bluuebunny/crossref_metadata_2025 huggingface dataset:
Constraining P-T conditions using a SEM Automated Mineralogy based workflow – an example from Cap de Creus, NE Spain
Authors: Wessels Richard , Kok Thijmen , van Melick Hans , Drury Martyn
Published: March 2022

The spatial distribution of mineral phases in a thin section provides information about the mineral reactions and deformation history of the sample. This information is often difficult to obtain using classical optical microscopy or SEM analyses, as the spatial resolution is too small to provide the necessary overview. SEM Automated Mineralogy (AM) delivers false colour mineral phase maps at the full thin section scale. Combined with full-sized PPL and XPL thin section scans, this provides an exceptional high-resolution overview of the mineral content and microstructures. Moreover, SEM-AM provides quantitative information about the mineral and bulk rock compositions, which can subsequently be used in thermodynamic modelling to establish P-T conditions for the entire, or a subset of, the rock sample.

The structural geology group at Utrecht University recently acquired a SEM-EDS system with Automated Mineralogy capabilities. The accuracy of the EDS system was compared against WDS microprobe measurements, while the SEM-AM based bulk rock composition of the thin section was compared against XRF data from the corresponding sample dummy. Subsequently, the SEM-AM bulk rock composition was used as input for thermodynamic modelling using Perple_X. Independent temperature estimates were established using; i) SEM-EBSD based CPO results on quartz, in conjunction with the quartz recrystallization mechanisms and recrystallized grain size; and ii) titanium-in-quartz using nano-SIMS analyses. Further constraints on fluid-rock-melt interactions were obtained by using LA-ICP-MS.

This workflow is applied to samples from the Cap de Creus region in northeast Spain. Located in the axial zone of the Pyrenees, the pre-Cambrian metasediments underwent HT-LP greenschist- to amphibolite-facies metamorphism, are intruded by pegmatite bodies, and overprinted by greenschist-facies shear zones. The SEM-AM workflow allowed to further constrain the prograde and retrograde P-T conditions in the different metamorphic zones. In addition, at the thin section scale, the results show temporal and spatial variations in the mineral reactions that occurred.  

In the near future, this workflow will be refined and included in the broader correlative microscopy workflow that will be applied in the H2020-funded EXCITE project (https://excite-network.eu/), a European collaboration of electron and x-ray microscopy facilities and researchers aimed at structural and chemical imaging of earth materials. The data will be made available in a FAIR manner through the EPOS (European Plate Observing System) data publication chain (https://epos-msl.uu.nl/).
A tree of Indo-African mantle plumes imaged by seismic tomography
Authors: Tsekhmistrenko Maria , Sigloch Karin , Hosseini Kasra , Barruol Guilhem
Published: March 2022

Mantle plumes are commonly envisioned as thin, buoyant conduits rising vertically from the core-mantle boundary (CMB) to the earth's surface, where they produce volcanic hot spots. Most hotspots are located in the sparsely instrumented oceans, creating poor prospects for the seismic resolution of thin conduits in the deep mantle. 

The RHUM-RUM experiment remedied this issue around the hotspot island of La Réunion by instrumenting 2000x2000 km2 of seafloor for 13 months with 57 broadband ocean-bottom seismometers (OBS). We present a 3-D P-wave tomography model computed from the RHUM-RUM waveform data, supplemented by a global data set of P-diffracted measurements and a selection of ISC picks. Multifrequency travel times were measured on the waveforms and inverted in a finite-frequency framework. We achieve high image resolution beneath the Indian Ocean hemisphere, and especially beneath La Réunion, from upper mantle to CMB.

We observe the Large Low-Velocity Province (LLVP) rising 800 km above the CMB, forming a cusp beneath South Africa. A low-velocity branch undulates obliquely from this cusp region towards the uppermost mantle beneath La Réunion. Hence La Réunion's connection to the lower mantle is more complex than previously envisioned, being neither a thin vertical conduit nor projecting down to an edge of the LLVP. The deep-mantle connections of the Afar and Kerguelen hotspots emerge from the same LLVP cusp beneath South Africa and extend towards the surface through tilted low-velocity branches. 

Our results provide the first high-resolution image of a western Indian Ocean plume cluster from the surface to the CMB. This represents a key advance for linking geophysical, geodynamic and geochemical observations.
Estimating average Nitrogen Oxide emissions from inland waterway vessels using MAX-DOAS measurements
Authors: Ripperger-Lukosiunaite Simona , Dörner Steffen , Donner Sebastian , Lauster Bianca , Beirle Steffen , Remmers Julia , Wagner Thomas
Published: March 2022

Nitrogen oxides (NOx = NO + NO2) have a negative impact on human health and play an important role in tropospheric air chemistry. Inland waterway vessels are equipped with long lasting diesel engines that emit NOx and might have a significant impact on the local air quality. This is particularly relevant for the residential areas that are located along intensively used waterways, e.g. the Rhine River. Monitoring of NOx emissions from inland waterway vessels could provide the local authorities with valuable information about ship contribution to air pollution.

In this presentation we show that ground-based MAX-DOAS (Multi AXis-Differential Optical Absorption Spectroscopy) measurements, performed at the Rhine River in western Germany, are feasible for the emission plume identification from individual inland waterway vessels. However, especially for ships with rather low emissions, not always an unambiguous detection is possible, especially if the tropospheric NO2 background is high and variable. For such cases we developed an automatic background correction, and we analysed the emissions in a more statistical way. The focus of this study is put on this method by investigating the height dependency of the averaging background-corrected NO2 signals and finally estimating average NOx emissions from inland ships.
An update on polar stratospheric clouds within CLaMS
Authors: Tritscher Ines , Grooß Jens-Uwe , Spang Reinhold , Pitts Michael , Müller Rolf
Published: March 2022

Polar ozone loss in late winter and early spring is caused by enhanced concentrations of active chlorine. The surface necessary for heterogeneous reactions activating chlorine species is provided by cold stratospheric aerosols and by polar stratospheric clouds (PSCs). Moreover, sedimentation of PSC particles changes the chemical composition of the lower stratosphere and alters the ozone depleting process by irreversible redistribution of nitric acid and water vapor.

Over the past few years, the Chemical Lagrangian Model of the Stratosphere (CLaMS) has been further developed by the implementation of a microphysical PSC scheme. Within the sedimentation module of CLaMS, nitric acid trihydrate (NAT) and ice particles nucleate, grow, sediment, and evaporate along individual trajectories. Results from different Arctic and Antarctic winters have been compared to measurements from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP), the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), and the Microwave Limb Sounder (MLS). For this study, we focus on characteristics of different PSC formation routes: Are there typical meteorological conditions which promote certain nucleation pathways? Are there general hemispheric differences? Do different nucleation pathways contribute differently to the total PSC volume? Vice versa, is it possible to conclude from observations which kind of nucleation mechanism took place?
The Secret of the Chalcolithic Shafts: Insights from the Portable Luminescence Method (pOSL)
Authors: Ackermann Oren , van den Brink Edwin C.M. , Jakoel Eriola , Anker Yaakov , Roskin Joel , Asscher Yotam
Published: March 2022

A late Chalcolithic period site was discovered in central Tel Aviv during a salvage excavation that was conducted by the Israeli Antiquities Authority. The remains included 113 pits and shafts which were divided according to their shape into four groups:

 

Group 1: Round pits: a group that includes three types: small (0.5–0.6m diameter); medium (c. 1m); large (c. 2m). Some pits contained brown sediment mixed with ceramic fragments, animal bones, and flint; others had no archaeological finds.

 

Group 2: Bell shape pits

 

Group 3: Narrow, deep shafts 1–2m diameter, 3–6m deep. This group includes three types of shafts that differ from each other according to their shape: shafts with uniform width; conical shafts narrowing towards the bottom; shafts with a wide niche in the lower third. In some of the shafts, the fill consisted of brown sediments; some contained archaeological finds and some did not. In some of the shafts, the fill contained fragments of aeolian sandstone, sand, and anthropogenic brown sediment on top that sealed the fill.

Group 4: Shaft that opens into an underground space. Only one shaft like this was exposed.

  

Many questions arise about the function of these diverse shafts including why were so many of them mined?

 

Examination using the pOSL (portable luminescence method), showed that some of the shafts were used for a long time, and some were probably used for a short time, or not at all. From this, it can be assumed that the large number of shafts may be the result of trial-and-error style probing.

 

The pits which contained sand and rock fragments (group 3) had a section with a wide niche in the lower third and a thin clay layer. This suggests that these shafts served as water wells for the site inhabitants, which raises a further question: why was it necessary to dig wells along the Ayalon River? 

 

This will be discussed in the presentation
Parameter estimation for interseismic surface deformation using data assimilation
Authors: Marsman Celine P. , Vossepoel Femke C. , van Dinther Ylona , Govers Rob
Published: March 2022

Geodetic data provide an opportunity to improve our understanding of the processes and parameters controlling the dynamics of deformation during the earthquake cycle at subduction zones. However, the observations contain noise and are temporally and spatially sparse, whereas dynamical models are unequivocally imperfect. Also, the relative contributions from various drivers of surface deformation are poorly constrained by independent observations. Some drivers may be static or vary slowly in time (e.g., plate motion), whilst others vary significantly during the earthquake cycle (e.g., viscoelastic relaxation). Data assimilation combines prior estimates of dynamical models with the likelihood of observations into posterior estimates of the state evolution and time-independent parameters of a physical process. We explore the usefulness of data assimilation by using a particle filter to estimate the (spatially variable) elastic thickness of the overriding plate and the extent of the locked zone. The particle filter uses a Monte Carlo approach to represent the state probability distribution by a finite number of realizations ("particles"). We assimilate vertical interseismic surface displacements into a conceptual 2D elastic flexural model. We perform synthetic and real data assimilation experiments. We apply an Empirical Orthogonal Function analysis to find spatial and temporal variability of the data time series, which we use to make realistic assumptions on the observational errors.

Synthetic experiments demonstrate that the particle filter effectively estimates 1D elastic thickness from synthetic observations. However, elastic thickness estimates for models with a landward increase in plate thickness show larger uncertainty near the coast as the sensitivity of surface displacements reduces with increasing plate thickness. Interestingly, the effectiveness of the elastic thickness estimation is highly sensitive to network aperture, including GPS/A which greatly increases the quality of the parameter estimation. However, results of the locked zone extent are not as expected, which could be due to missing physics in the relatively conceptual model. Assimilation of interseismic vertical velocities prior to the 2011 Tohoku-Oki earthquake show that model parameters cannot converge with continental data without applying additional parameter constraints. This is due to low wavelength solutions providing a better fit to the noisy observations given the conceptual model. Subsequently, we will set up a 2D elastic finite element model to include horizontal and vertical surface displacements.  The results of the conceptual model demonstrate the potential of the particle filter to better understand the geodynamic process parameters of the earthquake cycle at subduction zones.
Updated GHG emission factors for Irish peatlands: a review
Authors: Aitova Elena , Morley Terry , Wilson David , Renou-Wilson Florence
Published: March 2022

Peatlands are unique ecosystems and despite covering only 3% of our planet, they store twice as much carbon as global forest cover. Healthy, fully functioning peatlands are the most effective natural carbon store and therefore it is important to keep them wet. When disturbed, peatlands release greenhouse gasesinto the atmosphere and lose carbon via surface runoff. Since peatlands cover around 20% of the land area in the Republic of Ireland, their drainage status and condition are of particular significance to reduce national emissions from the Land Use, Land Use Change and Forestry (LULUCF) sector.

Ireland is obligated to report anthropogenic emissions from organic soils in annual National Inventory Reports (NIR) under the United Nations Framework Convention on Climate Change (UNFCCC) and the Kyoto Protocol requirements. Ireland’s National GHG inventories comply with the methodology described in the Intergovernmental Panel on Climate Change (IPCC) Guidelines and the Wetlands Supplement 2013. The latest provided globally applicable ‘default’ emission factors (EFs) for calculating emissions and removals from drained and rewetted organic soils. However, the default EFs were based on field data often collected from geographical areas climatically and ecologically dissimilar to Ireland. Moreover, these EFs were limited by data availability and the level to which they could be disaggregated. In our work, we developed further stratification of peatlands land use categories based on peatlands characteristics and management in Ireland.

Here we review GHG emissions studies within Ireland and for the first time derived country-specific emission factors (EFs). We combined emissions of carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) and fluvial losses (DOC, POC, DIC) into a new national database encompassing main land-use categories and types of organic soils in Ireland. We estimated total emissions from Irish peatlands at the national level (excluding horticulture and combustion) and identified the large uncertainties are associated with the estimated value. This new peatland emissions database will assist future NIR reporting and help calibrate widely used indirect land-use emission factor proxies that are currently based on data from continental European sites to more regionally appropriate estimates.
The role of karstic substratum of ancient mountainous agricultural terraces at the semi-arid environment 
Authors: Inbar Nimrod , Ackermann Oren
Published: March 2022

Agricultural terraces are a well-known phenomenon in mountainous regions throughout the globe. Those structures are said to have been in the service of agriculture for several hundred or several thousand years. In different places and environments, terraces had different roles. It has been claimed that its primary goal in the sub-humid and semi-arid environments, was to preserve winter precipitation water within the terrace body. Endemic and domesticated vegetation will then flourish utilizing this resource throughout the dry summer season. Agricultural terraces are widely described in the literature as having three main parts, (a) the base, which is normally a naturally inclined bedrock surface, (b) a manmade retaining wall supporting the weight of (c) the terrace body, usually made of soil and gravel. The terrace base is described in all reviewed literature as an impermeable rock layer. However, previously published calculations suggested that in the sub-humid main mountain ridge of Israel, evapotranspiration will prevent retaining water even in a thick terrace body for the entire summer period. Moreover, in many terraces scattered across the given area, a few centimeters thick soil body seems to support decades and centuries old trees. Therefore, water retention mechanism in the agricultural terraces has been examined. Our study indicate that karst substratum is the controlling factor on terrace water retention. We propose that a well-developed, soil filled, karst system at the terrace substratum impedes the conventional evaporation process of a simple homogeneous soil parcel. Under such conditions, thin body terraces are able to support non-irrigated ancient agriculture water demand in sub-humid environment.
Non-contact volumetric flow monitoring in a semi-arid regions’ Wadi
Authors: Peña-Haro Salvador , Lüthi Beat , Düster Rudolf , Hansen Issa , Vogel Kai , Gad Mohammed , Magdy Mohammed
Published: March 2022

Monitoring volumetric flow in arid and semi-arid regions is a major challenge due to their harsh and continuously changing environment (e.g. extreme temperature, severe sand storms). In these regions, hydrological events such as rainfall storms and flash flood events occur intermittently, time between major events may take years. Drainage water courses in these areas are often referred as Wadis, which are ephemeral drainage courses. Wadis are normally dry except after a rain event, often resulting in flash floods events with flood peak values occurring in the first few minutes of the event.

Monitoring the volumetric flow under these environments requires robust devices which record continuously at relatively short recording intervals, e.g. minutes or less, to be able to capture the steep ramp of the flood peak.

On April 2021 a DischargeKeeper, an image-based system for flow monitoring, with a PTZ camera was installed at the Wadi Naqab located in northern United Arab Emirates. The Wadi is approximately 50m wide and has been dry for most of the time. One event occurred at the beginning of January 2022, reaching a peak discharge of 78 m3/s just 15min after water started flowing. In this session we will show the system, its challenges and the results of the event.
Provenance Analysis of the Andrée Land Basin and the Paleogeography of Svalbard in the Devonian
Authors: Anfinson Owen , Odlum Margo , Piepjohn Karsten , Poulaki Erini , Shephard Grace , Stockli Daniel , Levang Devin , Jensen Maria
Published: March 2022

During the Devonian, the Svalbard Archipelago lay near the equator, occupying an important paleogeographic position at the intersection of Caledonian and Ellesmerian orogens. We provide new sediment provenance constraints, including detrital zircon U-Pb ages, from the Devonian Andrée Land Basin, Svalbard, to understand the tectonic history of the archipelago at that time. Sedimentary provenance analysis of Devonian aged strata can help reconstruct the sediment sources and paleogeography to understand the assembly of the domains that make up Svalbard, that are presently separated by Devonian sedimentary basins and(or) faults with syn- to post Devonian displacement. The studied Andrée Land Group strata in Dicksonland, which are part of the North Atlantic's Old Red Sandstone, consist of the Early Devonian Wood Bay Formation and Middle to Late Devonian Mimerdalen subgroup. Paleocurrent indicators from Lower to lower-Middle Devonian strata record north-directed sediment transport. Detrital zircon U-Pb data are dominated by ages sourced from Svalbard’s Northwestern and Southwestern Basement provinces. In Middle and Upper Devonian strata, paleocurrents and detrital zircon ages suggest a shift to a predominantly eastern-northeastern provenance, likely sourced from the uplifting Ny-Friesland block along the Billefjorden Fault Zone. The addition of significant late Ediacaran-early Cambrian detrital zircons in a sample from the uppermost Planteryggen Formation (Frasnian) indicate sources associated with the Timanian orogen and provide a useful palaeogeographic indicator when compared to other regional detrital zircon data sets. Detrital zircon ages and provenance data suggest Svalbard may have already been assembled, similar to the block we see today, with the Andrée Land Basin between modern exposures of the Southwestern/Northwestern and the Northeastern basement provinces. Comparison of detrital zircon ages from Andrée Land Group strata with those from other circum Arctic Lower, Middle, and Upper Devonian strata provides further insight on Svalbard’s paleogeographic position in the Devonian.
The evolution of a basal melt channel on the southern Filchner Ice Shelf
Authors: Zeising Ole , Christmann Julia , Corr Hugh F. J. , Helm Veit , Höyns Lea-Sophie , Hofstede Coen , Müller Ralf , Neckel Niklas , Nicholls Keith W. , Schultz Timm , Steinhage Daniel , Wolovick Michael , Humbert Angelika
Published: March 2022

Basal melt channels of ice shelves influence ice-ocean interaction and thus the current and future dynamics of ice sheets and ice shelves. Understanding their evolution is necessary to assess their influence on ice shelves’ stability. In this study, we investigate the evolution of a basal channel, up to 330 m high, located in the southern Filchner Ice Shelf where the ice thickness is between 1150 and 1400 m. Observations with a phase-sensitive Radio Echo Sounder (pRES) reveal decreasing melt rates within the channel, from 1.8 m/a to freezing with increasing distance from the grounding line of Support Force Glacier. At a distance of 20 km from the grounding line, melt rates within the channel fall below those of the ambient ice and the height of the channel starts to decrease. Calculating the evolution of this channel over 250 years, under present-day melt rates, reveals a mismatch when compared with its present geometry: the melt rates would have needed to have been twice as high as those of the present day to form today's channel geometry. In contrast, the present-day melt rates result in a closure of the channel. These results were confirmed by simulations with a viscoelastic model: while the present-day melt rates led to a closure of the channel, higher melt rates reproduced the current channel geometry. The type of melt channel in this study diminishes with distance from the grounding line and is therefore not a destabilizing factor for ice shelves.
Constraining future tropical land carbon-climate feedbacks by water
Authors: Liu Laibao , Seneviratne Sonia
Published: March 2022

Tropical land carbon-climate feedback is a key determinant of uncertainties in climate change projections. Temperature has been proposed as a primary driver for the land carbon sink and it has been widely used to characterize carbon-climate feedback metrics in the latest reports of the Intergovernmental Panel on Climate Change (IPCC). The historical interannual sensitivity of CO2 growth rate (CGR) to tropical temperature was further identified as an observational constraint that can significantly lower uncertainties in projected changes in tropical land carbon storage. Here, we utilize 1pctCO2 ensemble experiments from the 6th Coupled Model Intercomparison Project (CMIP6) and show that previous emergent constraints (ECs) on tropical land carbon-climate feedback relying on temperature derived from the previous set of CMIP experiments (C4MIP) do not perform well for CMIP6. Long-term climate-driven tropical land carbon uptake is more directly coupled with water availability (soil moisture as the proxy in models) than temperature at both regional and local scale in CMIP6, suggesting that water has a stronger role than temperature in directly determining tropical land carbon-climate feedbacks. We further find that there is a significant emergent relationship between long-term sensitivity of tropical land carbon uptake to drying and its interannual sensitivity to water in CMIP6 (R=0.91, n=16). Combining with observations of interannual sensitivity of CGR to terrestrial water storage during 2002-2018, the resulting EC shows that, compared with an unconstrained ensemble of ESMs in CMIP6 (-1.9±1.4 PgC/yr/ Tt H2O), tropical land carbon losses by drying per Tt H2O are much lower (-0.9±0.7 PgC/yr/Tt H2O). Nonetheless, this does not ensure a less actual carbon loss per degree of global warming, because it also depends on the sensitivity of tropical land drying to global warming. This study suggests a strong potential for constraining future climate-driven terrestrial carbon sink from the perspective of water-carbon limitations.
Writing a New Free Book on Using Direct GHG Measurements in Disciplines beyond Micrometeorology
Authors: Burba George
Published: March 2022

Directly measuring GHG gas emissions, carbon sequestration, evapotranspiration and heat fluxes via the Eddy Covariance method has been widely used by expert micrometeorologists for over 30 years, covering 2155 stationary locations globally, and numerous mobile campaigns over land and water surfaces. Latest measurement technologies and automated processing software are rapidly expanding the use of the method to non-micrometeorological research. Regulatory and commercial uses of the method also increase year-by-year.

Despite the widening adoption of the method, academic investigators outside the area of micrometeorology and the majority of non-academic investigators are still not familiar enough with the proper implementation of the method required for conducting high-quality, reliable, traceable, and defensible measurements in their respective areas of interest.

Although data collection and processing are now automated, the method still requires significant care to correctly design the experiment, set up the site, organize and analyze a large amount of data. Efforts of the flux networks (e.g., FluxNet, AmeriFlux, Asiaflux, ICOS, NEON, OzFlux, etc.) have led to major progress in the standardization of the method. The project-specific workflow, however, is difficult to unify because various experimental sites and purposes of studies demand different treatments, and site-, measurement- and purpose-specific approaches.

To address this situation, step-by-step simple instructions were created to introduce a novice to general principles, requirements, applications, processing, and analysis steps of the conventional Eddy Covariance technique in the form of the free electronic resource, a 660-page textbook titled "Eddy Covariance Method for Scientific, Regulatory, and Commercial Applications". The explanations are provided using easy-to-understand illustrations and real-life examples, and the text is written in a non-technical language to be practically useful to those new to this field.

Information is provided on the theory of the method (including the state of methodology, basic derivations, practical formulations, major assumptions, sources of errors, error treatments, etc.), practical workflow ow (e.g., experiment design, implementation, data processing, quality control, and analysis), data sharing and flux stations networking, key alternative methods, and the most frequently overlooked details.

The book is organized by topic for ease of access to specific information. Each topic is presented in a three-tier structure: an illustration and summary, more in-depth information, and references to more advanced textbooks, networking guidelines, and journal papers for further exploration.
Scale-dependent Kurtosis of magnetic field fluctuations in the solar wind: A multi-scale study with Cluster 2003-2015
Authors: Roberts Owen , Alexandrova Olga , Sorriso-Valvo Luca , Voros Zoltan , Nakamura Rumi , Fischer David , Varsani Ali , Escoubet C. Philippe , Volwerk Martin , Canu Patrick , Yearby Keith
Published: March 2022

The Cluster II mission was launched in 2000 to study three-dimensional space plasma processes. Over the past two decades, the Cluster spacecraft have collected data from various near-Earth space plasmas, including the solar wind. During the lifetime of the mission, the inter-spacecraft distances of Cluster in the solar wind have changed from the large scales (∼ 10,000 km) where fluid physics dominates the turbulent fluctuations, down to the scales of protons (∼ 200 km). More recently, as part of the Guest Investigator (GI) campaign, the mission achieved a novel formation where a pair of spacecraft were separated by  ∼7 km, close to electron scales. The small distances and the exceptional sensitivity of the search coil magnetometer provide an excellent data set for studying solar wind turbulence at electron scales. This study will investigate intermittency of the magnetic field fluctuations in the slow wind from fluid to kinetic scales,  using both time-lagged increments from a single spacecraft and spatially lagged increments using multiple spacecraft. As the turbulent cascade proceeds to smaller scales in the inertial range, the deviation from Gaussian statistics is observed to increase in both temporal and spatial increments. At ion scales, there is a maximum of kurtosis, and at sub-ion scales, the fluctuations are only weakly non-Gaussian. The observations show differences in kurtosis of time and space increments, indicating its spatial anisotropy.
Stability of Al-substituted jarosite in the presence of Fe(II)
Authors: Grigg Andrew , Notini Luiza , Kaegi Ralf , ThomasArrigo Laurel , Kretzschmar Ruben
Published: March 2022

Jarosite is a ferric iron sulfate mineral [(KFe3(SO4)2(OH)6] that is commonly formed in acidic environments that are rich in iron and sulfate, such as acid-sulfate soils or acid mine drainage. The stability of jarosite is important because the mineral contains embodied acidity and may scavenge trace elements by sorption and co-precipitation. Although stable under high Eh and low pH conditions, previous studies have shown that jarosite is prone to transformation by hydrolysis at circumneutral pH, or may undergo Fe(II)-catalysed transformation where ferrous ions are present [1-3]. Jarosite may be exposed to Fe(II) at circumneutral pH in reducing environments, such as in flooded acid-sulfate soils [2]. Jarosite is a member of the alunite supergroup and forms a solid solution series with alunite by substitution of Al for Fe. However, the effect of Al substitution on the stability of jarosite in the presence of Fe(II) has not previously been investigated. Here, we performed batch experiments using samples of a synthetic jarosite without aluminium substitution, and synthetic jarosite containing 7.3% Al-for-Fe substitution. Mineral samples were reacted with 0.5 mM and 5 mM Fe(II) at pH 7.1 (50 mM MOPS buffer) for up to 24 hours. Rietveld analysis of X-ray diffraction patterns was used to quantify mineral transformations and to determine the crystallinity of, and Al substitution in, product phases. Complete transformation of jarosite to mixtures of ferrihydrite, goethite and lepidocrocite occurred within several hours for all jarosite samples and Fe(II) treatments. The 10-fold increase in Fe(II) concentration resulted in a 50% increase in jarosite transformation rate, and pure jarosite transformed 110% to 280% faster than Al-substituted jarosite. The transformation products of Al-substituted jarosite contained a smaller proportion of lepidocrocite than the products of pure jarosite transformation, and the unit cell size of the lepidocrocite that initially formed from Al-substituted jarosite indicates that Al was substituted into the structure. These results demonstrate that structural Al can stabilise jarosite against transformation, which has implications for understanding the longevity of jarosite, and its importance to trace element cycling, in reducing environments.

1. Welch, S. A., et al. (2008) Chem. Geol. 254: pp. 73-86
2. Karimian, N., et al. (2017) Environ. Sci. Technol. 51: pp. 4259-4268
3. Whitworth, A. J., et al. (2020) Chem. Geol. 554 
Verification of the Streamer Parameter Model by comparing to Hydrodynamic Simulations
Authors: Lehtinen Nikolai , Marskar Robert
Published: March 2022

Streamers are an important stage of lightning, taking place before the formation of a leader discharge. The goal of the novel Streamer Parameter Model (SPM) is to explain the mechanism that determines the parameters of a streamer, such as its radius and propagation velocity. We demonstrate that SPM predictions agree well with the published hydrodynamic simulation (HDS) results [1]. The discrepancies between SPM and HDS were of the same order of magnitude as the discrepancies between different HDS codes. The comparison was performed for two different streamer propagation mechanisms: photoionization and background ionization. The largest discrepancies were for the case of low background ionization, which was also challenging for HDS. Electron diffusion did not change the streamer parameters significantly. We propose that SPM, despite the crudeness of the model, provides a computationally simple way to reliably assess streamer properties.
Comparison of horizontal post-seismic deformations induced by Maule, Iquique, and Illapel megathrust earthquakes: A clue to a linear asthenospheric viscosity?
Authors: Boulze Hugo , Fleitout Luce , Klein Emilie , Vigny Christophe
Published: March 2022

Spatial geodesy through GNSS allows to measure with a millimetric precision the displacement of the lithosphere during the seismic cycle. The post-seismic part of this cycle can last for decades, traduced by long-lasting surface deformations. One of the main physical processes involved in the postseismic deformation is the viscoelastic relaxation in the asthenosphere. However, a long term debate persists about the involved rheology of the asthenosphere:  Is the viscosity highly variable from one region to the next and is effective viscosity Newtonian (linear) or non-Newtonian (non linear)? 

To investigate these questions, we compare the horizontal post-seismic deformations induced by three Chilean megathrust earthquakes: Maule Mw8.8 (2010), Illapel Mw8.3 (2015) and Iquique Mw8.1 (2014). For each earthquake, we select permanent GPS stations along profiles perpendicular to the trench, extending as far as 1400 km. We calculate the ratio of the cumulative post-seismic (post) over 5 years and the coseismic (co) displacements for each station. Remarkably, at a given distance to the trench, the post/co ratios from the three earthquakes differ only slightly.

What can be the interpretation of this observation in terms of rheology of the asthenosphere? First we can analyse the response of the asthenosphere in the case of homothetic earthquakes of different magnitude. The post/co ratio obeys simple analytical relationships: For a Newtonian rheology, it is simply a function of the (time/viscosity) ratio. For a non-Newtonian viscosity with a stress exponent n=3, the timescale becomes inversely proportional to M**2, where M is the moment of the earthquake. We show that these relationships are only slightly modified when the earthquakes are no longer homothetic and that the post/co ratio is a good proxy to quantify the strain-rate and stress ratio in the underlying asthenosphere. As a conclusion, the post-seismic deformation following the three Chilean earthquakes reveals very similar viscosity. In particular, a Newtonian, rather than a non-Newtonian, effective viscosity is required to explain the post-seismic deformation process.
Measuring thermal comfort of courtyards by mobile measurements - a case study
Authors: Moderow Uta , Goldberg Valeri , Ziemann Astrid
Published: March 2022

Cities are currently becoming more densely built almost everywhere, thus reducing the possible amount of areas for public green spaces, which are even more relevant in light of climate change as they can mitigate thermal stress during hot summer days. Here, optimizing existing courtyards concerning their green structure might be an option in order to provide conditions of low thermal stress during these days. However, there is no vast amount of studies addressing this issue for temperate and cold climate and related typical urban structures by measurements. We present mobile measurements recorded in Erfurt (Germany) during a hot summer day in 2018. These measurements also covered three courtyards of different design and geometry. Differences in air temperature between the three courtyards were small, but larger differences in mean radiation temperature existed, which mainly contributed to differences in thermal stress for human beings. We used the Universal Thermal Climate Index (UTCI, Jendritzky et al. 2012; Błażejczyk et al. 2010) to assess human thermal comfort. Out of the three investigated courtyards the smallest courtyard with established trees showed the lowest thermal load providing conditions of no thermal stress almost throughout the whole day (UTCI range: 18°C – 28°C). Highest values of thermal stress were recorded for the most open spaced courtyard with a value of 31°C after midday. Thermal loads of the different courtyards were related to general aspects (size of courtyard, ratio of unvegetated and sealed areas to vegetated areas). However, the sample size is too small to draw general conclusions and underlines the necessity for further measurements. We hope that our work will help to broaden the base of available measurements for climatic conditions and typical urban structures for Middle Europe concerning courtyards.

References

Błażejczyk, K., Broede, P., Fiala, D., Havenith, G., Holmér, I., Jendritzky, G., Kampmann, B., and Kunert, A.: Principles of the New Universal Thermal Climate Index (UTCI) and its Application to Bioclimatic Research in European Scale, 14, 91–102, https://doi.org/10.2478/mgrsd-2010-0009, 2010.

Jendritzky, G., Dear, R. de, and Havenith, G.: UTCI—Why another thermal index?, Int J Biometeorol, 56, 421–428, https://doi.org/10.1007/s00484-011-0513-7, 2012.
The flash floods of April 2020 in Uvira (DR Congo): story of an event with extreme impacts
Authors: Mugisho Bachinyaga Josué , Deijns Axel , Ilombe Mawe Guy , Kervyn François , Michellier Caroline , Mugaruka Bibentyo Toussaint , Nkere Buliba Jaziel , Nzolang Charles , Smets Benoît , Dewitte Olivier
Published: March 2022

Uvira is a rapidly growing city of about 600,000 inhabitants in DR Congo. Squeezed between the shore of Lake Tanganyika and steep mountains hillslopes, and under the influence of a tropical climate, the city is familiar with flash floods. Nevertheless, the impacts of the flash flood event of April 2020 have been unprecedented in the last decades. Debris-rich flash floods led to at least 43 deaths, nearly 200 injuries, more than 5,500 houses destroyed and at least 70,000 people made homeless. Dozens of socio-economic infrastructures were damaged and nearly 280,000 people were left without hydroelectric power as a result of damage to water and electricity distribution networks in the city. In this work we explore the natural and anthropogenic causes of the exceptional impacts of these flash floods. To do so, we use satellite images, historical aerial photographs, social media reports, field observations, and details provided by local stakeholders and citizen observers. We show that a high-magnitude rainfall event, that occurred at the end of a wetter-than-usual rainy season, triggered, over an exceptionally large area for the region, hundreds of landslides in the upper parts of the watersheds. These landsides transported extra material to the flooded rivers, increasing their sediment content and lateral mobility. We also show that the landscapes of the watersheds where this compound event occurred remained rural in the last six decades and were not impacted by significant forest cover changes and road construction, hence eluding the role of key potential human activities on the magnitude of the flash floods. However, downstream, the city expanded with little consideration of the geomorphological context of the environment where the alluvial fans and flood plains of the rivers have been significantly urbanized in the last decades, often in an informal manner. The impacts of the April 2020 flash flood event are still present almost after two years  and are anticipated to remain at least a few more years; most remarkably, the disturbance of the river dynamics and the severe bank erosion caused by the large supply of sediment. Furthermore, often-uncontrolled sediment mining, seen here by the local people as an opportunity, exacerbates the unpredictable dynamics of the system. In the meantime, flooded areas where houses were destroyed are being resettled. Although authorities and inhabitants are aware of the danger, they face limited means to improve the management and planning of the city.
Detection of Double-Cropping Systems Using Machine Learning and Sentinel 2 Imagery - A Case Study of Bačka and Srem Regions, Serbia     
Authors: Marković Miljana , Lugonja Predrag , Brdar Sanja , Živaljević Branislav , Crnojević Vladimir
Published: March 2022

Increasing agricultural production is inevitable in the future since population growth and climate change have led to significant pressure on global food security. One of the ways is to intensify the existing cropland by multi-cropping practice, allowing multiple uses of a single field during one year.  This research aims to identify and map double-cropping land using multi-temporal Sentinel 2 imagery from 2021 and advanced machine learning models. The case study focus is on Bačka and Srem, regions located in the Autonomous Province of Vojvodina, Republic of Serbia. These regions are characterized by fertile land and widespread agriculture production. However, there is a low presence of double-cropping practice due to usually dry summers, but with a tendency to change as the number of irrigation systems increase.

Considering the small amount of double-cropping fields, there is a need for direct ground truth data collection. For that reason, the first step was to reduce the area of interest to get insight into the locations of potential double-cropping land. This result was obtained by using the threshold method based on the phenology of crops during the year. The NDVI (Normalized Difference Vegetation Index) time series was utilized to define appropriate thresholds for feature two peak values to discriminate double-cropping within each pixel. The identification of the results was used on-site for collecting ground truth data. Based on the collected data and the analyzed NDVI time series, besides double-crop, three more classes of arable land were distincted and included in the classification: single winter crops, single summer crops and clover. The collected data contained 46 parcels of double crops, 43 single winter crops, 55 single summer crops and 27 parcels of clover. We used time-series images to create a dataset for training the pixel-based Random Forest classification. The results showed a very high overall accuracy of 99% and an  F-score higher than 0.9 for each of the classes.

This methodology is a suitable approach for detecting double-cropping systems, with further potential to identify exact crop types and the main practice of combining crops. The findings of this study showed that only about 2% of the study area was under this production. Except for positive economic outcomes, utilizing these systems brings significant environmental benefits and rational use of the soil without expanding physical cropland but with the same advantages. Therefore, the resulting geospatial datasets of double cropping croplands could help solve important questions relevant to food security, irrigation and climate change.
Potential of natural language processing for metadata extraction from environmental scientific publications
Authors: Blanchy Guillaume , Albrecht Lukas , Koestel Johannes , Garré Sarah
Published: March 2022

Adapting agricultural management practices to changing climate is not straightforward. Effects of agricultural management practices (tillage, cover crops, amendment, …) on soil variables (hydraulic conductivity, aggregate stability, …) often vary according to pedo-climatic conditions. Hence, it is important to take these conditions into account in quantitative evidence synthesis. Extracting structured information from scientific publications to build large databases with experimental data from various conditions is an effective way to do this. This database can then serve to explain, and possibly also to predict, the effect of management practices in different pedo-climatic contexts.

However, manually building such a database by going through all publications is tedious. And given the increasing amount of literature, this task is likely to require more and more effort in the future. Natural language processing facilitates this task.  In this work, we built a database of near-saturated hydraulic conductivity from tension-disk infiltrometer measurements from scientific publications. We used tailored regular expressions and dictionaries to extract coordinates, soil texture, soil type, rainfall, disk diameter and tensions applied. The overal results have an F1-score ranging from 0.72 to 0.91.

In addition, we extracted relationships between a set of driver keywords (e.g. ‘biochar’, ‘zero tillage’, …) and variables (e.g. ‘soil aggregate’, ‘hydraulic conductivity’, …) from publication abstracts based on the shortest dependency path between them. The relationships were further classified according to positive, negative or absent correlations between the driver and variable. This technique quickly provides an overview of the different driver-variable relationships and their abundance for an entire body of literature. For instance, we were able to recover the positive correlation between biochar and yield, as well as its negative correlation with bulk density.
Exploring the Earth's mantle structure based on joint gravimetric and seismometric group-velocity dispersion curves of Rayleigh waves
Authors: Karkowska Kamila , Wilde-Piórko Monika , Dykowski Przemysław , Sękowski Marcin , Polkowski Marcin
Published: March 2022

Gravimetric data show excellent capabilities in long-period seismology. Tidal gravimeters can detect surface waves of periods even up to 500-600 s, while a typical broad-band seismic sensor, due to its mechanical limitation, can detect them only up to the periods of 200-300 s. Consequently, gravimetric data can complement seismic recordings for longer periods, depending on what seismometer the station is equipped with and what seismometer’s cut-off period is. A superconducting gravimeter can act as a single-dimension (only vertical component) of a very broad-band seismometer. 

We selected over a dozen stations worldwide with co-located typical broad-band seismic sensors and superconducting gravimeters. A time series from broad-band seismometers have been downloaded from Incorporated Research Institutions for Seismology (IRIS) database. The raw gravimetric data (1-Hz or 1-min) are available in the International Geodynamics and Earth Tide Service (IGETS) database. Some of the data were made available courtesy of the station’s operators. 

This study presents a joint analysis of the gravimetric and seismometric data to determine group-velocity dispersion curves of Rayleigh surface waves. We created a database of recordings of earthquakes for all stations and instruments. Following, we calculated the individual group-velocity dispersion curves of fundamental-mode Rayleigh waves. Simultaneous seismic and gravity recordings at the same location allow exploring a broader response for incoming seismic waves. In this way, one joint group-velocity dispersion curve of Rayleigh surface waves for a broader range of periods has been estimated for all stations. All curves were then inverted by linear inversion and Monte Carlo methods to calculate a distribution of shear-wave seismic velocity with depth in the Earth’s mantle.    

This work was done within the research project No. 2017/27/B/ST10/01600 financed from the Polish National Science Centre funds.