bluuebunny/crossref_metadata_2025 huggingface dataset:
Corrosion behavior of low carbon steel under different water conditions in compacted bentonite of China-Mock-Up
Authors: Wei Xin , Liu Yuemiao , Dong Junhua
Published: March 2020

In some countries, low carbon steel has been considered as the candidate material of the disposal container for high-level radioactive wastes (HLWs) due to its excellent anti-irradiation, high strength, low cost and fine processing performance. However, during the long-term geological disposal, the steel disposal container will suffer from the threat of corrosion damage under the coupled THMC conditions.

This work focused on the corrosion behavior of low carbon steel under different water conditions in compacted bentonite of China-Mock-Up by in situ electrochemical impedance spectroscopy (EIS) with the infiltration of groundwater from outside to inside. Based on the EIS results, the corresponding equivalent circuit models were proposed to interpret the evolution of electrochemical characteristics of low carbon steel with the increase of water content in compacted bentonite. In the initial stage of EIS measurement, water in bentonite around the electrochemical sensors from outside to inside was hygroscopic water and chemical bonding water successively. With the running of China-Mock-Up, water in outer bentonite transformed from hygroscopic water to free water. Meanwhile, the water in the inner bentonite blocks transformed from chemical bonding water to hygroscopic water, which caused a slight corrosion of low carbon steel. After China-Mock-Up running for 1202 days, the instantaneous corrosion rate of low carbon steel located in the inner bentonite blocks was just 0.002 mm/a. While in the outside bentonite blocks, the corrosion rate reached to 0.58 mm/a after 1155 days, indicating that the free water could cause a serious corrosion of low carbon steel.
Deciphering forcing mechanisms for dynamic sea level variations off the northeast US coast
Authors: Lee Tong , Wang Ou , Zhang Hong , Fenty Ian , fukumori ichiro
Published: March 2020

Regional sea level change is strongly societal relevant. The knowledge about the forcing mechanisms for contemporary regional sea level variation is important to the evaluation of climate models and the fidelity of projected sea level changes using these models. Dynamic sea level variation off the northeast US coast has been a subject of significant interest of late. However, there is inadequate understanding about the forcing mechanisms and the underlying oceanic processes. The Estimating the Circulation and Climate of the Ocean (ECCO) state estimate reproduced well the observed interannual-to-decadal variation of dynamic sea level in the region during the satellite altimeter era. Here we use the ECCO adjoint sensitivity tools to quantify the relative contributions of local and remote winds, surface heat flux, and surface freshwater flux on dynamic sea level variation in this region. We further characterize the salient oceanic processes associated with different surface forcings on different time scales.
Evaluation of rainfall-induced large-scale landslide potential using Scoops3D
Authors: Chiang Jie-Lun , Kuo Chia-Ming
Published: March 2020

Taiwan is located in the Pacific volcanic seismic zone and frequently suffers from landslides and debris flow caused by typhoons. On average, there are four typhoons which may cause tremendous disasters such as massive landslides in Taiwan mainly from July to September every year. The aim of this study is to evaluate the development of large-scale landslide area under various cumulative rainfalls. The study area of this study is Liouquei, Kaohsiung in southern Taiwan. Firstly, the relationship of rainfall and groundwater level were built. The equation of change of groundwater level and rainfall is h=38.2R, R2=0.83. Then, 10m digital elevation model (10m-dem) was used to evaluate elevation, slope, aspect and etc. Finally, geology and 10m-dem were used to build Scoops3D model of Liouquei area.

Scoops3D, which is released by the United States geological survey (USGS), evaluates slope stability throughout a digital landscape represented by a digital elevation model (DEM). The program uses a three-dimensional (3D) method of columns limit-equilibrium analysis to assess the stability of many potential landslides (typically millions) within a user-defined size range. We simulated the potential landslide area under a cumulative rainfall in 24 hours from 800mm~1600mm. The results show that landslide area contributed 65%~76% of the entire potential large-scale landslide area.
Corrosion study of low carbon steel under simulated geological disposal environments for HLW in China
Authors: Dong Junhua
Published: March 2020

In the multi-barrier system of HLW repository, overpack is the first barrier to isolate high-level radioactive nuclides from biosphere, and Low carbon steel has been considered to be a promising candidate material for manufacturing the oberpack due to its good mechanical performance and workability and weldability. However, during thousands of years of geological disposal, the corrosion resistance of low carbon steel and its corrosion evolution behavior are the first element that must be fully understood, because it determines the life cycle of the artificial barrier.

Conventional studies had suggested that the corrosion of low carbon steel under the deep geological environment was driven by hydrogen evolution reaction (HER) based on that the dissolved oxygen was completely depleted during the long term disposal. However, the residual oxygen content is a critical factor to determine the corrosion mode of cathodic reduction reaction. Thermodynamics data indicated that the initial ferrous corrosion products formed in the deaerated bicarbonate solution can be chemically oxidized into ferric substance by the trace content of dissolved oxygen, and the accumulated FeOOH as a cathodic depolarizer significantly increased the open circuit potential and enhanced the corrosion rate of the low carbon steel. Moreover, chloride and sulfate in the simulated groundwater can reduce the increase of open circuit potential but it still promotes the corrosion of the low carbon steel. As the environments contained aggressive anions and high concentration of dissolved oxygen, low carbon steel was prone to suffer from the localized corrosion and the corrosion rate was obviously increased. By alloying with some contents of Ni and Cu, the corrosion rate of low alloy steel was decreased by an order of magnitude and it was less prone to suffer from the localized corrosion.

Under the conditions of simulated groundwater with different content of GMZ bentonite，the bentonite colloidal particle layer attached to the surface of low carbon steel showed blocking effect on resisting oxygen diffusion to the steel substrate, which consequently decrease the further oxidation of ferrous to ferric substances and the corrosion rate of low carbon steel. However, the barrier performance of bentonite colloids would be deteriorated due to their coagulation caused by the ferrous ions dissolved from the steel substrate. High content of bentonite was beneficial to maintain and to prolong the stabilization of the barrier system. An equivalent circuit model which correlates with the interfacial structure between electrode substrate and rust and bentonite layer was proposed. The fitting results showed a very good match between the model and experimental data, and the evolution of the results was also in agreement with real changes.
Global Ion Density Distributions Observed by Advanced Ionospheric Probe Onboard FORMOSAT-5 Satellite
Authors: Chao Chi-Kuang
Published: March 2020

A FORMOSAT-5 satellite has been launched on 25 August 2017 CST into a 98.28° inclination sun-synchronous circular orbit at 720 km altitude along the 1030/2230 local time sectors.  The orbital coverage provides a great opportunity to survey terrestrial ionosphere from equatorial to polar region every two days.  Advanced Ionospheric Probe (AIP) is a piggyback science payload developed by National Central University for the FORMOSAT-5 satellite to measure ionospheric plasma concentrations, velocities, and temperatures.  It is also capable of measuring ionospheric plasma density irregularities at a sample rate up to 8,192 Hz over a wide range of spatial scales.  In this poster, global ion density distributions observed by FORMOSAT-5/AIP in the pre-midnight sector can be averaged monthly and seasonally from in-situ measurement since November 2017.  Wave-3 and wave-4 patterns are clearly detected from the distributions and varied with season and solar cycle.  It is adversely indicated that FORMOSAT-5/AIP can provide high quality data to identify long-term ionospheric ion density variations.
Spatial and Temporal Characterization of Drought Events in China Using the Severity-Area-Duration Method
Authors: Yang Xiaoli
Published: March 2020

Global climate change not only affects the processes within the water cycle but also leads to the frequent occurrences of local and regional extreme drought events. In China, spatial and temporal characterizations of drought events and their future changing trends are of great importance in water resources planning and management. In this study, we employed self-calibrating Palmer drought severity index (SC-PDSI), cluster algorithm, and severity-area-duration (SAD) methods to identify drought events and analyze the spatial and temporal distributions of various drought characteristics in China using observed data and CMIP5 model outputs. Results showed that during the historical period (1961–2000), the drought event of September 1965 was the most severe, affecting 47.07% of the entire land area of China, and shorter duration drought centers (lasting less than 6 months) were distributed all over the country. In the future (2021–2060), under both RCP[CF1]  4.5 and RCP 8.5 scenarios, drought is projected to occur less frequently, but the duration of the most severe drought event is expected to be longer than that in the historical period. Furthermore, drought centers with shorter duration are expected to occur throughout China, but the long-duration drought centers (lasting more than 24 months) are expected to mostly occur in the west of the arid region and in the northeast of the semi-arid region.
Anisotropic upper mantle structures in northeast Asia from Bayesian inversions of ambient noise data
Authors: Lee Sang-Jun , Kim Seongryong , Rhie Junkee
Published: March 2020

The northeast Asia region exhibits complex tectonic settings caused by interactions between Eurasian, Pacific, and Philippine Sea plates. Distributed extensional basins, intraplate volcanoes and other heterogeneous features in the region marked results of the tectonic processes, and their mechanisms related to mantle dynamics can be well understood by estimating radial anisotropy in the lithospherie and asthenospherie. We constructed a three-dimensional radial anisotropy model in northeast Asia using hierarchical and transdimensional Bayesian joint inversion techniques with different types of dispersion data up to the depth of the upper mantle (~ 160 km). Thick and deep layers with positive radial anisotropy (VSH > VSV) were commonly found at depths between 70 and 150 km beneath the continental regions. On the other hand, depths and sizes of layers with positive radial anisotropy become shallower and thinner (30 ~ 60 km) respectively beneath regions where experienced the Cenozoic extension. These variations in positive radial anisotropy for different tectonic regions can be understood with the context of extensional geodynamic processes in back arc basins within the East Sea (Japan Sea). Interestingly, the most predominant positive radial anisotropy is imaged along areas with large gradient of the litheosphere-asthnosphere boundary beneath intraplate volcanoes. These observations favor the mechanism of edge-driven convection caused by the difference in lithosphere thickness and localized sublithospheric lateral flow from the continental region to back arc basins.
Paleoclimate drivers of the Indonesian and South China Sea throughflows, the curious case of the IOD
Authors: Kannad Ankitha , Goodkin Nathalie F. , Murty Sujata A. , Ramos Riovie D. , Samanta Dhrubajyoti , Gordon Arnold L.
Published: March 2020

The Indonesian and South China Sea throughflows play an important role in global ocean circulation as the only low-latitude pathway for the exchange of heat and salt between the Pacific and Indian oceans. This transport is modulated by different climate systems including the El Niño Southern Oscillation (ENSO), the Pacific Decadal Oscillation (PDO) and the East Asian Monsoon. The interactions of these climate systems across the Southeast Asian region are still being understood, particularly the role of sea surface salinity (SSS) in inhibiting flow from the Makassar Strait into the Indian Ocean.

Reconstructions of SSS from corals provide an opportunity to study long-term trends in climate and ocean circulation. Coral records from north and south of the Luzon Strait, the Makassar Strait, and Lombok Strait for the period 1926 to 2010 are examined to evaluate their shared variability. Principal component analysis synthesizes these records for the boreal winter (December to March) and boreal summer (June to September). The first and second principal components or empirical orthogonal functions (EOF) describe over 55% of the shared variance in both seasons. In the winter, the EOF of both modes correlates to PDO and the first EOF correlates to the Indian Ocean Dipole (IOD). A high-pass filter of the first EOF for <10 years per cycle for the winter and summer significantly correlates to ENSO and IOD respectively. While several sites individually correlate with ENSO and PDO, no individual SSS record correlates to the IOD. This consistent relationship of the IOD to the winter EOF indicates a regional influence on salinity variance that is not identified locally. One hypothesis to explain IOD’s regional influence is that the interaction of the IOD and ENSO through the atmospheric bridge or the Madden Julian Oscillation (MJO) is influencing the region. Spectral analysis, and climatic and oceanographic models will be used to further investigate this connection.
Estimation and validation of electric power output from a fixed-type floating photovoltaic system
Authors: Suh Jangwon , Kim Sungmin , Choi Yosoon
Published: March 2020

An accurate estimation of electric power production (EPP) is a crucial first step to design a floating photovoltaics (PV) project. This study estimates the EPP of a floating PV system and validates the results by comparing with the actual EPP observed at the Hapcheon Dam, Korea. Typical meteorological year data and system design parameters were entered into System Advisor Model (SAM) software to estimate the hourly and monthly EPPs. Three-year average observed EPPs (2012, 2013, and 2015) were used as reference values for the validation. The results showed the seasonal EPPs were the highest in spring and the lowest in winter. The monthly estimated EPPs were lower than the monthly observed EPPs. These results are ascribed to the fact the SAM was unable to consider the natural cooling effect of the water environment on the PV module. The error results showed it was possible to estimate the monthly EPPs with an error of less than 15% simply by simulation. However, it may possible to estimate the monthly EPPs with an error of approximately 9% when considering empirical results: The floating PV efficiency was approximately 1.1 times (110%) the overland PV efficiency. This indicates that the approach of using empirical results can provide reliable monthly estimation of EPP in feasibility assessment stage of floating PV projects.
Application systems of the FIO ocean forecasting system using Lagrangian methods
Authors: Yin Liping , Qiao Fangli , Zhao Chang , Wang Guansuo
Published: March 2020

Lagrangian methods have been widely used and playing more and more essential roles in the analysis of ocean physical processes, pollution prediction, ecosystem protection and fisheries. Using the Lagrangian methods based on the high resolution coupled ocean model, we report several specific studies. The numerical modelling team from First Institute of Oceanography (FIO), Ministry of Natural Resources (MNR) of China, developed an ocean forecasting system based on the global (1/10°) wave-tide-circulation coupled model, as well as the regional model (1/24°) for China and adjacent seas. Basing on this system and its products, we developed the global ocean radionuclides model to investigate the long-term transport, distribution and evaluation of 137Cs in the ocean both from the Fukushima nuclear accident in March of 2011 and nuclear tests during the past 60 years; established the search and rescue system which has successfully applied in the rescue of the Phuket boat capsizing accident in July 2018; established the Enteromorpha prediction and tracking models for the protection of the marine environmental hazard from Enteromorpha, and to identify the origin area of this harmful green tide; developed the stock enhancement model of edible jellyfish to mimic the distribution of the human-released jellyfish and identify the connectivity between the releasing site and the fishing ground in Liaodong Bay of Bohai Sea, China. With the combination of the statistical methods, we established the near-term forecast and long-term projection system of the oil spill to forecast and evaluate the influence of the oil spill from the “Sanchi” collision accident on the ocean. All of these applications are verified and essential for protecting the oceans.
Long-term Temporal Variation of Mean Residence Time in Spring and Groundwater After Thinning at a Forested Headwater Catchment
Authors: Silveira Baptista Isabela , Tsujimura Maki , Onda Yuichi
Published: March 2020

Treatments on plantation forests, such as thinning, have a significant effect on the quality and quantity of water resources in the watersheds in Japan. However, few studies have performed intensive observations regarding the effects of thinning on the groundwater flow process with combined use of tracers, specially over a long period of time.

In this study, stable isotope analysis and hydrological observations were applied to investigate the temporal variation of spring water and groundwater mean residence time in a small watershed at Mount Karasawa, Tochigi Prefecture, Japan. We have monitored the research area since 2010, with periodical sampling once a month for 9 years, with a lack of data in some years after the thinning.  We analyzed the date for three different time periods, those are: Before Thinning, from July 2010 to September 2011, Soon After Thinning, from November 2011 to October 2013 and Long After Thinning, from September 2017 to August 2019.

The mean residence time of spring water and groundwater were evaluated by using the stable isotopes of hydrogen and oxygen as tracers, then estimating their d-excess variations using two Lumped-Parameter Models, Exponential-Piston Flow Model and Dispersion Model. The SF6 concentrations were used as an Apparent Age analysis for determination of the model’s parameters. Both models show a tendency of the mean residence time getting older Soon After Thinning and then getting younger again Long After Thinning.

According to a selection of the best model for this area, the Exponential-Piston Flow Model shows that the spring water mean residence time was 25 months Before Thinning, 30 months Soon After Thinning and 26 months Long After Thinning; the groundwater at 15m deep mean residence time was 39 months Before Thinning, 46 months Soon After Thinning and 38 months Long After Thinning and the groundwater at 30m deep mean residence time was 38 months Before Thinning, 47 months Soon After Thinning and 45 months Long After Thinning. These results suggest that Soon After Thinning there is a reduction of forest interception and tree evapotranspiration, leading to an increase in infiltration and groundwater storage. Then, Long After Thinning, the forest interception and tree evapotranspiration rise back again with the recovery of the understory vegetation, which leads to a decrease in infiltration and groundwater storage.
An Advanced Formulation of Kalman Filter Time Series Reference Frame Realization for Geophysical Applications
Authors: Wu Xiaoping , Haines Bruce , Heflin Michael , Landerer Felix
Published: March 2020

A Kalman filter and time series approach to the International Terrestrial Reference Frame (ITRF) realization (KALREF) has been developed and used in JPL. KALREF combines weekly or daily SLR, VLBI, GNSS and DORIS data and realizes a terrestrial reference frame in the form of time-variable geocentric station coordinate time series. The origin is defined at nearly instantaneous Center-of-Mass of the Earth system (CM) sensed by weekly SLR data and the scale is implicitly defined by the weighted averages of those of weekly SLR and daily VLBI data. The standard KALREF formulation describes the state vector in terms of time variable station coordinates and other constant parameters. Such a formulation is fine for station positions and their uncertainties or covariance matrices at individual epochs. However, coordinate errors are strongly correlated over time given KALREF’s unique nature of combining different technique data with various frame strengths through local tie measurements and co-motion constraints and its use of random walk processes. For long time series and large space geodetic networks in the ITRF, KALREF cannot keep track of such correlations over time. If they are ignored when forming geocentric displacements for geophysical inverse or network shift geocenter motion studies, the covariance matrices of coordinate differences cannot adequately represent those of displacements. Consequently, significant non-uniqueness and inaccuracies would occur in the results of studies using such matrices. To overcome this difficulty, an advanced KALREF formulation is implemented that features explicit displacement parameters in the state vector that would allow the Kalman filter and smoother to compute and return covariance matrices of displacements. The use of displacement covariance matrices reduces the impact of time correlated errors and completely solves the non-uniqueness problem. However, errors in the displacements are still correlated in time. Further calibrations are needed to accurately assess covariance matrices of derivative quantities such as averages, velocities and accelerations during various time periods. We will present KALREF results of the new formulation and their use along with newly reprocessed RL06 GRACE gravity data in a new unified inversion for geocenter motion.
Bayesian inversion and visualization of hierarchical geostatistical models
Authors: Reuschen Sebastian , Xu Teng , Nowak Wolfgang
Published: March 2020

Geostatistical inversion methods estimate the spatial distribution of heterogeneous soil properties (here: hydraulic conductivity) from indirect information (here: piezometric heads). Bayesian inversion is a specific approach, where prior assumptions (or prior models) are combined with indirect measurements to predict soil parameters and their uncertainty in form of a posterior parameter distribution. Posterior distributions depend heavily on prior models, as prior models describe the spatial structure of heterogeneity. The most common prior is the stationary multi-Gaussian model, which expresses that close-by points are more correlated than distant points. This is a good assumption for single-facies systems. For multi-facies systems, multiple-point geostatistical (MPS) methods are widely used. However, these typically only distinguish between several facies and do not represent the internal heterogeneity inside each facies.

We combine these two approaches to a joint hierarchical model, which results in a multi-facies system with internal heterogeneity in each facies. Using this model, we propose a tailored Gibbs sampler, a kind of Markov Chain Monte Carlo (MCMC) method, to perform Bayesian inversion and sample from the resulting posterior parameter distribution. We test our method on a synthetic channelized flow scenario for different levels of data available: A highly informative setting (with many measurements) where we recover the synthetic truth with relatively small uncertainty invervals, and a weakly informative setting (with only a few measurements) where the synthetic truth cannot be recovered that clearly. Instead, we obtain a multi-modal posterior. We investigate the multi-modal posterior using a clustering algorithm. Clustering algorithms are a common machine learning approach to find structures in large data sets. Using this approach, we can split the multi-modal posterior into its modes and can assign probabilities to each mode. A visualization of this clustering and the according probabilities enables researchers and engineers to intuitively understand complex parameter distributions and their uncertainties.
Correlation between shear wave velocity, void ratio and effective stress: Mapping Vs30 in Taiwan
Authors: Gao Jia Cian , Guo Jyun Liang , Dong Jia Jyun , Lee Chyi Tyi
Published: March 2020

Site effect is one of the critical factors influencing the seismic hazard evaluation. Among others, the average shear-wave velocity of the upper 30 meters of a soil profile (Vs30) has been widely used for assessing the ground-motion amplification. However, spatial resolution of shear wave velocity data is usually poor for reginal- or national-wise evaluation. Standard Penetration Test N-value, the most abundant geotechnical data, was then used to estimate the shear wave velocity (Vs) empirically and the uncertainty of the Vs30 map can be reduced. In this study, we use the state variables of soils (void ratio and effective stress) to evaluate the shear wave velocity and to map the Vs30 in Taiwan. Engineering Geological Database for TSMIP (EGDT) comprises soil profile, shear wave velocity measurements, groundwater table, and soil physical properties (such as void ratio, water content, specific gravity, and unit weight), was used to construct the correlation between Vs, void ratio, and effective stress. The drilling database of Taiwan CGS was then used to estimate the spatial distribution of Vs30, where the Vs is un-available. The results were compared with the previous version of Vs30 map of Taiwan. The uncertainty of the new Vs30 map was evaluated and the propagation of uncertainty to the seismic hazard can be evaluated accordingly.

 
A dynamic equation for 2D surface waves on deep water
Authors: Kachulin Dmitry , Dyachenko Alexander , Zakharov Vladimir
Published: March 2020

Using the Hamiltonian formalism and the theory of canonical transformations, we have constructed a model of the dynamics of two-dimensional waves on the surface of a three-dimensional fluid. We find and apply a canonical transformation to a water wave equation to remove all nonresonant cubic and fourth-order nonlinear terms. The found canonical transformation also allows us to significantly simplify the fourth-order terms in the Hamiltonian by replacing the coefficient of four-wave Zakharov interactions with a new simpler one. As a result, unlike the Zakharov equation (written in k-space), this equation can be written in x-space, which greatly simplifies its numerical simulation. In addition, our chosen form of a new coefficient of four-wave interactions allows us to generalize this equation to describe two-dimensional waves on the surface of a three-dimensional fluid. An effective numerical algorithm based on the pseudospectral Fourier method for solving the new 2D equation is developed. In the limiting case of plane (one-dimensional) waves, we found solutions in the form of breathers propagating in one direction. The dynamics of such nonlinear traveling waves perturbed in the transverse direction is numerically investigated.

The work was supported by the Russian Science Foundation (Grant No. 19-72-30028).
Local Scouring Characteristics Downstream of Arched Cross-Vane Structures
Authors: Lai You-Wei , Chen Po-An , Chan Hsun-Chuan
Published: March 2020

Groundsill is one of the hydraulic structures used to stabilize the riverbed and prevent the erosion of riverbank. Therefore, groundsill may have the negative effects on the ecological environment. Comparing with a traditional groundsill, a Cross-Vane concentrates the water flow and create a downstream pool. This may improve the diversity of the aquatic habitats. The aim of this research is to analyze the scour phenomena and morphologies downstream of an arched Cross-Vane with different geometrical dimensions in a straight channel by using the numerical model. The riverbed slopes of 0%, 2%, 4% and 6% were tested. Among them, the ratio (L/B) between the arc length of the structure (L) and the channel width (B) represents the camber of structures, including 13 kinds of arches. For each arch structure, Densimetric Froude numbers (Fd) , approach flow depths (h0) and drop heights (Δy) were tested in different flow rate, and the flow rate was between 0.01cms and 0.04cms.The results showed the downstream scour pattern of the arched Cross-Vane had a significant correlation with Fd and Δy, and could be classified according to the scour length (lm) and the ridge length (ln). Scour typology included five types of scour. Type 1 : lm/B > 2.5 and ln /B < 1. Type 2: lm/B was located about 2.0 to 2.5 and ln/B > 1. Type 3: lm/B=2.0 and ln/B < 1. Type 4: lm/B was located about 1.5 to 2.0 and ln/B > 1. Type 5 : lm/B < 1.5 and ln /B > 1. L/B was one of the most important parameters affecting the maximum scour depth and its position. When L/B was less than 1.4, the scour holes were similar to the traditional groundsill. When the L/B ranged between 1.4 and 2.3, the maximum scour depth was located at about 0.5 to 0.65 times of scour length downstream the Cross-Vane. When L/B was greater than 2.3, the maximum scour depth was located adjacent to the Cross-Vane.

Keyword : Cross-vane, Scour morphology, Numerical model
Seasonal comparison of potential denitrification rates and nitrogen functional genes with sediment depths in the wetland, Korea
Authors: Han Ji Yeon , Kim Dong-Hun , Oh Seolran , Moon Hee Sun
Published: March 2020

Wetlands provide not only habitats for a wide range of organisms but also ecological functions of degrading and removing pollutants from water body through a variety of physical, chemical and biological processes. Seasonal variation including recent increases in the frequency of floods and droughts have affected the hydrological environment of wetlands. Furthermore, these effects may result in changes in redox conditions in the nitrogen biogeochemical process in wetland sediments. Therefore, in this study, the potential denitrification rate and denitrification-related gene quantitative analysis was performed to investigate seasonal nitrogen dynamics of wetland sediments associated with surface and groundwater interactions in Baekseok reservoir wetlands (Gunsan-si, Jeollabuk Province, Korea). Sediment from two different sites (i.e., PA and PB) in wetland were collected with different depths in June and December 2019 to investigate seasonal effects on denitrification with sediment depths. Potential denitrification rate experiments were performed using the acetylene inhibition technique, and denitrification-related gene quantification was performed by qPCR analysis. As a result of potential denitrification rate, PA sites ranged from 2.67–3.27 ng N2O/g/hr and 3.13–15.13 ng N2O/g/hr in June and December, respectively. PB sites ranged from 2.43-6.30 ng N2O/g/hr and 5.47-6.30 ng N2O/g/hr. Overall, higher levels were observed at 0–10 cm, with higher denitrification rates in December than in June. The qPCR analysis showed that the narG, nirS and nosZ gene copy number ranges for the PA site in June showed 1.82 x 106 – 6.15 x 107 copies/g, and in December 7.71 x 105 – 5.97 x 108 copies/g. The narG, nirS and nosZ gene copy number ranges for the PB site in June showed 3.53 x 105 – 3.86 x 108 copies/g, and in December, 1.24 x 106 – 3.47 x 108 copies/g. Overall, both sites had higher copy numbers in December than in June, corresponding to an increase in potential denitrification rate in December.
Hourly elemental concentrations in ambient aerosols in four cities in Asia and Europe – comparison and source apportionment
Authors: Furger Markus , Rai Pragati , Slowik Jay G. , Tripathi Sachchida N. , Cao Junji , Necki Jaroslaw , Visser Suzanne , Prévôt André S. H. , Baltensperger Urs
Published: March 2020

Megacities worldwide are suffering from elevated air pollution due, e.g., to continuously increasing urbanization, and a sizeable amount of the population in such areas is exposed to particulate matter (PM) concentrations exceeding the WHO limits. Huge efforts are therefore undertaken to characterize the air pollution situation and to reduce or mitigate the impact on the population and the environment. Modern instrumentation allows for a quantitative determination of aerosol concentration and composition with high time resolution (minutes to hours), and subsequent source apportionment.

We collected PM10 and PM2.5 aerosols alternatingly with an online X-ray fluorescence (XRF) spectrometer in the cities of New Delhi (India) in 2019, Beijing (China) in 2017, and Krakow (Poland) in 2018, with time resolutions from 30 to 120 min, and in London (UK) in 2012 with 3-stage rotating drum impactors and subsequent offline SR-XRF analysis. Campaigns lasted for two to seven weeks in fall and winter. Elements from Al to Bi were analyzed in near-real time, except for London.

Our results show that some of the cities experience episodic extreme events, whereas extremely high elemental concentrations are chronic in others. Toxic metals are shown to be strongly location-dependent, and may occur in extreme plumes. Meteorological conditions also play an important role and will be discussed. The regional influence of fine PM, in comparison to the more local origin of coarse PM will be evaluated. The differences among the four cities, with substantially higher concentrations in the Asian cities than the European ones will be discussed. Highly time-resolved size-segregated sampling allowed for a rough classification of elements into five groups and will be described in detail. We demonstrate that the use of size information on toxic elements, diurnal patterns of targeted emissions, and local vs. regional effects are advantageous for formulating effective environmental policies to protect public health.
A Flow-dependent Targeted Observation Method
Authors: Tang Youmin , Wu Yaling
Published: March 2020

In this study, we developed a flow-dependent ensemble-based targeted observation method, by minimizing the analysis error variance under the framework of Ensemble Kalman filter (EnKF) data assimilation system. This method estimates the background error statistics as a flow dependent function. The covariance localization is also introduced for computing efficiency and alleviating the spurious observations.  As a test bed, an  optimal observation array of sea level anomalies (SLA) is designed for its seasonal prediction over the tropical Indian Ocean (TIO) region.  Furthermore, the observing system simulation experiments (OSSEs) is used to verify the resultant optimal observational array using our recently developed coupled data assimilation system. A comparison between this flow-dependent method and the traditional method is also given. ​
Possible explanations on the formative processes of the Tsugaru-Juniko landslide, northern Japan
Authors: Tsou Ching-Ying , Higaki Daisuke , Yamabe Kousei , Kiru Tomo , Sasagawa Takayoshi , Numata Shuhei
Published: March 2020

Identification of complex surficial and internal sedimentological characteristics of landslide deposits can provide insights into the emplacement mechanisms of mass movements. In this study, deposits of the Tsugaru-Juniko landslide, which was historically recorded triggered by an earthquake in 1704 (Imamura, 1935), in Aomori Prefecture, Japan were investigated. This landslide extended about 2 km from east to west with a volume of about 108 m3 (Furuya et al., 1987), of which deposit is represented by irregular topography and several lakes on and around the rim of it. We conducted field geological and geomorphological surveys and made geomorphological and geophysical analyses using a 1-m resolution LiDAR-DEM and 2D electrical resistivity tomography (ERT) measurement (10 m spacing of electrodes) over a 450 m wide landslide deposit. In plain view, the landslide deposit exhibits quite different features between its northern and southern parts, and each shows a clear sequential distribution of various features. At the northern part, the translation zone is characterized by hummocks and debris lobes containing mixtures of poorly sorted, angular, blocky rock debris of andesitic tuff. Prominent features on the debris lobes are debris-flow-ridges with lobate-shaped aprons extending NW to the downslope. In the accumulation zone, slope surface upheavals of compression origin and radial cracks are observed in the front part of the landslide. At the southern part, as compared to those features observed at the northern part, the slope is commonly marked by transverse ridges, oriented NE-SW, with prevalent steep cliffs on both sides, but generally steeper on the east. The ridges are separated from one another by trenches, elongated across the slope. Based on the distributions of these features, possible explanations on the formative processes of the landslide are complex associated with flowing and sliding at northern and southern parts, respectively. However, geological evidences from its internal structures are rare, ERT survey at the northern part of the landslide deposit reveals that up to 30-m-deep high-resistivity anomaly is associated with the landslide deposit, and low-resistivity anomaly with the bedrock consisting of pumice tuff, as also confirmed in the field. This may result from the high porosity of landslide deposit, because the displaced material deposited loosely.
How energy crops (Maize, Field grass, Cup Plant) affect soil microarthropods and their decomposition services
Authors: Dioh Lobe Pascaline , Schrader Stefan
Published: March 2020

Energy crops are grown at low cost and low maintenance used in making biofuels, such as bioethanol, or combusted to generate electricity or heat. Production of energy crops as an alternative to fossil fuels will help to reduce CO2 emission, thus leading to large scale changes in agricultural landscapes. Increase in the cultivation of annual energy crops such as maize (Zea mays) is assumed to decrease biodiversity in the agrarian landscape. This may lead to changes in soil properties, thereby affecting the soil biodiversity and its ecosystem functions and services like for instance soil microarthropod communities and their contribution to decomposition of plant litter. Perennial crops such as field grass (a mixture of Festulolium,  Dactylis glomerate, Loliuim perenne, Festuca pratensis and Festuca arundinacea) and cup plant (Silphium perfoliatum) are assumed to protect and promote soil biodiversity through less intensive management. The relationship between decomposer diversity and ecosystem functioning is little understood. So far, the role of soil microarthropods in decomposition is the most disputed aspect due to scarce empirical data.

The main aim of this field study was to assess the effect of soil microarthropods on litter of maize, field grass and cup plant, via decomposition using litter bags with 2 different mesh sizes (0.02 mm and 0.5 mm) for a period of 3 months during the vegetation period. At the end of the experiment, the decomposition rate was higher in cup plant followed by maize and field grass in the coarse mesh size, and higher in the cup plant followed by field grass and maize in the fine mesh size. A total of 55,464 soil microarthropods (73% mites, 25% collembola and 2% others) were extracted from the litter bags. The diversity and abundance of soil microarthropods was higher under cup plant cultivation followed by field grass and maize.
Mobility of silver nanoparticles in porous media: The impact of biological interface, water saturation, and nanoparticle aging
Authors: Leuther Frederic , Degenkolb Laura , Köhne John Maximilian , Metreveli George , Klitzke Sondra , Vogel Hans-Jörg
Published: March 2020

The sulfidation and aging of silver nanoparticles (Ag-NPs) with natural organic matter (NOM) are major transformation processes along their pathway in wastewater treatment plants and surface waters. Although porous media, such as soils or riverbank filtration systems, appear to be a sink for disposed Ag-NPs, the impacts of biological interfaces, the presence of NOM in the aquatic phase, and of variable water saturation on the transport and retention of Ag-NPs are still not fully understood.

We have performed two laboratory studies to examine the mobility of Ag-NPs in porous media under different conditions. At first, we investigated the mobility of citrate-coated Ag-NPs in sand obtained from an artificial riverbank filtration system comparing pristine and pond-water aged sediments as well as different flow velocities. Second, we investigated how the sulfidation of Ag-NPs (S-Ag-NPs) and the presence of NOM in the aquatic phase can change the transport characteristics in saturated and unsaturated sand at different transport velocities. Flow experiments inside an X-ray microtomograph enabled to study the impact of phase distribution (solid, water, air) and their interfaces on the retention of Ag-NPs.

Our experimental results show that the mobility of Ag-NPs in porous media is affected by the presence of biological components, the sulfidation of particles and, when unsaturated, the additional air phase. In saturated riverbank filtration systems, naturally occurring biological aging processes on sediments enhanced the efficiency of the system to retain citrate-coated NPs. The sulfidation of Ag-NPs to S-Ag-NPs decreased the mobility in porous media while the NP-aging with NOM re-established mobility to some extent. In unsaturated sand, the retardation of NOM aged S-Ag-NPs was strongly increased by decreasing water content, i.e. the propagation of an air phase, and decreasing flow velocity.
Hydro-mechanical modeling of seismogenic asperity loaded by aseismic slip through TOUGH-BIEM simulation
Authors: Aochi Hideo , Rutqvist Jonny
Published: March 2020

We consider seismogenic asperities loaded by aseismic slip on a fault, which is induced by fluid circulation, as a simple example of fault reactivation. For this purpose, we combine two methods. The TOUGH2 (Transport Of Unsaturated Ground water and Heat) code is used for modeling the pore pressure evolution within a fault and then a Boundary Integral Equation Method (BIEM) is applied for simulating fault slip, including aseismic slip on the entire fault plane and fast slip on seismogenic asperities. The fault permeability is assumed stress-dependent and therefore is not constant but varies during a simulation. We adopt the Coulomb friction and a cyclic slip-strengthening-then-weakening friction model governing the fault slip, which allows for repeated asperity slip. We were able to demonstrate the entire process from the fluid injection, pore pressure increase, aseismic slip to seismogenic asperity slip. We tested a step-like increase of injection rate with time, which is common for hydraulic fracturing and reservoir stimulation at deep geothermal sites. Under this configuration, the pore pressure increase is not proportional to the injection rate, as the permeability depends on the stress.  Fault slip on seismogenic asperities is triggered repeatedly by surrounding aseismic slip. We find, in a given example, that the reccurence of the fast slip on asperity is approximatively proportional to the injected fluid volume, inferring that the aseismic slip amount increases proporitionally to the fluid volume as well.
Assessing the value and quality of German soils under agricultural use
Authors: Säurich Annelie , Lilienthal Holger
Published: March 2020

Halting and reversing soil degradation as well as protection and sustainable use of soil as a resource are part of the United Nations Sustainable Development Goals. Despite the vital significance and essential functions of soil, massive amounts of fertile soil worldwide are lost due to improper land use. In Germany, approximately 66 ha of soil are damaged partly or completely in their soil functions daily. The main issues are soil erosion, land area claims for housing estate and transportation, and pollution. Until now, precise spatial location and assessment of the loss of valuable soil in terms of fertility and productivity has not been quantifiable and therefore not controllable.

In the SOIL-DE project, indicators to evaluate the functionality, potential, intensity of use, and vulnerability of soils are developed in order to be able to assess the quality and value of soils, both in retrospective and under current agricultural use. The aim of this survey is (i) to detect the loss of land over the past ten years in high spatial accuracy, (ii) to determine the fertility of the soil and (iii) to identify risk areas, i.e. regions with particularly high soil loss rates and high soil profitability. The threat to soil, the fertility and impairment of soil functions by changes in land use, are to be recorded nationwide and statewide. Therefore, the evaluation of time series from satellite images is used in combination with official soil information at different spatial resolution, as well as digital elevation models and climatic data. In this study, different rating systems are investigated including e.g. the Muencheberg Soil Quality Rating (ZALF), biotic potential yield, resistance to erosion, filter, buffer and transformation function, and runoff regulation. First results will be presented.
Ensemble Approach to Deep Learning and Numerical Ocean Modelling of Adriatic Storm Surges
Authors: Licer Matjaz , Žust Lojze , Kristan Matej
Published: March 2020

Storm surges are among the most serious threats to Venice, Chioggia, Piran and other historic coastal towns in Northern Adriatic. Adriatic Sea has a well defined lowest seiche period of approximately 22 hours and its amplitude decays on the scale of several days, reinforcing (or diminishing) the tidal signal, depending on the relative phase lag between tides and surges. This makes prediction of Adriatic sea level extremely difficult using conventional deterministic models. The current state-of-the-art predictions of sea surface height (SSH) hence involve numerical ocean models using ensemble forcing. These simulations are computationally-demanding and time consuming, making the method unsuitable for operational or civil rescue services with limited access to dedicated high-performance computing facilities.

Ensemble approach to deep learning offers a possible solution to the challenges described above. Even though training a deep network may involve substantial computational resources, the subsequent forecasting -- even ensemble forecasting -- is fast and delivers near-realtime SSH predictions (and associated error variances) on a personal computer. In this work we present an ensemble SSH forecast using new deep convolutional neural network for sea-level prediction in the Adriatic basin and compare it to the standard approach using state-of-the-art publicly available modelling components (NEMO ocean circulation model and TensorFlow libraries for deep learning).