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The surface water - groundwater interactions in a small anthropically affected mountain watershed (Salsipuedes River) in the Sierras Pampeanas (central Argentina) were analyzed and quantified by means of 222Rn mass balance modeling, and its implications in hydrochemistry and water quality were examined. Surface waters, springs and groundwater were sampled during the 2021–2022 hydrological year, and the major dissolved composition was determined. The studied waters are alkaline, showing an evolution from medium mineralized (1.5 < ∑+ < 3 meq L−1) to mineralized type (3 < ∑+ < 6 meq L−1) downstream. In general, waters are of the bicarbonate - calcium type with no spatial or seasonal variations. This composition is mainly controlled by silicates weathering. 222Rn modeling indicates that near the headwaters the Salsipuedes River recharges the aquifer, losing 1.2% and 2.4% of its discharge during the dry and wet seasons, respectively. Downstream, the system changes its hydrological behavior and the river acts as a gaining stream; i.e, it receives groundwater inflow. The magnitude of this inflow varies seasonally, being greater in the wet season (1.5–2.2% of the total flow) than in the dry season (less than 0.25%) due to a rise in the water table level as a result of direct recharge of the phreatic aquifer. Anthropic influence is noticeable in nitrate and chloride concentrations, which are derived from domestic wastes and septic tanks. The highest concentrations of these ions in surface waters are found in the urbanized area, where the river stretch corresponds to a gaining stream, reflecting that even small amounts of groundwater inputs can alter the chemical composition of streams. A temporal analysis also showed a variable response of the system to the increasing anthropic pressure and climatic events such as ENSO, which affect not only water availability but also its quality, highlighting the vulnerability of small mountain watersheds. • Hydrochemistry and water quality were examined in an urbanized mountain watershed. • Surface water - groundwater interactions were quantified using a222Rn mass balance. • Even slight groundwater inputs alter the chemical composition of the stream. • A temporal analysis showed a variable response to the increasing anthropic pressure. • Climatic events like ENSO affect water availability and quality. [ABSTRACT FROM AUTHOR]

Abstract Subtropical laterites are partially found in the Argentinian province of Misiones, covering the Jurassic-Cretaceous Serra Geral flood basalts (known as Posadas Formation in Argentina). Two hypotheses have been proposed to explain the origin of these laterites. The autochthonous theory attributes the origin of these deposits to the chemical weathering of the underlying tholeiitic basalts. However, during the last decade, an allochthonous "tropical loess" model was proposed. Several mineralogical/geochemical characteristics of a lateritic profile (~2 m thick, 26°9′58″S–54°35′3″W) are analyzed in this paper in order to constrain the nature of weathering processes in this region and the provenance of the lateritic layer. The basaltic bedrock at the sampling site exhibits intergranular texture and is mainly composed of clinopyroxene, plagioclase and opaque minerals (likely titanomagnetite and ilmenite). Altered glass and apatite were also identified in lower proportions. The X-ray diffraction of the clay-size fraction shows prevailing kaolinite and hematite in the most altered samples, complemented by amorphous Fe-Al (hydr)oxides. Serra Geral basalts-normalized spidergrams and mass balance calculations confirmed almost complete losses of all major oxides (i.e., ~50 g of material was removed by weathering from each 100 g of the original basalt) and depletions of some trace elements (e.g., Sc, V, Sr, Cr, Ni, Rb and U) in the uppermost and intermediate layers of the lateritic profile, reflecting the weathering of feldspars, clinopyroxenes, volcanic glass and apatite. In contrast, some elements are enriched in the topmost and intermediate layers, due to intrinsic immobility during weathering (e.g., Zr, Hf, Ta, Th) or adsorption onto clays (e.g., Cs). Rare earth elements (REEs) are depleted in the top layers and enriched in the middle section of the profile. The preferential leaching of REEs from the uppermost levels during weathering and its accumulation in the middle section can be caused by a pH increase in this level, the decomposition of organic matter and the consequent precipitation of REEs which exhibit an affinity to form aqueous organic complexes, or the presence of Fe and Mn (hydr)oxides in the intermediate level. Weathering intensity was appraised by means of different alteration indices, which showed the extreme leaching endured by the basaltic bedrock. The index of lateritization (IOL), which ranges between 35 and 55, and the accompanying SAF ternary plot (SiO 2 -Al 2 O 3 -Fe 2 O 3), indicate an increasing weathering trend towards the profiles' top, reflecting the modest loss of SiO 2 (relative to Al 2 O 3 and Fe 2 O 3) during kaolinitization. The geochemical approach used to constrain the origin of the lateritic mantle that partially covers Misiones province, clearly relates the analyzed laterites to the underlying tholeiitic basalts, supporting the autochthonous origin theory. Highlights • A geochemical mass balance in a subtropical basalt-derived profile was calculated. • Weathering removes >50% of rock volume with almost total losses of alkalis • REEs are enriched in the intermediate level. • The chemical weathering stage of kaolinitization was recognized in the profile. • Laterites derive from the underlying basalt, supporting an autochthonous origin. [ABSTRACT FROM AUTHOR]

Abstract: Laguna Mar Chiquita, a closed, shallow, hypersaline lake in central Argentina (∼30–31°S, 62–63°W), is a sensitive marker of high- and low-frequency changes in regional hydrology and, therefore, of climatic changes at middle latitudes in southeastern South America. Its drainage basin and neighboring areas, including the Sierras Pampeanas de Córdoba, and Sierra del Aconquija (27–33°S, 62–66°W), are under the influence of diverse climate drivers that determine a complex behavior in rainfall and runoff dynamics. Statistical (Mann–Kendall and seasonal Kendall trend tests) and spectral analyses (Fourier and wavelet transform) of the available data show that: (a) there is significant evidence that rainfall has increased in the region since the 2nd half of the 20th century; (b) concurrently, runoff has also increased, particularly in the northern tributaries (north of 31°S) of Mar Chiquita; (c) northern rainfall and discharge records mostly exhibit an apparent near-decadal (also near-bidecadal in runoff) climatic signature; and d) the ENSO influence on rainfall appears faint but discernible in the southern (south of ∼31°S) portion. [Copyright &y& Elsevier]

We report our first experience of treating an immunocompetent adult patient with acute respiratory distress syndrome (ARDS) due to type 1 herpes simplex (HSV1) pneumonitis, using extracorporeal membrane oxygenation (ECMO). Similar cases reported in literature are reviewed as well. The therapeutic options for this particular complication are discussed. Pneumonia caused by HSV1 is a rare finding in immunocompetent individuals; it occurs more often in immunosuppressed and ventilated patients. It is a severe illness; therefore, early diagnosis and initiation of treatment are imperative. Diagnosis is based on cytologic and histologic findings, viral cultures, or serologic methods. This condition can be reversible; however, often, it can progress into refractory ARDS with limited therapeutic options available. We demonstrate the causative role of HSV1 in refractory ARDS of a previously healthy 18-year-old man who presented to the intensive care unit with acute respiratory distress after a week of flulike syndrome. Due to severe hypoxemia and hypercarbia, the patient required mechanical ventilation and later emergent blood oxygenation with extracorporeal support. For the first time in this condition, we used venovenous ECMO management, to rest the lung, sustain blood oxygenation and end-organ oxygen delivery, and promote potential lung recovery. During ECMO and after our etiologic diagnosis, specific therapy was introduced. After viral negativization, corticosteroid therapy (Meduri protocol) was initiated. Extracorporeal membrane oxygenation allowed us to initiate therapy while maintaining end-organ oxygenation and support the patient until lung recovery. After 18 days of ECMO, our patient recovered completely. Near-normal lung structures and functions were documented on a chest x-ray/computed tomography, thoracic ultrasonography, and pulmonary functional tests at hospital discharge and at a 1-year follow-up. Data suggest that severe pulmonary involvement in HVS1 infection associated with septicemia/shock is a rare but often fatal in immunocompetent adult as well. We suggest that ECMO might be the selected treatment for severe refractory ARDS in this clinical scenario. It seems to be an effective and useful ultimate therapeutic strategy for preventing death and furthermore permitting near-full pulmonary function recovery. [ABSTRACT FROM AUTHOR]

The Paraná River basin is one of the largest hydrological systems in South America. The present study focuses on the mineralogical and chemical composition of the suspended sediments exported by the Paraná River to the Atlantic Ocean, with the aim of analyzing their provenance, the chemical weathering signature and the likelihood of sedimentary recycling. The particulate matter of the Middle Paraná River and its main tributaries (i.e., the Paraguay and the Upper Paraná rivers) is mostly composed of quartz, plagioclase, K-feldspar, and clays, such as illite and kaolinite. Different geochemical approaches indicate that the suspended sediments transported by the Paraná River preserve the chemical signature of its sources and its composition is not significantly modified during transport. These sediments are mainly supplied by acidic arc sources located in the Andean headwaters of the Bermejo and Pilcomayo rivers (and transported by the Paraguay River); and by tholeiitic basalts outcropping in the headwaters of the Upper Paraná River. The incomplete mixing of both main tributaries produces a transverse geochemical asymmetry in the particulate material of the Middle Paraná River, which was detected ~ 32 km downflow the confluence. The suspended load transported by the Paraguay River (which includes the contributions from the Bermejo and Pilcomayo rivers) indicates incipiently to moderately weathering, whereas the particulate matter exported by the Upper Paraná River reveals a higher degree of chemical alteration. This is the result of the different lithology and climatic regimes that prevail in the headwaters of both tributaries. The weathering signature of the Middle Paraná River's suspended load resembles that of the Paraguay River, which in turns supplies most of the particulate matter through the Bermejo River. This work also shows that the suspended load exported by the Paraná River basin has a mixed origin, where the chemical signatures from young materials derived from undifferentiated volcanic rocks, and from recycled materials affected by intracrustal differentiation can be distinguished. [ABSTRACT FROM AUTHOR]

Abstract: Stream waters draining granitic terrains from the highest part (850 to 2200m a.s.l.) of Sierras Pampeanas (Córdoba, Argentina, ∼32°S, ∼65°W) were sampled in order to define sources and distribution of dissolved rare earth elements (REE), and to describe the geochemical processes that govern their mobility. The contribution of the regional granite to the dissolved REE pool in stream water is limited due to the physical conditions predominating in the area (i.e., steep slopes and semiarid climate). Therefore, precipitation is considered a seasonally significant source controlling REE concentration in stream water. Dissolved REE concentrations are inversely correlated with monthly precipitation and rainfall frequency. During the rainy season (i.e., the austral summer) REE concentrations in stream water are lower than during the dry season (i.e., austral winter). Such low concentrations reflect the balance between the REE input from precipitation and their removal by adsorption. In contrast, during the dry season, the longer residence time of water within fractures and colluvium determines an increased REE concentration in the base flow. Lower pH values also contribute to raise REE concentration through desorption from mineral surfaces. [Copyright &y& Elsevier]

Major ion and stable isotopic compositions of a saline lake linked to the SW margin of Laguna Mar Chiquita, Argentina (30°55′ S, 62°51′ W) were studied. The groundwater inflow into the Laguna del Plata was quantified for the first time using a stable isotope mass balance. Shallow groundwater inflow is expected in the Laguna Mar Chiquita system since it represents the terminal water body of the catchment. Lake waters are alkaline and exhibit total dissolved solids contents >30 g L−1. The cationic relative abundance is Na+ ≫ Mg2+ > Ca2+ > K+, whereas that of major anions is Cl− ≫ SO 4 2− > HCO 3 − + CO 3 2−, which are mainly present as free aqueous ions. PHREEQC simulations indicate that lake waters are oversaturated in Ca2+ and Mg2+ carbonates (calcite, huntite, aragonite, dolomite, magnesite), which are expected to be the first minerals to precipitate due to evaporation processes. The main tributary of the lake (Suquía River) and the phreatic aquifer exhibit δ18O and δ2H values consistent with the isotopic signature of rainfall, whereas lake waters define an evaporation line (δ2H (‰) = 5.4 δ18O (‰) + 1.8). The confined aquifer shows a more depleted isotopic composition, reflecting an allochthonous recharge from the mountain ranges (Sierras Pampeanas). The δ18O mass balance indicates a groundwater inflow of ~4.7 m year−1 to the lake, confirming the hydrological conceptual model for the catchment. However, the groundwater contributions do not affect the chemical composition of lake waters, which mainly results from the evaporation processes as shown by the Spencer diagram. • Hydrochemistry and stable isotopic compositions of a small saline lake were studied. • Surface water-groundwater interaction was quantified using a stable isotope data. • The calculated groundwater inflow to the lake using δ18O mass balance is ~4.7 m y−1. • Chemical composition of lake waters mainly results from evaporation processes. [ABSTRACT FROM AUTHOR]