Stable Isotopes 18O Research Articles

Isotopic composition of snow and ice on the glaciers of Novaya Zemlya

In 2015–2016 during the research expeditions of Institute of Oceanology, Russian Academy of Sciences the study of stable water isotopes (18O and D) was conducted on glaciers of Novaya Zemlya. As a result, first data on isotopic composition of seasonal snow cover and glacial ice of different ages were obtained and its connection to recent climate change has been shown. The first studies of the isotopic composition of snow cover and glacial ice at Novaya Zemlya allowed determine the average values and the range of variability of δ18O and δD. It shown that for the Northern ice cap glacial ice δ18O vary within −13.91 ÷ −15.83 ‰ with an average value of −14.93 ‰ and −103,95 ÷ −116.75 ‰ for δD at −109.88 ‰ mean value. The maximum variations were recorded for summer snow samples (−8.35 ‰ for δ18O and −55.79 ‰ for δD), as well as for the horizon of superimposed ice (−20.67 ‰ for δ18O and −151.48 ‰ for δD) where isotopic composition has been inherited from winter precipitation. Insignificant differences in the coefficients of the meteoric water regression equation for precipitation on GNIP stations and glacial ice at Novaya Zemlya indicate similar conditions of air masses and precipitation formation both at GNIP station and on glaciers. Deuterium excess showed no seasonal fluctuations, and its values did not exceed 15 ‰, which shows that the proportion of continental precipitation of moisture is very low. Analysis of isotopic profiles obtained on the glaciers of Novaya Zemlya indicated the presence of significant melting. This applies not only to the modern shallow horizons, but also to the part of the glacial strata that formed in the highest part of the archipelago close to ice divide and came to the surface at the Serp i Molot Glacier tongue. Therefore, in terms of ice core palaeogeographic reconstructions the most interesting site is the highest part of the Northern ice cap where it is possible to assume the existence of colder horizons formed during the Little Ice Age and where the seasonal geochemical signal may be preserved.

Stable Isotopes and Hydrochemistry Approach for Determining the Salinization Pattern of Shallow Groundwater in Alluvium Deposit Semarang, Central Java

DOI: 10.17014/ijog.4.1.1-10A groundwater study has been conducted in the Semarang City in August 2014, aiming to determine the source of shallow groundwater salinization using stable isotopes (18O, 2H) and water chemistry approach, and supported by local hydrogeological data. A number of shallow groundwater samples were taken at several locations with a depth of 0 - 35 m. Based on geological data, shallow groundwater of Semarang alluvium is dominated by insertion of sand-gravel and sandy-clay with average porosity of around 56.0 %. This layer is thinning towards the south and then increasingly thickening to the north and north-east of the studied area. The results of the analyses show that the characteristics of shallow groundwater, i.e. approximately 51% of groundwater, still have the original composition as meteoric water and the remaining approximately 49% obtained a shift in the isotopic composition as caused by interaction with seawater and the little influence of evaporation. The results of chemical analysis of water indicates that in dry seasons, shallow groundwater aquifers in the Semarang City is dominated by chloride (Cl-) with NaCl of water type. While the parameters of bicarbonate, chloride, and Na/Cl ratio, shallow groundwater can be classified into two groups, namely unintruded groundwater around 51% spread from the foot hills to the south towards the hills with elevations of 9 - 142 m above sea level and intruded groundwater around 49% spread from the coastline to the urban direction.

Isotopic assessment of fog drip water contribution to vegetation during dry season in Junshan wetland, northern Dongting Lake

Stable isotopes 2H and 18O of fog drip water, lake water, soil profiles, and vegetation leaves in Junshan wetland of East Dongting Lake, China, were investigated to estimate the contribution of fog drip water to wetland vegetation. Because of its recycled terrestrial meteoric water source, fog drip water is characterized by isotopic compositions that plot above the local meteoric water line (LMWL). Lake water undergoes intense evaporation owing to its low water volume and long residence time. The isotopic compositions of soil water suggest that it is recharged by both recent rainfall and fog drip water. A binary mixing model shows that approximately 16% of unsaturated soil water originates from continuous recharge by fog drip water, reaching 31% in surface soil where the vegetation roots are mainly distributed. Inspired by the literatures on acidification of intercepted clouds and fog as the major factor in forest die-back in Europe, the findings in this study inform future investigations into the relationships between fog water deposition and wetland degradation especially in heavily industrialized foggy areas.

Hydro-chemical evolution of groundwater in a sequence of Tertiary Formations in Northwest Oman

Tertiary Formations, which are widely spread in the Arab Peninsula, are fundamental to the oil industry in the world’s largest oil producing area. These formations host major aquifers that satisfy water demands for oil production such as steam injection and reservoir pressure maintenance . The current study investigates the hydro-chemical evolution of groundwater in a sequence of Tertiary Formations in Northwest Oman in the Kingdom of Saudi Arabia and the United Arab Emirates borders. Stable isotopes (18O and 2H) show three different groundwater types: (1) groundwater formed from precipitation originating from the Mediterranean Sea, (2) groundwater formed from mixing of northern (Mediterranean) and southern (Indian Ocean) moisture sources, and (3) groundwater affected by evaporation. Radiogenic isotopes 14C and 3H indicate younger groundwater close to the recharge source in North Oman Mountains and older age in the plain desert area that constitutes the discharge zone. Groundwater chemistry notably evolves from Ca–Mg–HCO3 dominant in the recharge area to Na–Cl–SO4 dominant type in the discharge zone. Water–rock interaction is the main process controlling groundwater chemistry in the recharge zone while evaporation becomes progressively effective down the gradient. The geochemistry and stable and radiogenic isotopes of the Tertiary Formations indicate that the study area has witnessed wet periods during the Early Holocene with surface water bodies formed by groundwater discharge at distal parts. The sustainability of such old groundwater that is being exploited for oil production should be thoroughly investigated to secure future oil production.

Impact of agricultural practices on groundwater quality in intensive irrigated area of Chtouka-Massa, Morocco

The Plio-Quaternary aquifer of Chtouka is located in Southwestern of Morocco. The intensive agricultural activity in Chtouka basin requires the mobilization of 94% of fresh water resources for irrigation. This overexploitation, along with the succession of drought years, sea water intrusion and various sources of pollution, affected the quality and availability of groundwater resources. Several sampling campaigns were carried out in different sites of the study area in order to investigate the spatial variation of groundwater quality. The temporal evolution of groundwater level shows that the water table was subjected to a gradual decline during the last decade, indicating an intensive exploitation mainly in irrigated areas. In the Southern part around Belfaa and the irrigated area along Massa River, nitrate concentrations exceed 50mg/L, which is the threshold set by the World Health Organization, while in the northern part around Biougra and Ait Amira, the nitrate concentration is mostly below 50mg/L indicating a relative good groundwater quality. This finding can be explained by the improvement of agricultural practices, particularly the conversion of flood and sprinkler irrigation to drip irrigation (80% of the total irrigated area) in most of the developed farms in this part of the study area. Moreover, the exploitation of groundwater from the deep aquifer, due to the increasing water demand in the region, can also explain the low chemical concentrations since the deep aquifer is not affected by anthropogenic pollutants or marine intrusion. Stable isotopes (18O and 2H) highlight the different origins of groundwater, indicating the complexity of the aquifer system path flows, which is attributable to the intensive exploitation and irrigation water return.

Tracing Nitrate-Nitrogen Sources and Modifications in a Stream Impacted by Various Land Uses, South Portugal

The identification of nitrate-nitrogen (NO3–N) origin is important in the control of surface and ground water quality. These are the main sources of available drinking water. Stable isotopes (15N and 18O) for NO3–N and along with a 1-D reactive transport model were used to study the origin and processes that lead to nitrogen transformation and loss in a major stream that flows into a reservoir within an intensively cultivated catchment area (352 km2) in Alentejo-Portugal. Seasonal water samples (October–November 2008, March 2009 and September 2009) of stream surface water, wells and sediment pore water were collected. The results showed consistently increasing isotope values and decreasing NO3–N concentrations downstream. During winter (wet period, November 2008 and March 2009) slightly higher NO3–N concentrations were found in comparison to early fall (dry period: October 2008) and summer (dry period: September 2009). Isotopic composition of 15N and 18O values in surface water samples from the stream and wells indicated that the dominant NO3–N sources were derived mainly from the soil and fertilizers. There was also significant nitrification in surface water at the head of the stream. Sediment pore waters showed high NO3–N values near the sediment-water interface (reaching 25 mg·N·L−1) and NO3–N concentrations sharply decreasing with sediment depth, suggesting significant NO3–N consumption. Denitrification was also detected using the 15N signature in upstream waters, but not downstream where very low NO3–N levels were measured. In the stream, the calculated isotopic enrichment factor for NO3–N was −2.9‰ for 15N and −1.78 for 18O, this indicates that denitrification accounts for 7.8% to 48% of nitrate removal.

Illuminating hydrological processes at the soil‐vegetation‐atmosphere interface with water stable isotopes

AbstractWater stable isotopes (18O and 2H) are widely used as ideal tracers to track water through the soil and to separate evaporation from transpiration. Due to the technical developments in the last two decades, soil water stable isotope data have become easier to collect. Thus, the application of isotope methods in soils is growing rapidly. Studies that make use of soil water stable isotopes often have a multidisciplinary character since an interplay of processes that take place in the vadose zone has to be considered. In this review, we provide an overview of the hydrological processes that alter the soil water stable isotopic composition and present studies utilizing pore water stable isotopes. The processes that are discussed include the water input as precipitation or throughfall, the output as evaporation, transpiration, or recharge, and specific flow and transport processes. Based on the review and supported by additional data and modeling results, we pose a different view on the recently proposed two water world hypothesis. As an alternative to two distinct pools of soil water, where one pool is enriched in heavy isotopes and used by the vegetation and the other pool does not undergo isotopic fractionation and becomes recharge, the water gets successively mixed with newly introduced rainwater during the percolation process. This way, water initially isotopically enriched in the topsoil loses the fractionation signal with increasing infiltration depth, leading to unfractionated isotopic signals in the groundwater.

Assessment of interconnection between surface water and groundwater in Sawa Lake area, southern Iraq, using stable isotope technique

Interaction between surface water represented by the Euphrates River, natural springs, and Sawa Lake with groundwater (11 wells) in southern Iraq was investigated in this study. Water samples were collected for hydrochemistry and stable isotope (2H and 18O) analysis. Sampling of water from determined stations (10 stations along the Euphrates, 3 springs, and Sawa Lake) were carried out during two stages; the first was in October 2013(dry season) and the second one was in March 2014 (wet season). The aim of the research is to assess the interaction of groundwater–surface water, which includes Al-Atshan River (branch of the Euphrates River), Sawa Lake, and the groundwater in the study area by using hydrochemistry and stable isotope techniques. The results indicate that surface waters have a different type of water from that of groundwater. In δ 2H and δ 18O diagrams, all groundwater, springs, and Sawa Lake waters are plotted below the Global Meteoric Water Line (GMWL) and the local meteoric water line (LMWL) indicating the influence of evaporation processes and seasonal variation. The LMWL deviates by a d-excess about +13.71 toward the East Mediterranean meteoric water line (EMWL) indicating that the origin of the vapor source is the Mediterranean Sea. The river water has different isotopic compositions from that of groundwater, springs, and Sawa Lake. The final conclusion is that there is no clear influence of the groundwater on the river water while there is an intermixing between the groundwater in the different locations in the study area.

Groundwater recharge to ophiolite aquifer in North Oman: constrained by stable isotopes and geochemistry

The current study employs geochemical and isotopic tools to understand hydrochemical and recharge processes characterizing ophiolite aquifer in North Oman in conjunction with the Hajar Super Group (HSG) aquifer. A total of 57 samples were analyzed for major ions and stable isotopes 2H and 18O. The geochemical composition of groundwater indicates that water–rock interaction and mixing are the main processes controlling groundwater chemistry. Groundwater in the HSG is characterized by carbonate minerals dissolution contrary to the groundwater in the ophiolites where silicates dissolution dominates. This results in differences in the groundwater chemical composition in the two systems. Isotopic characteristics of precipitation collected during the study period indicate two main moisture sources from the Indian Ocean and the Mediterranean Sea. Groundwater δ2H and δ18O values suggest two recharge sources to the ophiolite aquifer: lateral flow from the HSG and direct infiltration. Recharge from direct infiltration in the highlands, which is depleted in δ2H and δ18O, retains the same isotopic signature of precipitation, whereas that in the low land substantially reflects an evaporation effect.

Self-Diffusion of the Constituent Elements in Alpha-Alumina, Mullite and Aluminosilicate Glasses

Aluminium is a key element in geological and man-made materials which has only one stable isotope and no radionuclides with half-life times suitable for standard experimental diffusion studies. Here we report on our method using the radioisotope 26Al (t1/2 = 7.4×105 a) as a quasi-stable tracer for aluminium in combination with SIMS depth profiling. First, our data for the aluminium bulk diffusivity in a-alumina are discussed jointly with published oxygen bulk diffusion coefficients. They clearly show that the relation DAl>>D0 is valid in the temperature range 1200 °C ≤ T ≤ 1800 °C. In an analogous manner, the two rare stable isotopes 18O and 30Si are used together with 26Al in diffusion studies of generic examples of materials which either consist of aluminium, silicon and oxygen only, or where these three elements are key constituents of the structure. For the crystalline aluminium silicate mullite our diffusivity data for aluminium, oxygen and silicon are used to explain the kinetics of the solid state formation reaction of mullite and the segregation kinetics of alumina from mullite. Finally, the diffusivities of oxygen and aluminium in model aluminosilicate glasses are presented as a function of temperature for different Al3+/Na+ ratios. For the aluminium silicate mullite and for the aluminosilicate glasses the relation D0>DAl>DSi is valid regardless of the exact composition. For the glass system the activation enthalpies of aluminium and oxygen diffusion decrease with decreasing Al3+/Na+ ratio.

Variability in isotopic composition of base flow in two headwater streams of the southern Appalachians

AbstractWe investigated the influence of hillslope scale topographic characteristics and the relative position of hillslopes along streams (i.e., internal catchment structure) on the isotopic composition of base flow in first‐order, forested headwater streams at Coweeta Hydrologic Laboratory. The study focused on two adjacent forested catchments with different topographic characteristics. We used stable isotopes (18O and 2H) of water together with stream gauging and geospatial analysis to evaluate relationships between internal catchment structure and the spatiotemporal variability of base flow δ18O. Base flow δ18O was variable in space and time along streams, and the temporal variability of base flow δ18O declined with increasing drainage area. Base flow became enriched in 18O moving along streams from channel heads to catchment outlets but the frequency of enrichment varied between catchments. The spatiotemporal variability in base flow δ18O was high adjacent to large hillslopes with short flow paths, and it was positively correlated with the relative arrangement of hillslopes within the catchment. These results point to influence of unique arrangement of hillslopes on the patterns of downstream enrichment. Spatial variability in base flow δ18O within the streams was relatively low during dry and wet conditions, but it was higher during the transition period between dry and wet conditions. These results suggest that the strength of topographic control on the isotopic composition of base flow can vary with catchment wetness. This study highlights that topographic control on base flow generation and isotopic composition is important even at fine spatial scales.

Event water detection in tile drainage runoff using stable isotopes and a water temperature in small agricultural catchment in Bohemian-Moravian Highlands, Czech Republic

The tile drainage runoff composition during rainfall–runoff (R–R) events was examined in a small agricultural catchment Dehtaře (Bohemian-Moravian Highlands, Czech Republic). Drainage systems in this region of crystalline bedrock are typically built in slopes and they have complicated runoff generation. For runoff separation, analysis of stable isotopes 18O and 2H was used and compared to sudden changes in drainage water temperature. The analysis of 18 hydrographs showed that the drainage runoff was composed of 1–58 % event water during summer events, with a maximum temporary share of 11 and 88 %. During winter events, the pre-event water significantly dominated. In all cases when event water was detected in the drainage runoff, a rapid change in the drainage water temperature was observed as well. Its values during R–R events converged toward the temperature of the precipitation, which was very similar to that of the air (R 2 = 0.98 %). As the magnitude of the water temperature change was proportional to the event water portion in the drainage runoff (R 2 = 0.91), it is possible to state that a sudden change in drainage water temperature indicates the presence of event water in the drainage runoff and it is possible to use water temperature successfully to separate the runoff components.

Hydrologic exchanges and baldcypress water use on deltaic hummocks, Louisiana, USA

AbstractCoastal forested hummocks support clusters of trees in the saltwater–freshwater transition zone. To examine how hummocks support trees in mesohaline sites that are beyond physiological limits of the trees, we used salinity and stable isotopes (2H and 18O) of water as tracers to understand water fluxes in hummocks and uptake by baldcypress (Taxodium distichum (L.) Rich.), which is the most abundant tree species in coastal freshwater forests of the southeastern U.S. Hummocks were always partially submerged and were completely submerged 1 to 8% of the time during the two studied growing seasons, in association with high water in the estuary. Salinity, δ18O, and δ2H varied more in the shallow open water than in groundwater. Surface water and shallow groundwater were similar to throughfall in isotopic composition, which suggested dominance by rainfall. Salinity of groundwater in hummocks increased with depth, was higher than in swales, and fluctuated little over time. Isotopic composition of xylem water in baldcypress was similar to the vadose zone and unlike other measured sources, indicating that trees preferentially use unsaturated hummock tops as refugia from higher salinity and saturated soil in swales and the lower portions of hummocks. Sustained upward gradients of salinity from groundwater to surface water and vadose water, and low variation in groundwater salinity and isotopic composition, suggested long residence time, limited exchange with surface water, and that the shallow subsurface of hummocks is characterized by episodic salinization and slow dilution. Copyright © 2016 John Wiley & Sons, Ltd.

Hydrochemical and isotopic (2H, 18O and 37Cl) constraints on evolution of geothermal water in coastal plain of Southwestern Guangdong Province, China

Geothermal energy is abundant in Guangdong Province of China, however, majority of it is still unexploited. To take full advantage of this energy, it is essential to know the information of geothermal system. Here, physical parameters such as pH and temperature, major ion (Na+, Ca2+, Mg2+, Cl−, SO42− and HCO3−), trace elements (Br−, Sr2+, Li+ and B3+) and stable isotopes (2H, 18O and 37Cl) in geothermal water, non-geothermal water (river water, cold groundwater) and seawater were used to identify the origin and evolution of geothermal water in coastal plain of Southwest of Guangdong. Two separate groups of geothermal water have been identified in study area. Group A, located in inland of study area, is characterized by Na+ and HCO3−. Group B, located in coastal area, is characterized by Na+ and Cl−. The relationships of components vs. Cl for different water samples clearly suggest the hydrochemical differences caused by mixing with seawater and water–rock interactions. It's evident that water–rock interactions under high temperature make a significant contribution to hydrochemistry of geothermal water for both Group A and Group B. Besides, seawater also plays an important role during geothermal water evolution for Group B. Mixing ratios of seawater with geothermal water for Group B are calculated by Cl and Br binary diagram, the estimated results show that about <1% to <35% of seawater has mixed into geothermal water, and seawater might get into the geothermal system by deep faults. Molar Na/Cl ratios also support these two processes. Geothermal and non-geothermal water samples plot around GMWL in the δ2H vs. δ18O diagram, indicating that these samples have a predominant origin from meteoric water. Most of geothermal water samples display δ37Cl values between those of the non-geothermal water and seawater samples, further reveals three sources of elements supply for geothermal water, including atmospheric deposition, bedrocks and seawater, which show a great potential to trace source of dissolved Cl− in geothermal water. Estimated reservoir temperatures show that geothermal reservoirs in study area are mid-low temperature geothermal reservoirs.

Oxygen-17 anomaly in soil nitrate: A new precipitation proxy for desert landscapes

The nitrogen cycle in desert soil ecosystems is particularly sensitive to changes in precipitation, even of relatively small magnitude and short duration, because it is already under water stress. This suggests that desert soils may have preserved past evidence of small variations in continental precipitation. We have measured nitrate (NO3−) concentrations in soils from the Atacama (Chile), Kumtag (China), Mojave (US), and Thar (India) deserts, and stable nitrogen and oxygen isotope (15N, 17O, and 18O) abundances of the soil NO3−. 17O anomalies (Δ17O), the deviations from the mass-independent isotopic fractionation, were detected in soil NO3− from almost all sites of these four deserts. There was a strong negative correlation between the mean annual precipitation (MAP) and soil NO3− Δ17O values (ΔONO3soil17). This MAP-ΔONO3soil17 correlation advocated ΔONO3soil17 as a new precipitation proxy and was then used to assess precipitation changes in southwestern US at the Pliocene–Pleistocene boundary, in South America during the Miocene, and the Sahara Desert in the past 10 kyr using NO3− Δ17O in paleosols or ancient aquifers. Global and the US maps of surface ΔONO3soil17 were also projected with available MAP datasets based on the MAP-ΔONO3soil17 model.

Hydrogeochemical and isotopic studies of groundwater in the middle voltaian aquifers of the Gushegu district of the Northern region

This work is to establish the hydrochemistry and origin of groundwater in some parts of the Gushegu district of the Northern Region of Ghana. Hydrochemical data from 19 groundwater and 7 rock samples have been used to evaluate water quality, water types, and sources of various ions as well as origin of the groundwater. The study results show that the quality of groundwater from the area is generally not good due to their fluoride (F−), bicarbonate (HCO3−) and electrical conductivity (EC) concentrations. The F− contents of the groundwater have values as high as 1.97 mg/L, with 53 % of the groundwater having concentrations of F− exceeding the WHO recommended allowable limits. These high F− values have the potential of causing serious health problems such as kidney failure, dental and skeletal fluorosis, reproductive problem and reduction in intelligent quotient of consumers. A plot of Gibbs diagram reveals that rock weathering and precipitation are the major hydrogeochemical processes regulating the water chemistry of the study area. Petrographic thin-section analyses of rock samples identify minerals present to be muscovite, plagioclase feldspars, quartz, sericite and iron oxide. Stable isotope (18O and 2H) composition of the waters reveals that most of the groundwater is likely to be recharged from local precipitation, indicating their meteoric origin. Some samples, however, showed considerable evaporation.

Prediction of Plant Vulnerability to Salinity Increase in a Coastal Ecosystem by Stable Isotope Composition (δ18O) of Plant Stem Water: A Model Study

Sea level rise and the subsequent intrusion of saline seawater can result in an increase in soil salinity, and potentially cause coastal salinity-intolerant vegetation (for example, hardwood hammocks or pines) to be replaced by salinity-tolerant vegetation (for example, mangroves or salt marshes). Although the vegetation shifts can be easily monitored by satellite imagery, it is hard to predict a particular area or even a particular tree that is vulnerable to such a shift. To find an appropriate indicator for the potential vegetation shift, we incorporated stable isotope 18O abundance as a tracer in various hydrologic components (for example, vadose zone, water table) in a previously published model describing ecosystem shifts between hammock and mangrove communities in southern Florida. Our simulations showed that (1) there was a linear relationship between salinity and the δ18O value in the water table, whereas this relationship was curvilinear in the vadose zone; (2) hammock trees with higher probability of being replaced by mangroves had higher δ18O values of plant stem water, and this difference could be detected 2 years before the trees reached a tipping point, beyond which future replacement became certain; and (3) individuals that were eventually replaced by mangroves from the hammock tree population with a 50% replacement probability had higher stem water δ18O values 3 years before their replacement became certain compared to those from the same population which were not replaced. Overall, these simulation results suggest that it is promising to track the yearly δ18O values of plant stem water in hammock forests to predict impending salinity stress and mortality.

Established methods and new opportunities for pore water stable isotope analysis

AbstractThe vadose zone plays a crucial role in the water cycle for storing water, providing water to vegetation and transporting solutes or degrading contaminants. Earth scientists have long acknowledged the importance of the vadose zone, and numerous methods have been developed to better understand and predict hydrological processes within this ‘critical zone’. For several decades, stable isotopes (18O and 2H) of pore water have been used as environmental tracers to gain insights into vadose zone water movement and other processes. To determine the pore water stable isotopic composition, various sampling procedures have been developed. We present the procedure and the accompanied advantages and drawbacks of each method. We further discuss possible opportunities and limitations regarding the scale of interest and the pore space that is sampled. The methodological review reveals that the choice of sampling method is crucial for the interpretation of pore water stable isotopes in the vadose zone, but a thorough comparison between the different methods is yet missing. Spiking experiments, where water of known isotopic composition is added to oven‐dried soil, have been shown to be questionable, as the extracted water is usually depleted compared with the standard water. A comparative study analysing soil samples with the recently developed direct water vapour equilibration method and the widely used cryogenic extraction shows deviations, which can only be partly explained, but discloses the need for a more thorough experimental comparative study. Especially promising are developments of continuous isotope measurements based on laser‐based spectrometry that will open up new opportunities for analysing pore water isotopes with higher temporal and spatial resolutions, revealing new insights into hydrological processes across various temporal and spatial scales. Copyright © 2015 John Wiley &amp; Sons, Ltd.

Scenarios of groundwater chemical evolution in a region of the Canadian Shield based on multivariate statistical analysis

Abstract Study region The study of groundwater chemistry of the Charlevoix/Haute-Cote-Nord (CHCN) region in the province of Quebec in Canada is part of a regional hydrogeological characterization project. Study focus Groundwater was sampled in 113 wells over the 4500 km 2 study area and analyzed for 39 parameters including major, minor, trace and inorganic constituents, plus stable isotopes 2H and 18O. Two multivariate statistical methods, hierarchical cluster analysis (HCA) and R-mode factor analysis (RFA) were combined with graphic methods to classify the samples according to plausible levels of groundwater evolution in that region. New hydrological insights for the region Four sample clusters were identified. Cluster 1 is composed of low-salinity Ca-HCO 3 groundwater corresponding to recently infiltrated water in surface granular aquifers in recharge areas. Cluster 4 Na-(HCO 3 -Cl) groundwater is more saline and corresponds to more evolved groundwater probably from confined bedrock aquifers. Cluster 2 and Cluster 3 (Ca-Na)-HCO 3 and Ca-HCO 3 groundwater, respectively, correspond to mixed or intermediate water between Cluster 1 and Cluster 4 from possibly interconnected granular and bedrock aquifers. This study identifies groundwater recharge, water–rock interactions, ion exchange, solute diffusion from marine clay aquitards, saltwater intrusion and also hydraulic connections between the Canadian Shield and the granular deposits, as the main processes affecting the hydrogeochemical evolution of groundwater in the CHCN region.

Mineralogy of Holocene Sediments of Shallow Lakes in the Baikal Region: A Connection with Paleoclimate

The results of a comprehensive study of the Holocene terrigenous-evaporite section of bottom sediments from one of the shallow saline lakes with carbonate sedimentation, located on the territory of the Barguzin basin (Republic of Buryatia) are provided. The researches were carried out using a wide complex of methods: x-ray diffractometry (XRD), IR spectroscopy, laser granulometry, determination of stable isotopes 18O and 13C and other techniques. The method of mathematical modelling of XRD patterns of endogenic carbonate minerals is established that they are represented by calcite and low-Mg calcite. The dynamics of change in content of carbonates in lake sediments from the base to the roof of the section (from ~4900 years ago to the present day) was seen. The obtained carbonate record, supplemented by results of other analyses reveals the evolution of the lake basin during the Holocene depending on changes in regional climate and environment.