Partial radiogenic heat model for Earth revealed by geoneutrino measurements

The Earth has cooled since its formation, yet the decay of radiogenic isotopes, and in particular uranium, thorium and potassium, in the planet’s interior provides a continuing heat source. The current total heat flux from the Earth to space is 44:2±1.0 TW, but the relative contributions from residual primordial heat and radiogenic decay remain uncertain. However, radiogenic decay can be estimated from the flux of geoneutrinos, electrically neutral particles that are emitted during radioactive decay and can pass through the Earth virtually unaffected. Here we combine precise measurements of the geoneutrino flux from the Kamioka Liquid-Scintillator Antineutrino Detector, Japan, with existing measurements from the Borexino detector, Italy.We find that decay of uranium-238 and thorium-232 together contribute 20.0^(+8.8)_(-8.6)TW to Earth’s heat flux. The neutrinos emitted from the decay of potassium-40 are below the limits of detection in our experiments, but are known to contribute 4TW. Taken together, our observations indicate that heat from radioactive decay contributes about half of Earth’s total heat flux. We therefore conclude that Earth’s primordial heat supply has not yet been exhausted

Extraction and Analysis of Coral Reef Core Samples from Broward County, Florida.

The reefs off Broward County exist as three shore-parallel, sequentially deeper terraces named the inner , middle , and outer reefs and also a shallower, nearshore ridge complex. These structures span the continental coast of southeast Florida from Palm Beach County to southern Miami-Dade County and were characterized as relict, early Holocene shelf-edge and mid-shelf reefs along with limestone ridges. Presently, the reefs are colonized by a fauna characteristic of West Atlantic/Caribbean reef systems. Scleractinian coral cover is low except for a few dense patches of Acropora cervicornis, while Acropora palmata is absent except for a few individual living colonies. Coral reef core-drilling is a useful analytical tool to extract observable and datable geological samples from within reefs. This technique was employed to retrieve 4 cores from the inner reef off Broward County to better understand its age, composition, and Holocene growth history. Sub-samples from corals in cores provided 7 new radiocarbon ages ranging from 7,860-5,560 cal BP, and reef accumulation rates of l.7-2.45 m/1,000 yrs were calculated from these ages. In addition, coral species composition and taphonomic characteristics were analyzed to identify former reef environments/reef zonation, and signals for inner reef termination. Reef zonation was detectable but no clear taphonomic signal for inner reef termination was evident. Current data and radiocarbon ages from all three Broward County reefs suggest that the outer reef accumulated from ~10.6-8 ka cal BP, the middle reef from at least ~5.8-3.7 ka cal BP, and the inner reef from ~7.8-5.5 ka cal BP. A lack of significant age overlaps between the three reefs has led to the assertion that they represent backstepping reefs in response to Holocene sea-level rise. This study has provided the oldest and youngest ages from the inner reef thus far, and confirms that reef backstepping from the outer reef to the inner reef occurred within just a few hundred years after the termination of the outer reef. The middle reef remains poorly understood and thus a definitive Holocene growth history and ultimately an understanding of their formation are still largely unknown

On the Influence of Afforestation on Soil Erosion and Soil Carbon in a Subtropical Chinese Forest Ecosystem - Results from a tree diversity experiment

Die Wälder im subtropischen China erfuhren in den letzten Jahrzehnten große Verände-rungen durch umfassende Entwaldungen. Aufforstungen können nicht nur dazu beitra-gen, die Holzproduktion zu steigern, sondern auch Dienstleistungen von Waldökosys-temen wie z.B. Schutz gegen Bodenerosion, Verbesserung von Bodeneigenschaften oder Kohlenstoffspeicherung sicherzustellen und damit einen Beitrag zur Eindämmung des Klimawandels zu leisten. Die hügelige „Red Soil“ Region in Südchina ist auch trotz zahlreicher, langfristiger Aufforstungsprojekte nach wie vor mit hohen Bodenerosionsra-ten konfrontiert. Dies kann u.a. auf funktionelle Mängel der ausgewählten Baumarten und der für die Aufforstung geplanten Baumartendiversität zurückzuführen sein. Es ist daher von großem Interesse, wie Baumarten und Baumartenvielfalt, sowie insbesonde-re der Zusammenhang zwischen Artenvielfalt und Ökosystemfunktionen die Bodenero-sion beeinflussen. Darüber hinaus befassen sich nur wenige Studien mit der Rolle der Aufforstung für den Kohlenstoff- und Stickstoff-Haushalt, sowie deren Transport durch Bodenerosionsprozesse unter Wald. Diese Fragestellungen sind für die Bodenfrucht-barkeit und die Bewertung von Kohlenstoff- und Stickstoffflüssen vom Boden zu an-grenzenden aquatischen Ökosystemen sowie zur Atmosphäre von großer Wichtigkeit. Weiterhin ist bisher auch nur wenig über die Dynamik des organischen Kohlenstoffs im Boden in frühen Phasen der Aufforstung bekannt. Dies gilt insbesondere für subtropi-sche Waldökosysteme unter intensiver menschlicher Nutzung. Im Rahmen eines Biodiversitätsprojekts innerhalb eines subtropischen chinesischen Waldgebietes (BEF China) wurden in dieser Arbeit zunächst Punktwolkendaten von terrestrischen Laserscannern (TLS) und Splash Cups verwendet, um den räumlichen Blattflächenindex (LAI) zu analysieren und das Potenzial der Splash-Erosion im Be-standsniederschlag (TKE) vorherzusagen. Während der Regenzeiten von 2013 bis 2015 wurden Messungen der Sedimentfracht mit Erosionsmessplots durchgeführt, um zeitli-che Veränderungen der Erosionsraten und der Kohlenstoff- und Stickstoffflüsse im Bo-den zu erfassen und die Auswirkungen von Baumarten und Baumartendiversität auf diese zu untersuchen. In den Jahren 2010 und 2014 wurden 132 Bodenprofile in fünf Tiefenstufen (0-5 cm, 5-10 cm, 10-20 cm, 20-30 cm, 30-50 cm) untersucht, um die Veränderungen der Kohlenstoff-Bestände im Boden zu beurteilen. Die Ergebnisse zeigen, dass lognormale und exponentielle lineare Modelle geeignet sind, die vertikale und horizontale LAI-Verteilung ausgewählter Baumarten zu beschrei-ben. Die vertikalen Verteilungen von LAI und TKE verschiedener Baumarten waren signifikant unterschiedlich. Innerhalb des BEF China Projektes lassen sich auch nach 6 Jahren Baumwachstum noch immer starke Erosionsraten nachweisen. LAI und biologi-sche Bodenkrusten waren die beiden Haupteinflussfaktoren auf Bodenerosionsprozes-se in Baumbeständen mit unterschiedlichem Artenreichtum. Eine höherer Baumarten-diversität führte zu einer abnehmenden Bodenerosion durch positive Auswirkungen der Kronendächer und flächendeckender biologischer Bodenkrusten. Die Konzentrationen von C und N im Sedimentabtrag stiegen im Untersuchungszeitraum an, während die jährlichen Abflüsse von C und N in den beobachteten drei Jahren zusammen mit der Sedimentabgabe signifikant um 50 % zurückgingen. Die C- und N-Flüsse waren auch nach 6 Jahren Baumwachstum so hoch wie in Entwaldungsgebieten. Die junge Auffors-tung im BEF China Experiment führte zu einer Reduktion von insgesamt ca. 274 Mg Bodenkohlenstoff von 2010 bis 2014. Die Reduktion des Kohlenstoffs erfolgte haupt-sächlich im Oberboden (0-20 cm). Aufgeforstete Flächen mit höheren ursprünglichen C-Beständen zeigten höhere Verluste. Baumwachstum und Streufall als wichtiger Koh-lenstoffeintrag in den Boden konnten die Reduzierung des C-Bestands in der frühen Phase der Aufforstung nicht kompensieren.Forests in subtropical China were undergoing great changes in the last decades, mainly caused by extensive deforestation. Afforestation in turn can help not only to increase the production of timber but also to enhance forest ecosystem services such as soil erosion control, soil properties, carbon storage and thus help mitigating climate change. However, even after long-term afforestation projects the hilly red soil region in southern China is still facing serious soil erosion. This might result from structural shortcomings of the tree species chosen and tree species richness planed for afforestation. Therefore, it is urgent to answer the question how tree species and tree diversity and especially the relationship between diversity and ecosystem functioning affect soil erosion. In addition, little research addresses the role of afforestation for carbon (C) and nitrogen (N) turno-ver and transport by soil erosion under forest, which is important for soil fertility and the assessment of carbon and nitrogen fluxes from soil to adjacent aquatic ecosystems as well as to the atmosphere. Moreover, in the earlier stage of afforestation after defor-estation, soil organic carbon (SOC) dynamics are still unclear, especially in subtropical areas with intensive human impacts on forest ecosystems. Based on a biodiversity and ecosystem functioning project in China (BEF China), this dissertation firstly used point cloud data from terrestrial laser scanners (TLS) and splash cups to analyze spatial leaf area index (LAI) and to predict the potential of splash ero-sion in subtropical forests. Measurements of sediment delivery were conducted during the rainy seasons from 2013 to 2015 to detected temporal changes of soil erosion and soil carbon and nitrogen fluxes and investigate the influences of tree species and diver-sity. Finally, 132 soil profiles at five increments (0-5 cm, 5-10 cm, 10-20 cm, 20-30 cm, 30-50 cm) were sampled in 2010 and 2014 to assess changes of SOC stocks. Results showed that lognormal and exponential linear models were suitable to describe the vertical and horizontal LAI distribution of selected tree species, respectively. Vertical distributions of LAI and throughfall kinetic energy (TKE) of different tree species were significantly different. BEF China is still suffering from severe soil erosion even after 6 years of tree growth. Leaf area index (LAI) and biological soil crusts (BSCs) were the two main factors driving soil erosion within tree stands of different species richness. Higher tree species richness lead to decreasing soil erosion by positive effects on tree canopies and surface covering BSCs. Sediment C and N concentrations increased while annual soil C and N fluxes significantly decreased at a rate of 50% in the ob-served three years together with sediment delivery. Soil C and N fluxes in the study were as high as in deforestation areas even after 6 years of tree growth. Earlier affor-estation in BEF China resulted in a reduction of approximately 274 Mg SOC from 2010 to 2014 in total. The reduction of SOC is mainly from the 0-20 cm topsoil. Afforested areas with higher original SOC stock showed higher losses. Tree growth and litter fall as an important carbon input to soil could not compensate SOC stock reduction in the ear-lier stage of the afforestation

Reactor-based Neutrino Oscillation Experiments

The status of neutrino oscillation searches employing nuclear reactors as sources is reviewed. This technique, a direct continuation of the experiments that proved the existence of neutrinos, is today an essential tool in investigating the indications of oscillations found in studying neutrinos produced in the sun and in the earth's atmosphere. The low-energy of the reactor \nuebar makes them an ideal tool to explore oscillations with small mass differences and relatively large mixing angles. In the last several years the determination of the reactor anti-neutrino flux and spectrum has reached a high degree of accuracy. Hence measurements of these quantities at a given distance L can be readily compared with the expectation at L = 0, thus testing \nuebar disappearance. While two experiments, Chooz and Palo Verde, with baselines of about 1 km and thus sensitive to the neutrino mass differences associated with the atmospheric neutrino anomaly, have collected data and published results recently, an ambitious project with a baseline of more than 100 km, Kamland, is preparing to take data. This ultimate reactor experiment will have a sensitivity sufficient to explore part of the oscillation phase space relevant to solar neutrino scenarios. It is the only envisioned experiment with a terrestrial source of neutrinos capable of addressing the solar neutrino puzzle.Comment: Submitted to Reviews of Modern Physics 34 pages, 39 figure

Barozh 12: formation processes of a late Middle Paleolithic open-air site in western Armenia

© 2020 Elsevier Ltd Barozh 12 is a Middle Paleolithic (MP) open-air site located near the Mt Arteni volcanic complex at the margins of the Ararat Depression, an intermontane basin that contains the Araxes River. Sedimentology, micromorphology, geochronology, biomarker evidence, together with an assessment of artifact taphonomy permits the modelling of site formation processes and paleoenvironment at a level of detail not previously achieved in this area. Obsidian MP artifacts were recovered in high densities at Barozh 12 from four stratigraphic units deposited during marine oxygen isotope stage 3 (MIS 3) (60.2 ± 5.7–31.3 ± 3 ka). The MIS 3 sequence commences with low energy alluvial deposits that have been altered by incipient soil formation, while artifact assemblages in these strata were only minimally reworked. After a depositional hiatus, further low energy alluvial sedimentation and weak soil formation occurred, followed by higher energy colluvial (re)deposition and then deflation. Artifacts in these last stratigraphic units were more significantly reworked than those below. Analysis of plant leaf wax (n-alkane) biomarkers shows fluctuating humidity throughout the sequence. Collectively the evidence suggests that hunter-gatherers equipped with MP lithic technology repeatedly occupied this site during variable aridity regimes, demonstrating their successful adaptation to the changing environments of MIS 3

Tracing the water cycle in the Atacama Desert using water isotopes (δ2H, δ17O, δ18O) and pedogenic salt distributions

Stable isotope ratios of water (18O/16O and 2H/1H) are widely used in hydrological studies. In contrast to classic tracers (δ2H–δ18O, d-excess), the triple oxygen isotope system (δ17O–δ18O, 17O excess) is virtually insensitive to changes in temperature and salinity, providing additional information on processes in the hydrological cycle. Large isotope effects associated with evaporation occur mainly in response to humidity. These isotope effects can be quantified by the classic Craig-Gordon evaporation model. The main objective of this thesis is to investigate the potential of combined analysis of hydrogen (2H/1H) and triple oxygen (18O/17O/16O) isotopes of structurally bonded water of gypsum (CaSO4 · 2H2O) to quantitatively estimate paleo-humidity and reconstruct past changes in the climatic conditions of the presently hyperarid Atacama Desert. The first study serves to investigate recent dynamics in the isotopic composition of lake water in the complex hydrological system of the Salar del Huasco, Altiplano, Chile, that receives inflow from multiple sources and is affected by seasonal variability in precipitation, temperature and relative humidity. Isotope analyses of lakes and ponds from the Salar del Huasco revealed that their hydrological balance is mainly controlled by evaporation and recharge. Inflow from multiple sources and temporal variability in their isotopic composition lead to scattering of pond data along the evaporation trendline predicted by the Craig-Gordon model. Sporadic flooding events after heavy rainfalls can provoke significant mixing and lead to the emergence of non-recharged lakes. Evaporation without recharge as well as mixing processes can be identified by triple oxygen isotope analysis. The potential occurrence of episodic mixing processes, e.g. due to frequent flooding, should be taken into account in paleo-applications. The second study presents first results of isotope analyses of structurally bonded water of gypsum from paleo-lake deposits in the Atacama Desert. The isotopic compositions of analyzed samples fall on distinct evaporation trends indicating the preservation of the primary isotope signal of paleo-lake water. A Craig-Gordon model together with a Monte Carlo simulation was used to determine the relative humidity that best fit the isotope data in both d-excess vs δ18O space and 17O-excess vs δ18O space. The model output humidity is less affected by changes in the isotopic composition of source water and atmospheric vapor, however, can strongly depend on the selected wind induced turbulence coefficient and the limitations of the recharge rate (E/I). The model provides reasonable humidity values if the input parameters are set within ranges reasonable for the site. Results imply humid conditions in the northern Atacama Desert about 3.5 million years ago that may have been facilitated by permanent El Niño like conditions in the Early Pliocene Warm Period (4.5 – 3.0 Ma). The third study aims to improve the understanding of soil formation and secondary redistribution and transformation processes of evaporites in Atacama Desert soils, which is crucial for the interpretation of isotopic compositions of structurally bonded water of pedogenic gypsum. In this study, thin surface crusts, powdery surface material and subsurface concretions from up to 40 cm depth were sampled along several latitudinal transects between 19.5–25°S and 68.5–70.5°W. Results imply that long-term aridity gradients, sources and secondary mobilization processes control the spatial distribution of highly soluble salts – chlorides and nitrates – as well as gypsum and anhydrite in Atacama Desert soils. Hyperaridity is most persistent between 19-22°S. Exceptionally high chloride contents below the altitude of the atmospheric temperature inversion layer (< 1200 m) as well as Na/Cl ratios of 0.83 – close to the global sea water ratio of 0.86 – suggest sea spray as the primary source of halite. Generally, gypsum and anhydrite are the major minerals in Atacama Desert soils. The association of high anhydrite abundances with high chloride and nitrate contents indicate that anhydrite is a secondary product of dissolution-reprecipitation reactions in highly saline brines. This thesis expands our knowledge of processes controlling the isotopic composition of structurally bonded water of lacustrine and pedogenic gypsum. The results contribute to the development of a powerful isotope tool that can allow for a quantitative reconstruction of past climatic mean states in the Atacama Desert

On the Origin of saline compounds in acidic salt flats (Central Andean Altiplano)

Volcanism, aridity, and endorheism converge in the central zone of the Andean Cordillera (Bolivia, Chile, and Argentina, between latitudes 19◦ S and 27◦ S). The Gorbea and Ignorado basins are pristine Andean sites in which the transfer of saline compounds from endogenous to exogenous environments occurs. In this area the regional volcanic rocks display strong argillic alteration, with Al and Fe (alunite, jarosite) and Ca (gypsum/ anhydrite) sulfates. Native sulfur is also present in paleosolfataras. The Gorbea salt flat is covered by a discontinuous layer of selenitic gypsum of varying thickness (maximum 2 m). The discontinuity of the layer as well as its variable thickness is due to the fact that the original bed has been partially destroyed mainly by dissolution but also by deflation. Saline pond brines (Cl-SO4-Na [-Mg]) are strongly acidic reaching pH values lower than 2. The high temperature processes that caused the hydrothermal alteration in the Gorbea and Ignorado basins occurred in the Miocene (14 Ma) coinciding with a wet period that reached 9 Ma. Subsequently, the weather up to 120 ka was predominantly hyper-arid with a less arid interval between 6 and 3 Ma and the epithermal sulfates were recycled in saline lakes mainly in the Late Pleistocene wet period (120 to 11.7 ka). Evolution into the current salt flat occurred in the mid-early Holocene (11.7 to 4 ka), through a salt lake that first evolved into a 'salina' environment that gave rise to a selenitic gypsum layer (6.4 ka), and later to the final dryness. The highest values of δ34SVCDT and δ18OVSMOW found in the selenitic gypsum layer (+20¿ and + 28¿, respectively) show that the recycling was locally produced, mainly from isotopically heavier hypogene sulfates. The δ18OVSMOW (and less clearly, δ34SVCDT) values are higher in the basal part of the gypsum crust (about +27¿), which suggests an initial hypogene source that decreased towards the top due to mixing with supergene sulfate inputs. Bacterial activity, although catalyzing the supergene reactions, does not appear to have had a significant influence on the isotopic composition of sulfates. The crystallization water of the gypsum is isotopically lighter in the basal part of the selenitic layer (δ18OVSMOW ≈ +7¿), which indicates that the brines of the saline lake were still poorly evolved. These brines evolved to heavier (approximately +13¿) towards the top of the layer and towards the center of the salt flat, before the final drying. The partial destruction of the selenitic gypsum layer occurred during more recent wet periods over the last 4 ka that have been identified in wetlands and lakes in the Central Andean area. Isotopic data (δ34SVCDT and δ18OVSMOW) clearly suggest that sulfates in the saline compounds and evaporites from the entire Central Andean arid area have mostly a thermal origin with contributions from atmospheric deposition and locally, near the Pacific coast, marine aerosols. In addition, the great difference in altitude (approximately 3000 m) between the Altiplano and the lands located to the west, up to the Pacific coast, generated a constant flow of groundwater containing saline compounds that gave rise, to the salt flats of the basins located in lower topographic areas (Atacama, Punta Negra, Hilaricos, Soledad, Tamarugal, Salar de Pintados, Salar Grande) throughout the Cenozoic. Such salt flats have lower δ34SVCDT and δ18OVSMOW valuesmostly for two reasons: the secular mixing with atmospheric sulfate, and the isotope fractionation related to repetitive dissolution (or leaking)¿migration¿precipitation along the hydraulic gradient, a process that occurred throughout a large part of the Cenozoic. The last process also explains that the evaporites of some of these salt flats (e.g., Salar de Atacama, Salar Grande) display very high Cl/SO4 ratios

Diversity and ecology of bacterial communities at the deep seafloor

Understanding biodiversity and its distribution across space, time, and along environmental gradients, is crucial in order to assess the ecological functions of groups of organisms in the environment and gain insights into overall ecosystem functioning. In contrast to the distribution patterns of larger organisms, little is known about the structuring of bacterial communities in the environment. The reason being, that appropriate tools for the study of microbial ecology have only become available during the last decades. Today, molecular tools like fingerprinting or next-generation sequencing enable a time- and cost-effective, high-throughput processing of environmental samples to study bacterial diversity patterns. The application of such tools has revealed non-random patterns of bacterial diversity across space and time, and along environmental gradients in a variety of habitats. However, research on microbial community ecology is just starting to pick up pace, and entire ecosystems, such as the deep seafloor, remain largely uncharted. The deep sea represents the largest ecosystem on Earth and at the same time remains one of the least explored regions on our planet. Bacterial communities play an essential role for carbon and nutrient cycling in deep-sea sediments, and are thus an important component of benthic deep-sea ecosystems. Therefore, the specific investigation of bacterial diversity and its distribution at the deep seafloor in the context of environmental parameters were major objectives of this thesis. The influence of both spatial distance, as an indicator for dispersal limitation, and contemporary environmental factors on bacterial communities were investigated at different spatial scales