Geotechnical data compilation for evaporitic rocks in Abu Dhabi, UAE: A resource for engineers.

The durability and degradability of evaporitic rocks are always a critical concern in geological, civil, and geotechnical engineering applications, necessitating careful consideration for reliable, secure, and sustainable construction. This dataset is based on a comprehensive collection of geotechnical data involving both mechanical and physical properties as well as geochemical analyses for the evaporitic rocks in Abu Dhabi and its vicinity. The purpose of this dataset is to be an important source for construction professionals, engineers, and decision-makers in the region by providing basic insights into the challenges associated with building projects on and in evaporitic rocks. This data is obtained from extensive field investigations and laboratory analyses and will help to ensure that construction activities are carried out safely and efficiently when dealing with evaporitic rock formations. The prevalence of evaporitic rocks in Abu Dhabi highlights the importance of this geotechnical data compilation in facilitating informed decision-making and supporting safe construction.

Effects of soil heterogeneity and preferential flow on the water flow and isotope transport in an experimental hillslope.

Soil water movement plays vital roles in hillslope runoff generation and groundwater and surface water interaction. However, there are still knowledge gaps about the impacts of soil heterogeneity and preferential flow on the internal water flow and transport process. In this study, the vertical soil heterogeneity focused on the variations in soil retention capacity, and the consideration of lateral preferential flow emphasized the higher hydraulic conductivity. We combined isotopic tracing and numerical modeling in an artificial hillslope, focusing on monitored processes of the artificial rainfall and isotopic tracing experiment. The results showed that the soil moisture quickly accumulated at the bottom of the hillslope during rainfall events, while the 2H enrichment occurred in the topsoil derived from enriched isotope injection in the second artificial rainfall. The evaporation process slowed down the mixing of new water in the topsoil and old water in the lower layer. We found that the vertical soil heterogeneity had significant influences on the internal water and isotope transport paths within the hillslope. The lateral preferential flow played an important role in the water flux and transport time to the seepage face. The coupling of isotopic tracing, which reflects the water transport and mixing with the hillslope, effectively improved the model simulation and mechanism analysis of hillslope water flow. Our findings provide new insights into the mechanisms governing soil water flow and transport dynamics in hillslopes, taking into account vertical soil heterogeneity and lateral preferential flow.

Geochemistry and Sr, S, and O stable isotopes of Miocene Abu Dhabi evaporites, United Arab Emirates.

This study investigates for the first time the subsurface Miocene evaporite facies (Gachsaran Formation) in Abu Dhabi, United Arab Emirates. Forty-five evaporite rock samples were selected for petrographic, mineralogical, and geochemical investigations and stable isotope analyses to decipher their origin and constrain their age. Secondary gypsum with anhydrite relics dominates the investigated evaporitic rocks, with minor amounts of clays, dolomicrite, Fe/Ti oxides, and celestite. These samples are characterized by their excellent purity and low variability in geochemical composition. The distribution of trace element concentrations is significantly influenced by continental detrital intake. The main focus of the study is to determine the strontium, sulfur, and oxygen stable isotope compositions. The measured 87Sr/86Sr values of 0.708411-0.708739 are consistent with Miocene marine sulfates and indicate ∼21.12-15.91 Ma (Late Aquitanian-Burdigalian). The δ34S and δ18O values are 17.10‰-21.59‰ and 11.89‰-19.16‰, respectively. These values are comparable to those of Tertiary marine evaporites. The relatively low values of δ34S suggest that non-marine water possesses little influence on S distribution. The geochemical composition and Sr, S, and O isotope distributions of the Abu Dhabi gypsum facies from the Gachsaran Formation reveals that their source brines were marine (coastal saline/sabkha) with subordinate continental input.

Effects of groundwater and distilled water on the durability of evaporitic rocks.

Evaporitic rock durability induced by groundwater cause several construction challenges, but representative experimental studies to evaluate such conditions are still missing. Therefore, this study intended to provide better and more realistic degradability features of evaporites with groundwater besides a comparison with distilled water as slaking fluids. Forty-eight evaporitic rock blocks were collected from Abu Dhabi area, United Arab Emirates. 96 slake durability index (SDI) tests were performed, 48 with each of the slaking fluids; groundwater and distilled water, and their textural, mineralogical, and geochemical attributes were also examined before and after the SDI tests. In comparison to mineralogical and textural modifications, slaking fluid had a greater impact on the chemical composition of evaporitic rock. The study shows that the degradability of evaporites with groundwater and distilled water indicates a wide range from very low to high. The mean weight loss values after four cycles with groundwater and distilled water vary from 11 to 77 and from 4 to 81 wt.%, respectively. Consequently, slaking with groundwater illustrates a wide range compared to the slaking with distilled water. This could be due to quick interactions between groundwater and evaporites and fast hydration-dehydration process than distilled water due to the chemical composition of the groundwater. It is recommended to investigate the attributes of evaporitic rocks as well as groundwater geochemistry for safe, cost-effective, and sustainable structures.

127I and 129I species in the English Channel and its adjacent areas: Uncovering impact on the isotopes marine pathways.

Radioactive iodine-129 has been released from the La Hague nuclear fuel reprocessing facility (NRF) into the English Channel, but the distribution and transformation of the isotope species, and environmental consequences have not been fully characterized in the Channel. Here we present data on iodine isotopes (129I and 127I) species in surface water of the English Channel and the southern Celtic Sea. Compared to 127I species, the concentrations of 129I- and 129IO3- show more variations, but iodate is the major species for both 129I and 127I. Our data provide new information regarding iodide-iodate inter-conversion showing that water dilution and mixing are the main factors affecting the 127I and 129I species distribution in the Channel. Some reduction of iodate occurs within the English Channel and mainly in the west part because of biotic processes. The 129I species transformation is overall insignificant, especially in the eastern Channel, where a constant value of 129IO3-/129I is observed, which might characterize the La Hague wastewater signal. In the Celtic Sea, oxidation of iodide can be traced by 127I and 129I species. On a larger scale, 129I generally experienced an oxidation process in the Atlantic Ocean, while in the coast of shallow shelf seas, new produced 129I- can be identified, especially in the German Bight and the Baltic Sea. The data of 129I species in the English Channel can provide estimate of redox rates in a much broader marine areas if the transit time of 129I from La Hague is well-defined. Furthermore, estimate of inventories for 129I and its species in the Channel, and fluxes of 129I species from the English Channel to the North Sea add important information to the geochemical cycle of 129I.

A multi-isotopic evaluation of groundwater in a rapidly developing area and implications for water management in hyper-arid regions.

Management of water resources in hyper-arid areas faces vital challenges in a global climate change context. Consequently, understanding the effects on groundwater sources can help mitigating the problem of water scarcity and the negative impact of human intervention on the environment. A case study area in the hyper-arid climate of the United Arab Emirates, was tackled here with the focus on applying stable isotopes as tools for evaluating groundwater sources and quality assessment. The results of major ions indicate variable increase in groundwater salinity moving away from Al Hajar Mountains recharge areas to the discharge areas (Arabian Gulf coast). The data of stable isotopes (δ18OH2O, δ2HH2O, δ18ONO3, δ15NNO3, δ18OSO4, δ34SSO4, δ11B) suggest impact of paleo-groundwater in the abstractions of the wells nearest to the coast. Nitrate isotopes indicate farming activities sources that can be masked due to the contribution from the nitrate-poor paleo-groundwater. Nitrate reduction processes are expected near to the recharge front. Sulphate and boron isotopes further suggest that influence of ancient evaporite dissolution in salinization. Management efforts should be focused on the diffuse sources of quality mitigations that can be vital in fingerprinting local and regional (transboundary) effects.

Anthropogenic 236U and 233U in the Baltic Sea: Distributions, source terms, and budgets.

The Baltic Sea receives substantial amounts of hazardous substances and nutrients, which accumulate for decades and persistently impair the Baltic ecosystems. With long half-lives and high solubility, anthropogenic uranium isotopes (236U and 233U) are ideal tracers to depict the ocean dynamics in the Baltic Sea and the associated impacts on the fates of contaminants. However, their applications in the Baltic Sea are hampered by the inadequate source-term information. This study reports the first three-dimensional distributions of 236U and 233U in the Baltic Sea (2018-2019) and the first long-term hindcast simulation for reprocessing-derived 236U dispersion in the North-Baltic Sea (1971-2018). Using 233U/236U fingerprints, we distinguish 236U from the nuclear weapon testing and civil nuclear industries, which have comparable contributions (142 ± 13 and 174 ± 40 g) to the 236U inventory in modern Baltic seawater. Budget calculations for 236U inputs since the 1950s indicate that, the major 236U sources in the Baltic Sea are the atmospheric fallouts (∼1.35 kg) and discharges from nuclear reprocessing plants (> 211 g), and there is a continuous sink of 236U to the anoxic sediments (589 ± 43 g). Our findings also indicate that the limited water renewal endows the Baltic Sea a strong "memory effect" retaining aged 236U signals, and the previously unknown 236U in the Baltic Sea is likely attributed to the retention of the mid-1990s' discharges from the nuclear reprocessing plants. Our preliminary results demonstrate the power of 236U-129I dual-tracer in investigating water-mass mixing and estimating water age in the Baltic Sea, and this work provides fundamental knowledge for future 236U tracer studies in the Baltic Sea.

Holocene monsoon dynamics at Kunlun Pass on the northeastern Qinghai-Tibet Plateau.

Various proxy records have been used for the understanding of environmental and climate variations during the Holocene. Here, for the first time, we use meteoric 10Be isotope measurements performed on sediments from a drill core collected at the Kunlun Pass (KP) on the northeastern Qinghai-Tibet Plateau (NETP) to investigate hydroclimate changes during the Holocene. The 10Be flux suggests relative low levels in the Early Holocene, followed by a sharp increase to high values at around 4 ka BP (4 ka BP = 4000 years before present). Afterwards, the 10Be flux remains on a high level during the Late Holocene, but decreases slightly towards today. These 10Be deposition patterns are compared to moisture changes in regions dominated by the Indian Summer Monsoon (ISM), East Asian Summer Monsoon (EASM), and the Westerlies. Different from the gradual changes in monsoon patterns, the 10Be data reveal low levels during the Early Holocene until ~4 ka BP when an obvious increase is indicated and a relative high level continues to this day, which is relatively more in agreement with patterns of the Westerlies. This finding provides a new evidence for a shift in the dominant pattern of atmospheric circulation at the KP region from a more monsoonal one to one dominated by the Westerlies. Our results improve the understanding of non-stationary interactions and spatial relevance of the EASM, the ISM and the Westerlies on the Qinghai-Tibet Plateau.

An unknown source of reactor radionuclides in the Baltic Sea revealed by multi-isotope fingerprints.

We present an application of multi-isotopic fingerprints (i.e., 236U/238U, 233U/236U, 236U/129I and 129I/127I) for the discovery of previously unrecognized sources of anthropogenic radioactivity. Our data indicate a source of reactor 236U in the Baltic Sea in addition to inputs from the two European reprocessing plants and global fallout. This additional reactor 236U may come from unreported discharges from Swedish nuclear research facilities as supported by high 236U levels in sediment nearby Studsvik, or from accidental leakages of spent nuclear fuel disposed on the Baltic seafloor, either reported or unreported. Such leakages would indicate problems with the radiological safety of seafloor disposal, and may be accompanied by releases of other radionuclides. The results demonstrate the high sensitivity of multi-isotopic tracer systems, especially the 233U/236U signature, to distinguish environmental emissions of unrevealed radioactive releases for nuclear safeguards, emergency preparedness and environmental tracer studies.

Solar and meteorological influences on seasonal atmospheric 7Be in Europe for 1975 to 2018.

Assessing the transport of natural radionuclides in the atmosphere provides a powerful tool to study air mass circulation. Here, we investigated the seasonal atmospheric distribution of the naturally produced 7Be in surface air over Europe between 40° N and 68° N during the period 1975-2018. The results suggest that the inter-annual variability of 7Be reflects production rates of the radionuclide induced by solar modulation of cosmic rays. Further analysis of the meteorological influences indicates that the meteorological influences on 7Be concentrations are geographically and seasonally dependent. We found that, in general, the tropopause pressure plays an important factor influencing 7Be activity for winter and spring seasons while the sea level pressure and temperature are more dominant during summer and autumn seasons. The combination of tropospheric production rates and meteorological parameters explains 24%-79% variances of the seasonal 7Be activity. We further applied a three-box model to study the influence of stratosphere-troposphere exchanges on 7Be concentrations. The simulation supports that the seasonal cycle of 7Be in Europe is controlled by two main factors: the changing height of the troposphere (seasonality of the tropopause height) and seasonal variations of the stratosphere-troposphere exchanges.

Circulation of Circumpolar Deep Water and marine environment traced by 127I and 129I speciation in the Amundsen Sea Polynya, Antarctica.

The long-lived anthropogenic 129I released from human nuclear activities has been widely employed as an effective oceanographic tracer to investigate circulation of water masses in marine environment. Depth profiles of seawater collected from the Amundsen Sea Polynya, Antarctica were analyzed for total 129I and 127I, as well as their species of iodide and iodate. The measured 129I concentrations ((1.15-3.43) × 106 atoms/L) and 129I/127I atomic ratios ((0.53-1.19) × 10-11) indicate that anthropogenic 129I has not only reached the Antarctic surface marine environment but also the deep water due to a strong vertical mixing of water masses. The Circumpolar Deep Water (CDW) flowed southward along continental shelf towards the ice shelf zone (74.25°S) at a depth of 1025 m and then migrated upward and northward to the polynya and finally to the sea ice zone (71.95°S). The maximum upwelling depth of the CDW was around 200 m in the polynya. The source of 129I- in the polynya is predominantly the intrusion of source waters rather than the in-situ reduction of iodate by phytoplankton, implying a considerably slow reduction process of iodate to iodide in this region.

Multiradionuclide evidence for an extreme solar proton event around 2,610 B.P. (∼660 BC).

Recently, it has been confirmed that extreme solar proton events can lead to significantly increased atmospheric production rates of cosmogenic radionuclides. Evidence of such events is recorded in annually resolved natural archives, such as tree rings [carbon-14 (14C)] and ice cores [beryllium-10 (10Be), chlorine-36 (36Cl)]. Here, we show evidence for an extreme solar event around 2,610 years B.P. (∼660 BC) based on high-resolution 10Be data from two Greenland ice cores. Our conclusions are supported by modeled 14C production rates for the same period. Using existing 36Cl ice core data in conjunction with 10Be, we further show that this solar event was characterized by a very hard energy spectrum. These results indicate that the 2,610-years B.P. event was an order of magnitude stronger than any solar event recorded during the instrumental period and comparable with the solar proton event of AD 774/775, the largest solar event known to date. The results illustrate the importance of multiple ice core radionuclide measurements for the reliable identification of short-term production rate increases and the assessment of their origins.

Use of 10Be isotope to predict landscape development in the source area of the Yellow River (SAYR), northeastern Qinghai-Tibet Plateau.

The magnitude of soil and sediment erosion and accumulation processes can profoundly affect landscape development and hamper efficient management of natural resources. Consequently, estimating the rates and causes of these processes is essential, particularly in remote regions, for prediction of changes in landform and river evolution and protection of local ecosystem. We here present the results of a soil and sediment erosion investigation in the Source Area of the Yellow River (SAYR), northeast Qinghai-Tibet Plateau based on a combined analysis of 10Be cosmogenic isotope and Soil and Water Assessment Tool (SWAT) simulation modelling. The data reveal variable soil erosion trends that range between 103 and 830 t km-2 a-1. The low values occur in the western part of the basin that are associated with low sediment yield, while the high values appear in the dominant sediment export part of the basin along the main stream of the Yellow River in the east. Generally, soil and sediment accumulation is characterized by high 10Be concentration in the western part and the northwest of Ngöring Lake. The style of landform development by the erosion/accumulation processes is closely linked to the distribution and degradation extent of the permafrost in the study region. Soil surface erosion increases with more permafrost degradation from the western to the eastern part of the basin, and surface soil particles are dominantly removed from the surface rather than deeper layers.

Assessment of groundwater quality and 222Rn distribution in the Xuzhou region, China.

Evaluation of groundwater quality represents significant input for the development and utilization of water resources. Increasing exploitation of groundwater and man-made pollution has seriously affected the groundwater quality of the North China Plain, such as in the Xuzhou region which is the target of this investigation. The assessment of the groundwater quality and sources in the region was based on analyses of water chemistry and 222Rn activity in samples collected from wells penetrating unconfined and confined aquifers. The results indicate that most of the untreated groundwater in the region is not suitable for the long-term drinking based on permissible limits of the Chinese Environmental Agency and the World Health Organization. However, the groundwater can be used as healthy source of drinking water when they can pass the biological test and softening water treatment. Most of the groundwater is suitable for irrigation. Excessive amounts of SO42- and NO3- are attributed to mainly influence of wastewater, irrigation, and dissolution of sulfate minerals in local coal strata. The major source of the groundwater is meteoric recharge with addition from irrigation and wastewater discharges. Variability of the water quality seems to be also reflecting the type of aquifers where the highest concentration of HCO3- occurs in water of the carbonate fractured aquifer, while the highest Cl- concentration in the unconfined aquifer. Source of 222Rn activity is mainly related to the rock-water interaction with possible addition from the agricultural fertilizers. Protection of groundwater is vital to maintain sustainable drinking quality through reducing infiltration of irrigation water and wastewater.

Evaluation of groundwater discharge into surface water by using Radon-222 in the Source Area of the Yellow River, Qinghai-Tibet Plateau.

Understanding hydrological processes in the Source Area of the Yellow River (SAYR), Qinghai-Tibet Plateau, is vital for protection and management of groundwater and surface water resources in the region. In situ water measurements of exchange rates between surface water and groundwater are, however, hard to conduct because of the harsh natural conditions of the SAYR. We here present an indirect method using in situ 222Rn measurements to estimate groundwater discharge into rivers and lakes in the SAYR. 222Rn was measured in rivers, lakes, groundwater and springs during three sampling periods (2014-2016), and the results indicate large variability in the concentration of the isotope. The data also indicate decreasing 222Rn trends in groundwater in the cold season (the Feb-2015 sampling period) which may be linked to frequency of capturing 222Rn in the frozen ground caused by geocryogenic processes. In addition, permafrost spatial extent and freeze-thaw processes have strongly affected the hydrological conditions in the region.

Iodine isotopes (129I and 127I) in the hydrosphere of Qinghai-Tibet region and South China Sea.

The radioactive isotope 129I, with a half-life of 1.57 × 107 years, is widely used as a tracer to assess nuclear safety, to track environmental and geological events and to figure out the details of the stable iodine geochemical cycle. This work investigated the 129I and 127I distribution in water samples collected from the terrestrial (rivers, lakes and springs) and marine water systems (estuary and sea) in China. The measured 129I concentrations of (1-51) × 106 atoms/L and 129I/127I ratios of (0.03-21) × 10-10 shows the variability of 129I level in the water systems. The local permafrost and seasonal frozen environment play a key role in groundwater recharge in the Qinghai-Tibet region, which is reflected in the 129I distribution in surface water. The depth distribution of 129I in the water column of the South China Sea reflects the effluence of different currents. The results also indicate that the hydrosphere of China contains one to three orders of magnitude less 129I compared to those reported in Europe. Despite the large distance, the European nuclear fuel reprocessing facilities represent the major source of 129I in the hydrosphere of China through atmospheric transport. The contribution of the Fukushima nuclear accident to 129I levels in the hydrosphere of China was negligible.

Detecting the leakage source of a reservoir using isotopes.

A good monitoring method is vital for understanding the sources of a water reservoir leakage and planning for effective restoring. Here we present a combination of several tracers (222Rn, oxygen and hydrogen isotopes, anions and temperature) for identification of water leakage sources in the Pushihe pumped storage power station which is in the Liaoning province, China. The results show an average 222Rn activity of 6843 Bq/m3 in the leakage water, 3034 Bq/m3 in the reservoir water, and 41,759 Bq/m3 in the groundwater. Considering that 222Rn activity in surface water is typically less than 5000 Bq/m3, the low level average 222Rn activity in the leakage water suggests the reservoir water as the main source of water. Results of the oxygen and hydrogen isotopes show comparable ranges and values in the reservoir and the leakage water samples. However, important contribution of the groundwater (up to 36%) was present in some samples from the bottom and upper parts of the underground powerhouse, while the leakage water from some other parts indicate the reservoir water as the dominant source. The isotopic finding suggests that the reservoir water is the main source of the leakage water which is confirmed by the analysis of anions (nitrate, sulfate, and chloride) in the water samples. The combination of these tracer methods for studying dam water leakage improves the accuracy of identifying the source of leaks and provide a scientific reference for engineering solutions to ensure the dam safety.

Water Circulation and Marine Environment in the Antarctic Traced by Speciation of 129I and 127I.

Emissions of anthropogenic 129I from human nuclear activities are now detected in the surface water of the Antarctic seas. Surface seawater samples from the Drake Passage, Bellingshausen, Amundsen, and Ross Seas were analyzed for total 129I and 127I, as well as for iodide and iodate of these two isotopes. The variability of 127I and 129I concentrations and their species (127I-/127IO3-, 129I-/129IO3-) suggest limited environmental impact where ((1.15-3.15) × 106 atoms/L for 129I concentration and (0.61-1.98) × 10-11 for 129I/127I atomic ratios are the lowest ones compared to the other oceans. The iodine distribution patterns provide useful information on surface water transport and mixing that are vital for better understanding of the Southern Oceans effects on the global climate change. The results indicate multiple spatial interactions between the Antarctic Circumpolar Current (ACC) and Antarctic Peninsula Coastal Current (APCC). These interactions happen in restricted circulation pathways that may partly relate to glacial melting and icebergs transport. Biological activity during the warm season should be one of the key factors controlling the reduction of iodate in the coastal water in the Antarctic.

Multiradionuclide evidence for the solar origin of the cosmic-ray events of ᴀᴠ774/5 and 993/4.

The origin of two large peaks in the atmospheric radiocarbon ((14)C) concentration at AD 774/5 and 993/4 is still debated. There is consensus, however, that these features can only be explained by an increase in the atmospheric (14)C production rate due to an extraterrestrial event. Here we provide evidence that these peaks were most likely produced by extreme solar events, based on several new annually resolved (10)Be measurements from both Arctic and Antarctic ice cores. Using ice core (36)Cl data in pair with (10)Be, we further show that these solar events were characterized by a very hard energy spectrum with high fluxes of solar protons with energy above 100 MeV. These results imply that the larger of the two events (AD 774/5) was at least five times stronger than any instrumentally recorded solar event. Our findings highlight the importance of studying the possibility of severe solar energetic particle events.