Stable isotopes in water vapor and rainwater over Indian sector of Southern Ocean and estimation of fraction of recycled moisture

Hydrochemical and isotopic characteristics on the southern and northern slopes of the Himalayas: spatio-temporal controls and source apportionment

Water-soluble ions, inorganic nitrogen, and stable isotopes in precipitation were assessed from the southern (Koshi Tappu and Khandbari) and northern slopes (Lhasa and SET) of the Himalayas to understand the sources, chemistry of regional precipitation, and climatic processes. Water soluble ions showed distinct seasonal variation, with higher concentrations in the non-monsoon. The concentration of ionic species was highest in Koshi Tappu, followed by Lhasa, SET, and Khandbari. The sources were from the terrigenous (Ca2+, HCO3-), marine (Na+ and Cl-), anthropogenic (SO42-, NO3-, and NH4+), terrigenous and marine (Mg2+), and biomass-burning (K+). The southern slope, relative to the northern, was more prone to anthropogenic emissions with higher deposition. Among all sites, inorganic nitrogen deposition at Koshi Tappu was higher than the threshold value (10 kg ha-1 y-1). The isotopic composition during the study period was higher in non-monsoon, started declining from June, and depleted in July and August compared to other months, i.e., the monsoon mature phase, along the south-to-north transect. The diminished value of stable isotopes in precipitation with increasing altitude underlines the evidence of the orographic effect in isotopic composition. Our study delineated that the higher/lower d-excess value increased with altitude on the southern/northern slope of the Himalayas. The backward trajectory analysis and the National Centers for Environmental Prediction's Final (NCEP FNL) datasets identified that most of the trajectories arrived from warm and humid low-latitude regions during monsoon and westerlies in non-monsoon. Thus, the chemical characteristics and stable isotopic composition of precipitation differed on the southern and northern slopes of the Himalayas by orographic effect and various sources. This study provides new insights into the atmospheric environment and climatic control of stable isotopes in the Himalayan Tibetan Plateau and facilitates monitoring of transboundary air pollution.

A tipping point in stable isotope composition of Antarctic meteoric waters during Cenozoic glaciation

Triple oxygen isotopes of Cenozoic intrusive rocks emplaced along the Ross Sea coastline in Antarctica, reveal that meteoric-hydrothermal waters imprinted their stable isotope composition on mineral phases, leaving a clear record of oxygen and hydrogen isotope variations during the establishment of the polar cap. Calculated O- and H-isotope compositions of meteoric waters vary from -9 ± 2‰ and -92 ± 5‰ at 40 ± 0.6 Ma, to -30 and -234 ± 5‰ at 34 ± 1.9 Ma, and intersect the modern Global Meteoric Water Line. These isotopic variations likely depict the combined variations in temperature, humidity, and moisture source regions, resulting from rearrangement of oceanic currents and atmospheric cooling during the onset of continental ice cap. Here, we report a paleo-climatic proxy based on triple oxygen geochemistry of crystalline rocks that reveals changes in the hydrological cycle. We discuss the magnitude of temperature changes at high latitudes during the Eocene-Oligocene climatic transition.

Stable isotope tracing internal recycling and evaporation losses in saline lakes on the Qinghai-Tibet Plateau

Direct measuring of internal lake recycling and evaporation losses remains challenging for lakes on the Qinghai-Tibet Plateau (QTP). Stable isotope techniques provide an effective approach for estimating water vapor cycling ratios and evaporation losses of lakes on the QTP. In this study, the stable isotope values of saline lakes on the QTP were modeled using the stable isotope values of the sampled lake water and their influencing factors. The water vapor recycling ratio and evaporation loss (E/I) of 135 saline lakes on the QTP were evaluated and their influencing factors were revealed. The results showed that stable isotopes in saline lakes on the QTP showed significant spatial variability. Their stable isotopes were affected by the source of water vapor, recharge patterns, and local evaporation conditions. It's worth noting that the average water vapor recycling ratio of saline lakes on the QTP was 20.16 %, one-fifth of the saline lakes had a water vapor recycling ratio beyond 30 %. Saline lakes lose 26 % of their water through evaporation. 26 % of the saline lakes experienced high evaporation losses of >40 % of the total inflow. We found that the main factors controlling the water vapor recycling ratio and evaporation loss in saline lakes on the QTP were precipitation and altitude, respectively. Interestingly, the control factors of water vapor recycling ratio and evaporation loss in saline lakes with elevation above 4500 m showed significant differences compared to saline lakes with elevation below 4500 m. Therefore, the strengthening of lake system monitoring can provide reliable data support for security assessment and effective management of water resources on the QTP.

Determination of exogenous water in grape juice through the isotopic analysis of 18O/16O

Abstract The consumption of grape juice has been growing significantly, so its quality is becoming an issue of great importance, both for the consumer and for the industry. However, identifying adulteration in juice is a great challenge and requires a reliable analytical process. The isotope ratio (18O/16O) is an important tool to determine the addition of exogenous water in beverages, however, there is no official method for juice in Brazil. This study aimed to develop and validate a method for detecting exogenous water in grape juice through isotopic analysis of 18O/16O. The development and validation of the analytical method were performed using Isotope Ratio Mass Spectrometry (IRMS). The effect of temperature and evaporation of δ18O in experimental juices was evaluated, and reference values were found for juices based on the δ 18O of musts. The influence of the juice industrial production process on 18O values was verified, and commercial juices were evaluated in relation to the values of reference regarding the addition of water. The temperature and evaporation parameters did not influence the results of the 18O of the juice, as they presented differences lower than the method uncertainty. The heat exchanger system did not influence the proposed method. The reference values for juice can come from the musts, without affecting the interpretation of the final results. Of the thirty real juices analyzed, nine had exogenous water, three proved to be reconstituted juices and eighteen were considered to have no exogenous water. The method proposed and validated in this study presented values for the limit of detection (LOD) of 0.24‰, the limit of quantification (LOQ) of 0.97‰ and measurement uncertainty of 0.71‰, proving to be effective for the detection of exogenous water in grape juice, through of the analysis of the isotopic ratio of 18O/16O by IRMS.

Spectroscopic investigation of hydrogen and triple-oxygen isotopes in atmospheric water vapor and precipitation during Indian monsoon season

Water vapor, the most important greenhouse gas in the atmosphere, has four natural stable isotopologues (H₂¹⁶O, H₂¹⁷O, H₂¹⁸O and HD¹⁶O), and their isotopic compositions can be used as hydrological tracers. But the underlying processes and pattern-dynamics of the isotopic compositions of atmospheric water vapor and precipitation in response to various meteorological conditions during monsoon season in a tropical hot and humid region is poorly understood. Here, we present results of H and triple-O-isotopes of water in precipitation and atmospheric water vapor during monsoon season exploiting high-resolution integrated cavity output spectroscopy technique. We observed a distinct temporal variation of the isotopic compositions of water at different phases of the monsoon. The diurnal patterns of the isotopic variations were influenced by the local meteorological factors such as temperature, relative humidity and amount of precipitation. We also investigated the monsoonal dynamics of the second-order isotopic parameters, so-called d-excess and ¹⁷O-excess along with the influence of local meteorological factors on isotopic variations to improve our understanding of the underlying isotopic fractionation processes. Consequently, our results provide a unique isotopic-fingerprint dataset of rainwater and atmospheric water vapor for a tropical region and thus shed a new light on hydrological and meteorological processes in the atmosphere.

Earth's water reservoirs in a changing climate

Progress towards achieving a quantitative understanding of the exchanges of water between Earth's main water reservoirs is reviewed with emphasis on advances accrued from the latest advances in Earth Observation from space. These exchanges of water between the reservoirs are a result of processes that are at the core of important physical Earth-system feedbacks, which fundamentally control the response of Earth's climate to the greenhouse gas forcing it is now experiencing, and are therefore vital to understanding the future evolution of Earth's climate. The changing nature of global mean sea level (GMSL) is the context for discussion of these exchanges. Different sources of satellite observations that are used to quantify ice mass loss and water storage over continents, how water can be tracked to its source using water isotope information and how the waters in different reservoirs influence the fluxes of water between reservoirs are described. The profound influence of Earth's hydrological cycle, including human influences on it, on the rate of GMSL rise is emphasized. The many intricate ways water cycle processes influence water exchanges between reservoirs and thus sea-level rise, including disproportionate influences by the tiniest water reservoirs, are emphasized.