bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetotactic bacteria in Tengchong hot springs, China
Authors: Liu Jia , Zhang Wensi , Yuan Fang , Pan Yongxin , Lin Wei
Published: March 2020

Magnetotactic bacteria (MTB) biomineralize intracellular magnetic nanocrystals and can use the geomagnetic field to navigate towards specific microenvironments in water columns and sediments. MTB are a model system to study the mechanisms of microbial magnetoreception and biomineralization. The majority of MTB identified so far are from environments with pH values near neutral and at the normal range of temperature. MTB from extreme environments, such as hot springs, has not been observed and described until recently. However, our knowledge on extremophilic MTB is still very limited. Here we report the identification and characterization of various MTB in Tengchong hot springs, China, with a temperature range of 41.3-69.5 °C and a pH range of 7.1-8.6. Although MTB are diverse in cell morphology, they all form bullet-shaped magnetite magnetosomes organized into either one chain or multiple bundles of chains. Through genome-resolved metagenomics, we have reconstructed five genome bins of hot spring MTB that are all affiliated within the Nitrspirae phylum. Genomic analyses and metabolic reconstructions are now in progress. These results will help to better understand the extremophilic MTB and may shed new lights on the origin and evolution of microbial magnetoreception and biomineralization.
Quantitative assessment of check dam system impacts on catchment hydrological response - a case in the Loess Plateau, China
Authors: Wang Tian , Li Zhanbin , Hou Jingming , Cheng Shengdong , Xiao Lie , Lu Kexin
Published: March 2020

The purpose of this study is to investigate the impact of check dams on catchment hydrological response in a small catchment on the Chinese Loess Plateau by applying a GAST (GPU Accelerated Surface-water and Transport model) numerical model at 2 m resolution DEM. The results showed that check dams significantly increase the so-called runoff lag times (lag to generation, lag to peak and lag to end of runoff) at the channel outlet compared to catchments without check dams. Furthermore, the peak runoff discharge at the catchment outlet without check dams decreased by 93.0% compared to with check dams. The total outlet discharge, surface water stored, and infiltration were respectively 20.1%, 74.9% and 5.0% of the total precipitation in the check dam catchment, while 75.4%, 22.6% and 2.0% in the system without check dams. Installation of check dams also altered the spatial water distribution of maximum discharge, moving the occurrences of maximum discharge further upstream and, thus, increasing safety downstream. Channel connectivity was found to have a direct relationship with peak discharge and with discharge volume at the basin mouth. In conclusion, implementing check dams significantly and effectively mitigated flood processes and increased runoff infiltration upstream.
Normal-mode Magnetoseismology as a Virtual Plasma Mass Density Instrument and Its Use in Investigation of Oxygen Torus during Magnetic Storms
Authors: Wilcox Brian , Chi Peter , Takahashi Kazue , Denton Richard
Published: March 2020

Previous studies have demonstrated that the field line resonance (FLR) frequencies detected on closed magnetospheric field lines can be used to estimate the plasma mass density in the inner magnetosphere. This method, also known as “normal-mode magnetoseismology,” can act as a virtual instrument that turns spacecraft measurements of magnetic and/or electric field into plasma mass density, which is a fundamental physical quantity that is difficult to measure directly but important to investigations involving the MHD timescales, reconnection rates, or instability/wave growth rates.

In this study, we use normal-mode magnetoseismology to help investigate the characteristics of the oxygen torus, which is the narrow region of enhanced O+ density in the vicinity of the plasmapause that may form during the storm recovery phase. The formation of the oxygen torus is still an outstanding question, and the geomagnetic mass spectrometer effect and the direct ring current heating of the ionosphere have been proposed as two possible causes. We identify the location and timing of oxygen torus occurrence by examining the FLR-inferred plasma mass densities in Magnetospheric Multiscale (MMS) and Van Allen Probes (RBSP) observations and compare them with the charge densities derived from the upper hybrid resonance frequency detected by the respective plasma wave experiments on the spacecraft. We find that, while MMS and RBSP could both observe clear enhancements of heavy ions during a magnetic storm, the degree and the width of O+ enhancement can vary with location. The timing of oxygen torus occurrence may differ from storm to storm. In RBSP measurements, we also compare the bulk densities with the partial densities of low-energy ions detected by the HOPE instrument. While the average ion mass can be greater for 30 eV – 1 keV ions than that for the bulk plasma in the oxygen torus, it is evident that the majority of the ions in the oxygen torus are below 30 eV, confirming the need to examine the bulk mass and charge densities through electromagnetic sounding methods.
The characteristics of microbial communities along the littoral gradient of a proglacial lake in Qinghai-Tibet Plateau
Authors: Lu Meiqing , Luo Xin , Jiao Jiu Jimmy , li Hailong , Kuang Xingxing , Mao Rong , Shi Xiaoyan , Feng Yuqing
Published: March 2020

The information of microorganisms in aquifers can advance the understanding of the aquifer environments. Ranwu Lake is a proglacial lake located at the headwaters of Parlung Zangbo River in the Qinghai-Tibet Plateau (QTP). The information of microbial communities along the littoral gradient of Ranwu Lake can be a good indicator of water chemistry exchange between groundwater and surface water in proglacial environments. The study investigates the vertical distribution of microbial diversity and compositions in five sediment columns (two onshore, two offshore and one at the shoreline) taken from a cross section along the littoral gradient of Ranwu Lake. Along the cross section, the microbial diversity decreases toward the lake, becomes lowest in the column at the shoreline, then increases slightly in the two offshore columns. This is probably ascribed to the transition of redox conditions. Vertically, the diversity of the microbes is highest at the top and bottom of the columns. The sequencing results from the samples present 19 phyla, 38 classes, and 44 genera. Proteobacteria, Chloroflexi, and Acidobacteria are the three largest phyla. Except the offshore most column, the abundance of Proteobacteria shows a consistent pattern, while the abundance of Chloroflexi presents an inverse pattern in related to the microbial diversity. Their diversity, compositions, and abundance of microbes show a significant variation along the vertical direction and littoral gradient of the glacial lake, likely regulated by both the exchange between groundwater and surface water, and the hydrogeological properties. The variable distribution of microbial community in turn affects the physio-chemical properties of sediments and waters.
Improvement of agriculture water resources management in large arid river basin through an integrated hydrological modeling approach
Authors: Tian Yong
Published: March 2020

The ability to dynamically simulate the supply and demand of irrigated water in arid and semi-arid regions is needed to improve water resources management. To meet this challenge, this study developed an agriculture water resources allocation (WRA) module and coupled this module to an integrated surface water-groundwater model GSFLOW. The original GSFLOW, developed by USGS, is able to simulate the entire hydrological cycle. The improved GSFLOW with the WRA module allows the simulation, analysis and management of nearly all components of agriculture water use. It facilitates the analysis of agricultural water use when limited data is available for surface water diversion, groundwater pumpage, or canal information. It can be used to simulate and analyze historical and future conditions. The improved GSFLOW program was applied to the Heihe River Basin (HRB), which is the second largest inland river basin in China. The calibration and validation results of the program shows that the program is capable of simulating both hydrological cycle and actual agriculture water use with limited data. Then the model was used to analyze a set of agriculture water use scenarios, for example, limiting groundwater pumpage, adjusting water allocations between the middle stream and the lower stream. Based on these scenarios, it was found that the improved model could be used as a decision tool to provide better agriculture water resources management strategies. The improved model could be easily used in other basins.
Deformation timing and strain in Neoproterozoic strata, Jebel Akhdar, northern Oman
Authors: Bailey Christopher , Rae Claire
Published: March 2020

Neoproterozoic rocks exposed in the Jebel Akhdar massif of northern Oman preserve glaciogenic deposits associated with multiple Cryogenian glaciations. Although the depositional history of these rocks is well understood, the significance of post-depositional deformation is poorly constrained. In this study, we examine low-grade metasedimentary rocks exposed in the Ghubrah Bowl, an erosional window in the Jebel Akhdar massif, in order to quantify the 3D finite strain, understand deformation kinematics, and determine the timing of deformation/metamorphism.

In the Jebel Akhdar massif, the older Ghubrah (Sturtian glaciation) and younger Fiq (Marinoan glaciation) formations comprise a >1 km thick sequence of diamictite interbedded with sandstone, siltstone, conglomerate, volcanic rock, and minor carbonate. Diamictites contain abundant clasts of siltstone and sandstone, with lesser amounts of granite and metavolcanic rock in a fine-grained quartz + sericite ± chlorite matrix. Clasts range from granules to boulders. Harder clasts tend to be subangular and poorly aligned with low aspect ratios, whereas fine-grained rock clasts are well-aligned with large aspect ratios. Bedding generally dips to the NW, but is gently folded in accord with the overall structure of the Jebel Akhdar massif. A penetrative foliation strikes E-W and dips to the S. At some locations, a prominent elongation lineation/pencil structure occurs and plunges gently to moderately to the S.

Rf/phi strain analysis in the diamictites reveals a range of 3D strain geometries (apparent flattening to apparent constriction) with strain ratios up to 2.8 in XZ sections. Strain is strongly partitioned, as clasts of igneous rock have low aspect ratios and are only weakly aligned. Penetrative strain in clast-supported sandstones is negligible (XZ ratios of <1.2). Outsized clasts of granite and sandstone are mantled by distinctive symmetric pressure shadows (double-duckbill structures) that include more recrystallized minerals than elsewhere in the diamictite. 40Ar/39Ar geochronology of sericite in pressure shadows yields ages as young as 90 Ma, which are interpreted as mixed ages containing an older detrital component and a younger fraction formed during growth. Deformation is associated with southward emplacement and loading by the Oman ophiolite & Hawasina Group sediments over the autochthonous sequence in the late Cretaceous.
A slip law for glaciers on deformable beds
Authors: Zoet Lucas , Iverson Neal
Published: March 2020

Slip of marine-terminating ice streams over beds of deformable till is responsible for most of the contribution of the West Antarctic Ice Sheet to sea-level rise. Flow models of the ice sheet and till-bedded glaciers elsewhere require a law that relates slip resistance, slip velocity, and water pressure at the bed. We present results of the first experiments in which pressurized ice at its melting temperature is slid of over a water-saturated till bed. Steady-state slip resistance increases with slip velocity owing to sliding of ice across the bed, but above a threshold velocity till shears at its rate-independent, Coulomb strength. These results motivate a generalized slip law for glacier-flow models that combines processes of hard-bedded sliding and bed deformation.
Estimating daily evaporation and transpiration at field scale (100 m) based on TSEB and data fusion using MODIS and Landsat data in irrigated agriculture area
Authors: Li Yan , Huang Chunlin
Published: March 2020

In semiarid and arid regions, irrigated agriculture consumes most of water resources via evapotranspiration (ET) that mainly consists of evaporation (E) from bare soil and transpiration (T) from plant tissue. Generally, T is regarded as beneficial water use that contribute to plant production but E is considered as water waste. Therefore, daily ET and ET components E and T at filed scale are often required for improving water resource management strategy in semiarid and arid regions. Recently, time-continuous daily ET at filed scale have been achieved based on remote sensing-based ET model and multi-satellite data fusion, but few study focus on estimating of daily field-scale ET component of E and T. In this study, a daily filed-scale ET partitioning method based on the two source energy balance (TSEB) model and the spatial and temporal adaptive reflectance fusion model (STARFM) was applied and verified in a typical arid area dominated by irrigated cropland and natural desert. The comparisons of instantaneous land surface fluxes and daily ET modeled from proposed method and that derived from eddy covariance (EC) systems and automated weather stations (AWS) set up in irrigated cropland and desert indicate that reasonable surface fluxes partitioning and daily ET can be estimated by using this method. The root mean square error (RMSE) for cropland and desert are 0.87 mm and 0.84 mm, respectively. Evaluations of E and T partitioning capabilities of this proposed method based on E/ET and T/ET derived from isotopic technology at the irrigated cropland site show that the modeled E/ET and T/ET agree well with observations in terms of both magnitude and dynamics. Finally, the multi-year spatiotemporal patterns of modeled ET, E and T at filed scale with reasonable seasonal variation and spatial diversity were produced using the ET partitioning method to provide reasonable information for monitoring water use in study area.
Long-term soil water content and exchangeable Ca interact to stabilize organic matter
Authors: Shabtai Itamar , Das Srabani , Inagaki Thiago , Kogel-Knabner Ingrid , Lehmann Johannes
Published: March 2020

Organo-mineral interactions stabilize soil organic matter (SOM) by protecting from microbial enzymatic attack. Soil water content affects aggregation, mineral weathering, and microbial respiration, thus influencing the relative importance of SOM stabilization mechanisms. While the response of microbial respiration to momentary changes in water content is well established, it is unclear how microbial activity will impact stabilization mechanisms under different long-term moisture contents.

To understand how long-term soil moisture affects SOM stabilization mechanisms we studied fallow soils from upstate New York situated on a naturally occurring water content gradient. Wetter (but not saturated) soils contained more exchangeable Ca and had more strongly stabilized SOM, resulting in SOM accumulation. But it was not clear whether Ca-driven surface interactions or occlusion in micro-aggregates was more important, and if interactions with Fe and Al played a role in the Ca-poor soils. Also, the role of biotic drivers in SOM stabilization at different water contents was unknown.

We tested which mechanisms governed SOM stabilization by determining C and N contents and natural isotope abundances in particulate and mineral-associated organic matter fractions. We also extracted the C bound to Ca and to reactive Fe+Al phases. Wetter, Ca-rich soils had higher oPOM content, and in the heavy mineral fraction, higher relative concentrations of Ca-bound C, lower C:N values, and more oxidized C forms. In addition, wetter soils had greater microbial biomass. Together, these results showed that high long-term soil moisture increased microbial SOM cycling, and that processed SOM was better stabilized, in agreement with the recent notion that stable SOM consists of processed labile C. Additionally, higher soil moisture augmented the role of Ca in SOM stabilization over that of Al+Fe phases. We then manipulated the exchangeable Ca content and incubated soils with 13C15N labeled plant litter. Ca-amended soils emitted less CO2 while incubated with litter, confirming that Ca is instrumental in SOM stabilization. Tracing the labeled isotopes in the gaseous phase and soil fractions will allow us to gain a clearer understanding of how water content and soil Ca interact to stabilize SOM.  
Evaluating the Integral Suspension Pressure method for measuring the particle size distribution in soils with high organic matter content
Authors: Contreras Cristina , Acevedo Sara , Martínez Sofía , Bonilla Carlos
Published: March 2020

Typical information in soil databases is the soil texture and particle size distribution. These properties are used for soil description or predicting other soil properties such as bulk density or hydraulic conductivity. Measuring particle size distribution with standards methods such as the pipette or hydrometer is time-consuming because of the sample pre-treatment used to remove organic matter or iron and the sample post-treatment. Nowadays, there are new methodologies for determining soil particle size distribution, such as the Integral Suspension Pressure (ISP) method, which measures the silt content in a semi-automatized process. Thus, the main objective of this study was to evaluate the suitability of the ISP method compared to standard techniques used in soil analysis and evaluate the effect of organic matter content in the ISP measurements. The main results showed that the ISP method is equivalent in accuracy to the pipette, especially for soils rich in silt or sand content. Also, the results demonstrate the convenience of removing the soil organic matter when using the ISP for soils with more than 1.5% organic matter.
NOAA/NCEI‘s Challenges in Meeting New Open Data Requirements
Authors: Ritchey Nancy
Published: March 2020

The U.S. National Oceanic and Atmospheric Administration’s (NOAA) National Centers for Environmental Information (NCEI) stewards one of the world’s largest and most diverse collections of environmental data. The longevity of this organization has led to a great diversity of digital and physical data in multiple formats and media. NCEI strives to develop and implement processes, guidance, tools and services to facilitate the creation and preservation of independently understandable data that is open and FAIR (Findable, Accessible, Interoperable, Reusable).

The Foundations for Evidence-Based Policymaking Act (Evidence Act) (PL 115-435), which includes the Open, Public, Electronic, and Necessary Government Data (OPEN) Act (2019), requires all U.S. Federal data to be shared openly. Meeting the requirements of the Evidence Act, FAIR and OPEN has many challenges. One challenge is the requirements are not static, they evolve over time based on the data lifecycle, changes within the designated user community (ex. user needs and skills) and transition to new technology such as cloud. Consistently measuring and documenting compliance is another challenge. 

NCEI is tackling the challenges of ensuring our data holdings meet the requirements of OPEN, FAIR and the Evidence Act in multiple areas through the consistent implementation of community best practices, knowledge of current and potential user communities, and elbow grease.

This presentation will focus on NCEI’s experiences with taking data beyond independently understandable to meeting the Evidence Act, FAIR, and OPEN.

 
Linking erosion-deposition to geomorphic units changes in a high-gradient stream in the Central Chilean Andes
Authors: Carrillo Ricardo , Mao Luca
Published: March 2020

Geomorphic changes in rivers often happen after either single high magnitude floods or several following ordinary flood events. Erosion and deposition have been well documented in all types of rivers, as well as the formation and destruction of step-pool sequences. However, there are less evidence available on the link between erosion-deposition at the reach scale and the formation-destruction of geomorphic units. This work is based on a series of field surveys carried out in a small glacierized basin in the central Chilean Andes. The location and extent of erosion/deposition were quantified using the photogrammetric technique with a drone before and after a high magnitude flood occurred during autumn 2016. High-resolution Digital Elevation Models (DEMs) were computed to generate erosion-deposition maps (DoD; Difference of DEMs). Also, orthomosaics were used to derive maps of geomorphic units for a 100-m long study reach, before and after the studied flood event. Results show an overall deposition of sediments in the study reach, but a decrease in the number of step-pool sequences from 20 to 14. Step-pool destruction is linked to depositional patterns, whereas the formation of new step-pool sequences is more likely to occur in erosional zones. Rapids and cascades also change in number, increasing from 1 to 4 units, and their formation was related to the deposition of sediments. These results may have larger implications in terms of ecological habitat dynamics and are also important for planning and management in civil projects like bridges and hydropower water intakes
Large-Scale Atmospheric Drivers of Snowfall on Thwaites Glacier
Authors: Maclennan Michelle , Lenaerts Jan
Published: March 2020

High snowfall events on Thwaites Glacier are a key influencer of its ice mass change. In this study, we diagnose the mechanisms for orographic precipitation on Thwaites Glacier by analyzing the atmospheric conditions that lead to high snowfall events. A high-resolution regional climate model, RACMO2, is used in conjunction with MERRA-2 and ERA5 reanalysis to map snowfall and associated atmospheric conditions over the Amundsen Sea Embayment. We examine these conditions during high snowfall events over Thwaites Glacier to characterize the drivers of the precipitation and their spatial and temporal variability. Then we examine the seasonal differences in the associated weather patterns and their correlations with El Nino Southern Oscillation and the Southern Annular Mode. Understanding the large-scale atmospheric drivers of snowfall events allows us to recognize how these atmospheric drivers and consequent snowfall climatology will change in the future, which will ultimately improve predictions of accumulation on Thwaites Glacier.
Wave effect from sea level dynamics on density-dependent groundwater flow at a sandy beach
Authors: Yu Shengchao , Wang Chaoyue , Luo Xin , Jiao Jiu Jimmy , Li Hailong
Published: March 2020

Dynamic coastal forces, such as waves and tides which are typically coexisting in coastal environments, impact groundwater flow and salt transport in the intertidal zone. In this study, firstly, an iterative least-squares fitting method for tidal level and wave height was introduced, and the wave height can be acquired from measured sea level and then further verified by wind speed. Groundwater flow and salt transport were then simulated using a code called MARUN under different seaward boundary conditions with and without wave effects. Comparison of measured and simulated water level and salinity indicates that the model which included wave setup can accurately reproduce the measured data in the observation wells. Simulation results show that water and salt fluxes across the aquifer-ocean interface are increased and the groundwater circulation in the intertidal zone is more active after considering wave setup. Most of the influx occurs in the intertidal zone, while a considerable amount of efflux occurs in the subtidal zone, and the maximum influx of water and salt moves toward the high tide line compared to the model results without wave setup. The water influx and efflux rates increase greatly especially during the period of high wave height. After wave effects considered, fresh submarine groundwater discharge only takes up a small proportion of submarine groundwater discharge, which is dominated by recirculated seawater. It is concluded that the presence of waves significantly increases the amount of seawater circulation.
Modelling free-surface flow in water distribution systems with regulating gates
Authors: Mao Zhonghao , Guan Guanghua , Zhu Zheli
Published: March 2020

Canal automatic control is an important tool to improve the management level of water distribution systems, while an important method to evaluate the effect is controller is using numerical simulations. The free-surface flow in such system can be modelled using the Saint-Venant equations, while the regulating gates are usually treated as inner boundaries where gate discharge formula is adopted. In the previous research, the Saint-Venant equations are normally discretized using the implicit finite difference methods because of their accuracy and simplicity. However, it is difficult to incorporate the inner boundary conditions in the computation of implicit method. To circumvent this problem, this paper presents a hybrid discretization method, which adopts the state-of-art finite volume methods at regulating gates and finite difference methods elsewhere. This new discretization method can preserve the computational speed advantage of finite difference method and capture the wave propagation near the regulating gates. Which can provide reliable evidence for the design of controllers.
Icy Moon Ice-Salt Measurements for Dielectric and Thermal Properties
Authors: Frampton Robert
Published: March 2020

The REASON ground penetrating radar (GPR) on Europa Clipper and the RIME GPR on JUICE will produce radargrams for Europa to determine the nature and depth of the ice overlying a putative ocean. The REASON radar is dual frequency, 9 MHz and 60 MHz, and the RIME frequency is 9 MHz. The surface temperature of Europa is between 50 and 100 Kelvin. At 9 MHz, the REASON GPR could map relative permittivity to about 30 km with a resolution of 150 m. These two GPRs may be able to spot pockets of water within the ice shell that could serve as a passageway for chemicals between the surface and the ocean below. The upper ice crust is expected to contain magnesium and sodium sulfates, and perhaps calcium sulfate [J. Moore, 1999].

To fill this gap in knowledge about the properties of the ice crust on Europa, we will make laboratory measurements of the relative permittivity (complex dielectric coefficient using impedance spectroscopy) and thermal properties (thermal conductivity and specific heat) of ice-salt mixtures at 9 and 60 MHz, over the temperature range 50 to 100 Kelvin, for the ice-salt mixtures given in Table X. This Table was provided by Kevin Collins (UCF). We do not plan to include any dust content in these ice-salt mixtures. These laboratory data may assist in the interpretation of future radargrams from RESSON and RIME

 

   TABLE 1, Europan ice-salt specimens for electrical and thermal property measurements.

Experiment NumberSalt SpeciesSalt Concentration (wt. %)Physical Texture1Sulfuric acid hydrate5Dispersed in particulate ice2Magnesium sulfate5Dispersed in particulate ice3Magnesium chloride5Dispersed in particulate ice4Sodium chloride5Dispersed in particulate ice5Magnesium sulfate1Dispersed in particulate ice6Magnesium sulfate10Dispersed in particulate ice7Magnesium sulfate25Dispersed in particulate ice8Magnesium sulfate + sulfuric acid hydrate5 (each)Dispersed in particulate ice9Magnesium sulfate5Solid block10Magnesium sulfate5Layered structure

 

We are planning also to make similar measurements of the electrical and thermal properties of ice on Titania (moon of Uramus), over temperature range of 60 to 90 Kelvin, and at 9 MHz. The surface of Titania is mainly water ice, with some frozen carbon dioxide and possibly salts. We will devise a table of salt-ice mixtures that is appropriate for Titania, based on available information on surface content.
Development of a Drought Damage Estimation Technique for Living and Industrial Water Using Water Estimation Technique
Authors: Park Joohyuk , Park moojong
Published: March 2020

In recent years, the number of extreme disasters such as floods, droughts, and heat waves worldwide has been increasing. In the case of droughts, it is most important to manage water that is most closely related to human life in the event of a disaster and to anticipate and respond to damage in advance.

In this study, the methods for calculating domestic and foreign life and industrial water damage were reviewed, and the methods for estimating the amount of drought damages were developed so that local disaster managers could make decisions in the event of a drought, based on the living and industrial water data, which contained quantitative data.

This research was supported by a grant(2019-MOIS31-010) from Fundamental Technology Development Program for Extreme Disaster Response funded by Korean Ministry of Interior and Safety(MOIS).
The outgassing of carbon dioxide from aquatic ecosystems of Western Siberia (ZOTTO area) and implications for the regional carbon budget
Authors: Anatoly Prokushkin , Alexey Panov , Daria Polosukhina , Anastasia Urban , Jan Karlsson
Published: March 2020

The lateral migration of dissolved carbon dioxide (CO2) with soil solutions to fresh water aquatic systems and in situ mineralization of soil-derived organic carbon (OC) often causes supersaturation of the inland waters with CO2. An evasion of excess CO2 from lake and stream surfaces to the atmosphere is important, but underestimated, pathway of carbon flux in the coupled terrestrial-aquatic carbon cycle. As a result, the loss of terrestrial OC as CO2 through the drainage networks remains poorly accounted in regional carbon budgets estimated on the basis of eddy covariance measurements. In this study we have made an attempt to quantify fluxes of dissolved CO2 (pCO2) and CO2 emissions (fCO2) in fluvial and lacustrine waterbodies located within the peat-bog dominated landscape of Western Siberia (ZOTTO area, 60oN, 89oE). For two consecutive years (2018-2019) we studied the seasonal and diurnal dynamics of pCO2 and fCO2 in several different order streams (1-4) and ponds within a peatbog. Dissolved pCO2 was measured by portable IRGA Vaisala GMP222 placed in PTFE membrane. Carbon dioxide emissions were analyzed using floating chamber equipped with same portable IRGA (Vaisala GMP222). Despite, the pCO2 values were highest in winter season (350-820 umol/l) we did not detect sizeable emissions from water surface in that period. The peaks of pCO2 in summer-fall season (up to 360 umol/l) occurred at stormflow regimes. The frost-free season emission of CO2 from stream surfaces ranged from 0.2 to 7.5 umol/m2/s and decreased with the order of stream. An averaged for the season CO2 evasion from the Razvilki stream (2nd order stream) was 4.9±1.3 umol/m2/s, which is comparable to the seasonal mean of soil CO2 emissions in the study area. However, in opposite to soil respiration, which maxima often corresponds to highest soil temperatures, peaks of CO2 outgassing occur at high flow regimes. The fCO2 values were correlated with discharge (r = 0.60, p<0.05) and DOC concentrations (r = 0.69, p<0.05). Aquatic C losses are still under analysis in terms of surface water area estimation.
Impact of Climate change on tropical terrestrial water use efficiency
Authors: Kumari Shweta , Adams Mark A
Published: March 2020

Variability in precipitation and temperature are key markers of climate change. Extreme events like heat waves, droughts, frosts, wind storms, flooding rains and fires greatly affect ecosystem and terrestrial carbon balance. Tropical regions in particular make strong contributions to the global carbon cycle and are the focus of our research. Our initial analysis confirmed the long-known pattern of large variability in rainfall in the tropical southern hemisphere (i.e. between the Tropic of Capricorn and the Equator) w.r.t. the north, with less variation in temperature between the hemispheres. In the follow-up analysis, we focus on exchanges of carbon and water and water use efficiency, based on 39 eddy covariance flux sites which represent 25 years of data across the tropics. Our working hypothesis is that long-term increases in temperature and significant changes (+/-) in rainfall will be reflected in changes in water use efficiency and cropping period, albeit with greater spatial and temporal variation in the south than in the north. We are also investigating relationships between water use efficiency of tropical regions calculated using eddy covariance flux data, with that calculated using tree ring data. We seek to combine methodologies that can help drive our understanding of the impact of climate change on water use efficiency of tropical regions.

Keywords: Eddy covariance, Tropics, Water use efficiency, Carbon cycle, Tree ring data
Molecular Characterization of Firework-Related Urban Aerosols using FT-ICR Mass Spectrometry
Authors: Xie Qiaorong , Fu Pingqing
Published: March 2020

Firework (FW) emissions have strong impacts on air quality and public health. However, little is known about the molecular composition of FW-related aerosols especially the organic fraction. Here we describe the detailed molecular composition of Beijing aerosols collected before, during, and after a FW event in New Year's Eve evening. Subgroups of CHO, CHNO, CHOS, and CHNOS were characterized using ultrahigh resolution Fourier transform-ion cyclotron resonance (FT-ICR) mass spectrometry. We found that high molecular weight compounds with relatively low H/C and O/C ratios and high degree of unsaturation were greatly enhanced during the New Year’s Eve, which are likely to be aromatic-like compounds. They plausibly contributed to the formation of brown carbon and affect the light absorption properties of atmospheric aerosols. Moreover, the number concentration of sulfur-containing compounds especially the nitrooxy-organosulfate was increased dramatically by the FW event, suggesting the important effect of nighttime chemistry on their formation. But, the number concentration of CHO and CHON doubled after the event with photooxidation. The co-variation of these subgroups was suggested to be associated with multiple atmospheric aging processes of aerosols including the multiphase redox chemistry driven by NOx, O3, and ·OH. Our study provides new insights into the anthropogenic emissions for urban SOA formation.
In situ UV-Vis sensors record spatially and temporally different diurnal patterns in solute concentrations in tropical montane headwater streams: reality or artefact?
Authors: Jacobs Suzanne , Weeser Björn , Rufino Mariana , Breuer Lutz
Published: March 2020

There is a need to better understand the driving factors of and interactions between hydro-biogeochemical processes at different temporal and spatial scales to inform water management. Especially for tropical montane ecosystems, which are recognized as important freshwater sources, the required data and knowledge are missing. To address this knowledge gap, a long-term hydrological monitoring network was set up in the Mau Forest Complex, Kenya. The network covers three sub-catchments (27–36 km²) dominated by either tropical montane forest, smallholder agriculture or commercial tea plantations, within a 1021 km² mixed land use catchment. A 5-year dataset of nitrate and dissolved organic carbon concentrations measured at 10-minute interval with in situ UV-Vis sensors was analysed for short-term changes in solute concentrations. The analysis revealed small diurnal patterns (amplitude <0.25 mg N or C L−1, decreasing with increasing discharge) in solute concentrations in all streams. In addition, the timing of the minima and maxima differed between catchments and seasons, suggesting and influence of land use and seasonality on the occurrence of in-stream biogeochemical processes. However, unusual and abrupt changes in the diurnal patterns were observed after a change in sensor position or exchange of sensors. We therefore developed an experiment to test the validity of the observed diurnal patterns. A second, mobile sensor was installed at each site for a period of more than three weeks. After measuring in parallel position to the fixed sensor for two weeks, the position (orientation, depth) was changed or the measurement gap was shaded. In parallel position, the patterns in solute concentrations recorded by the mobile sensor agreed better with those measured by the fixed sensor for dissolved organic carbon (r>0.98) than for nitrate (r=0.43–0.81). However, shading the sensor or a position change resulted in inconsistent changes in the recorded patterns. Larger changes in solute concentrations, e.g. as a result of rainfall events, were reproduced well by the mobile sensor. The results of our study suggest that diurnal changes in solute concentrations with an amplitude close sensor accuracy measured with in situ UV-Vis sensors should be interpreted with caution. The experiment was not conclusive as to what caused the differences in observed patterns. Further experimental work is required to understand the causes and to develop recommendations for the use of UV-Vis sensors in hydro-biogeochemical research.
Hydrological Processes Changes in the Transboundary Rivers of Central Asia
Authors: Chen Yaning , Li Zhi , Fang Gonghuan , Li Weihong
Published: March 2020

Central Asia, which is one of the most complex regions in the world, is crisscrossed with transboundary rivers shared by several countries. This work analyzes the effects of climate change and human activities on hydrological processes and water resources in these transboundary rivers over the past half century. The results show that the average temperature in the Tienshan Mountains experienced “sharp” increases in 1998, with the average temperature after 1998 being 1.0°C higher than that during 1960–1998. This rapid warming has accelerated glacier shrinkage and decreases in snow cover. These changes influenced the hydrological processes, causing an earlier runoff peak and aggravated extreme hydrological events. Changes in mountainous hydrological processes affected regional water availability and intensified future water crisis in Central Asia. The mismatched spatial distributions of water and land resources, along with the intense human activities (e.g., overexploitation of water resources), have ultimately led to the present water crisis in Central Asia's river basins. This is the main reason for ongoing water conflicts in the region's transboundary rivers. In addition, with the ongoing high temperature prevailing over the central Asia region, the normalized difference vegetation index (NDVI) of natural vegetation in Central Asia during 1982–2013 exhibited an increasing trend at a rate of 0.004 per decade prior to 1998, after which the trends reversed, and the NDVI decreased at a rate of 0.003 per decade. Shrub cover and patch size exhibited a significant increase in 2000–2013 compared to the 1980s–1990s, including shrub encroachment on grasslands. The ecological crisis has not been alleviated due to the increased precipitation.
Heterogeneous modification and reactivation of craton margin in northeast Asia: insight from teleseismic traveltime tomography of the Korean Peninsula
Authors: Song Jung-Hun , Kim Seongryong , Rhie Junkee
Published: March 2020

Margins of craton lithosphere are prone to ongoing modification process. Marginal tectonism such as slab subduction, continental collision, and mantle dynamics significantly influence properties of lithosphere in various scales. Thus, constraints on the detailed properties of craton margin are essential to understand the evolution of continental lithosphere. The eastern margin of the Eurasian plate is a natural laboratory that allows us to study the strong effects from multiple episodes of continental collision and subduction of different oceanic plates since their formation. Extensive reworking and destruction of the cratonic lithosphere mainly occurred in eastern China during the Mesozoic to Cenozoic, which leaves distinct geochemical and geophysical signatures. Specifically, the Korean Peninsula (KP) is known to consist of Archean–Proterozoic massifs (e.g., Gyeonggi, Yeongnam Massif) located in the forefront in northeast Asia, where current dynamics in the upper mantle and effects due to nearby subducting slabs are the most significant.

Here we present, for the first time in detail, 3-D velocity structure of KP by teleseismic body wave traveltime tomography. Detailed P-wave and S-wave images of the crust and upper mantle were constructed by approximately 5 years of data from dense arrays of seismometers. We newly found a thick high-velocity body beneath the southwestern KP with a thickness of ~150 km, which is thought as a fragment of lithospheric root beneath the Proterozoic Yeongnam Massif. Also, we found low velocities beneath the Gyeonggi Massif, eastern KP margin, and Gyeongsang continental arc-back-arc system, showing significant velocity contrasts (dlnVp of ~4.0% and dlnVs of ~6.0%) to the high-velocity structure. These features indicate significantly modified regions. In addition, there was a clear correlation of the upper mantle low-velocity anomalies and areas characterized by Cenozoic basaltic eruptions, high heat flow, and high tomography, suggesting that there are close associations between mantle dynamics and recent tectonic reactivation.

The presence of a remnant cratonic root beneath the KP and contrasting lithospheric structures across the different Precambrian massifs suggests highly heterogeneous modification along the Sino-Korean craton margin, which includes the KP and North China Craton. A striking localization of lithosphere modification among the different Precambrian massifs within the KP suggests that the structural heterogeneity of the craton margin is likely sharp in scale and thickness within a confined area. We suggest that intense interaction of upper mantle dynamics and inherent structural heterogeneities of a craton margin played an important role in shaping the current marginal lithosphere structure in northeast Asia.
How do tropical peatland greenhouse gas emissions respond in the immediate aftermath of a fire?
Authors: Smith Thomas , Evers Stephanie , Lupascu Massimo , Chiu Hayli
Published: March 2020

Southeast Asia is a region where forest clearance, drainage of peatlands for agriculture, and ongoing use of fire to ‘manage’ land leads to extensive emissions of greenhouse gases to the atmosphere, and significant disturbance to peatland soils. While recent campaigns investigating tropical peatland fire emissions have improved our knowledge and understanding of ‘direct’ greenhouse gas emissions during fires, there remains a significant gap in our knowledge of the immediate post-fire impacts on peat respiration and methanogenesis. Ongoing research shows that peatland microbial communities (responsible for respiration), including methanogens and methanotrophs (responsible for controlling net methane emissions), are considerably altered following fire disturbance. As such, we hypothesise that peatland fires will lead to significant alterations to GHG emissions, compared to sites that have not burned. Further, we also hypothesise that the magnitude of this post-fire effect will be predictably interrelated to different forms of peatland degradation and land-use history.

Here we present results from seven fire locations (recently burnt) and their corresponding neighbouring control sites (not recently burnt), three of our fire locations were associated with forest clearance fires, while the other four locations were slash fires on oil palm plantations. We characterize the post-fire disturbance emissions of carbon dioxide (CO2) and methane (CH4) in situ, in the immediate aftermath of a fire (within days or weeks), and in the subsequent months following a fire at our burn sites. For comparison, we also measure CO2 and CH4 emissions from neighbouring control sites that remained unburnt. We find substantial, significant differences in CH4 emissions between the burn sites and control sites for all seven of our measurement locations. We suggest a number of mechanisms responsible for this post-fire effect, including disturbance to the methanotroph microbial communities at the burn sites, as well as reduced elevation at the burn sites, leading to higher water tables.
Computing LPO for Geodynamic Models in ASPECT
Authors: Billen Magali , Fraters Menno
Published: March 2020

When modeling subduction processes, the results are usually constrained by looking at the geological surface expressions, geochemistry and geophysical observations such as tomography and seismic anisotropy. Of these observations, seismic anisotropy is the only type of observation that can potentially be directly linked to the spatial flow pattern in the mantle. Seismic anisotropy in the mantle is due to lattice-preferred orientation (LPO) of olivine minerals. In subduction environments, which can have complex and changing flow patterns, it is not expected that the LPO necessarily aligns with the flow pattern. This is partly due to the fact that it takes time to realign the LPO and partly because the olivine fast axis alignment depends on the water content and the magnitude of stress. To overcome this problem, the LPO must be computed for realistic and end member subduction zones in order to be able to relate seismic anisotropy to mantle flow and thereby slab dynamics.

There are many ways to compute LPO. For this study we have used DREX (Kaminski et al., 2004), because the underlying method is accurate and fast enough for use in geodynamic models. To achieve a good and native integration with ASPECT (Kronbichler et al., 2012; Heister et al., 2017; Bangerth et al,. 2019), we have rewritten DREX in CPP as a plugin for ASPECT. In this presentation we will show how it was implemented and what the limitations and possibilities are. Furthermore, we will show initial results from 3D subduction models to study the link between seismic anisotropy and mantle flow.
Timescales of electrons wave-particle interactions with chorus and hiss in the outer radiation belts
Authors: Agapitov Oleksiy , Mourenas Didier , Artemyev Anton , Mozer Forrest , Bonnell John
Published: March 2020

Electron scattering by chorus and hiss waves is an important mechanism that can lead to fast electron acceleration and loss in the inner magnetosphere. Making use of Van Allen Probes measurements, we present the factors found recently to affect the efficiency and control the predominance of the precipitation or acceleration regimes. The dependence of VLF waves frequency on latitude [1], so that the relative wave frequency goes down, leads to decreasing the electron scattering resonance latitudes. This provides an effective increase of wave amplitude due to whistler-mode wave amplitude distribution on latitude. High latitude wave extent and wave amplitude distribution on latitude determine the regime of scattering (higher latitudes) or acceleration (lower latitudes). Wave normal angle distribution and the existence of the significant oblique whistler population influence efficiency of electron scattering affects significantly the scattering rates and potentially shifts the wave-particle interaction regime during geomagnetic storms from mostly scattering to mostly acceleration [2]. Dynamics of plasma characteristics during disturbed periods, such as ωpe/Ωce decreases (especially in the night sector) sometimes leading to very short time scales for quasi‐linear MeV electron acceleration in agreement with Van Allen Probes observations [3].  ωpe/Ωce dynamics in the plasmasphere increases the efficiency of electron scattering by hiss.

 

References

[1] Agapitov et al. (2018) Journal of Geophysical Research, https://doi.org/10.1002/2017JA024843

[2] Artemyev et al., (2016). Space Science Reviews, https://doi.org/10.1007/s11214-016-0252-5

[3] Agapitov et al., (2019) Geophysical Research Letters, https://doi.org/10.1029/2019GL083446