bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of the integrated and angular aerosol scattering coefficients at Valencia (Spain)
Authors: Matos Tejera Violeta , Camarasa Fayos Josep , Esteve Martínez Anna Raquel , Estellés Leal Víctor , Utrillas Esteban María Pilar , Martínez-Lozano Jose Antonio
Published: March 2021

Atmospheric aerosols are an essential climate forcing agent and play a critical role in global climate change. Its effect on Earth’s radiative budget is determined by their optical properties, it is, the scattering and absorption coefficients. The ability of the aerosol to interact with solar radiation is dependent upon particle size and composition, both related to variation in sources. By scattering the solar radiation, the aerosols contribute to the cooling of the underlying atmosphere and the surface; by absorbing the solar radiation, they contribute to the heating of the atmosphere. Different techniques have been developed to measure and characterize different properties of the aerosols in the column and at surface level. At surface level, nephelometers have predominantly been used to measure light scattering properties.

In 2017, two nephelometers Aurora 3000, manufactured by Ecotech Company, where deployed at the Burjassot campus from the University of Valencia, for the determination of the total scattering coefficients in wet and dry conditions. In 2019, an Ecotech Aurora 4000 polar nephelometer was added in the Burjassot site for the determination of the scattering coefficients at different angle intervals. The Aurora 4000 model has been specifically designed with a backscatter shutter that can be set any angle between 10º and 90º at up to 17 different positions. It then has the ability to improve the determination of the aerosol asymmetry parameter. Measurements of the total scattering coefficient at ambient conditions, performed with a TSI 3563 nephelometer without sample conditioning, are also available since 2006.  

The Burjassot measurement site is located in the suburbs of Valencia city, with a total population of about 1 million inhabitants in its metropolitan area, and it is representative of urban conditions. It is mainly affected by anthropogenic aerosols originated by traffic, and sporadically regional agricultural or forest fires, but also by natural aerosols of marine (Mediterranean Sea) and desert (Saharan) origin.

In this work, we analyze the total and angular measurements of the scattering coefficient obtained with the total and polar Aurora nephelometers at Burjassot site, including its temporal variability and trends. Specific scenarios characterized by different atmospheric conditions are also studied in order to relate in situ measurements with the composition of atmospheric aerosols from different sources (Saharan dust, forest fires, traffic, etc).

 

This work is supported jointly by the Spanish Ministry of Economy and Competitiveness (MINECO) and the European Regional Development Fund (FEDER) under Projects CGL2017-86966-R, RTI2018-096548-B-I00 and PRE2018-084799.
Performance of a rotational sensor at Etna, Italy focusing on back-azimuth estimations of volcano-seismic events
Authors: Rosskopf Martina , Eibl Eva P. S. , Currenti Gilda , Jousset Philippe , Wassermann Joachim , Vollmer Daniel , Larocca Graziano , Pellegrino Daniele , Pulvirenti Mario , Contrafatto Danilo
Published: March 2021

The field of rotational seismology has only recently emerged. Portable 3 component rotational sensors are commercially available since a few years which opens the pathway for a first use in volcano-seismology. The combination of rotational and translational components of the wavefield allows identifying and filtering for specific seismic wave types, estimating the back azimuth of an earthquake, and calculating local seismic phase velocities.

Our work focuses on back-azimuth calculations of volcano-tectonic and long-period events detected at Etna volcano in Italy. Therefore, a continuous full seismic wavefield of 30 days was recorded by a BlueSeis-3A, the first portable rotational sensor, and a broadband Trillium Compact seismometer located next to each other at Mount Etna in August and September of 2019. In this study, we applied two methods for back-azimuth calculations. The first one is based on the similarity of the vertical rotation rate to the horizontal acceleration and the second one uses a polarization analysis from the two horizontal components of the rotation rate. The estimated back-azimuths for volcano-tectonic events were compared to theoretical back-azimuths based on the INGV event catalog and the long-period event back-azimuths were analyzed for their dominant directions. We discuss the quality of our back azimuths with respect to event locations and evaluate the sensitivity and benefits of the rotational sensor focusing on volcano-seismic events on Etna regarding the signal to noise ratios, locations, distances, and magnitudes.
Signal analysis between DAS and geophones in a vertical borehole from active and passive sources
Authors: Isken Marius Paul , Dahm Torsten , Heimann Sebastian , Wollin Christopher , Ohrnberger Matthias , Reinsch Thomas , Krawczyk Charlotte M.
Published: March 2021

We present an analysis and qualitative comparison between acoustic data recorded on a distributed acoustic sensing (DAS) instrument (Silixa iDAS, version 2) and a three-component geophone chain colocated in a 400 m deep ICDP borehole in the magmatically active Vogtland area, Germany. A tight buffer single-mode fiber optic cable with a structured surface was installed and cemented behind casing down to total depth of the well. Additionally, a vertical array of 10 Hz geophones is suspended within the borehole.At the surface, further geophones were installed to shape a permanent three-dimensional seismic array. For this experiment the DAS system sampled strain-rate data at 10 m gauge length and 1 m spacing, yielding a high-resolution image of the wave field. Both seismic systems recorded data for 24 hours at 1 kHz sampling rate.

Within these 24 hours of recording, we shot a vertical seismic profile (VSP) with a 300 kg heavy and 2.4 m tall drop weight source moving up to a distance of 400 m away from the wellhead. Furthermore, passive seismic events at local and regional distances were recorded.

We compare the signal quality between the DAS system and the calibrated three-component geophones using the active and passive signals, to determine the sensitivity, signal-to-noise ratios and frequency response. Further we investigate the noise characteristics of both systems in this natural and remote environment, and evaluate the feasibility of borehole DAS behind casing for micro-earthquake monitoring. We give an outlook how dense DAS data can be utilized for VSP experiments with the aim to develop methods for fault detection and characterisation for application in DAS data recorded at the surface.
Study on Deep Seated Gravitational Slope Deformation in the Slate Belt of the Backbone Range, Central Taiwan
Authors: Hsieh Yu-Chung , Chen Mien-Ming , Tai Tung-Lin , Chi Chung-Chi
Published: March 2021

In the mountain area, Deep seated gravitational slope deformation (DSGSD) is a phenomenon that causes rock mass deformation under long-term gravity. In the Slate Belt of the Backbone Range where mainly slate distributed, it is more susceptible to develop DSGSD. After Typhoon Morakot, the high-resolution LiDAR digital terrain data of the entire island of Taiwan could be applied to visual interpretation with the potential landslide area. In this study, we used existing high-resolution LiDAR data and the latest computerized 3D environments to conduct and explore preliminary geological information at the regional scale and potential large-scale landslide distribution with detailed topographical characteristics. Through field investigations and UAV application in Lusan area of central Taiwan, the features caused by regional tectonic effects or DSGSD could be clarified and discussed possible mechanism of rock mass failure caused by these DSGSD. The results help to understand the deformation mechanism of the slate area in the Central Range of Taiwan. In the future, we could further explore the possible causes of why DSGSD transform into catastrophic landslides.
Quantitively and novelty source fingerprinting N and P pollutants in sediment: Case study in a small catchment, North China 
Authors: Yu Hanqing , Adu-Gyamfi Joseph
Published: March 2021

The intensive farmland in north China accounts for more than 17% of China's arable land area and is main producing area of wheat and corn in China. The response of sources and loads of sediment of N and P pollutants to the high-intensity agricultural activities in north China still remains unclear. The study aims to quantify the source and magnitude of N and P pollutants in the sediment from different land use types using a novel application of compound-specific δ13C isotopes (CSSI), 137Cs and 210Pbex (FRNs), in a representative agricultural catchment (Jiangou). Surface (0-2 cm) soil and sediment samples were collected from different plant species for CSSI and FRNs, while subsurface (5-30 cm) soil samples were collected from channel bank for FRNs. The 137Cs cores (0-60 cm) collected at the outlet of the catchment and also at reference sites. Sediment sources from surface and subsurface soils were derived by FRNs data which accounted by 83±6% and 17±6%, respectively, while the sediment sources from maize, bean, vegetable farmlands and forestlands on the surface soil areas were identified by CSSI data. Combining FRNs and CSSI fingerprinting techniques, the dominant sediment source was derived from maize farmland which contributed by 60±8%, followed by channel bank, bean farmland and vegetable farmland which accounted for 17±6%, 12±3% and 8±3%, respectively, and the least contribution was from forestland (3±1%). According to the 137Cs cores (0-60 cm) collected at the outlet of Jiangou catchment, a sedimentation rate of 23.38±0.22 t ha-1 yr-1 of this study catchment was quantified. The 137Cs inventory of the reference site was 1162±131Bq m-2. Based on the measured of N and P concentrations in source samples, and areas of land uses in this catchment, we quantitatively estimated the N pollutant in sediment (t yr-1) from maize (2.19), bean (0.42), vegetable farmlands (0.31), forestland (0.49) and channel bank (0.05), while P pollutant (t yr-1) were 4.39 for maize, 0.18 for beans, 0.28 for vegetable farmland, 0.37 for forestland and 0.04 for channel bank. This study shows that the novel conjunctive use of FRNs and CSSI techniques could quantify the N and P pollutants in sediment from different land uses in catchment, which is critical to assess and implement effective agricultural and land management practices.
Drought risk in urban areas: a monetization of drought risk in 97 cities around the globe
Authors: Stolte Tristian , Ward Philip , de Moel Hans , van Veldhoven Felix , Garg Snigdha , Farhad Neuni
Published: March 2021

This research attempts to monetize drought risk in 97 cities around the globe, using multiple climate and socioeconomic scenarios. Subsequently, it identifies possible adaptation actions to mitigate drought risk in these cities. This study is essential because whilst much effort has been put into modelling drought on all spatial scales in recent decades, urban areas are often not explicitly included in these analyses, even though we live in a rapidly urbanizing world. Two types of drought risks for cities are identified and investigated: (1) drought induced food shortages and increased food prices (agricultural drought), and (2) municipal surface water supply shortages (hydrological drought). To assess agricultural drought risk, we represent the hazard using the Standardized Soil Moisture Index, and exposure using physical agricultural areas. For hydrological drought risk, we represent the hazard by linking discharge data from climate models to water withdrawals per city, with exposure data on the total population of a city. The risks are monetized by estimating the replacement costs of freshwater by means of alternative water sources like desalination. Vulnerability is qualitatively included by spatially overlapping the monetized values with vulnerability indicators and primarily gives context to the risk estimates. Finally, an inventory of reactive, preventive and transformative adaptation actions is developed to provide cities with a perspective for action. Cities may use this inventory to identify a mix of adaptation measures, where a combination of the three approaches would be an adequate way to address both short- and long-term risks and opportunities. The overall goal of this research is to provide an order of magnitude of potential drought risk, as well as to identify possible next steps in drought risk research in urban areas.
Global coronal and heliospheric magnetic field modelling for Solar Orbiter
Authors: Wiegelmann Thomas , Neukirch Thomas , Chifu Iulia , Inhester Bernd
Published: March 2021

Computing the solar coronal magnetic field and plasma
environment is an important research topic on it's own right
and also important for space missions like Solar Orbiter to
guide the analysis of remote sensing and in-situ instruments.
In the inner solar corona plasma forces can be neglected and
the field is modelled under the assumption of a vanishing
Lorentz-force. Further outwards (above about two solar radii)
plasma forces and the solar wind flow has to be considered.
Finally in the heliosphere one has to consider that the Sun
is rotating and the well known Parker-spiral forms.
We have developed codes based on optimization principles
to solve nonlinear force-free, magneto-hydro-static and
stationary MHD-equilibria. In the present work we want to
extend these methods by taking the solar rotation into account.
The impact of sediment resuspension on non-cyanobacterial nitrogen fixation along the Southern Baltic coastline
Authors: Liesirova Tina , Aarenstrup-Launbjerg Tobias , Riemann Lasse , Voss Maren
Published: March 2021

Benthic nitrogen fixation by heterotrophic non-cyanobacterial diazotrophs (NCDs) is common in anoxic marine sediments, however, it is currently unclear how resuspension of sediments affects this activity. Moreover, physical mixing processes are strongest in shallow coastal waters where permeable sediments prevail and anoxic conditions rarely occur. It is therefore of interest to understand whether such coastal sites provide ecological niches for NCDs. In order to gain insight into NCD nitrogen fixation during sediment resuspension, slurry incubations were carried out with nearshore sediments from stations along the Southern Baltic coastline and, for comparison, with anoxic sediments from the Gdansk Deep. Parallel to this, we carried out separate incubations treated with sodium molybdate, an inhibitor of sulfate reducing bacteria (SRB), to differentiate SRB activity from total NCD activity. Our data show low rates of nitrogen fixation by NCDs and indicate that SRBs (e.g. Desulfovibro) are actively fixing nitrogen. Nitrogen fixation rates varied greatly between locations, influenced by sediment grain size and POC-loading. Interestingly, nitrogen fixation took place despite of micromolar concentrations of inorganic nitrogen, which implies that NCDs may be more resilient towards N-stress than formerly expected. In conclusion, our experimental study supports previous findings of stimulation of nitrogen fixation by sediment resuspension, even in permeable sediments, however, at low rates.
Wind-forced submesoscale symmetric instability around deep convection in the NW Mediterranean Sea
Authors: Bosse Anthony , Testor Pierre , Damien Pierre , Estournel Claude , Marsaleix Patrick , Mortier Laurent , Prieur Louis , Taillandier Vincent
Published: March 2021

During the winter from 2009 to 2013, the mixed layer reached the seafloor at about 2500m in the NW Mediterranean. Intense fronts around the deep convection area were repeatedly sampled by autonomous gliders, mainly as part of the MOOSE observatory of the NW Mediterrnean Sea (https://www.moose-network.fr/). Subduction down to 200-300m, sometimes deeper, below the mixed layer was regularly observed testifying of important frontal vertical movements. Potential Vorticity dynamics was diagnosed using glider observations and a high resolution realistic model at 1-km resolution (SYMPHONIE model, https://sirocco.obs-mip.fr/ocean-models/s-model/).

During down-front wind events in winter, remarkable layers of negative PV were observed in the upper 100m on the dense side of fronts surrounding the deep convection area and successfully reproduced by the numerical model. Under such conditions, symmetric instability can grow and overturn water along isopycnals within typically 1-5km cross-frontal slanted cells. Two important hotpspots for the destruction of PV along the topographically-steered Northern Current undergoing frequent down-front winds have been identified in the western part of Gulf of Lion and Ligurian Sea. Fronts were there symmetrically unstable for up to 30 days per winter in the model, whereas localized instability events were found in the open-sea, mostly influenced by mesoscale variability. The associated vertical circulations also had an important signature on oxygen and fluorescence, highlighting their under important role for the ventilation of intermediate layers, phytoplankton growth and carbon export.
New Method for Estimating Double-Diffusive Dissipation Rates
Authors: Middleton Leo , Fine Elizabeth , MacKinnon Jennifer , Alford Matthew , Taylor John
Published: March 2021

Understanding the transport of heat in the Arctic ocean will be vital for predicting the fate of sea-ice in the decades to come. Small-scale turbulence is an important driver of heat transport and one of the major forms of this turbulence is known as `double-diffusive convection'. Double diffusion refers to a variety of turbulent processes in which potential energy is released into kinetic energy, made possible in the ocean by the difference in molecular diffusivities between salinity and temperature.  The most direct measurements of ocean mixing require sampling velocity or temperature gradients on scales <1mm, so-called microstructure measurements. Here we present a new method for estimating the energy dissipated by double-diffusive convection using temperature and salinity measurements on larger scales (100s to 1000s of metres). The method estimates the up-gradient diapycnal buoyancy flux, which is hypothesised to balance the dissipation rate. To calculate the temperature and salinity gradients on small scales we apply a canonical scaling for compensated thermohaline variance (or `spice') and project the gradients down to small scales. We apply the method to a high-resolution survey of temperature and salinity through a subsurface Arctic eddy (Fine et al. 2018) and compare the results with simultaneous microstructure measurements. The new technique can reproduce up to 70% of the observed dissipation rates to within a factor of 3. This suggests the method could be used to estimate the dissipation and heat fluxes associated with double-diffusive convection in regions without microstructure measurements. Finally, we show the method maintains predictive skill when applied to a sub-sampling of the CTD data at lower resolutions.
SDR (Seaward Dipping Reflectors) types in the water area of the Mendeleev Rise, Arctic Ocean
Authors: Rodina Elizaveta , Nikishin Anatoly , Startseva Ksenia
Published: March 2021

The Mendeleev Rise is represented by an asymmetric uplifted crustal block with strongly rugged by half-graben and horst structures. High-amplitude reflectors similar to SDR (Seaward Dipping Reflectors) were found in half-grabens. Similar structures were found in the Toll and Podvodnikov basins.

The top of the SDR complex is usually relatively well defined and corresponds to the rift-post-drift boundary with an age of about 100 Ma. Small, sharp conical build-ups with a chaotic internal structure are often observed at the top of the SDR – probably submarine volcanoes. There may have been two stages of volcanism. The bottom of the SDR complex corresponds to the top of the acoustic basement (about 125 Ma). The thickness of one wedge is about 1, 5 - 3 sec. The length of distinct wedges in the Mendeleev Rise’s area is about 25-50 km, in the Podvodnikov basin’s area – 50-100 km.

Several types of SDR have been identified. The first type is identified within the Toll basin and the Mendeleev Rise. This is the most classic type.  Wedges of this type are characterized by greater thickness, but less length. Wedges are strongly curved. Several distinct wedges stand out. Distinct wedges overlap each other towards the stretch center and start from one point. SDR have longer wedges and slightly less thickness in the Podvodnikov basin’s area. The SDR complex is highly spaced apart. Wedges are less curved. Distinct wedges are located in separate half-grabens and have no common starting point. The reflectors cool down and become brighter in the central part of the Podvodnikov basin, near the axial horst. Both complexes are characterized by probable existence volcanic edifices in the top.

We traced the distribution and direction of SDRs, the bottom of the grabens, the position of probable volcanic edifices and made a map. There is symmetry and logic in the distribution of SDR. In the Toll basin, reflectors fall into each other – from the Mendeleev Rise and from the Chukotka plateau – and meet at a structure reminded of an interrupted rift. The rift is parallel to the Mendeleev Rise and the Chukotka Plateau. We can see at on Magnetic Anomalies Map. This probably corresponds to the central axis of extension of the Toll basin. Oppositely directed SDRs from the Mendeleev Rise and the Lomonosov Ridge meet near a raised block in the Podvodnikov basin. Nature of raised block is not fully understood. We call it axial horst. This uplift is subparallel to the Mendeleev Rise. This is probably associated with the central extension axis for the Podvodnikov basin.

Mendeleev Rise, Podvodnikov and Toll basins were formed approximately at the same time according to the seismic correlation.

This study was supported by RFBR grant (18-05-70011).
Trends in shoreline variability driven by anthropogenic change, EThekwini Municipality, South Africa
Authors: Wiles Errol , Leuci Rio , Thakeray Zane , Vella Godfrey
Published: March 2021

It is well-known that the coastal zone attracts human populations like no other. There is ever increasing demand on the coastal zone by tourists, residents and developers alike; it is named as the fastest growing sector of the blue economy. Hence, coastal zone processes require better understanding to be effectively managed in the context of sustainable development of the asset. While sea level may be rising over the long-term, and many global-resolution studies lament the loss of sandy beaches as a result, coastal managers work over far shorter time-scales thus require site specific information to manage the coastal zone on a daily and monthly basis. In this contribution we discuss nine years of morphological change along a sandy beach in Durban, South Africa. The beach is managed by the eThekwini Municipality who are responsible for maintaining a coastal zone of ca. 100 km. The morphological data of this study were collected on a near monthly basis over 9.6 km of sandy beach between October 2011 and March 2020. From these data, beach volume and area are calculated and the variation is documented over time in conjunction with wave data recorded from a proximal directional wave buoy. Over the study period, the beach has experienced a net loss of 177 885m3 and 29 375 m2 in volume and area respectively. However, the beach response has not been uniform throughout the study area. The southern three-quarters of the beach were affected by significant losses while the northern one-quarter gained in volume and area over the same period. The summer wave climate is characterised by increased variability in swell origin with greater easterly contributions than other seasons, and typically lacks the frequency of large swell (>3.5 m) events (7% of events) common to autumn (20%), winter (35%) and spring (38%). Winter, followed by spring then autumn seasons have more focused swell origins and southerly contribution, particularly in terms of large swell events. During periods of reduced event frequency allow for partial beach recovery, while erosion is associated with periods of increase event frequency. The sediment budget has been significantly reduced though impoundments on the proximal river catchment, compounded by un-managed sand mining. Rather than sea level, these near-field controls on sediment availability likely play a major role in beach volume and area in response to wave climate. There is less sediment available to nourish the beach naturally following erosional events; artificial nourishment will likely be required to maintain the sandy beach in the future.
Detecting Climate Fingerprints in Southern Ocean Carbon using a Biogeochemical Ocean Model
Authors: Wright Rebecca , Le Quéré Corinne , Buitenhuis Erik , Bakker Dorothee
Published: March 2021

The Southern Ocean plays an important role in the uptake, transport and storage of carbon by the global oceans. These properties are dominated by the response to the rise in anthropogenic CO2 in the atmosphere, but they are modulated by climate variability and climate change. Here we explore the effect of climate variability and climate change on ocean carbon uptake and storage in the Southern Ocean. We assess the extent to which climate change may be distinguishable from the anthropogenic CO2 signal and from the natural background variability. We use a combination of biogeochemical ocean modelling and observations from the GLODAPv2020 database to detect climate fingerprints in dissolved inorganic carbon (DIC).

We conduct an ensemble of hindcast model simulations of the period 1920-2019, using a global ocean biogeochemical model which incorporates plankton ecosystem dynamics based on twelve plankton functional types. We use the model ensemble to isolate the changes in DIC due to rising anthropogenic CO2 alone and the changes due to climatic drivers (both climate variability and climate change), to determine their relative roles in the emerging total DIC trends and patterns. We analyse these DIC trends for a climate fingerprint over the past four decades, across spatial scales from the Southern Ocean, to basin level and down to regional ship transects. Highly sampled ship transects were extracted from GLODAPv2020 to obtain locations with the maximum spatiotemporal coverage, to reduce the inherent biases in patchy observational data. Model results were sampled to the ship transects to compare the climate fingerprints directly to the observational data.

Model results show a substantial change in DIC over a 35-year period, with a range of more than +/- 30 µmol/L. In the surface ocean, both anthropogenic CO2 and climatic drivers act to increase DIC concentration, with the influence of anthropogenic CO2 dominating at lower latitudes and the influence of climatic drivers dominating at higher latitudes. In the deep ocean, the anthropogenic CO2 generally acts to increase DIC except in the subsurface waters at lower latitudes, while climatic drivers act to decrease DIC concentration. The combined fingerprint of anthropogenic CO2 and climatic drivers on DIC concentration is for an increasing trend at the surface and decreasing trends in low latitude subsurface waters. Preliminary comparison of the model fingerprints to observational ship transects will also be presented.
Carbon degradation in Subarctic organic permafrost (peat plateaus) after thawing – what constraints CO2 and CH4 production? 
Authors: Kjær Sigrid Trier , Nedkvitne Nora , Westermann Sebastian , Althuizen Inge , Dörsch Peter
Published: March 2021

Rapid warming in Subarctic areas releases large amounts of frozen carbon which can potentially result in large CO2 and CH4 emissions to the atmosphere. In Northern Norway vast amount of carbon are stored in peat plateaus, but these landscape elements have been found to decrease laterally since at least the 1950s. Peat plateaus are very sensitive to climate change as the permafrost is relatively warm compared to permafrost found in the arctic. So far, only limited information is available about potential degradation kinetics of organic carbon in these ecosystems. We sampled organic matter from depth profiles along a well-documented chronosequence of permafrost degradation in Northern Norway. After thawing over-night, we incubated permafrost and active layer for up to 3 months at 10°C. To determine factors constraining degradation, we measured gas kinetics (O2, CO2, CH4) under different conditions (oxic/anoxic, loosely packed/stirred suspensions in water, with altered DOC content and nutrient amendments) and related them to pH, DOC, element (C, N, P, S) and δ13C and δ15N signatures of the peat. Organic matter degradation was strongly inhibited in the absence of oxygen. By contrast, CH4 production or release seemed to be related to soil depth rather than incubation conditions and was found to be highest in samples from the transition zone between active layer and permafrost. Degradation rates and their dependencies on peat characteristics will be compared with permafrost characteristics along the chronosequence and additional experiments exploring the role of O2, DOC and other nutrients for carbon degradation will be discussed.
Tauride Carbonate Platform Bauxite Deposits (Turkey) as an Alternative Source for Gallium
Authors: Bayram Hatice Nur , Bakkalbasi Ali Erdem , Doner Zeynep , Unluer Ali Tugcan , Kocaturk Huseyın , Yıldırım Demet , Budakoğlu Murat
Published: March 2021

Mediterranean type karstic bauxite deposits are considered as the primary source for aluminum (Al) production in Europe. During the Al production, Gallium (Ga) is extracted from the so called Bayer-liquor during the processing of bauxite to alumina. Ga, a rare metal, is widely used in modern chemistry and electronic industry. During the past decades, the worldwide demand for Ga has been continuously increasing. In Turkey, karstic bauxite deposits are generally found with shallow marine carbonate rocks which were deposited during Mesozoic period and located in Tauride Carbonate platform. Most of these karstic bauxite deposits can be hosted considerable Ga enrichments, with other immobile elements such as rare earth elements (REE), titanium (Ti), lithium (Li), and iron (Fe). This work focuses on the revealing of the potential Ga enrichments in bauxides from different deposits of Turkey (Mortaş-Doğankuzu, Konya; Küçükkoraş, Karaman; Acıelma-Yoğunoluk, Kahramanmaraş bauxite deposits). Geochemical data of major and trace elements of studied bauxite deposits show that these deposits have significant Ga enrichments (up to 72.6 ppm), as well as the REE (up to 580 ppm), Ti (up to 1.8%), and Li (up to 428 ppm) enrichments. In addition, the Ga enrichments show strong positive correlation with heavy rare earth elements (HREE) and moderate positive correlation with Al, Fe, Ti, Li and Sn elements. In this context, it can be concluded that the most probable source for Ga is rock forming aluminosilicates of the source rock due to the substitution with Al3+ and Fe3+. During weathering process Ga exhibiting immobile behavior much like Al and Fe. Gallium is than incorporated into Al-bearing phases and thus enriched in the bauxite. Presence of Li content can be also interpreted as a contribution from micaceous source such as meta-carbonate rocks of Tauride platform. Moreover, geochemical association between Ga, Ti, Li, tin (Sn) and HREE can be explained by the redox and pH conditions causing other ions seperated from shallow environments.
Crustal structure of La Palma and Tenerife (Canary Islands) from receiver function analysis.
Authors: Ortega Víctor , D'Auria Luca , Cabrera-Pérez Iván , Barrancos José , Padilla Germán D. , Pérez Nemesio M.
Published: March 2021

The receiver function analysis (RF) is a commonly used and well-established method to investigate crustal and mantle structures, removing the source, ray-path and instrument signatures. RF gives the unique signature of sharp seismic discontinuities and information about P and S wave velocities beneath a seismic station. In particular, using the direct P wave as a reference arrival time, and the relative arrival time of P-to-S (Ps) conversions and multiple reflections allow constraining the principal crustal structures and studying the effects of dipping interfaces and crustal layering.

We have applied RF analysis to the active volcanic islands of Tenerife and La Palma (Canary Islands). In recent years, both islands have increased their seismic activity and showed variation in geochemical parameters attributed to a magmatic-hydrothermal activity. Previous studies evidenced in La Palma and Tenerife a seismic Moho depth at 14 km and 12 and 15 km, respectively, but it is not clear because there are some others discontinuities under the stations (Lodge et al., 2012). Other RF studies indicated a depth of seismic Moho discontinuity between 16 and 30 km beneath the eastern islands to 11-15 km under the western isles, observing a thinning of the crust towards the west (Martinez-Arévalo et al., 2013). 

We processed 313 teleseisms recorded by 17 stations for Tenerife and 252 teleseisms recorded by six stations for La Palma. Since the receiver functions display a significant complexity, as expected in oceanic volcanic islands, we applied a transdimensional inversion approach to image the 1D velocity structure beneath each station. We observe at least three discontinuities related with the oceanic crust and the overlying volcanic rocks layer. We compare the retrieved crustal structure with the seismicity recorded in recent years, showing how earthquakes have a radically different origin on these two islands. While in Tenerife they seem to be related to the dynamics of a shallow hydrothermal system, in La Palma they are related to magmatic intrusions in the upper mantle beneath the island.

References

Lodge, A., Nippress, S. E. J., Rietbrock, A., García-Yeguas, A., & Ibáñez, J. M. (2012). Evidence for magmatic underplating and partial melt beneath the Canary Islands derived using teleseismic receiver functions. Physics of the Earth and Planetary Interiors, 212, 44-54.

Martinez-Arevalo, C., de Lis Mancilla, F., Helffrich, G., & Garcia, A. (2013). Seismic evidence of a regional sublithospheric low velocity layer beneath the Canary Islands. Tectonophysics, 608, 586-599.
Eco-evolutionary responses of plant communities to drought and rainfall variability
Authors: Joshi Jaideep , Stocker Benjamin , Hofhansl Florian , Zhou Shuangxi , Brännström Åke , Prentice Iain Colin , Dieckmann Ulf
Published: March 2021

The future Earth is projected to experience elevated rainfall variability, with more frequent and intense droughts, as well as high-rainfall events. Increasing CO2 concentrations are expected to raise terrestrial gross primary productivity (GPP), whereas water stress is expected to lower GPP. Plant responses to water stress vary strongly with timescale, and plants adapted to different environmental conditions differ in their functional responses. Here, we embed a unified optimality-based theory of stomatal conductance and biochemical acclimation of leaves we have recently developed [Joshi, J. et al. (2020) Towards a unified theory of plant photosynthesis and hydraulics. bioRxiv 2020.12.17.423132] in an eco-evolutionary vegetation-modelling framework, with the goal to investigate emergent functional diversity and associated GPP impacts under different rainfall regimes.

The model of photosynthesis used here simultaneously predicts the stomatal responses and biochemical acclimation of leaves to atmospheric and soil-moisture conditions. Using three hydraulic traits and two cost parameters, it successfully predicts the simultaneous declines in CO2 assimilation rate, stomatal conductance, and leaf photosynthetic capacity caused by drying soil. It also correctly predicts the responses of CO2 assimilation rate, stomatal conductance, leaf water potential, and leaf photosynthetic capacity to vapour pressure deficit, temperature, ambient CO2, light intensity, and elevation. Our model therefore captures the synergistic effects of atmospheric and soil drought, as well as of atmospheric CO2 changes, on plant photosynthesis and transpiration.

We embed this model of photosynthesis and transpiration in a trait-height-patch structured eco-evolutionary vegetation model. This model accounts for allometric carbon allocation, height-structured competition for light, patch-structured successional dynamics, and coevolution of plant functional traits. It predicts functional species mixtures and emergent ecosystem properties under different environmental conditions. Using this model, we investigate the evolution of plant hydraulic strategies under different regimes of drought and rainfall variability. Our approach provides an eco-evolutionarily consistent framework to scale up the responses of plant communities from individual plants to ecosystems to provide ecosystem-level predictions of functional diversity, primary production, and plant water use, and could thus be used for reliable projections of the global carbon and water cycles under future climate scenarios.
ROBOTS for MOON EXPLORATION
Authors: Litvak Maxim , Mitrofanov Igor , Zelenyi Lev , Tretyakov Vladislav , Kozlova Tatiana , Mokrousov Maxim , Kozyrev Alexander , Nosov Artem , Yakovlev Vladislav
Published: March 2021

Russian lunar program includes several landing missions of Luna-25, Luna-27, Luna-28 which should be implemented step by step to explore mineralogical, chemical, and isotopic compositions of the lunar polar regolith, search for volatile compounds, deliver soil samples to the Earth and prepare future manned expeditions to Moon.

The successful implementation of these missions requires employing of excavation and drilling of lunar regolith to the different depths with extraction of soil samples for the farther analysis (in situ or sample return).The first mission in row Luna-25 will be launched in October 2021 and landed at the area located north of Boguslawsky crater. This lander is equipped with the Lunar Manipulation Complex (LMC) – the robotic arm that should excavate lunar regolith (down to 5 – 25 cm) and deliver sample of lunar soil to the analytical instrumentation for the elemental and isotopic analysis. The robotic arm is already passed through the validation, functional and calibration tests in lunar-like conditions (low pressures and low temperatures) to imitate interaction with lunar soil simulant enriched with different content of water.

The Luna – 27 and Luna – 28 will be landed at southern polar regions (landing site selection is in progress). They will be equipped with Deep Drill Systems (DDS) to take samples of polar regolith enriched with water ice and other volatiles from 1-2 m depths. The DDS for Luna-27 , as part of the PROSPECT suit, shall be contributed by ESA. The DDS for Luna – 28 (the sample polar return mission) is being developed by Space Research Institute.In this presentation we report the results of ground tests with LMC units and DDS prototype.In addition to DDS, it is expected that Luna – 28 will carry a small sized lunokhod (~100 kg) to support sample collection and proceed with geological survey program (up to 30 km around the landing site per one year). The lunokhod will study elemental/isotopic/mineral composition of lunar regolith along rover traverse to estimate accessibility of lunar resources (first of all, water ice as a source of hydrogen and oxygen) applicable for potential industry utilization and support of manned expeditions. 

The Russian lunar program assumes synergy of robotic and manned missions. Beyond Luna -25,27,28, it is expected that the next lunar missions will deliver to Moon surface heavy lunokhod, which will prepare the landing of the manned mission.  Finally, as part of testing program for manned lander (without cosmonauts), it is proposed to deliver multifunctional robotic equipment to support  the following arrival of cosmonauts. 
The unit peak discharge as a tool for flood magnitude comparison and analysis
Authors: Balasch Josep Carles , Tuset Jordi , Barriendos Mariano , Castelltort Xavier , Pino David
Published: March 2021

To analyze the river floods dynamics, it is common to fix the observations of the flow at a characteristic checkpoint of the basin, showing its evolution over time:  the hydrograph. A less common way of studying this hydrological phenomenon is the analysis of the unit peak discharge of the flood (i.e., the peak flow divided by the contributory area of the basin) along different checkpoints of the drainage axis.

If this second methodology is chosen for the analysis of the river flooding, the circulation of flows through the river network generally shows that as the contributory area of the basin increases the unit peak discharge decreases. This is due to the reduction in the amount of precipitation and the slope of the riverbed with the increase of the basin area as it moves away from the headwaters. However, this simple scheme can have very different behavior depending on factors such as the spatial and temporal distribution of precipitation, the presence of snow, the soil moisture, the geological substrate, land uses, or human activities.

This study compares the hydrological data of several historical and recent floods in NE basins of the Iberian Peninsula from the perspective of observing the unit peak flows depending on the size of the drained basin (i.e., the spatial evolution of the specific maximum discharge). These basins are small in size (usually below 500 km2) and drain regions such as the central Pyrenees (Garonne, Noguera Pallaresa), the Ebro Depression (rivers Ribera Salada, Sió, Ondara, Corb) and the Catalan Coastal System (Francolí), that is, they belong to very diverse geographical environments.

The results allow to compare the magnitude of the unit peak flows in the headwaters and the decreasing of this variable when moving downstream. The unit peak discharges of the tributaries of the Ebro Depression, near the Catalan Coastal System are much higher when comparing with the flow of the Pyrenean rivers. For many floods of the Ebro basin of medium magnitude, the unit peak flow is reduced by the runoff infiltration in the flood plains favored by agricultural activities. In the Pyrenean rivers the spatial decrease of the unit peak discharge is gentle than in those of the Ebro Depression. The results show different patterns of flow generation and propagation that have implications for managing the dangerousness of flood risk, especially in very small basins (< 10 km2), where peak flows can be unexpectedly large and devastating.
Effect of Southern Hemisphere Westerlies on hydroclimate and seasonality from the Last Glacial Maximum: Using the fossil charcoal and pollen records from Elands Bay Cave and Boomplaas Cave, South Africa
Authors: Khumalo Wendy , Hare Vincent , Pickering Robyn
Published: March 2021

Palaeoproxy records during the Last Glacial Maximum (LGM) in Southern Africa have not offered consistent results regarding hydroclimate of the region. Similarly, models from the Palaeoclimate/Coupled Modelling Intercomparison Project (PMIP/CMIP) show varying results with regards to the movement of the Southern Hemisphere (SH) Westerlies. An equator-wards shift in the SH Westerlies has long been used to account for increased precipitation in Southern Africa during the LGM. Palynological studies have supported this narrative citing the presence of higher precipitation species during the LGM as evidence of increased precipitation. This project uses the fossil charcoal and pollen assemblages from Elands Bay Cave (EBC) and Boomplaas Cave (BPC) to quantify the change in Mean Annual Temperature (MAT) and Total Annual Precipitation (TAP) using the recalibrated age models at both sites to understand the change in hydroclimate of the region. These sites are both spatially and temporally ideal to track changes in the SH Westerlies with both sites recording floral assemblages from the Last Glacial Period, the LGM, and deglaciation at EBC in the Winter Rainfall Zone (WRZ) and BPC in the Year-round Rainfall Zone (YRZ). Both rainfall zones receive precipitation from mid-latitude frontal systems associated with the SH Westerlies. The YRZ is associated with both the mid-latitude frontal systems and tropical disturbances. A database of the modern-day distribution of the taxa identified in the stratigraphy at EBC and BPC was created using the Global Biodiversity Information Facility and paired with modern climate data from WorldClim to perform a Weighted Average – Partial Least Squares (WA-PLS) regression to predict MAT and TAP. Most of the WA-PLS regression models predict temperatures around 7°C at the LGM, consistent with regional records. The predicted TAP at the LGM is mostly lower than that of the Last Glacial Period. In the case of EBC in the WRZ, decreased precipitation is consistent with a decrease in intensity of the frontal system and/or a polewards shift in the SH Westerlies at the LGM. Similarly, decreased precipitation in BPC in the YRZ implies decrease in intensity of frontal systems and/or a polewards shift in the SH Westerlies. This poleward shift in the SH Westerlies has been demonstrated in some climate models, the parameters of which need further interrogation.
Multifractal analysis of extinction coefficient and its consequences in characterizing atmospheric visibility
Authors: Jose Jerry , Gires Auguste , Tchiguirinskaia Ioulia , Schertzer Daniel
Published: March 2021

Extinction coefficient (σe) is a measure of light attenuation in the atmosphere, due to absorption and scattering properties of constituent gases and aerosols. In meteorological context, σe is used to understand transparency of the atmosphere, by estimating visibility or meteorological observable range (MOR). An accurate representation of visibility is required for safe functioning of various domains such as transport sectors, free optic communication, etc., and for understanding regional variations in air quality and climate. As the measurement of visibility is subjective and dependent on the instrument and range of measurement, here we attempt to characterize the same using extinction coefficient. σe was investigated under the framework of universal multifractals (UM), which is widely used to analyze and characterize geophysical fields that exhibit extreme variability over measurement scales.

For this study, σe was extracted from forward scattering visibility data by disdrometer (Campbell Scientific PWS100) located in the Paris area (France), operated by Hydrology, Meteorology, and Complexity laboratory of École des Ponts ParisTech (HM&Co, ENPC). As governing nonlinear equations of the atmosphere such as Navier-Stokes possess scale invariance, it was assumed here that the behavior of light attenuating particles should inherit similar scaling properties and hence be treated as multifractal fields. σe extracted from MOR measured at Paris-Charles de Gaulle airport was also subjected to multifractal analysis during the same time period for comparison. With direct analysis and simulations, it was found that σe exhibits multifratcal properties but are influenced by upper limit of visibility range in the instrument used for measurement. From the study, we suggest usage of extinction coefficient (σe) for characterizing atmospheric visibility as the former is a more physically relevant quantity which is objectively measured by instruments and directly related to particles in the atmosphere; while emphasizing the need to consider biases from instrumental range.