In the aftermath of the end‐Permian mass extinction, Early Triassic sediments record some of the largest Phanerozoic carbon isotopic excursions. Among them, a global Smithian‐negative carbonate ...carbon isotope excursion has been identified, followed by an abrupt increase across the Smithian–Spathian boundary (SSB; ~250.8 Myr ago). This chemostratigraphic evolution is associated with palaeontological evidence that indicate a major collapse of terrestrial and marine ecosystems during the Late Smithian. It is commonly assumed that Smithian and Spathian isotopic variations are intimately linked to major perturbations in the exogenic carbon reservoir. We present paired carbon isotopes measurements from the Thaynes Group (Utah, USA) to evaluate the extent to which the Early Triassic isotopic perturbations reflect changes in the exogenic carbon cycle. The δ13Ccarb variations obtained here reproduce the known Smithian δ13Ccarb‐negative excursion. However, the δ13C signal of the bulk organic matter is invariant across the SSB and variations in the δ34S signal of sedimentary sulphides are interpreted here to reflect the intensity of sediment remobilization. We argue that Middle to Late Smithian δ13Ccarb signal in the shallow marine environments of the Thaynes Group does not reflect secular evolution of the exogenic carbon cycle but rather physicochemical conditions at the sediment–water interface leading to authigenic carbonate formation during early diagenetic processes.
The Early Triassic is generally portrayed as a time of various, high ecological stresses leading to a delayed biotic recovery after the devastating end-Permian mass extinction. This interval is ...notably characterized by repeated biotic crises (e.g., during the late Smithian), large-scale fluctuations of the global carbon, nitrogen and sulfur cycles as well as harsh marine conditions including a combination of ocean acidification, anoxia, extreme seawater temperatures and shifting productivity. Observations from different paleolatitudes suggest that sulfidic (H2S-rich) conditions may have developed widely during the Early Triassic, possibly reaching up to ultra-shallow environments in some places. However, the existence and the spatio-temporal extent of such redox swings remain poorly constrained. In order to explore Early Triassic paleoceanographic redox changes and their potential influences on the biotic recovery, we analyzed multiple sulfur isotopes (32S, 33S, 34S, and 36S) of sedimentary pyrite and carbonate associated sulfate (δ34SCAS) from the Mineral Mountains section, Utah. Sediments from this section were mainly deposited in shallow waters and span the Smithian and lower Spathian. We report a 68‰ range of variations in δ34Spy associated with Δ33Spy varying from −0.01‰ to +0.12‰, whereas the δ34SCAS varies between +19.5‰ and + 34.8‰. We interpret the observed signal of multiple sulfur isotopes as reflecting the operation of pore-water synsedimentary microbial sulfate reduction in open system with respect to sulfates before the late Smithian, evolving to a closed system, sulfate limited, Rayleigh-type distillation across the Smithian/Spathian boundary (SSB) and immediately after the SSB. We argue that this marked change is driven by the effectiveness of the connection between the sedimentary pore waters and the overlying water column, which is, in this case, controlled by the local sedimentological conditions such as the bioturbation intensity and the sedimentation rate. Therefore, our results suggest that changes in the sulfur cycle before and across the SSB at Mineral Mountains is probably a local consequence of the loss of the mixed sedimentary layer during the late Smithian extinction event, as opposed to reflecting the development of a lethal anoxic ocean at the global scale.
Mediterranean areas are characterized by complex hydrogeological systems, where water resources are faced with several issues such as salinity and pollution. Fifty-one water samples were gathered ...from the Bou-areg coastal and the Gareb aquifers to evaluate the source of water salinity and to reveal the processes of the different sources of pollution using a variety of chemical and isotopic indicators (δ2H–H2O, δ18O–H2O, δ34S–SO4, and δ18O–SO4). The results of the hydrochemical analysis of water samples show that the order of dominated elements is Cl− > HCO3− > SO42- > NO3− and Na+ > Ca2+ > Mg2+ > K+ and evidenced extremely high salinity levels (EC up to 22000 μS/cm). All samples exceeded the WHO drinking water guidelines, making them unfit for human consumption. Ion ratio diagrams, isotopic results, and graphical comparing indicate that the mineralization of groundwater in the area, is controlled by carbonate dissolution, evaporite dissolution, ion exchange, and sewage invasion. The return of irrigation water plays a significant role as well in the groundwater recharge and its mineralization by fertilizers mainly. Evaporites (Gypsum), sewage, and fertilizers constitute the main sources of sulfates in the investigated water resources. These scientific results will be an added value for decision-makers to more improve the sustainable management of groundwater in water-stressed regions. The use of chemical and isotopic tracers once again shows their relevance in such zones where systematic monitoring is lacking.
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•Groundwater salinization and contamination sources were investigated.•Water chemistry and stable isotopes data were combined.•Salinity is due to mineral dissolution, ion exchange, and sewage invasion.•Evaporites, sewage, and fertilizers were the main sulfate sources.
Groundwater resources are the main supply of freshwater for human activities. Nevertheless, during the last 50 years, groundwater has become very susceptible to chemical pollution due to human ...activities. The groundwater vulnerability assessment constitutes a worldwide recognized tool for water management and protection. In this study, the GIS-based DRASTIC and pollution risk models have been used to assess the intrinsic vulnerability and risk to pollution of the Gareb and Bou-Areg aquifers, the main irrigated areas in the northeast of Morocco, by analyzing available hydrogeological attributes. The seven hydrogeologic factors used to assess vulnerability were depth to aquifer, net recharge, aquifer media, soil media, topography, impact of the vadose zone, and hydraulic conductivity, while an eighth parameter has been added to assess the pollution risk which is the land use. The resultant vulnerability map reveals that about 0.06% of the study area is in low vulnerability zones, 83.68% is moderately vulnerable, and 16.26% is highly vulnerable to groundwater pollution. The results also reveal that groundwater is highly vulnerable in the Gareb aquifer and the coastal zone, where the water table is very low, the slope is gentle, and the geological formations are permeable. In addition, moderate to low vulnerability is found towards the west of the study area where the groundwater is located in deep aquifers. The groundwater pollution risk map is obtained by overlaying the land use with the DRASTIC vulnerability. The central and western parts of Bou-Areg as well as the south of Gareb are dominated by high and very high pollution risk classes, and present 43.07% of the study area, which is strongly influenced by urban areas, agricultural activities, and shallow groundwater systems. 30.11% of the surface is moderately vulnerable, mainly in areas where human activity is not widely observed, while the very low and low pollution risk classes represent a total of 26.82% of the total area. The mapping models were validated using nitrate concentration and electrical conductivity data in groundwater as an indicator of pollution. A positive correlation was observed when validating these models. The resultant groundwater vulnerability and pollution risk maps might provide an early warning to policy maker and manager to manage and avoid further stress on this invaluable resource.
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Soil salinization poses a significant challenge to the sustainable advancement of agriculture on a global scale. This environmental issue not only hampers plant growth and soil fertility but also ...hinders the advancement of the national economy due to restrictions on plant development. The utilization of organic and/or inorganic amendments has demonstrated the ability to mitigate the detrimental impacts of salt stress on plant life. At the outset, this review, in addition to summarizing current knowledge about soil amendments for saline-sodic soils, also aims to identify knowledge gaps requiring further research. The organic or inorganic amendments modify soil conditions and impact plant development. For instance, organic amendments have the potential to improve the structure of the soil, augment its capacity to retain water, and stimulate microbial activity. As this occurs, salts gradually leach through the porous structure of the soil. Conversely, inorganic amendments, such as gypsum and phosphogypsum, displace sodium from soil-negative sorption sites reducing the salinity, they also increase base saturation, altogether positively impacting plant growth conditions. This review emphasizes that, under adequate rates, the combination of organic and inorganic amendment has a high potential to enhance the poor physicochemical properties of saline-sodic soils, thereby reducing their salinity. Consequently, an in-depth examination of the mineral composition, texture, and chemical composition of the soil is required to choose the most effective amendment to implement. Future research necessitates a thorough investigation of techno-economic and life cycle assessment, with active involvement from stakeholders, to enhance the decision-making process of the amendments in specific localities.
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•Biochar and compost have been extensively researched as organic amendments.•Gypsum and phosphogypsum show great potential as inorganic amendments.•Macroporous leaching and Na+ exchange with Ca2+ are the mechanisms responsible for saline soil desalination.•High salinity may be decreased while adhering to a circular economy strategy by valorizing waste as an amendment.
Neogene plains around the Mediterranean basin are characterized by considerable groundwater salinization. Some studies have misidentified seawater intrusion as the main source of salinity. Across ...northern Morocco, we gathered δ18OSO4 and δ34SSO4 data from coastal and inland aquifers, Messinian marls, and volcanic products. Differences in the isotopic composition between Messinian marls and some groundwater in all aquifer samples indicate that salinization in groundwater is a consequence of dissolution of Messinian evaporite deposits; nevertheless, modern agriculture and wastewater strongly influence depletion in levels of δ34SSO4. Our novel approach enables effective investigation of processes governing salinity in Neogene basins to support more informed water resource management and governance.
The geological and hydrogeological approach of the structure of the basin OuladBouSbaâ led to the definition of the geometry of the main aquifers. In general, the profiles show the complexity of the ...geological configuration. The filling of the depression of OuladBouSbaâ is from the Eo-Cretacian. At this level, the aquifer is recharged by direct water infiltration. The quaternary, Eocene, and Cenomanian-Turonian formations constitute the main aquifers. Horizontal as well as vertical heterogeneity lead to a higher diversification of aquifer characteristics. To define the origins and understand the groundwater flows in this complex zone, we used a multi-tracer approach with the analysis of major elements and the isotopes of δ2H and δ18O. The chemical composition is mainly governed by the interaction with the rock with low electrical conductivity except in areas around domestic landfills. Geochemical results analyzing groundwater in the Piper diagram show two distinct chemical facies: the sulfated calcium and magnesium, and the hyper-chloride calcium. The levels of δ18O range from −7.60 to −4.25 while those of δ2H vary between −53.07 and −27.03. Analyses of signature isotopes differentiate two groups. The first contains high levels of heavy isotopes (highest levels of δ2H and δ18O) having therefore been submitted to evaporation. The second with lower levels of δ2H and δ18O did not undergo evaporation. The first one belongs to the unconfined free aquifer while the second corresponds to the captive aquifer.
A 64-year-old male with no underlying disease presented with the development of multiple skin nodules, loss of sensation in the extremities, hoarseness, macroglossia, and pain in the oral cavity. ...Direct laryngoscopy showed nodules involving the oral cavity, oropharynx, supraglottic region, and vocal cords. Biopsy from skin nodules showed amyloid deposits staining with Congo red. Immunohistochemical staining was used for AA protein and was positive. Biopsy from the oral floor was also positive for amyloid. Oto-Rhino-Laryngology (ORL) involvement has been reported in approximately 40 percent of AL amyloidosis patients, but does not appear to be frequent in AA amyloidosis. Cutaneous manifestations in AA amyloidosis are rare, although cases with lesions presenting as purpura are reported occasionally; we are not aware of other cases of ORL nodular involvement in systemic AA.
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