Signature Of Water Research Articles

Composição do fitoplâncton da Baía do Araçá e Canal de São Sebastião, São Paulo, Brasil

Abstract Despite its small area, Araçá Bay (AB) holds cultural, historical, and economic value and displays great benthic biodiversity. Thus, it is crucial to monitor its environmental health, including knowing the main groups of phytoplankton and their temporal variability. The shallow waters of Araçá Bay are continuously modified by the complex hydrography of the adjacent São Sebastião channel (SSC), challenging standard experimental designs for phytoplankton collection. Here we report changes in phytoplankton composition at intervals of five to six weeks from September 2013 to August 2014 in both Araçá Bay and SSC. Samples were collected twice daily for three consecutive days to increase taxonomic resolution. Our goal was to provide an inventory of species occurrences to aid future public policies and environmental management of the area. Analyses revealed high species richness and 166 different phytoplankton taxa. Diatoms and dinoflagellates were always numerically dominant, but taxa occurrence changed markedly. Diatoms of the genera Pseudo-nitzschia were abundant during spring and summer concurrently to signatures of South Atlantic Central Water in the SSC, while Thalassiosira occurred when waters displayed relatively lower salinity. The inventory demonstrated several potentially harmful species of microalgae and cyanobacteria, strongly suggesting investments in monitoring programs in this area that currently experience an increase in population.

An overview of the design and development of lunar rover (Chandrayaan-2) for space applications

The paper gives an brief overview of the design and development of lunar rover (Chandrayaan-2) for space applications. The Moon has always been the center of attention for mankind, more than any other heavenly body in More than any other heavenly body in the night sky, the Moon has long been the focus of human interest. The Moon has always presented mankind with a challenge to learn more about it and to marvel at its wonders because it bears the early history of the solar system. We can uncover the early evolution of the solar system and that of planet Earth by having a better understanding of the Moon. With the 2008 launch of the Chandrayaan-1 orbiter mission to the Moon, India's planetary exploration program was launched by the Indian Space Research Organization (ISRO). India launched Chandrayaan-2, its second lunar exploration mission, nearly twelve years after its first lunar exploration mission. Chandrayaan-2, India's most technologically advanced aircraft, is on an unprecedented mission. The South Polar Region of the Moon will be studied by India's second lunar trip, which will draw on nearly ten years of scientific and Engineering advancement. A major accomplishment for both India and humanity, Chandrayaan-2 was the first mission ever to be sent to the southern pole of the moon. Both the high cold and constant darkness in this area make it extremely unsafe and have a bad impact on missions. India faced a tremendously difficult assignment as a result, and the entire world was interested in its outcome. Chandrayaan-1's eleven remote-sensing scientific instruments from ISRO, NASA, and ESA have made important discoveries, such as the identification of a water signature, the discovery of spinel minerals, lunar lava tubes, signs of recent volcanism, impact-triggered boulder movements, and the detection of sputtered atomic oxygen and backscattered helium on the lunar surface. Three components made up Chadrayaan-2: an orbiter, a lander, and a rover. 2019 saw the launch of this mission. During this mission, the Orbiter was successful in reaching the moon's orbit, but communication with the Lander was lost, which caused Lander to perform poorly and crash with the Pragyan rover and other scientific equipment. The work given here is a mini-project that is taken up as a part of the curriculum completed by electronics and communication engineering students in the second year of the electronics & communication engineering department at Dayananda Sagar College of Engineering in Bangalore.

Geochemistry and palaeo-hydrogeology of the weathered zone in the Opalinus Clay

The effects of weathering and decompaction on the Opalinus Clay in northern Switzerland were studied on the basis of a 146 m long drillcore profile. Below 6 m of Quaternary sediments, the rock down to 16 m depth is affected by partial or complete dissolution of siderite, calcite, pyrite and organic matter, with goethite as the only identified product. The reduction level of Fe (Fe2+/Fetot) in the rock increases with depth from <20% to >80% in unweathered rock below 24 m. Porosity reaches 0.39 in the shallowest samples before dropping to normal values of around 0.13 below 30 m. Pore-water composition obtained by rock squeezing evolves with depth from fresh water of the Ca-SO4-HCO3 type to a 10–12 g/L Na-SO4-Cl type in unweathered rock below 40 m. Ground-water samples taken in the weathered zone indicate reducing conditions at present and therefore reflect a remaining redox buffering capacity even in the strongly oxidised rock. The interpretation of the rock properties, in conjunction with the chemical and isotopic signatures of ground and pore waters, suggests that substantial weathering occurred primarily during stages with a lower ground-water table in the Pleistocene, providing access to oxygen via gas diffusion across the partially unsaturated zone. Three evolutionary stages can be distinguished: 1) Long-term pyrite oxidation during Pleistocene surface exposure under dry climate and diffusive transport of SO42− into the formation. This explains the higher SO42− pore-water concentrations even in the unweathered rock at depth when compared to regional data from deep boreholes. 2) Build-up of the curved Cl− and water-isotope diffusion profiles since ∼50–60 ka with a depth penetration of 40–80 m. 3) Holocene rise of the water table, leading to self sealing of fractures and the establishment of a diffusive regime in the weathered zone. Under saturated conditions, the depth penetration of rock oxidation is quite limited, which illustrates the substantial buffering capacity of the Opalinus Clay against external geochemical disturbances.

A TWELVE-HUNDRED-YEAR STABLE OXYGEN ISOTOPE CHRONOLOGY CONSTRUCTED USING SUBFOSSIL WOOD FROM SCHWARZENSEE LAKE, AUSTRIAN ALPS

This study presents a new stable oxygen isotope chronology, covering the years 800-2000 AD, constructed using modern and subfossil wood derived from trees growing around Lake Schwarzensee in Austria. The climatic signal imparted in the chronology is conditioned mainly by the direct influence of environmental factors on the isotopic signature of source water, which in turn is regulated by evaporation and condensation mechanisms. The second driver of stable oxygen isotope is the physiological response of trees to changing weather conditions, most importantly rates of transpiration. The chronology of stable oxygen isotopes corresponds well with both temperature (r = 0.485; p < 0.05) and total precipitation (r = -0.548; p < 0.05) during the growing season (May-September). This mixed signal results from the fact that the relationship between the content of stable oxygen isotopes and the influence of climate is multifactorial. Moreover, the effect exerted by meteorological conditions on stable isotope ratio changes over time. This is most probably linked to interannual variation in climatic and environmental factors.

Seismic Signature of Rain and Wind Inferred From Seismic Data

AbstractSeismic stations are increasingly used to monitor river activity and to quantify sediment transport during flood events. In tropical regions, cyclone‐induced floods are often associated with heavy rain and strong wind episodes, generating complex seismic records involving the simultaneous signature of water, sediment, rainfall and wind. Hence, seismic characterization of rain and wind is then required to better decipher each process and improve our understanding of the river seismic signature. In this study, we investigate experimentally the seismic response of rain and wind using data recorded by geophones deployed in various soil types and at different burial depth (BD), co‐located with various meteorological instruments. Our results show that the power spectral density (PSD) of the seismic noise intensifies at a frequency between 60 and 500 Hz for rain and 5 and 500 Hz for wind, in the presence of rain precipitation as low as 0.025 mm/min and/or wind speed ≥3 m/s. PSD analysis indicates that the seismic signal associated with rain decreases with the BD with a value of ∼2–5 dB in a depth difference of 10 cm. We also observe that each soil type has its own seismic signature. The 4‐min root mean square correlation between the seismic signal amplitude and the rain precipitation suggests that they best correlate with Pearson coefficient &gt;0.90 at BD of 30 cm. The transfer function between the precipitation rate (or kinetic energy) and the seismic signal amplitude shows that the signal recorded by the geophone can be used as a robust proxy for these parameters.

Characterization of seasonal groundwater origin and evolution processes in a geologically heterogeneous catchment using geophysical, isotopic and hydro‐chemical techniques (Lough Gur, Ireland)

AbstractLough Gur is a shallow groundwater fed eutrophic lake situated within a small agricultural catchment containing volcanic and karst rock features in mid‐west Ireland. Seasonally active conduits linking two spring discharge locations from the lake under high flow conditions were revealed using dye tracing and a terrestrial geophysical survey, highlighting the architecture of the conduit flow path from Lough Gur to its discharge spring. A radon survey combined with a lake geophysical survey identified the locations of in‐lake discharge springs and thickness of the lakebed sediments. Falling head hydraulic characterization experiments illustrated the heterogenous nature of lakebed sediments and hydrograph analysis coupled with stable isotopes of water (δ18O and δ2H) revealed significant surface water ‐ groundwater interaction during high flow periods. Significantly, δ18O and δ2H signatures plot above the global meteoric water line and local meteoric water line indicating hydration of silicate minerals and direct isotope exchange of δ18O between water and rock minerals. Groundwater δ18O and δ2H signatures during low flow periods indicate that recharge sources are influenced by enriched surface waters and precipitation while a wider range of signatures during high flow periods indicates a greater variation of sources. D‐excess signatures illustrate rapid rainfall infiltration under high flow conditions, thereby demonstrating the vulnerability of the groundwater, while lake water signatures confirm widespread surface water‐groundwater interaction/mixing. Hydrochemical analyses confirm both silicate weathering and carbonate dissolution as primary geochemical processes with Mg/Ca ratios suggesting greater groundwater residence time during low flow periods. Correlations between δ13CDIC and dissolved organic carbon suggest a seasonal switch in the source of DIC to groundwaters between the oxidation of organic matter in summer and dissolution of carbonate minerals in winter. The SI saturation index for calcite (SIC) illustrates calcium carbonate precipitation along with CO2 evasion to be a perennial processes. Finally, the spatial variation for nitrate isotopic signatures (δ18ONO3‐ and δ15NNO3‐) suggests a number of nitrate sources to groundwaters including soil organic nitrogen, manure and/or domestic effluent with indications of denitrification processes under low flow conditions.

Illuminating isotopic offset between bulk soil water and xylem water under different soil water conditions

The temporal and spatial heterogeneity of soil water content affects the isotopic composition of bulk soil water and xylem water. However, there is a lack of systematic assessment of the impact of soil water conditions on the widely reported bulk soil–xylem water isotopic offset. For this purpose, we measured δ2H and δ18O values of xylem water of the shrub plant Caragana korshinskii and bulk soil water, for two consecutive years at two sites with contrasting water conditions. At Site 1, with moister conditions, xylem water showed a clear isotopic deviation towards more negative values relative to the bulk soil water values in both years (< 20% overlap), with a mean of 10.7‰ for the bulk soil–xylem water line-conditioned offset (Δlc-excess) and −9.1‰ for the soil water line conditioned excess (SW-excess). However, xylem water was strongly matched with immobile water in the dry year. At Site 2, with drier conditions, an isotopic offset occurred in the wet year, with a 20% overlap between xylem water and bulk soil water. Mean Δlc-excess and SW-excess were 13.7‰ and −11.8‰, respectively. Interestingly, the overlap reached 97% in the dry year, with the xylem water falling within the isotope space of bulk soil water. At Site 2, soil water content was positively correlated with Δlc-excess and negatively correlated with SW-excess. These results suggest that the isotopic signatures of xylem water and immobile water tend to overlap, supporting the “two water worlds” hypothesis. The bulk soil–xylem water isotopic offset is likely to be closely associated with the heterogeneity of soil water isotopes driven by soil water content. Our results elucidate changes in the isotopic signals of xylem water and bulk soil water under different water conditions and help better understand how plants take up water in a heterogeneous soil.

Snowmelt Water Use at Transpiration Onset: Phenology, Isotope Tracing, and Tree Water Transit Time

AbstractStudies of tree water source partitioning have primarily focused on the growing season. However, little is yet known about the source of transpiration before, during, and after snowmelt when trees rehydrate and recommence transpiration in the spring. This study investigates tree water use during spring snowmelt following tree's winter stem shrinkage. We document the source of transpiration of three boreal forest tree species—Pinus banksiana, Picea mariana, and Larix laricina—by combining observations of weekly isotopic signatures (δ18O and δ2H) of xylem, soil water, rainfall and snowmelt with measurements of soil moisture dynamics, snow depth and high‐resolution temporal measurements of stem radius changes and sap flow. Our data shows that the onset of stem rehydration and transpiration overlaps with snowmelt for evergreens. During rehydration and transpiration onset, xylem water at the canopy reflected a constant pre‐melt isotopic signature likely showing late fall conditions. As snowmelt infiltrates the soil and recharges the soil matrix, soil water shows a rapid isotopic shift to depleted‐snowmelt water values. While there was an overlap between snowmelt and transpiration timing, xylem and soil water isotopic values did not overlap during transpiration onset. Our data showed 1–2‐week delay in the shift in xylem water from pre‐melt to clear snowmelt‐depleted water signatures in evergreen species. This delay appears to be controlled by tree water transit time that was in the order of 9–18 days. Our study shows that snowmelt is a key source for stem rehydration and transpiration in the boreal forest during spring onset.

Plateau archives of lithosphere dynamics, cryosphere and paleoclimate: The formation of Cretaceous desert basins in east Asia

Southeastern Eurasia is a global window to the Cretaceous paleoclimate and lithosphere coupling. China contains one of the most complete and complex sedimentary records of Mesozoic desert basins on planet Earth. In this study, we perform the spatio-temporal tracking of 96 Cretaceous palaeoclimate indicators during 79 Myr which reveal that the plateau paleoclimate archives from East Asia resulted from an Early to Mid-Cretaceous ocean–atmosphere coupling and a shift to a preponderant role of Late Cretaceous lithosphere dynamics and tectonic forcing on high-altitude depositional systems linked to the subduction margins of the Tethys and Paleo-Pacific realms beneath the Eurasian plate. The crustal response to tectonic processes linked with the spatio-temporal evolution of the Tethyan and Paleo-Pacific margins defined the configuration of major sedimentary basins on this region. The significant increase and decrease in the number of active sedimentary basins that occur during the Cretaceous, from 16 in the Early Cretaceous, to 28 in the Mid-Cretaceous, and a decreasing to 20 sedimentary basins in the Late Cretaceous, is a direct response of lithospheric dynamics associated with the two main subduction zones (Tethys and Pacific domains). A shift in subduction style from an Early Cretaceous Paleo-Pacific Plate slab roll back to a Late Cretaceous flat-slab mode might have triggered regional plateau uplift, blocked intraplate volcanism, thus enhancing the denudation and sediment availability, and created wind corridors that led to the construction and accumulation of extensive Late Cretaceous aeolian sandy deserts (ergs) that covered Mid-Cretaceous plateau salars. At the same time, plateau uplift associated with crustal thickening following terrane assembly in the Tethyan margin triggered altitudinal cryospheric processes in sandy desert systems. Evidence of an active Cretaceous cryosphere in China include Valanginian-Hauterivian glacial debris flows, Early Aptian geochemical signature of melt waters from extensive ice sheets, and Cenomanian–Turonian ice-rafted debris (IRD). These cryospheric indicators suggest an already uplifted plateau in southeastern Eurasia during the Cretaceous, and the marked correlation between cold plateau paleoclimate archives and marine records suggests a strong ocean-atmosphere coupling during Early and Mid-Cretaceous cold snaps. We thus conclude that lithospheric tectonics during Cretaceous played a fundamental role in triggering high-altitude basin desertification and spatio-temporal plateau paleohydrology variability in the Cretaceous of south-eastern Eurasia.

Causes and Factors of Cryogenic Extraction Biases on Isotopes of Xylem Water

AbstractCryogenic vacuum extraction (CVE) has been considered as the standard technique for the analysis of plant water stable isotopes in ecohydrological research. Recent studies reported that CVE can introduce significant bias in stable isotope analyses, yet the causes and influencing factors of the CVE‐induced deuterium offsets remain poorly understood. Here, we performed rehydration experiments on plant samples from two species and three organs with two distinct‐isotopic spiking waters. Centrifugation and high‐pressure mechanical squeezing were used to separate sap water and tissue water for stable isotope analyses. Plant waters extracted by CVE differed significantly from reference waters in δ2H, but not in δ18O. The δ2H bias was linearly correlated to the xylem water content, and this relationship is affected significantly by plant organs/species and the isotopic signature of the spiking water. Moreover, the δ2H bias induced by CVE (−8.52 ± 0.90‰) was significantly greater than the δ2H difference between the tissue and sap waters (−3.33 ± 0.76‰) for apple stems possessing similar water contents. Thus, hydrogen‐exchange between plant organics and water, and isotopic heterogeneity within plants both contribute to the negative δ2H bias, but the former is the dominant cause. The multiple factors governing the CVE‐induced δ2H bias, make it difficult to establish a unified bias correction equation. Our results question the usefulness of cryogenic extraction as a standard for plant water extraction.

A comparative study of plant water extraction methods for isotopic analyses: Scholander-type pressure chamber vs. cryogenic vacuum distillation

Abstract. Recent tracer-based studies using stable isotopes of hydrogen and oxygen showed that different methods for extracting water from plant tissues can return different isotopic compositions due to the presence of organic compounds and because they extract different plant water domains. One of the most used methods to extract plant water is the cryogenic vacuum distillation (CVD), which tends to extract total plant water. Conversely, the Scholander-type pressure chamber (SPC), which is commonly used by tree physiologists to measure water potential in plant tissues and determine plant water stress, is expected to extract only the more mobile plant water (i.e., xylem and inter-cellular water). However, only few studies reported the application of SPC to extract plant water for isotopic analyses, and therefore, inter-method comparisons between SPC and CVD are of great value. In this work, we analyzed the variability in the isotopic composition of plant water extracted by SPC and CVD, also considering the potential variability in the isotopic signature of the plant water extracted by CVD from various tissues (i.e., leaves, twig without bark, twig with bark, twig close to the trunk of the tree, and wood core) and from different plant species (i.e., alder, apple, chestnut, and beech). The extraction of plant water by SPC is simple, can be carried out in the field, and it does not require specific laboratory work as in the case of CVD. However, the main limitation of SPC is the very small water volume that can be extracted from the lignified twigs under water stress conditions compared to CVD. Our results indicated that plant water extracted by SPC and CVD were significantly different. The difference in the isotopic composition obtained by the two extraction methods was smaller in the beech samples compared to alder, apple, and chestnut samples. The isotopic signature of alder, apple, and chestnut plant water extracted by SPC was more enriched in δ2H and δ18O, respectively, than the samples obtained by CVD. We conclude that plant water extraction by SPC is not an alternative for CVD as SPC mostly extracts the mobile plant water, whereas CVD tends to retrieve all water stored in the sampled tissue from both living and dead cells. However, studies aiming to quantify the relative contribution of the soil water sources to transpiration should rely more on the isotopic composition of xylem water (which is theoretically sampled by SPC) than the isotopic composition of total plant water (sampled by CVD), which also contains a fraction of water that could be stored in plant tissues for a longer time.

Tracing thermal and non-thermal water circulations in shear zones of Eastern Ghats Mobile Belt zone, Eastern India- inferences on sustainability of geothermal resources

The development of the geothermal resources in India has not progressed mainly due to inadequate understanding of the deeper thermal regime and uncertainty over the sustainability of heat source. In this study, isotopes, hydrochemical techniques and integrated geothermometric models have been applied to a low-medium enthalpy geothermal system belonging to shear zones of Mahanadi graben, Eastern Ghats Mobile Belt (Eastern India) to gain better insights. Isotope results indicate that thermal waters are meteoric in nature and absence of δ18O-shift suggests that the subsurface temperatures are below 200 °C. Distinct isotopic and hydrochemical signatures of thermal waters clearly suggest their origin from different geothermal reservoirs. Thermal waters at Atri/Tarabalo sites are derived from the southern part of the graben while at Athmalik, from northern part. Away from graben in southern direction (Taptapani site), the thermal waters are derived from rain occurring at elevated regions. Seasonal variations in chemical and isotope data are minimum in thermal waters. The estimated reservoir temperatures range between 92 and 124 °C with reservoir depths 1.6 – 2.4 km. Tritium data suggests that thermal waters are old and have 12–63% mixing with non-thermal water. The modelled radiocarbon age of thermal waters (13.3 – 20.7 Ka) suggests paleo-recharge of the reservoirs during Last Glacial Maximum (LGM), characterized by arid climate and low rainfall. A conceptual isotope model illustrating the genesis and circulation patterns of thermal and non-thermal waters is presented. The study highlights the potential of isotope-based studies in expanding the geothermal energy utilization in India.

Effect of soil thickness on rainfall infiltration and runoff generation from karst hillslopes during rainstorms

AbstractKnowledge of water movement from the hillslope critical zone is important for water management. However, the runoff process resulting from extreme rainfall events remains unclear due to rare field‐based natural monitoring data. We investigated rainwater infiltration and runoff generation processes in two plots with deep and relatively shallow soil thicknesses (66 vs. 35 cm depth on average, respectively) on karst hillslopes. Rainwater, soil water and lateral discharge runoff in the soil‐epikarst system were monitored using hydrometric and 18O isotope methods in September 2020, which was the wettest month on record at the study s, including three normal rainfalls (29.6 mm in 8.5 h, 25 mm in 8.5 h, and 27.4 in 3.5 h) and three extreme rainstorms (335 mm in 11.5 h, 77.8 mm in 9 h, and 129.2 mm in 5 h). Soil moisture and water table responded rapidly (&lt;30 min) during the extreme rainfall. However, the soil‐epikarst interface exhibited the strongest stability (coefficient variation [CV] &lt; 8.18%) and collected more pre‐event water, reflected by the isotopic signature of the soil water. Accordingly, low permeability at the soil‐epikarst interface played an important role in buffering rainwater infiltration. Controlled by infiltration‐excess and saturation‐excess runoff mechanisms, the contribution of surface runoff to total discharge was less than 3% during normal rainfall events, which was significantly less than that during extreme rainfall events (13%–60%). This was supported by the evolution of δ18O values of surface runoff that were similar to rainwater and more 18O‐depleted than that of subsurface runoff. Higher rainfall intensity which exceeded soil permeability during extreme rainstorms further increased the possibility of exceeding infiltration‐saturation processes. For the deep soil plot (DSP), surface runoff (&gt;44%) dominated the extreme rainfall process; while for the shallow‐soil plot (SSP), surface runoff (60%) dominated only during the maximum rainfall events. Moreover, the surface runoff contribution to total runoff in DSP was greater than that in SSP. Surface runoff from slopes with thicker soil layers is an important part of karst watershed flood processes in extreme rainfall events, which should be considered carefully for water resource management.Highlights Hydrometric and isotope methods are used to assess extreme hydrological processes. The surface runoff of extreme rainfalls is much higher than that of normal rainfall. The infiltration‐excess mechanism dominates the surface runoff of extreme rainfall. Slopes with thicker soil layers are more vulnerable to flooding in the karst region.

Dissolved organic matter signatures in urban surface waters: spatio-temporal patterns and drivers

Abstract. Advances in analytical chemistry have facilitated the characterization of dissolved organic matter (DOM), which has improved understanding of DOM sources and transformations in surface waters. For urban waters, however, where DOM diversity is likely to be high, the interpretation of DOM signatures is hampered by a lack of information on the influence of land cover and anthropogenic factors such as nutrient enrichment and release of organic contaminants. Here we explored the spatio-temporal variation in DOM composition in contrasting urban water bodies, based on spectrophotometry and fluorometry, size-exclusion chromatography, and ultrahigh-resolution mass spectrometry, to identify linkages between DOM signatures and potential drivers. The highly diverse DOM we observed distinguished lakes and ponds, which are characterized by a high proportion of autochthonous DOM, from rivers and streams where allochthonous DOM is more prevalent. Seasonal variation in DOM composition was apparent in all types of water bodies, apparently due to interactions between phenology and urban influences, such as nutrient supply, the percentage of green space surrounding the water bodies and point source pollution. Optical DOM properties also revealed the influence of effluents from wastewater treatment plants, suggesting that simple optical measurements can be useful in water quality assessment and monitoring, providing information about processes both within water bodies and in their catchments.

A one-million-year isotope record from siderites formed in modern ferruginous sediments

Abstract Ancient iron formations hold important records of environmental conditions during the Precambrian eons. Reconstructions of past oceanic systems require investigation of modern ferruginous analogs to disentangle water column and diagenetic signals recorded in iron-bearing minerals. We analyzed oxygen, iron, and carbon isotopes in siderite, a ferrous carbonate phase commonly used as an environmental proxy, from a 100-m-long record spanning a 1 Ma depositional history in ferruginous Lake Towuti, Indonesia. Combining bulk sediment and pore water geochemistry, we traced processes controlling siderite isotope signatures. We show that siderite oxygen isotope compositions (δ18O) reflect in-lake hydrological and depositional conditions. Low iron isotope values (δ56Fe) record water column oxygenation events over geological timescales, with minor diagenetic partitioning of Fe isotopes by microbial iron reduction after deposition. The carbon isotope compositions (δ13C) reflect the incorporation of biogenic HCO3–, which is consistent with sediment organic matter remineralization lasting over ca. 200 ka after burial. Positive δ13C excursions indicate an increased production of biogenic methane that escaped the sediment during low lake levels. Diffusion across the sediment–water interface during initial formation of siderites tends to align the isotope signatures of bottom waters to those of pore waters. As microbial reduction of ferric iron and oxidation of organic matter proceed and saturate pore water conditions with respect to siderite, overgrowth on nuclei partially mutes the environmental signal inherited from past bottom waters over ca. 1 Ma. Because high depositional fluxes of ferric iron and organic matter in early oceans would have promoted similar microbial processes in ferruginous deposits prior to lithification, the environmental record contained in siderite grains can successively integrate depositional and early diagenetic signals over short geological timescales.

The Transmission Spectrum of WASP-17 b From the Optical to the Near-infrared Wavelengths: Combining STIS, WFC3, and IRAC Data Sets

We present the transmission spectrum of the inflated hot Jupiter WASP-17 b, observed with the STIS and WFC3 instruments aboard the Hubble Space Telescope, allowing for a continuous wavelength coverage from ∼0.4 to ∼1.7 μm. Observations taken with IRAC channels 1 and 2 on the Spitzer Space Telescope are also included, adding photometric measurements at 3.6 and 4.5 μm. HST spectral data were analyzed with Iraclis, a pipeline specialized in the reduction of STIS and WFC3 transit and eclipse observations. Spitzer photometric observations were reduced with the TLCD-LSTM method, utilizing recurrent neural networks. The outcome of our reduction produces incompatible results between STIS visit 1 and visit 2, which leads us to consider two scenarios for G430L. Additionally, by modeling the WFC3 data alone, we can extract atmospheric information without having to deal with the contrasting STIS data sets. We run separate retrievals on the three spectral scenarios with the aid of TauREx 3, a fully Bayesian retrieval framework. We find that, independently of the data considered, the exoplanet atmosphere displays strong water signatures and, potentially, the presence of aluminum oxide and titanium hydride. A retrieval that includes an extreme photospheric activity of the host star is the preferred model, but we recognize that such a scenario is unlikely for an F6-type star. Due to the incompleteness of all STIS spectral light curves, only further observations with this instrument would allow us to properly constrain the atmospheric limb of WASP-17 b, before the James Webb Space Telescope or Ariel will come online.

Using Stable Water Isotopes to Analyze Spatiotemporal Variability and Hydrometeorological Forcing in Mountain Valley Wetlands

Wetlands in Montane and Subalpine Subregions are increasingly recognized as important hydrologic features that support ecosystem function. However, it is currently not clear how climate trends will impact wetland hydrological processes (e.g., evaporative fluxes) across spatiotemporal scales. Therefore, identifying the factors that influence wetland hydrologic response to climate change is an important step in understanding the sensitivity of these ecosystems to environmental change. We used stable water isotopes of hydrogen and oxygen (δ2H and δ18O), coupled with climate data, to determine the spatiotemporal variability in isotopic signatures of wetland source waters and understand the influence of evaporative fluxes on wetlands in the Kananaskis Valley. Our results show that the primary runoff generation mechanism changes throughout the growing season resulting in considerable mixing in wetland surface waters. We found that evaporative fluxes increased with decreasing elevation and that isotopic values became further removed from meteoric water lines during the late peak- and into the post-growing seasons. These findings suggest that a change in the water balance in favor of enhanced evaporation (due to a warmer and longer summer season than present) will not only lead to greater water loss from the wetlands themselves but may also reduce the water inputs from their catchments.

Classification of groundwater using multivariate statistical methods: a case study from a part of Haryana, northwestern India.

This article aimed to estimate the local underground water associations, which will, in turn, be applied to discuss the location of each underground water cluster in the flow system. Additionally, this investigation intended to evaluate underground water's aptness from aquifers of the study area for domestic agricultural activities and the prime sources of alteration in the water chemistry. Geographically, the region does not have the privilege of the river (except the Yamuna in the eastern part) running through it and thus, has to rely heavily on groundwater. Therefore, it is necessary to study the groundwater characteristics in this region. This investigation manifested two sub-surface water associations (groups) showing two prime underground water types in the study area: the calcium-magnesium-bicarbonate water-types, groups (clusters) 1 member; and the sodium-bicarbonate-chloride water-types consisting of Group 2 members during post-monsoon and pre-monsoon periods. Group 1 is typical of underground water in recharge regions of the underground water flow system. It is the cleanest underground water type in part except for a few groundwater samples. The highest mean salinity was vested in group 2, the signature of underground waters in discharge regions of the underground water flow system. This investigation observes that three principal elements controlled the hydro-chemistry of underground water in the study area: chemical fertilizers from farms, carbonate mineral weathering, calcite, fluorite, silicate minerals, and exchange of cations in the region. All the underground water groups had high sodium (Na) concentrations and will cause the Na-hazard when applied for agricultural activities. Most samples of groups 1 and 2 were within the class II and I area of Doneen's plot during both periods and were therefore acceptable for agricultural activities in the investigation region.

Sea‐Ice Detection From Near‐Nadir Ku‐Band Echoes From CFOSAT/SWIM Scatterometer

AbstractSWIM on board CFOSAT is the first spaceborne, low incidence, rotating scatterometer, aiming at measuring in near‐real time ocean waves spectra. With five off‐nadir beams at incidences between 2° and 10° plus one nadir beam, it covers the Earth in 13 days, including polar regions thanks to its polar orbit. This work aims at exploiting SWIM data over ice regions with two objectives. An off‐nadir data‐based sea‐ice flag is here proposed that allows, first, to eliminate sea‐ice polluted echoes for improving the wave spectrum retrieval, and second, to open perspectives for application of sea‐ice monitoring with near‐nadir Ku‐band active sensors. To this end, the signature of both open water and sea‐ice radar backscatter is parameterized into Geophysical Model Functions. Then, comparisons with observed profiles through a Bayesian scheme provide a probability of sea‐ice presence. After comparison with both model (ECMWF‐IFS) and radiometer (SSMI) derived reference data sets, the proposed flag is found to be ready for operational use. At latitudes greater than 40° in absolute value, the proposed flagging algorithm exhibits accuracies of approximately 98% for all beams compared to SSMI data. Beam to beam performances are characterized and show potential for the characterization of sea‐ice at Ku‐band.

Chemical fingerprinting of organic micropollutants in different industrial treated wastewater effluents and their effluent-receiving river

Industry wastewater is considered one of the worst polluters of our precious water ecologies. However, the types of pollutants present in wastewater from industrial wastewater treatment plants (IWTPs) are still unclear. In this study, a simple and effective chemical fingerprinting method for checking the source-sink relationships among different industrial wastewaters and their effluent-receiving river was established. 107, 228, 155, and 337 chemicals were screened out in wastewater from electronics, steel, textile, and printing and dyeing plants, respectively. Chemical fingerprinting of the detected chemicals was performed, and results showed that aromatic compounds were the most prevalent among the pollutant categories (i.e., 56, 189, and 168 in electronics, iron and steel, and printing and dyeing plants, respectively). The traceability analysis of the chemicals selected in the effluent determined the characteristic pollutants of different industrial enterprises. Sixty-eight compounds were identified as the characteristic pollutants in the different process stages of wastewater of the four IWTPs. Of the 84 effluent-receiving river water signature pollutants, 47.6% (n = 40) were also detected in the effluent from the four IWTPs. Effective screening of organic pollutants in industrial wastewater and determining their sources will help accelerate the improvement of industrial wastewater treatment technology.