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Made available in DSpace on 2021-06-25T11:57:10Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-04-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Financiadora de Estudos e Projetos (FINEP) The use of stable isotopes of hydrogen and oxygen is a tool widely used to trace water paths along the hydrological cycle, providing support for understanding climatic conditions in different spatial scales. One of the main synoptic scale events acting in southeastern Brazil is the South Atlantic Convergence Zone (SACZ), which causes a large amount of precipitation from southern Amazonia to southeastern Brazil during the southern summer. In order to determine the isotopic composition of precipitation during the action of SACZ in Sao Francisco Xavier in southeastern Brazil, information from the Weather Forecasting and Climate Studies Center of the National Institute for Space Research (CPTEC) was used regarding SACZ performance days, the retrograde trajectories of the HYSPLIT model, and images from the GOES-16 satellite, in addition to the non-parametric statistical tests by Spearman and Kruskal-Wallis. A high frequency of air mass trajectories from the Amazon to southeastern Brazil was observed when the SACZ was operating. During the SACZ events, the average isotopic composition of precipitation was more depleted, with a delta O-18 of -9.9 parts per thousand (+/- 2.1 parts per thousand), a delta H-2 of -69.3 parts per thousand (+/- 17.9 parts per thousand), and d-excess of 10.1 parts per thousand (+/- 4.0 parts per thousand). When disregarding the SACZ performance, the annual isotopic composition can present an enrichment of 1.0 parts per thousand for delta O-18 and 8.8 parts per thousand for the delta H-2. The long-term monitoring of trends in the isotopic composition of precipitation during the SACZ events can assist in indicating the evapotranspiration contribution of the Amazon rainforest to the water supply of southeastern Brazil. Natl Inst Space Res INPE, BR-12227010 Sao Jose Dos Campos, Brazil Fed Univ Campina Grande UFCG, Acad Unit Atmospher Sci, BR-58428830 Campina Grande, Paraiba, Brazil Sao Paulo State Univ, Environm Studies Ctr, BR-13506900 Rio Claro, Brazil Sao Paulo State Univ, Environm Studies Ctr, BR-13506900 Rio Claro, Brazil CAPES: 2180/2017 FAPESP: 2018/16791-0 Financiadora de Estudos e Projetos (FINEP): 01.16.0076.00

Phytoplankton contribute half of the primary production in the biosphere and are the major source of energy for the Arctic Ocean ecosystem. While primary production measurements are therefore fundamental to our understanding of marine biogeochemical cycling, the extent to which current methods provide a definitive estimate of this process remains uncertain given differences in their underlying approaches and assumptions. This is especially the case in the Arctic Ocean, a region of the planet undergoing rapid evolution as a result of climate change, yet where primary production measurements are sparse. In this study, we compared three common methods for estimating primary production in the European Arctic Ocean: 1) production of 18O-labeled oxygen (GPP-18O), 2) changes in dissolved oxygen (GPP-DO) and 3) incorporation rates of 14C-labelled carbon into particulate organic carbon (14C-POC) and into total organic carbon (14C-TOC, the sum of dissolved and particulate organic carbon). Results show that primary production rates derived using oxygen methods showed good agreement across season and were strongly positively correlated. While also strongly correlated, higher scatter associated with seasonal changes was observed between 14C-POC and 14C-TOC. The 14C-TOC-derived rates were, on average, approximately 50 % of the oxygen-based estimates. However, the relationship between these estimates changed seasonally. In May, during a spring bloom of Phaeocystis sp., 14C-TOC was 52 % and 50 % of GPP-DO and GPP-18O respectively, while in August, during post-bloom conditions dominated by flagellates, 14C-TOC was 125 % of GPP-DO and 14C-TOC was 175 % of GPP-18O. Varying relationship between C and O rates may be the result of varying importance of respiration, where C-based rates estimate Net Primary Production (NPP) and O-based rates estimate Gross Primary Production (GPP).However, uncertainty remains in this comparison, given differing assumptions of the methods and the photosynthetic quotients.The median O:C ratio of 4.75 in May is within the range of that observed for other regions of the world's ocean. However, the median O:C ratio for August is < 1, lower than in any other reported region. Our results suggest further research is needed to estimate O:C in Arctic waters, and at different times of the seasonal cycle. © 2019 Sanz-Martín, Vernet, Cape, Cano, Delgado-Huertas, Reigstad, Wassmann and Duarte., This study is a contribution to the Carbon Bridge (RCN-226415) project funded by the Norwegian Research Council to MR. MS-M was supported by a predoctoral fellowship from the Fundación La Caixa and the unemployment benefit of Ministry of Labour, Migrations and Social Security, Spain. MV was partially funded by a fellowship from the Hanse-Wissenchaftskolleg, Delmenhorst, Germany and by a United States National Science Foundation award PLR-1443705. MC was partially funded by the NASA Headquarters under the NASA Earth and Space Science Fellowship Program – grant NNX12AN48H.

The site of Ulucak is pivotal in exploring the Neolithic of the eastern Aegean and western Anatolia. It has an impressive stratigraphic sequence stretching from the first half of the seventh millennium BC to the first half of the sixth millennium BC. Recent zooarchaeological analyses have provided insight into the importance of animal husbandry practices and dairying at the site throughout the Neolithic but also raised questions about the changing nature of herd management strategies and whether these differed for sheep and goat. The faunal data, coupled with the significance of the site and condition of the assemblage, prompted the application of a number of methodological techniques to assess differences between sheep and goat. In this paper, we combine traditional osteomorphological analysis, ancient DNA, collagen peptide mass fingerprinting (zooarchaeology by mass spectrometry, or ZooMS), and stable isotope analysis of δ18O and δ13C from tooth enamel carbonate as well as δ13C and δ15N from bone collagen. As such, this is the first study of its kind. We evaluate the juxtaposition of these four approaches and their application in this important case, with relevance for future studies in the region.

Increasing biodiversity has been linked to higher primary productivity in terrestrial ecosystems. However, the underlying ecophysiological mechanisms remain poorly understood. We investigated the effects of surrounding species richness (monoculture, two‐ and four‐species mixtures) on the ecophysiology of Lithocarpus glaber seedlings in experimental plots in subtropical China. A natural rain event isotopically labelled both the water uptaken by the L. glaber seedlings and the carbon in new photoassimilates through changes of photosynthetic discrimination. We followed the labelled carbon (C) and oxygen (O) in the plant–soil–atmosphere continuum. We measured gas‐exchange variables (C assimilation, transpiration and above‐ and belowground respiration) and δ13C in leaf biomass, phloem, soil microbial biomass, leaf‐ and soil‐respired CO 2 as well as δ18O in leaf and xylem water. The 13C signal in phloem and respired CO 2 in L. glaber in monoculture lagged behind those in species mixture, showing a slower transport of new photoassimilates to and through the phloem in monoculture. Furthermore, leaf‐water 18O enrichment above the xylem water in L. glaber increased after the rain in lower diversity plots suggesting a lower ability to compensate for increased transpiration. Lithocarpus glaber in monoculture showed higher C assimilation rate and water‐use efficiency. However, these increased C resources did not translate in higher growth of L. glaber in monoculture suggesting the existence of larger nongrowth‐related C sinks in monoculture. These ecophysiological responses of L. glaber, in agreement with current understanding of phloem transport are consistent with a stronger competition for water resources in monoculture than in species mixtures. Therefore, increasing species diversity in the close vicinity of the studied plants appears to alleviate physiological stress induced by water competition and to counterbalance the negative effects of interspecific competition on assimilation rates for L. glaber by allowing a higher fraction of the C assimilated to be allocated to growth in species mixture than in monoculture.

International audience; Tree ring δ18O chronologies from two native species (Fitzroya cupressoides and Nothofagus pumilio) in northern Patagonia were developed to assess their potential for paleoclimate reconstructions. The five annually resolved cellulose δ18O chronologies (two for F. cupressoides and three for N. pumilio) are located on the Andes along the steep west-to-east precipitation gradient. Over the common 60 years long interval, the five site-δ18Ocell chronologies exhibit a strong common signal as indicated by the significant mean intercorrelation (r = 0.61, p \textless 0.05) and the high percentage (65%) of total variance explained by the first empirical orthogonal function. Although correlation analyses reveal that the two mean species-δ18Ocell chronologies are mainly modulated by December\textendashMay temperature, the N. pumilio chronology shows a greater sensitivity to record temperature variations (r = 0.57, p \textless 0.05). The δ18Ocell of N. pumilio contains a regional temperature signal representative of a large area in southern South America under the influence of the Southern Annular Mode. This study indicates that δ18Ocell in N. pumilio is a promising proxy to reconstruct past variations in temperature in South America south of 38°S.

Combined oxygen (O) and nitrogen (N) stable isotope analyses are commonly used in the source determination of nitrate . The source and fate of are studied based on distinct O and N isotopic signatures (d18O and d15N) of various sources and isotopic effects during transformation processes, which differ between sources like fertilizer, atmospheric deposition, and microbial production (nitrification). Isotopic fractionation during production and consumption of further affects the d18O and d15N signal. Regarding the d18O in particular, biochemical O exchange between O from and H2O is implicitly assumed not to affect the d18O signature of . This study aimed to test this assumption in soil-based systems. In a short (24 h) incubation experiment, soils were treated with artificially 18O and 15N enriched . Production of from nitrification during the incubation would affect both the 18O and the 15N enrichment. Oxygen exchange could therefore be studied by examining the change in 18O relative to the 15N. In two out of the three soils, we found that the imposed 18O enrichment of the declined relatively more than the imposed enrichment. This implies that O exchange indeed affected the O isotopic signature of , which has important implications for source determination studies. We suggest that O exchange between and H2O should be taken into consideration when interpreting the O isotopic signature to study the origin and fate of in ecosystems. Highlights ¿ The oxygen isotopic signature of nitrate is commonly used to study its source and fate in ecosystems. ¿ The effect of oxygen exchange is in such studies generally not taken into account. ¿ We used a novel ‘enrichment ratio’ approach to evaluate changes the isotopic signature of NO3. ¿ Our study shows that oxygen exchange can affect the oxygen isotopic signature of nitrate in soils.

International audience; Water vapor isotopes represent an innovative and excellent tool for understanding complex mechanisms in the atmospheric water cycle over different time scales, and they can be used for a variety of applications in the fields of paleoclimatology, hydrology, oceanography, and ecology. We use an ultrasensitive near‐infrared spectrometer, originally designed for use on airborne platforms in the upper troposphere and lower stratosphere, to measure the water deuterium and oxygen‐18 isotope ratios in situ, in ground‐level tropospheric moisture, with a high temporal resolution (from 300 s down to less than 1 s). We present some examples of continuous monitoring of near‐surface atmospheric moisture, demonstrating that our infrared laser spectrometer could be used successfully to record high‐concentration atmospheric water vapor mixing ratios in continuous time series, with a data coverage of ∼90%, interrupted only for daily calibration to two isotope ratio mass spectrometry–calibrated local water standards. The atmospheric data show that the water vapor isotopic composition exhibits a high variability that can be related to weather conditions, especially to changes in relative humidity. Besides, the results suggest that observed spatial and temporal variations of the stable isotope content of atmospheric water vapor are strongly related to water vapor transport in the atmosphere.

International audience; Due to its resistance to oxidation, TaSiN is a promising candidate as an electrically conductive barrier layer for integration of high permittivity oxides in advanced memory devices. In this study we report on the properties of TaSiN thin films deposited by reactive magnetron sputtering of a TaSi2 target in an Ar/N-2 atmosphere. We especially focus on the influence of deposition parameters (pressure and power density) on TaSiN film properties. To study oxidation resistance, films are processed by rapid thermal annealing in O-18(2) at 650 degrees C. The concentration depth profiles of O-18 were measured via the narrow resonance of O-18(p,alpha)N-15 at 151 keV (FWHM = 100 eV). Whatever the power density, films deposited above 2 Pa are porous and exhibit high resistivity. Ta26Si47N27 deposited at 0.5 Pa with a power density of 2.65 W/cm(2) exhibits high density, low resistivity, and good oxidation resistance. (c) 2006 Elsevier B.V. All rights reserved.

Sogenannte Multi-Tracer-Studien sind eine effektive Methode um die Fließbedingungen von Grund- wässern zu bestimmen. Stabile und radioaktive Isotope sowie gasförmige Spurenstoffe wurden zu- sammen mit wasserchemischen Untersuchungen angewandt, um die mittlere Verweilzeit, Herkunft, Mischungstypen von Grundwässern sowie die Regionen der Grundwasserneubildung abzuschätzen. Verschiedene Methoden wurden zur Grundwasserdatierung verwendet (Tritium, C-14, FCKW-11, FCKW-12 und FCKW-113). Tritium lieferte Verweilzeiten von fast null bis größer 50 Jahre für „Piston Flow“ und 73 bis größer 300 Jahre für das Exponentialmodell. Der Vergleich zwischen H-3 und FCKW offenbarte große Abweichungen der berechneten „Grundwasseralter“. Die Diskrepanz könnte mit der Anreicherung der FCKWs durch Pumpen oder dem Bewässerungsrückfluss begründet werden. Trotzdem konnten die FCKWs zur Abschätzung des Grundwasserfließmodells herangezogen werden, wobei das Exponentialmodell die Fließbedingungen im Untersuchungsgebiet am besten beschreibt. Die Abschätzung der mittleren Verweilzeiten mit Hilfe von Radiokohlenstoff erwies sich aufgrund großer Unsicherheiten in der Abschätzung der delta C-13 - Werte für Bodenluft und Karbonate als sehr problematisch. Eine qualitative Betrachtung der C-14 - Konzentrationen lässt allerdings in einigen Fällen die Existenz von fossilen Wässern mit Verweilzeiten von mehreren tausend Jahren erkennen. Die Interpretation der chemischen Analysen und des Strontiums offenbart die Gruppierung der Mehrheit der Proben in zwei Grundwassertypen. Ein Typ ist überwiegend in den Randbereichen des Untersuchungsgebietes zu finden während der zweite Wassertyp im Zentrum des Beckens verteilt ist. Grundwassermischungstypen mit Hilfe von Strontiumisotopenverhältnissen zu erkennen erwies sich als schwierig, da die hohen Strontiumkonzentrationen in den Karbonaten der Sedimente die Unterschiede der Sr-87 / Sr-86 - Signaturen verschiedener Grundwässer überdeckten. Deuterium und O-18 zeigten Verdunstungseffekte im Grundwasser auf, das möglicherweise größere Anteile an Paläowasser hat. Der Vergleich mit Daten eines früheren Berichtes lässt eine zunehmende Anreicherung von H-2 and O-18 erkennen was mit dem Rückfluss von Bewässerungswasser begründet wird. Die Chloridmassenbilanzmethode wurde eingesetzt, um die Regionen der Grundwasserneubildung zu erkennen, die in den Randbereichen des Untersuchungsgebietes zu finden sind. Die höchsten Neubil- dungswerte zeigten dabei die Sierra de Guanajuato und die Erhebungen im Osten und Süden. Weil zur Berechnung nur unzureichende Chloridmessungen im Niederschlag zur Verfügung standen, konn- ten die Ergebnisse lediglich qualitativ bewertet werden., Multitracer studies are an effective tool to determine flow conditions and mean residence times of groundwater. Stable and radioactive isotopes and gaseous tracers together with water chemistry are used to estimate mean residence time, origin and mixing of groundwaters and recharge regions in the aquifer of Silao-Romita. To determine residence times, different methods were applied (tritium, C-14, CFC-11, CFC-12 and CFC-113). Tritium yielded mean residence times of almost zero to more than 50 years for piston flow and 73 to more than 300 years for the exponential model. Comparing tritium and CFC “ages”, large differences became apparent which may be due to enrichment of CFCs caused by pumping or possi- ble irrigation return flow. Nonetheless CFCs provided plausible information to determine the ground- water flow model. The exponential model (EM) appeared to be most appropriate. The determination of mean residence times by radiocarbon was very problematic due to huge uncertainties in estimating delta C-13 of soil air and carbonates. A qualitative estimation revealed in some cases the existence of fossil waters with mean residence times of several thousand years. The interpretation of chemical analyses and strontium showed a grouping of the majority of the sam- ples into two types of groundwater. One is primarily present at the margins of the study area and the other in the centre of the basin. A detection of mixtures by strontium isotope ratios was problematic due to the high strontium content of the carbonates in the sediments which masks possible differences in Sr-87 / Sr-86 signatures of different groundwaters. Using H-2 and O-18 revealed evaporative effects in the extracted groundwater which possibly contains larger proportions on paleowaters. A comparison with data of a former report shows increasingly en- riched values which are attributed to irrigation return flow. Chloride Mass Balance (CMB) was applied to identify recharge regions which are at the margins of the study area. The Sierra de Guanajuato and the hills in the east and south showed the highest recharge values. Due to poor precipitation data of chloride these values were not reliable and interpretation was done qualitatively., research

The highest oxygen isotope ratios ever measured in the Galaxy have been recorded in silica-rich grains from the Murchison meteorite. The excess oxygen-18 and oxygen-17 could be the result of nucleosynthesis in a single exotic star in the early Solar System or evidence of irradiation by highly accelerated particles produced during an active early phase of the Sun. The origins of the building blocks of the Solar System can be studied using the isotopic composition of early planetary and meteoritic material. Oxygen isotopes in planetary materials show variations at the per cent level that are not related to the mass of the isotopes1,2; rather, they result from the mixture of components having different nucleosynthetic or chemical origins1,2,3. Isotopic variations reaching orders of magnitude in minute meteoritic grains are usually attributed to stellar nucleosynthesis before the birth of the Solar System, whereby different grains were contributed by different stars4,5. Here we report the discovery of abundant silica-rich grains embedded in meteoritic organic matter, having the most extreme 18O/16O and 17O/16O ratios observed (both ∼10-1) together with a solar silicon isotopic composition. Both O and Si isotopes indicate a single nucleosynthetic process. These compositions can be accounted for by one of two processes: a single exotic evolved star seeding the young Solar System6, or irradiation of the circumsolar gas by high energy particles accelerated during an active phase of the young Sun. We favour the latter interpretation, because the observed compositions are usually not expected from nucleosynthetic processes in evolved stars, whereas they are predicted by the selective trapping of irradiation products.