan Orogenic Belt, is composed of the Lailisigao’er Mo deposit, No. 3571 Cu prospect and Qixing Pb-Zn deposit. Lailisigao’er is a typical porphyry deposit with characteristic veinlet-disseminated ores and potassic, phyllic and propylitic alterations. No. 3571, situated in the peripheral of Lailisigao’er, is characterized by large amounts of oxidized ores at surface with limited intrusions outcropped. Qixing, about 3 km from Lailisigao’er, is characterized by quartz-sulfide veins controlled by fractures. This study aims to examine the genetic relationships between these deposits and/or occurrences, and discuss the significance for further exploration in the orefield and elsewhere in the region. LA-ICP-MS U-Pb dating on zircons from the ore-bearing porphyry in the Lailisigao’er deposit yielded an age of 367.5 ± 4.8 Ma. The molybdenite Re-Os and sphalerite Rb-Sr isochron ages recalculated from previously published data are 365.9 ± 2.1 Ma for Lailisigao’er and 362.0 ± 5.7 Ma for Qixing, respectively, suggesting that they are coeval and both related to the granodiorite porphyries. Three types of fluid inclusions occur in the Mo-bearing quartz from Lailisigao’er, including two-phase aqueous inclusions (Type I), solid mineral-bearing aqueous inclusions (Type II) and CO2-H2O inclusions (Type III). The total homogenization (Th) temperatures cluster from 260 to 320 °C (to liquid) for type I inclusions, 310 to 332 °C (to liquid) for type II inclusions, and 268 to 324 °C (to CO2 phase) for type III inclusions. The salinities are mainly in the ranges of 2.0–8.0, 32.9–42.0, and 1.4–5.5 wt% NaCleq for types I, II and III inclusions, respectively. By contrast, only type I inclusions were identified in the Pb-Zn-bearing quartz from Qixing, with Th values of 149–261 °C and salinities of 1.7–5.3 wt% NaCleq. The δ34SCDT values of hydrothermal sulfides from Lailisigao’er, No. 3571 and Qixing range from 2.8‰ to 4.0‰, 4.0‰ to 4.6‰ and 0.7‰ to 4.9‰, respectively. Sulfides from these three locations have uniform Pb isotopic compositions. The (87Sr/86Sr)0 ratios of fluid inclusions (average 0.70971) in Mo-bearing quartz at Lailisigao’er and sphalerite (average 0.71020) at Qixing are similar to those of Mo-mineralized porphyries (average of 0.70886) from Lailisigao’er. The δ18OH2O and δDH2O values of Pb-Zn-bearing quartz from Qixing are similar to those of Mo-bearing quartz from Lailisigao’er, both plotting close to the field of magmatic water but shifted toward the meteoric line. These geochronological, fluid inclusions and isotopic data suggest that the mineralization at different localities in the Nailenggele orefield constitutes part of an integrated magmatic-hydrothermal system centered on the Lailisigao’er porphyry Mo deposit, with the Qixing Pb-Zn polymetallic deposit representing a distal end-member. Both metals and sulfur were dominantly derived from porphyritic intrusions, whereas the ore-forming fluids were initially derived from the magmatic intrusions, with increasing involvement of meteoric water in time and distance from magmatic-hydrothermal center. Fluid immiscibility in the early stage and fluid mixing in the later stage, together with cooling, were responsible for ore precipitation. Based on this mineralization model, it is inferred that concealed porphyry Cu-Mo mineralization may be developed underneath the No. 3571 and Qixing.

The influence of the Carpathian Mountains on the variability of stable isotopes in precipitation and the relationship with large-scale atmospheric circulation

Abstract In this chapter, we analyse the influence of the Carpathian Mountains on the variability of stable isotopes in precipitation by employing a combination of observed and model data. Overall, the mean value of the stable isotopes in precipitation over the Carpathian Mountains, based on observational data, was −9.8‰ for δ 18 O and −68.6‰ for δ 2 H. The local meteoric line, using all samples from the study sites, was δ 2 H = 7.65 × δ 18 O + 5.82. The simulated δ 18 O, based on the ECHAM5-wiso isotopes enable model, showed good agreement with the observed isotopic data. By comparing all the monthly values of the observed isotopic data from all analysed stations and the corresponding model data, a correlation coefficient of 0.76 ( n = 455, p &lt; 0.001) was obtained. The spatial distribution of the simulated δ 18 O values in precipitation had the lowest values over the Romanian Carpathian Mountains and the highest values over the extra-Carpathian area, with the maximum in southeastern Romania. This pattern was strongly influenced by the Carpathian Mountains orography. Using the simulated δ 18 O data, we show that the spatial distribution of the δ 18 O values increases with temperature and decreases with altitude and latitude (−0.5‰ for δ 18 O per degree of latitude). The continental gradient is characterized by a polynomial trend of the second degree in the form of a large-open ‘U’ shape, and the general pattern of the δ 18 O values follows the spatial distribution of the Carpathian Mountains.

Can summer monsoon moisture invade the Jade Pass in Northwestern China?

Heavy precipitation events are increasingly concerned because their significant contribution to annual precipitation in the Northwestern China, which might be related to invasion of summer monsoon moisture. It is interest whether or not the same is Jade Pass as being outside the control of the Asian summer monsoon. In this work, six heavy precipitation events were selected based on the 95 percentiles of the daily precipitation at the 12 weather stations around the Jade Pass from 1970–2000, with consideration of the influences of elevation. The event on June 19th, 2013 was chosen for a detailed examination due to the fact that the day has a large-scale precipitation as revealed by a gridded precipitation dataset over a large region. Using a Weather Research and Forecasting Model (WRF) simulation with high spatiotemporal resolution and in situ isotopic tracing (δ18O, δD), under a large-scale heavy precipitation event, this study provides ambitious view at the synoptic scale. A dramatic decrease in the δ18O, δD and deuterium (d)-excess of precipitation, very high relative humidity (98%), and reduced air temperature indicate that the precipitation was a result of long-distance-transported monsoon vapor. In addition, the slope of the local water meteoric line (LWML) of the precipitation for this event was very close to that of the global meteoric water line (GWML), indicating the source of moisture was from the ocean. Meanwhile, the WRF simulation confirms that the precipitation at the Jade Pass was not caused by local convection, but by summer monsoon. Both WRF simulation and isotopic tracing support the view that the monsoon moisture could invade Jade Pass at the synoptic scale and impact on precipitation, which need be further investigated.

Chemical variation of surface water and groundwater in relation to water balance in the watershed of El Pescado Creek (Central-Eastern Argentina)

The watershed of El Pescado Creek has been established as a protected landscape; however, it is currently exposed to an intense land use and coverage change process, based on the conversion of grassland areas into greenhouse horticulture and urbanized areas. The aim of this work was to analyze hydrochemical modifications in this changing scenario, to identify parameter variations associated to water balance. The monitory network included surface water and groundwater samplings during winter, spring and summer of 2017. Daily water balance was estimated throughout the annual cycle. Electrical conductivity and pH were determined together with major ions (Na+, K+, Mg2+, Ca2+, CO32−, HCO3−, Cl−, SO42− and NO3−). The analysis of water stable isotopes (δ18O and δ2H) was performed for one sampling date. Water-balance variations during short-term periods affected surface water chemistry, although no relevant influence on deep groundwater was registered. Major ions variation in the surface water of the upper watershed might be related to runoff alteration caused by recently established impervious cover and by the dynamic of groundwater inputs. Isotopic analysis of surface water shows deviation from local meteoric line, with an isotopic enrichment following a tendency associated to evaporation processes. Deep groundwater samples express a recharge process by rainfall infiltration, with little or no previous evaporation (deuterium amounts were similar to those corresponding to local rainfall). Incipient evaporation processes are registered for shallow groundwater, possibly occurring before infiltration in the non-saturated zone, or right from the phreatic, when it is near the surface.

Hydrodynamic and hydrochemistry of wet meadows and shallow lakes in areas of the Patagonian basaltic plateaus, Argentina

Extra-Andean Patagonia, located in the south end of South America, is a wide arid region where the basaltic plateau landscape dominates. Associated with the basaltic plateaus, wet meadows and shallow lakes make up environments of relevance due to the ecosystemic services they provide. The aim of this work was to define the processes and factors that condition the hydrodynamics and hydrogeochemistry of wet meadows and shallow lakes in a sector of the Patagonian plateau basalts. For this, detailed geological and geomorphological studies were carried out and water was sampled at 29 points for the analysis of major ions and, in some samples, stable isotopes of the water molecule. Values of δ18O and δ2H similar to the local meteoric line in the water of wet meadows indicate that rainwater quickly infiltrates through the fractures of the basaltic plateaus and stores in the underlying sediments. Groundwater discharge occurs in the scarp zone due to changes in sediment permeability. The weathering of silicates in basalts, ion exchange in the sediment clays, and the dissolution of soluble salts provided by the dust control water chemistry of this wetland. Water from wet meadows drains into saline endorheic basins of sodium chloride composition where the isotopic signal is indicative of evaporation percentages close to 95%. The high evaporation rates cause the precipitation of evaporitic salts at the edges of shallow lakes with carbonate, sulfate, and chloride species controlled by the dominance of sodium in the water.

Isotopic and chemical facies for assessing the shallow water table aquifer quality in Goly Region, White Nile State, Sudan: focusing on nitrate source apportionment and human health risk

Groundwater from the shallow water table aquifer is the main supply of drinking water for residents in Goly Region, White Nile State, Sudan. The residents have complained about groundwater quality. This study aims to evaluate groundwater quality in in Goly Region and to assess the possible health risk of toxicants with focusing on nitrates. The study examined groundwater from wells distributed in 23 sites for hydrogeological, physiochemical, and isotopic facies. The ranges of facies levels (mg/L) were as follows: nitrate (6.2–655.6), fluoride (0.00–2.16), sodium (36.4–293.2), total dissolved solids (349–908), carbonate (0.00–24.0), nitrite (0.026–0.828), sulfate (1.00–77.00), ammonia (0.00–0.40), and chloride (12.78–42.60), besides pH (6.93–8.48). According to the National Sudanese Guidelines and the World Health Organization guidelines, 12 wells recorded unhealthy levels for nitrate, 1 well recorded unhealthy level for fluoride, and 2 wells recorded unhealthy levels for sodium, while all wells recorded healthy levels for the rest of facies. Additionally, groundwater consumption from 14 sites put both children and adults at potential health risk from nitrates based on hazard risk index. The Piper diagram shows that the trend of cation exchange in the aquifer was from (calcium + magnesium) to (sodium + potassium). Significant positive correlations were observed between several parameters, e.g. the combinations of static water level-depth (0.51), electrical conductivity (EC)-nitrate (0.60), EC-sulfate (0.73), EC-fluoride (0.55), EC-chloride (0.76), EC-sodium (0.84), pH-fluoride (0.73), and pH-sodium (0.59). The principal component analysis of the examined facies shows that the first two principal components, which have similar loadings (≈ 22% of each), represented natural and anthropogenic sources of major ions. The isotopes levels and relationship of δ15N and δ18O revealed that nitrate contamination was from animal waste and/or sewage. The relation between δ18O and δ2H isotopes of water demonstrates that groundwater samples were deviated from Meteoric Line of the Sudan and Global Meteoric Water Line.