bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessment of AOD by 16 CMIP6 Models Based on Satellite-Derived Dataset from 2000-2014 over Eastern Center China
Authors: li xiao , wang minghuai , liu yawen , jiang yiquan , dong xinyi
Published: March 2021

Knowledge of aerosol concentration, type, and physical and chemical properties is necessary to understand their role in Earth’s climate system. However, CMIP6 models’ performance of AOD simulation in China lacks a comprehensive evaluation and the potential improvement for CMIP6 models is still unclear. Here, we assess the performance of CMIP6 models in simulating annual mean AOD climatology and its seasonality over China from 2000 to 2014 and explore the underlying reasons for its performance. Compared with CMIP5, CMIP6 models can better capture the annual mean AOD climatology magnitude over Eastern Central China (ECC) with a notable enhancement of 52.98% due to a significant increase in the dominate sulfate aerosol. However, the majority of CMIP6 models fail to capture the observed inverted “V-like” pattern that depicts two centers of maximum AOD in spring over northeast China (NEC) and in summer over southeast China (SEC), respectively. The deficiency of two maximums by CMIP6 models is separately due to the negative bias in the simulation of organic aerosol (OA) AOD and sulfate AOD. Our analysis suggests that the deviation of simulated precipitation, relative humidity (RH), and liquid water path (LWP) in CMIP6 models contributes to the deviation of simulated sulfate AOD through affecting sulfate aerosol concentration by wet deposition and aqueous-phase production. Therefore, this study illustrates the urgent need to improve AOD simulation in global climate models.
Using ecosystem service bundles to evaluate spatial and temporal impacts of large-scale landscape restoration on ecosystem services on the Chinese Loess Plateau
Authors: Chen Hao , Fleskens Luuk , Schild Johanna , Moolenaar Simon , Wang Fei , Ritsema Coen
Published: March 2021

From 1999 onwards, China has initiated a large-scale landscape restoration project on the Chinese Loess Plateau, which has had profound but variable impacts on the local ecosystem services supply. In this study, we evaluate the spatial and temporal dynamics in 11 ecosystem services in the Yan’an area on the Chinese Loess Plateau from 1990 to 2018 based on the InVEST model and statistical yearbook data. To consider trade-offs and synergies between ecosystem services, the concept of ecosystem service bundles was used to understand the dynamics of ecosystem services. A significant increase of fruit production, sediment retention, habitat quality, aesthetic landscape value as well as learning and inspiration value was found over time in Yan’an area, while a decrease of timber production and water yield was also observed. Synergistic relations were found between sediment retention, carbon sequestration, habitat quality and outdoor recreation, while trade-offs were observed between timber production and water yield. The majority of ecosystem services bundles of Yan’an area were transformed from having a focus on timber production to aesthetic landscape value. The dynamics of ecosystem services change by land restoration was discovered, to start with increasing regulating services at expense of provisioning services, cultural services exceeding regulating services and occupied the main proportion subsequently. The most obvious change was observed in 2000, coinciding with the start of large-scale restoration activities. The implementation of the large-scale restoration project is recognized as a key driving force inducing these changes. Based on the results, it is recommended that the Yan’an government pays attention to local water resource management and timber supply.
High-orders methods and high-precision arithmetics make direct scattering transform for the Korteweg-De Vries equation robust.
Authors: Gudko Aleksandr , Gelash Andrey , Mullyadzhanov Rustam
Published: March 2021

Similar to the theory of direct scattering transform for nonlinear wave fields containing solitons within the focusing one-dimensional nonlinear Schrödinger equation [1], we revisit the theory associated with the Korteweg–De Vries equation. We study a crucial fundamental property of the scattering problem for multisoliton potentials demonstrating that in many cases position parameters of solitons cannot be identified with standard machine precision arithmetics making solitons in some sense “uncatchable”. Using the dressing method we find the landscape of soliton scattering coefficients in the plane of the complex spectral parameter for multisoliton wave fields truncated within a finite domain, allowing us to capture the nature of such anomalous numerical errors. They depend on the size of the computational domain L leading to a counterintuitive exponential divergence when increasing L in the presence of a small uncertainty in soliton eigenvalues. Then we demonstrate how one of the scattering coefficients loses its analytical properties due to the lack of the wave-field compact support in case of L→∞. Finally, we show that despite this inherent direct scattering transform feature, the wave fields of arbitrary complexity can be reliably analyzed using high-precision arithmetics and high-order algorithms based on the Magnus expansion [2, 3] providing accurate information about soliton amplitudes, velocities, positions and intensity of the radiation. This procedure is robust even in the presence of noise opening broad perspectives in analyzing experimental data on propagation of surface waves on shallow water.

The work is partially funded by Russian Science Foundation grant No 19-79-30075.

[1] Gelash A., Mullyadzhanov R. Anomalous errors of direct scattering transform // Physical Review E 101 (5), 052206, 2020.

[2] Mullyadzhanov R., Gelash A. Direct scattering transform of large wave packets // Optics Letters 44 (21), 5298-5301, 2019.

[3] Gudko A., Gelash A., Mullyadzhanov R. High-order numerical method for scattering data of the Korteweg—De Vries equation // Journal of Physics: Conference Series 1677 (1), 012011, 2020.

 

 
Impact of natural hazards on the evolving COVID-19 pandemic: cases from Greece
Authors: Mavrouli Maria , Mavroulis Spyridon , Lekkas Efthymios
Published: March 2021

The first confirmed COVID-19 case was reported in December 2019. Over the first months of 2020, the novel SARS-CoV-2 virus was spread worldwide resulting in the declaration on March 11, 2020 of a global COVID-19 pandemic by the World Health Organization. The evolving pandemic has resulted in over 1900000 fatalities worldwide (as of January 8, 2021), while all sectors of the everyday life has been affected in numerous and varied ways. Natural hazards did not stop for the novel coronavirus. When the natural hazards cross the path of an evolving pandemic, compound emergencies emerge and are characterized by various effects and new unprecedented challenges.

Greece was no exception. Geological, hydrological and meteorological hazards took place in several parts of the country and they affected the local population, the natural and the built environment including buildings, infrastructures and lifelines. Among the most destructive effects in terms of human and economic losses was the March 21, 2020, Mw=5.7, Epirus (northwestern Greece) earthquake, the August 9, 2020, Evia (central Greece) flood, the September 17, 2020, Ianos medicane and the October 30, 2020, Mw=7.0, Samos (Eastern Aegean Sea) earthquake.

In order to identify the potential impact of the aforementioned disasters on the evolution of the COVID-19 pandemic in the disaster-affected areas, the officially reported laboratory-confirmed daily COVID-19 cases for the pre- and post- disaster periods from the disaster-affected areas were used. The impact of disasters in the evolution of the pandemic in the studied disaster-affected areas comprises increasing and decreasing trends and stability of the COVID-19 cases during the post-disaster period. More specifically, the geological and the hydrological hazards and the induced disasters negligibly affected the evolution of pandemic in the affected areas, while the hydrometeorological hazards resulted in increasing trends of the post-disaster reported COVID-19 cases in various affected areas.

The detected trends are strongly associated with the pre-existing viral load and infection rate in the disaster-affected areas, to the emergency response actions adapted to adopt provisional measures for the mitigation and elimination of COVID-19 consequences, to demographic features of the affected areas and to the intensity of the induced disasters and their effects on the local population (fatalities and injuries), the natural environment (primary and secondary environmental effects) and the built environment (structural damage to buildings, infrastructures and lifelines).
Finite difference forward modelling across the Tyrrhenian basin
Authors: Nardoni Chiara , De Siena Luca , Cammarano Fabio , Mattei Elisabetta , Magrini Fabrizio
Published: March 2021

Strong lateral variations in medium properties affect the response of seismic wavefields. The Tyrrhenian Sea is ideally suited to explore these effects in a mixed continental-oceanic crust that comprises magmatic systems. The study aims at investigating the effects of crustal thinning and sedimentary layers on wave propagation, especially the reverberating (e.g., Lg) phases, across the oceanic basin. We model regional seismograms (600-800 km) using the software tool OpenSWPC (Maeda et al., 2017, EPS) based on the finite difference simulation of the wave equation. The code simulates the seismic wave propagation in heterogeneous viscoelastic media including the statistical velocity fluctuations as well as heterogeneous topography, typical of mixed settings. This approach allows to evaluate the role of interfaces and layer thicknesses on phase arrivals and direct and coda attenuation measurements. The results are compared with previous simulations of the radiative-transfer equations. They provide an improved understanding of the complex wave attenuation and energy leakage in the mantle characterizing the southern part of the Tyrrhenian Sea and the Italian peninsula. The forward modelling is to be embedded in future applications of attenuation, absorption and scattering tomography performed with MuRAT (the Multi-Resolution Attenuation Tomography code – De Siena et al. 2014, JVGR) available at https://github.com/LucaDeSiena/MuRAT.
Dynamically informed covariance modelling in data assimilation
Authors: Bannister Ross , Petrie Ruth
Published: March 2021

Data assimilation systems are progressively getting better, resulting in improved analyses and forecasts. One important reason for this is thought to be the improved representation of the multivariate PDF of a-priori errors seen by the assimilation. This means that observations can influence the trajectory/ies of the numerical model in more physically meaningful ways. While some improvement is gained by modelling deviations of the PDF from Gaussianity, and by statistical modelling of Gaussian covariances with ensembles, there is still scope to improve the structure of the `B-matrix' used in pure and hybrid versions of 3D/4D-Var.

Our hypothesis is that a good B-matrix for geophysical data assimilation applications should have multivariate structure functions that reflect the dynamics of the underlying physical system. So, if the underlying system is close to some balanced manifold, then the assimilation should not disturb that property. Existing practice is to impose any balances explicitly, but this is difficult when the balances are weak or difficult to determine, such as in convective-scale or tropical applications, etc. In this talk we look at how such covariances can be modelled, including an approach that uses the normal modes of the underlying dynamics.
High-temperature three-axis IRM Lowrie test
Authors: Surovitskii Leonid , Kosterov Andrei , Kovacheva Mary , Kostadinova-Avramova Maria , Salnaya Natalya , Smirnov Aleksey
Published: March 2021

The three-axis isothermal remanent magnetization (IRM) test (the Lowrie test; Lowrie, 1990, Geophys. Res. Lett., 17, 159-162) is a useful tool to identify ferromagnetic minerals by their coercivity and unblocking temperature spectra. In this study, we explore a variant of the Lowrie test in which measurements are conducted directly at elevated temperatures, and compare its performance with the results of the conventional stepwise procedure. IRM acquisition fields applied along three orthogonal axes were 1 T, 200 mT and 40 mT, respectively. The field value for the soft component was chosen so as to include ca. 90% of its coercivity spectrum. For the hard component the maximum available field was used. The test is applied to characterize the magnetic mineralogy of archaeological baked clays and bricks from Bulgaria and Russia. Bulgarian samples are baked clays from various Neolithic (5700-5300 BCE) archaeological sites and several bricks of the Roman epoch (III-IV c. AD). Samples from Russia are bricks originating from several regions with ages from XIII to early XIX c. AD.

The low- and intermediate-coercivity components of IRM in the studied samples are typically demagnetized by 520-550°C, compatible with substituted or cation-deficient magnetite or, possibly, maghemite. This is supported by the absence of the Verwey transition in studied samples (Kosterov et al., 2021, Geophys. J. Int., 224(2), 1256-1271). The high-coercivity component appears to be carried by two mineral phases with very distinct unblocking temperatures, 120-200°C and 500 to 640°C. The first phase is similar to the high coercivity, low unblocking temperature (HCSLT) phase described by McIntosh et al., 2007 (Geophys. Res. Lett., 34, L21302, doi: 10.1029/22007GL031168), and the second one appears to be hematite with variable degree of substitution.

Performance of the high-temperature variant of the Lowrie test compares favorably with the classical procedure, while the former is also significantly faster and yields a superior temperature resolution.

This study is supported by Russian Foundation of the Basic Research, grant 19-55-18006, and by Bulgarian National Science Fund, grant KP-06-Russia-10.
Reduced winter land sea contrast and its effects on mid-latitude atmospheric variability
Authors: Portal Alice , Pasquero Claudia , D'Andrea Fabio , Davini Paolo , Hamouda Mostafa
Published: March 2021

Long term projections of the Northern Hemisphere winter climate show an overall increase of surface temperatures that is particularly amplified at Arctic latitudes. On top of this, projections agree in predicting a faster temperature increase on land than on sea surface, therefore a reduced winter land-sea contrast in the mid latitudes. Despite the robustness of this feature in climate projections, the response of the atmospheric system to a strongly reduced winter land-sea contrast has been scarcely investigated. Here, we study how it affects the low and high frequency variability in the extratropics using a simplified GCM, with a focus on the Atlantic and Pacific jets. Moreover, different sea surface temperatures are applied to the North Atlantic and North Pacific basins in order to simulate the presence of a differential warming, as in the well-known scenario of a North-Atlantic warming hole. 
Reconciling the carbon balance of northern Scandinavia through the integration of observations and modelling
Authors: Sathyanadh Anusha , Monteil Guillaume , Scholze Marko , Klosterhalfen Anne , Laudon Hjalmar , Wu Zhendong , Gerbig Christoph , Schaik Erik van , Bastrikov Vladislav , Nilsson Mats B. , Peichl Matthias
Published: March 2021

The boreal biome is an important component of the global carbon (C) cycle. However, current estimates of its sink-source strength at regional scales and its responses to climate change rely primarily on models and thus remain uncertain. We investigated the C balance over a north Scandinavian boreal region by integrating observations of land-atmosphere fluxes and atmospheric CO2 concentrations at landscape to regional scales. We also placed a special focus to understand the impact of 2018 drought on the region. Flux estimates can be obtained through various techniques such as in-situ flux measurements, eddy covariance (EC) observations, vegetation modelling and inverse modelling of CO2 observations. These techniques are however typically relevant at very different spatial scales ranging from plot scale to country-scale, which makes it difficult to compare them. The -Svartberget site (SVB), an established ICOS (Integrated Carbon Observation System) station in Northern Sweden offers a unique range of observations, from in-situ flux measurements to EC fluxes and tall-tower concentration measurements. Here we used several vegetation models and an atmospheric transport model to connect the different scales for the period 2016-2018. The land-atmosphere carbon fluxes are from four different vegetation models (VPRM, LPJ-GUESS, ORCHIDEE and SiBCASA) and are used in the LUMIA/FLEXPART atmospheric transport model (Lund University Modular Inversion Algorithm) to generate estimates of atmospheric CO2 concentration. We found that the northern Sweden region remained as a C sink for the study period with models differed in sink strength. It was also noticed that the site SVB can be taken as a representative for the northern Sweden region. All models indicate similar but small reductions in the net CO2 uptake for the drought year 2018 in northern Sweden except LPJ-GUESS that reveal limitations which call for further model improvement. Our work highlights the interest of using combined ecosystem,-atmosphere ICOS sites such as SVB in the Scandinavian region and shows that it is a promising way forward to monitor CO2 fluxes at the regional scale.
Quantifying the responses of ecosystem production and respiration to drought time scale, intensity, timing and lagged response: A FLUXNET synthesis
Authors: Jiao Wenzhe , Wang Lixin
Published: March 2021

Drought is not only a multiscale (e.g., temporal, spatial) but also a multidimensional (e.g., onset, offset, duration, frequency, magnitude, intensity) phenomenon, and ecosystem production and respiration may respond to each drought dimension differently.  Although multiple reports exist in literature on the drought impact on ecosystem productivity, it remains unclear how each component of drought impacts ecosystem gross primary production (GPP), ecosystem respiration (RECO), and net ecosystem exchange (NEE) and how the different drought dimensions interacted with each other on their impacts. In this study, we conducted a comprehensive drought impact assessment on forest GPP, NEE, and RECO including all the drought dimensions using FLUXNET observations and multiple time-scales of Standardized Precipitation-Evapotranspiration Index (SPEI). Our results indicated that while most earlier drought studies focused on simultaneous and post-drought conditions, the cumulative drought impacts and drought timing are more significantly impacting forest carbon uptake than simultaneous drought severity. Temporal standardization based meteorological drought indices could be used to accurately reflect plant water stress if antecedent and cumulative drought conditions are considered.
Triassic volcanic-sedimentary strata in the basement of Songliao Basin, discovered by International Continental Scientific Drilling Borehole, SK-2
Authors: Yin Yongkang , Wang Pujun , Gao Youfeng , Liu Haibo
Published: March 2021

In the Songliao Basin, the existence of lower Mesozoic strata remains a debatable issue. Previous studies indicated the absence of Triassic to Lower and Middle Jurassic strata in northeastern China because of uplift and erosion events associated with the return of geo-synclinal folds and orogenic movement during the Late Permian–Early Jurassic. To date, geochronological studies of intrusive and metamorphic rocks in the basement of the Songliao Basin have also confirmed Carboniferous, Permian, and Late Jurassic ages for the basement formations in general. In the International Continental Scientific Drilling Project (ICDP) in the Songliao Basin, radiometric dating has been carried out for the entire drilling core of the SK-2 east borehole. As a result, we have discovered Triassic volcanic-sedimentary strata in the basement of the Songliao Basin. Laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U–Pb geochronology was used in this research. Errors in individual analyses by LA-ICP-MS are given at the 1σ level, whereas errors in pooled ages are given at the 95% (2σ) confidence level. Triassic volcanic-sedimentary strata revealed by the SK-2 east borehole consist of andesitic volcanic breccias at the bottom; andesites, sandstones, and conglomerates in the middle; and andesites at the top. The total thickness of these strata is over 500 m. The formation age of the andesite at the depth of 6,031.9 m is 242.4 ± 2.1 Ma (MSWD = 0.06, n = 7). The youngest peak age of the sandstone at the depth of 6,286.2 m is 242.2 Ma. The formation age of the andesite at the depth of 6,286.2 m is 242.6 ± 1.5 Ma (MSWD = 1.02, n = 18). This study demonstrates that in the Songliao Basin, there are not only Carboniferous and Permian strata, but also a Triassic volcanic-sedimentary succession in the basement of the basin. The SK-2 drilling core reveals that this volcanic-sedimentary sequence has great thickness. These Triassic volcanic-sedimentary strata provide new clues for the study of the origin and development of the Songliao Basin. As both volcanic and sedimentary rocks can be oil and gas reservoirs, this discovery also provides a new target for oil and gas exploration deep in the Songliao Basin.
Silicon fertilizer and biochar effects on plant and soil PhytOC concentration and soil PhytOC stability and fractionation in subtropical bamboo plantations
Authors: Huang Chengpeng , Wang Li , Gong Xiaoqiang , Huang Zhangting , Zhou Miaorong , Li Jiong , Wu Jiasen , Chang Scott X. , Jiang Peikun
Published: March 2021

The use of exogenous silicon (Si) amendments, such as Si fertilizers and biochar, can effectively increase crop Si uptake and the formation of phytoliths, which are siliceous substances that are abundant in numerous plant species. Phytolith-occluded carbon (C) (PhytOC) accumulation in soil plays an important role in long-term soil organic C (SOC) storage. Nevertheless, the effects of both Si fertilizer and biochar application on PhytOC sequestration in forest plant-soil systems have not been studied. We investigated the impact of Si fertilizer and biochar applications on 1) the PhytOC pool size, the solubility of plant and soil phytoliths, and soil PhytOC in soil physical fractions (light (LFOM) and heavy fractions of organic matter (HFOM)) in Moso bamboo (Phyllostachys pubescens) forests; and 2) the relationships among plant and soil PhytOC concentrations and soil properties. We used a factorial design with three Si fertilizer application rates: 0 (S0), 225 (S1) and 450 (S2) kg Si ha−1, and two biochar application rates: 0 (B0) and 10 (B1) t ha−1. The concentrations of PhytOC in the bamboo plants and topsoil (0–10 cm) increased with increasing Si fertilizer addition, regardless of biochar application. Biochar addition increased the soil PhytOC pool size, as well as the LFOM- and HFOM-PhytOC fractions, regardless of Si fertilizer application. The Si fertilizer application increased or had no effect on soil phytolith solubility with or without biochar application, respectively. Soil PhytOC was correlated with the concentration of soil organic nitrogen (R2=0.32), SOC (R2=0.51), pH (R2=0.28), and available Si (R2=0.23). Furthermore, Si fertilizer application increased plant and soil PhytOC by increasing soil available Si. Moreover, biochar application increased soil PhytOC concentration in LFOM-PhytOC and the unstable fraction of PhytOC. We conclude that Si fertilizer and biochar application promoted PhytOC sequestration in the plant-soil system and changed its distribution in physical fractions in the Moso bamboo plantation in subtropical China.
Potential of typical highland and mountain forests in the Czech Republic for climate-smart forestry: ecosystem-scale drought responses
Authors: Jocher Georg , Kowalska Natalia , Acosta Manuel , Krejza Jan , Marková Irena , Marshall John , Uchytilová Tereza , Pavelka Marian , Marek Michal
Published: March 2021

Climate-smart forestry (CSF) consists of an extensive framework of actions directed to mitigating and adapting to global climate change impacts on the resilience and productivity of forest ecosystems. This study investigates the impact of the pan-European 2018 drought on carbon exchange dynamics in typical highland and mountain forests in the Czech Republic, including two coniferous (Norway spruce at Bílý Kříž and Rajec) and one deciduous (European beech at Štítná) stand. Our results show annual net ecosystem CO2 uptake at Rajec to be reduced by 50% during the drought year in comparison to a reference year with normal climatic conditions. Bílý Kříž is less affected by drought, as the local microclimate ensures sufficient water supply. The European beech forest at Štítná is most resilient against drought and its negative impacts: there we detect no differences in carbon exchange dynamics between the drought year and the reference year. We consider the matching of tree species to site conditions as crucial in the context of CSF, specifically regarding the stand response to water limitation and water supply and demand. Successively replacing spruce with beech trees in areas with high water demand but limited water supply, like Rajec, will support the goals of CSF.
GNSS Carrier Phase Integer Single Difference Times and Frequency Transfer Accuracy Evaluation
Authors: Xu Wei , Shen Wen-Bin , Cai Cheng-hui , Ning An , Shen Zi-yu
Published: March 2021

Due to the influence of pseudo-range noise, traditional GNSS common view method is difficult to improve the accuracy of time-frequency transfer. GNSS carrier phase precise point positioning (PPP) time-frequency transfer has become a research hotspot because of its high accuracy. In this paper, a time-frequency transfer model of GNSS carrier phase single difference (SD) and Integer Single Difference (ISD) between any two ground stations is studied. In order to solve the problem that the SD ambiguity cannot be fixed due to the influence of the phase biases at the receivers, a method of SD ambiguity fixing is proposed, that is the SD ambiguity is fixed with the constraint of the fixed double difference ambiguity among several stations and satellites. Here taking four time-frequency links between pairs of ground stations, BRUX-OPMT (262.3km), BRUX-PTBB (454.6km), BRUX-WTZR (637.7km) and BRUX-CEBR (1331.6km) as examples, the multi-GNSS time-frequency transfer experiment of SD, ISD and PPP method is carried out. The results show that the SD and PPP time-frequency transfer accuracy is equivalent, the stability of ISD is improved compared with SD, and the difference RMS between epochs is less than 10 ps. High precision carrier phase SD, ISD and PPP technology can be applied to the study of determining the gravity potential based on time-frequency measurements. This study is supported by the National Natural Science Foundations of China (NSFC) under Grants 42030105, 41721003, 41804012, 41631072, 41874023, Space Station Project (2020)228, and the Natural Science Foundation of Hubei Province of China under Grant 2019CFB611.
The Future of Conferences: Lessons Learnt from EGU20: Sharing Geoscience Online
Authors: Illingworth Sam , Gibson Hazel , Buiter Susanne
Published: March 2021

In the spring of 2020, as the coronavirus swept across the globe, millions of people were required to make drastic changes to their lives to help contain the impact of the virus. Among those changes, scientific conferences of every type and size were forced to cancel or postpone in order to protect public health. Included in these was the European Geosciences Union (EGU) 2020 General Assembly. After a six-week pivot to an online alternative, attendees of the newly designed EGU20: Sharing Geoscience Online took part in the first geoscience conference of its size to go fully online.
 
This work explores the feedback provided by participants following this experimental conference and identifies four key themes that emerged from analysis of the questions: what did people miss from a regular meeting; and to what extent did going online impact the event itself, both in terms of challenges and opportunities?
 
The themes identified are: connection, engagement, environment, and accessibility; and include discussions of the value of informal connections and spontaneous scientific discovery during conferences, the necessity of considering the environmental cost of in-person meetings, and the opportunities for widening participation in science by investing in accessibility.
 
The responses in these themes cover both positive and negative experiences of participants and raise important questions about what conference providers of the future will need to do to meet the needs of the scientific community in the years following the coronavirus outbreak.
Stability and dissolution of silver nanoparticles in sediment-laden water: Influence of suspended sediment and associated dissolved organic matter
Authors: Zhao Jian , Li Yang
Published: March 2021

The released silver nanoparticles (AgNPs) will inevitably interact with suspended sediment (SS), because of the ubiquity and abundance of SS in aquatic systems. However, the effect mechanism of SS on the transformation of AgNPs remains unknown and unpredictable. This research investigated the effect of SS on the aggregation, settling, and dissolution of polyvinylpyrrolidone-coated (PVP) AgNPs under environmentally diverse salinity conditions. By determining the morphology of AgNP–SS heteroaggregates and using the DLVO analysis, we revealed that the heteroaggregation between AgNPs and SS was dependent on ionic strength. The formation of AgNP-SS heteroaggregates eventually lead to the rapid settling of AgNPs. Besides, the interactions of sediment-associated dissolved organic matter (SS-DOM) with AgNPs interfered the dissolution of AgNPs under different NaCl concentrations. The fate (i.e., aggregation, dissolution and settling) of AgNP in sediment-laden water has been found to be strongly dependent on the presence of SS, SS-DOM and ionic strength. This work provides novel insight into the interaction between suspended particulate matter and AgNPs as well as its effect on AgNP physicochemical transformation in aquatic environment.
Analyzing Ca-41 sample at 1E-15 abundance level with cold atom trap techniques
Authors: Xia Tian , Xia Tong-Yan , Sun Wei-Wei , Jiang Wei , Lu Zheng-Tian
Published: March 2021

On earth, Calcium-41 is produced as a cosmogenic isotope via neutron capture process, leaving a natural isotopic abundance of 10-15 on earth surface. Calcium is also of vital importance for the metabolism of biological organisms. Consequently, analysis of the long lived radioactive isotope Calcium-41 is of great importance in geoscience, archeology and life sciences. The half-life of Calcium-41 is 1.03 x 105 years. It is a good candidate in dating rock and bone samples ranging from 50,000 to 1,000,000 years old.

The available techniques for trace analysis of Calcium-41 include accelerator mass spectrometry (AMS) and resonance ionization mass spectroscopy (RIMS). The detection limit of RIMS is on the level of 10-11 due to the interference of Potassium-41, which is difficult to remove from the sample. The analysis with high-energy AMS is more expensive than the table top apparatus, and it also faces similar problem as RIMS method.

We develop an atom trap trace analysis(ATTA) apparatus for Calcium-41 analysis to the sensitivity of 10-15 abundance level by one hour of single atom counting. ATTA uses laser tuned at the resonant wavelength for a specific element and isotope to slow down and capture single atom by fluorescence radiation. It has a very high selectivity of element and isotope, which is more advantageous than AMS and RIMS to avoid isobar interference. ATTA has been used in analysis of Krypton-81, Argon-39 dating of the hydrological samples. This work on high sensitivity Calcium-41 analysis is very promising in dating the geochemical sample to determine the exposure ages of rocks or in cosmochemistry for investigations on terrestrial ages.
Field testing of a portable two-filter dual-flow-loop 222Rn detector
Authors: Chambers Scott , Morosh Viacheslav , Griffiths Alan , Williams Alastair , Röttger Stefan , Röttger Annette
Published: March 2021

An overlapping need exists between the climate science, air quality and radiological protection communities for a robust, portable and direct monitor of atmospheric 222Rn concentrations typical of the ambient outdoor atmosphere. To reliably characterise afternoon radon concentrations, or resolve daytime vertical radon gradients in the atmospheric boundary layer (requirements for radon measurements to be used to evaluate the performance of chemical transport models), detection limits of ≤0.2 Bq m-3 at an hourly temporal resolution are required. Commercial portable radon detectors are mainly designed for indoor use, and the best of these has a detection limit of ≥2 Bq m-3 for hourly sampling, with an approximate uncertainty of 60% at typical outdoor daytime radon concentrations.  Here we introduce a portable (200 L) version of the two-filter dual-flow-loop radon detector, designed and built by ANSTO in collaboration with the EMPIR 19ENV01 traceRadon project. While not as compact as commercial monitors (standing 1.6 m tall, and 0.48 m wide), its longest component is 1.2 m, enabling transportation in a standard utility vehicle or 4x4 (and can fit inside a 19” instrument rack). Constructed of marine grade stainless steel, it is weather resistant, robust, and suitable for long-term, continuous, autonomous deployment; in fact it is fully remotely controllable if a networked computer is available. The estimated lower limit of detection is 0.17 Bq m-3 for hourly observations, and the counting uncertainty at typical ambient outdoor radon concentrations is around 7%. Additional uncertainty associated with current calibration techniques, which inject calibration gas on top of ambient sampled air, varies from 2-6%. Some objectives of the traceRadon project include establishing direct calibration traceability to the SI and developing an improved closed-loop calibration technique, using a new, low activity Radium-226 source. If successful, the absolute accuracy of the 200 L radon detector at typical ambient outdoor concentrations could be kept well below 15% for hourly observations. This project has received funding from the EMPIR programme co-financed by the Participating States and from the European Union's Horizon 2020 research and innovation programme. 19ENV01 traceRadon denotes the EMPIR project reference.
Determination of the Geopotential Difference between Atomic Clock Ensemble in Space (ACES) and Ground Station using the Tri-Frequency Combination (TFC) Method
Authors: Ashry Mostafa , Shen Wenbin , Shen Ziyu , A. Abd-Elmotaal Hussein , ruby Abdelrahim , Pengfei Zhang
Published: March 2021

According to general relativity theory, a precise clock runs at different rates at positions with different geopotentials. Atomic Clock Ensemble in Space (ACES) is a mission using high-performance clocks and links to test fundamental laws of physics in space. The ACES microwave link (MWL) will make the ACES clock signal available to ground laboratories equipped with atomic clocks. The ACES-MWL will allow space-to-ground and ground-to-ground comparisons of atomic frequency standards. This study aims to apply the tri-frequency combination (TFC) method to determine the geopotential difference between the ACES and a first order triangulation station in Egypt. The TFC uses the uplink of carrier frequency 13.475 GHz (Ku band) and downlinks of carrier frequencies 14.70333 GHz (Ku band) and 2248 MHz (S-band) to transfer time and frequency. Here we present a simulation experiment. In this experiment, we use the international space station (ISS) orbit data, ionosphere and troposphere models, regional gravitational potential and geoid for Africa, solid Earth tide model, and simulated clock data by a conventionally accepted stochastic noises model. The scientific object requires stabilities of atomic clocks at least 3 × 10 −16 /day, so we must consider various effects, including the Doppler effect, second-order Doppler effect, atmospheric frequency shift, tidal effects, refraction caused by the atmosphere, and Shapiro effect, with accuracy levels of decimetres. This study is supported by the National Natural Science Foundations of China (NSFC) under Grants 42030105, 41721003, 41804012, 41631072, 41874023, Space Station Project (2020)228, and the Natural Science Foundation of Hubei Province of China under Grant 2019CFB611.
Remote sensing inversion of water quality in coastal sea area based on machine learning: a case study of Shenzhen bay, China
Authors: Zhu Xiaotong , Huang Jinhui Jeanne
Published: March 2021

Remote sensing monitoring has the characteristics of wide monitoring range, celerity, low cost for long-term dynamic monitoring of water environment. With the flourish of artificial intelligence, machine learning has enabled remote sensing inversion of seawater quality to achieve higher prediction accuracy. However, due to the physicochemical property of the water quality parameters, the performance of algorithms differs a lot. In order to improve the predictive accuracy of seawater quality parameters, we proposed a technical framework to identify the optimal machine learning algorithms using Sentinel-2 satellite and in-situ seawater sample data. In the study, we select three algorithms, i.e. support vector regression (SVR), XGBoost and deep learning (DL), and four seawater quality parameters, i.e. dissolved oxygen (DO), total dissolved solids (TDS), turbidity(TUR) and chlorophyll-a (Chla). The results show that SVR is a more precise algorithm to inverse DO (R2 = 0.81). XGBoost has the best accuracy for Chla and Tur inversion (R2 = 0.75 and 0.78 respectively) while DL performs better in TDS (R2 =0.789). Overall, this research provides a theoretical support for high precision remote sensing inversion of offshore seawater quality parameters based on machine learning.
Effects of Content of Soil Rock Fragments on Calculating of Soil Erodibility
Authors: Yang Miaomiao , Yang Qinke , Zhang Keli , Li Yuru , Wang Chunmei , Pang Guowei
Published: March 2021

【Objective】Rock fragments (>2mm diameter) are an important component of soil, and its presence has a significant impact on soil erosion and sediment yield. So it is essential to take into full account content of the rock fragments for accurate calculation of soil erodibility factor (K). 【Method】In this paper, based on the data available of the content of rock fragments and classes of soil texture with a resolution of 30 arc-second, influence of the content of rock fragments, including rock fragments in the soil profile (RFP) and gravels on the surface of the soil (SC), on K was assessed at a global scale, using the equation (Brakensiek, 1986) of the relationship between saturated hydraulic conductivity and grade of soil permeability, and the equation (Poesen) of soil erodibility attenuation under a rock fragment cover. 【Result】Results show: (1) The existence of rock fragments in the soil increased K by 4.43% and soil permeability by 5.68% on average in grade and lowering soil saturated hydraulic conductivity by 11.57% by reducing water infiltration rate of the soil and increasing surface runoff. The gravels on the surface of the mountain land and desert/gobi reduced K by 18.7% by protecting the soil from splashing of rain drops and scrubbing of runoff; so once the content of rock fragments in the soil profile and gravels on the surface of the land are taken into account in calculation, soil K may be 5.52% lower; (2)In the areas dominated with the effect of rock fragments, about 62.7% of the global land area, soil K decreased by 0.0091( t•hm2•h)•( hm-2•MJ-1•mm-1) on average, while in the area affected mainly by rock fragments in profile, about 31.1% of the global land area, soil K increased by 0.0019( t•hm2•h)•( hm-2•MJ-1•mm-1); and (3)The joint effect of rock fragments in profile and gravels on the surface reduced the soil erosion rate by 11.8% in the 6 sample areas. 【Conclusion】 The presence of RFP increases soil K while the presence of SC does reversely. The joint effect of the two leads to decrease in soil erosion. In plotting regional soil erosion maps, it is essential to take both of the two into account so as to improve accuracy of the mapping.
Mine water heat and heat storage research opportunities at the UK Geoenergy Observatory in Glasgow, UK
Authors: Monaghan Alison , Starcher Vanessa , Barron Hugh , Fordyce Fiona , Taylor-Curran Helen , Luckett Richard , Shorter Kirsty , Walker-Verkuil Kyle , Elsome Jack , Kuras Oliver , Abesser Corinna , Boon David , Palumbo-Roe Barbara , Dearden Rachel , Spence Michael
Published: March 2021

Mine water geothermal heat production and storage can provide a decarbonised source of energy for space heating and cooling, however the large resource potential has yet to be exploited widely. Besides economic, regulatory and licensing barriers, geoscientific uncertainties such as detailed understanding of thermal and hydrogeological subsurface processes, resource sustainability and potential environmental impacts remain.

The UK Geoenergy Observatory in Glasgow is a research infrastructure for investigating shallow, low-temperature coal mine water heat energy resources available in abandoned and flooded mine workings at depths of around 50-90 m. It is an at-scale ‘underground laboratory’ of 12 boreholes, surface monitoring equipment and open data. The Glasgow Observatory is accepting requests for researchers and innovators to undertake their own experiments, test sensors and methods to increase the scientific evidence base and reduce uncertainty for this shallow geothermal technology.
The Variscan structure of the western Cantabrian Mountains (NW Spain) from ambient noise interferometry
Authors: Acevedo Jorge , Fernández-Viejo Gabriela , Llana-Fúnez Sergio , Pando Luis , Pérez-Millán Diego , Ruiz Mario , Díaz Jordi
Published: March 2021

The Variscan belt was formed as a consequence of the collision of two major continents, Laurasia and Gondwana, in the late Paleozoic. Nowadays, it constitutes the basement of the Iberian peninsula (Iberian Massif) and a large part of western and central Europe. In the NW of Spain, the convergence between Iberia and Europe in the Cenozoic originated the uplift of the Cantabrian mountains (CM). In its central sector, the erosion of the Mesozoic sedimentary cover during orogenesis led to the exhumation of the underlying Variscan basement in their western sector. The section of the Variscan belt that is currently exposed in the CM illustrates the transition from the internal zones of an orogen, in the west, to the external ones, to the east.

In order to acquire new passive data from this region, a portable seismic network consisting of 13 three-component broadband stations was deployed (GEOCANTÁBRICA-COSTA, doi:10.7914/SN/YR_2019). The recorded ambient noise seismic signal was cross-correlated using the phase cross-correlation (PCC) processing technique and the resulting daily cross-correlograms were stacked to obtain the empirical Green’s function of the medium between each station pair. Since the vertical and the rotated horizontal components were processed, Rayleigh- and Love-wave group velocity dispersion curves were extracted. From these measurements, group velocity tomographic maps at periods between 2 – 14 s were calculated. Based on this set of tomographic maps, a final 3D S-wave velocity model (2 - 12 km) was derived from the joint inversion of the pseudo-dispersion curves created by extracting the Rayleigh and Love velocity values for each point of a dense grid.

Both the surface-wave and the S-wave velocity maps highlight essential elements of the surface geology of the area. The velocity pattern shows the boundary between two main geological domains: The Cantabrian Zone (CZ), to the east, which constitutes the foreland fold and thrust belt of the Variscan orogen; and the West Asturian-Leonese Zone (WALZ), to the west, the slate belt representing the low grade part of the internal zones. An E-W cross-section of the study area shows a high velocity unit to the west thrusting the lower velocity rocks of the CZ at the transition between the WALZ and the CZ.
When the sea become a monster? The social impact of the Storegga tsunami, 8200 BP, on the Mesolithic of northern Europe
Authors: Nyland Astrid , Warren Graeme , Walker James
Published: March 2021

Around 8200 years ago, the Storegga tsunami, caused by a massive submarine landslide off the coast of Central Norway, struck the coasts of west Norway, Scotland and Doggerland. This event is well known from wide ranging geological and palaeobotanical work undertaken over the last 30 years. What has been less explored, however, is the potential social impact that this natural freak event had on the Mesolithic hunter-gatherer societies living on the coasts and shores of the North Sea. What happened in the tsunami’s aftermath? It has been widely assumed to have been a disaster – but was it? What constituted a disaster in the Mesolithic? In the Mesolithic, people were hunter-gatherer-fishers, they lived by, off, and with the sea. Settlement sites in West Norway were concentrated along the outer coast. People lived on the shores of islands and headlands, or along resource rich tidal currents. Eastern Scottish Mesolithic sites are also found on contemporary coasts, while the coasts of central Doggerland have long since become submerged. What happened to groups in these landscapes on the day the sea became a monster and in the years that followed? In this paper, we will outline a newly started project that will investigate the social impact of the tsunami in areas of the North Sea that have distinctive Mesolithic histories. These coastal inhabitants had, for millennia, developed their own traditions to engage with and learn how to exploit and keep safe from the sea. What can we learn about Mesolithic societies by investigating how communities handled the forces of a tsunami? Responses identified in the archaeological material and environmental archives can potentially inform us of social structures, institutions or ways of living that made the existing societies resilient or vulnerable.
Theory of best integer equivariant estimation for contaminated normal and multivariate t-distribution with applications
Authors: Teunissen Peter
Published: March 2021

Best integer equivariant (BIE) estimators provide minimum mean squared error (MMSE) solutions to the problem of GNSS carrier-phase ambiguity resolution for a wide range of distributions. The associated BIE estimators are universally optimal in the sense that they have an accuracy which is never poorer than that of any integer estimator and any linear unbiased estimator. Their accuracy is therefore always better or the same as that of Integer Least-Squares (ILS) estimators and Best Linear Unbiased Estimators (BLUEs).

Current theory is based on using BIE for the multivariate normal distribution. In this contribution this will be generalized to the contaminated normal distribution and the multivariate t-distribution, both of which have heavier tails than the normal. Their computational formulae are presented and discussed in relation to that of the normal distribution. In addition a GNSS real-data based analysis is carried out to demonstrate the universal MMSE properties of the BIE estimators for GNSS-baselines and associated parameters.

 

Keywords: Integer equivariant (IE) estimation · Best integer equivariant (BIE) · Integer Least-Squares (ILS) . Best linear unbiased estimation (BLUE) · Multivariate contaminated normal · Multivariate t-distribution . Global Navigation Satellite Systems (GNSSs)