bluuebunny/crossref_metadata_2025 huggingface dataset:
Origin and Evolution of the North Atlantic Oscillation
Authors: Nie Ji , Song Zhihong
Published: March 2024

The North Atlantic Oscillation (NAO) is the dominant variability mode in the North Atlantic region and plays important roles in weather and climate. When did the NAO first emerge in the past, and how did it evolve over geological timescales? To answer these questions, we examined a set of time-slice paleoclimate simulations with varying continental configurations from ~160 million years ago (Ma). We show that the present-day-like NAO mode emerges stably at around 80 Ma when the North Atlantic Ocean is wide enough to form a high-pressure system that separates the North Atlantic jet from the Euro-Asia jet. A set of idealized simulations confirms that a robust NAO mode will emerge when the width of the ocean basin is greater than 40°. This study depicts the evolutionary history of NAO over geological time and reveals the essential nature of NAO and its relationship with topography.
Role of mineral-organic matter interactions in carbon cycling in permafrost peatlands
Authors: Joshi Prachi , Chauhan Ankita , Voggenreiter Eva , Wunsch Katrin , Kappler Andreas
Published: March 2024

Permafrost peatlands, primarily occurring at northern latitudes, are a major stock of organic carbon. Although these peatlands have historically acted as a carbon sink, they are expected to transition to a carbon source due to the mobilization and rapid decomposition of accumulated organic carbon by microorganisms upon thawing. Predictions of the timescale of this transition are limited by insufficient understanding of the controls on organic carbon decomposition. One major control on microbially mediated decomposition and release of greenhouse gases carbon dioxide (CO2) and methane (CH4) is the interaction of organic carbon with minerals (predominantly high surface area iron minerals). Although well studied in common soil systems, the role of organic carbon-mineral interactions in carbon cycling is poorly understood in permafrost peatlands. This knowledge gap is particularly critical in the case of permafrost thaw, during which redox conditions may switch from oxic to anoxic due to extensive waterlogging.            In this work, we investigated the interaction between organic carbon and minerals and their effect on carbon cycling in thawing permafrost peatlands. We chose Stordalen mire near Abisko, Sweden, as a representative field site as it includes a thaw gradient from intact permafrost plateaus to thaw ponds and fully thawed wetlands. Specifically, we investigated whether interaction with iron minerals protected organic carbon from microbial decomposition and release as CO2 and CH4 over thaw in field manipulation and laboratory microcosm experiments. To do this, we synthesized iron mineral-organic carbon phases using organic matter from the peatlands and added them to the soil. We then followed dissolved organic carbon dynamics as well as CO2 and CH4 release. In addition, we tracked the fate of the minerals over thaw. In a complementary study, we characterized mineral-organic carbon phases present within the soil and thaw ponds. Upon addition of the mineral-organic carbon phases to the soil, we observed a small decrease in greenhouse gas release over the short term, consistent with the results from other soil systems. However, over the timescale of weeks, the greenhouse gas release increased substantially relative to control experiments, especially in the case of CO2 (up to 130%). This increase could be attributed to the use of iron within the mineral-organic carbon phases as an electron acceptor by microorganisms, promoting organic carbon decomposition. The results of this work suggest that (a) iron mineral-associated organic carbon in permafrost peatlands may not be protected from microbial decomposition, and (b) increased water levels in permafrost peatlands due to thaw may result in increased greenhouse gas release, particularly CO2.
Evaluating the Behavior of Uranium Through Column Experiments Using Artificial Groundwater and Coaly Slate from a Natural Analogue Study Site in Korea
Authors: Lim Soyeon , Cho Hakyung , Noh Suyeong , Jeen Sung-Wook
Published: March 2024

The deep geological disposal method is a prominent approach for the management of high-level radioactive waste, and understanding the behavior of uranium under various geochemical conditions is essential for this purpose. To predict the behavior of uranium in the field, it is necessary to evaluate not only the transport of uranium but also the reactions between host rock and groundwater at the field site. In this regard, we evaluated the behavior of uranium in the underground environment by analyzing the temporal and spatial changes in uranium geochemistry in response to water-rock reactions. This was achieved through column experiments using rocks containing uranium ore bodies and groundwater from a natural analogue study site in Korea. Two columns (NA-PJ1 and NA-PJ2) were prepared by collecting coaly slate materials containing uranium minerals sourced from the Okcheon Metamorphic Belt in Korea. NA-PJ1 was filled with coaly slate (0.025 ~ 2 mm grain size) collected from the study area, while NA-PJ2 included a mixture of coaly slate and limestone (10 wt%) to provide pH buffering. The input solutions to the columns were artificial groundwater manufactured with a chemistry similar to that of the groundwater at the study site. The artificial groundwater was purged with Ar gas before the experiment to minimize the ingress of dissolved oxygen (DO) from the atmosphere. To observe spatial and temporal changes in geochemistry resulting from the interactions between the artificial groundwater and the reactive materials inside the columns, water samplings were performed at 0, 5, 10, 15, 20, 25, 30, 35, and 40 cm from the column influent. The results consistently showed low and stable DO concentrations in both columns. The pH in NA-PJ1 initially exhibited the highest value at 0 cm but gradually decreased to below 4.5. This was attributed to the insufficient carbonate buffering capacity to neutralize hydrogen ions generated by the oxidation of iron sulfide in coaly slate. In NA-PJ2, in contrast, the pH remained around 8. Uranium concentration in NA-PJ1 increased gradually with distance. It was determined that uranium was released through the dissolution of uranium minerals (i.e., uraninite and ekanite). Subsequently, the released uranium formed uranium aqueous complexes with dissolved F or SO4 induced by iron sulfide oxidation. Furthermore, it was shown that uranium in NA-PJ1 formed UO2CO3(aq) complexes closer to the column influent, while it formed more UO2SO4(aq) complexes with increasing distance. This study contributes to understanding the transport and reaction characteristics of uranium in groundwater, ultimately aiding in the management of high-level radioactive waste in a deep geological disposal site.
Reaction Mechanisms of Simultaneous Removal for Nitrate and Phosphate in Groundwater Using Ca-citrate Complex
Authors: Kang Jiyoung , Lim Soyeon , Jeen Sung-Wook
Published: March 2024

Ca-citrate complex has been proposed as a substance capable of simultaneously removing both nutrients (i.e., nitrate and phosphate), which may lead to serious environmental issues such as eutrophication. Citrate serves as a carbon source for denitrification process, and calcium precipitates to form phosphate minerals. The purpose of this study was to comprehend the mechanisms involved in the removal of nitrate and phosphate. In this study, column experiments were conducted to simulate the simultaneous removal of nitrate and phosphate. Upon injecting the Ca-citrate complex into the column, both nutrients were eliminated. In the process, bacterial communities in the soil and effluent were investigated to identify removal mechanism for nitrate. The bacterial communities significantly differed between the soil and the effluent. The bacteria in the soil (Bacillus, Enterobacter, and Arthrobacter) were primarily involved in processes of NO3 or NO2 reduction, while those in the effluent (Pelosinus, Azospirillum, and Pseudomonas) carried out the complete denitrification process. These results suggested an active denitrification process in the column, resulting in the complete removal of nitrate to N2 gas. Meanwhile, in order to identify the removal mechanism of phosphate, phosphate minerals for the soil samples after the reactions with Ca-citrate complex were observed using electron probe micro analysis (EPMA). In the raw soil, silicate minerals were abundant, including quartz and plagioclase feldspar group such as anorthite, oligoclase, and orthoclase. Silicon (Si), oxygen (O), and aluminum (Al) were abundantly distributed throughout the scanned area, supporting that the presence of silicate minerals. On the other hand, for the soil after 24 hours of the reaction, phosphate minerals found included hydroxyapatite (Hap), calcium-deficient hydroxyapatite (CDHA), and amorphous calcium phosphate (ACP). The Ca/P molar ratio was a range of 1.61–1.66, supporting that the phosphate was removed by precipitation of Hap. Moreover, CDHA and ACP serve as intermediaries in Hap crystallization, indicating that the experimental environment was in Hap formation phase. After 120 hours, anapaite was observed in the soil, which is a type of Ca-Fe-P-mineral. In this study, the experimental condition was a highly reducing environment, as indicated by the changes of iron concentration. Ultimately, phosphate was precipitated with calcium and iron. The EPMA results indicate that Ca-citrate can remove the phosphate by precipitation of phosphate minerals (e.g., hydroxyapatite, amorphous calcium phosphate, and anapaite). This study concluded that the simultaneous removal mechanisms for nitrate and phosphate involved denitrification and precipitation by the Ca-citrate complex.
Method for Calculating Potential Direct Loss of Water Shortages by Water Use Type and Deducing Optimal Applications
Authors: Gwon Yonghyeon , Kim Darae , Lee Haewon , Yoo Mina , Choi SoHyun , Park Jongpyo
Published: March 2024

  In recent years, Korea has witnessed a surge in both drought and heat waves during the spring and summer seasons. In contrast to other natural disasters such as floods, drought is challenging to quantify, and the damage from water shortage tends to develop gradually but persist for an extended period. Due to the challenging task of quantifying potential losses associated with drought, which are associated with diverse forms of damage, there is a need for research to estimate the damages caused by water shortages. Currently, in Korea, official records do not exist for data pertaining to damage or recovery costs categorized by the stage of each drought (only information about individuals experiencing damage and the duration of drought is documented and maintained). Furthermore, identifying the effects of support for damages during water shortages or determining the suitable extent of support is challenging. This difficulty arises from variations in damage assessment standards across different administrative districts and a limited number of relevant cases. Therefore, it is essential to quantify the potential losses from water shortages by deducing the primary influencing factors necessary for calculating such losses.  Thus, this study aimed to develop a method for calculating potential direct losses associated with water shortages categorized by water use type (household, industrial, agricultural). Additionally, the study aimed to derive optimal strategies for each water use type by analyzing the changes in potential direct losses according to different stages of water shortage scenarios.  First, cases of major water shortage in the past and pertinent damage data were investigated to establish the process for calculating potential direct losses, and influencing factors were deduced for each water use type to select items for benefit calculation and specific details.This study proposed a methodology and calculation equation according to the process for each water use type and thus designed a “tool box” capable of calculating potential direct losses by inputting influencing factors related to damages in affected areas.   The anticipated outcomes from calculating potential direct losses due to water shortages are expected to contribute to establishing a system that strengthens the competency of water shortage response. This system would include an analysis of water shortage damage reduction scenarios based on basin and water-use types and optimal water supply scenarios (involving a switch between various water use types) in consideration of social and economic aspects.AcknowledgementsThis work was supported by Korea Environment Industry & Technology Institute(KEITI) through Water Management Program for Drought Project, funded by Korea Ministry of Environment(MOE).(RS-2023-00230286)  
Combination of Hydrogeological Simulation and Geological Modeling: A Case Study of Conglomerate and Sandstone Distributed Site.
Authors: Chen Liang-Gu , Tong Cong-Zhang
Published: March 2024

In general, some parameters assumption or model simplifications are needed for hydrogeological simulation by the limitations of computing loading and lack of survey data. In addition, the hydrogeological simulation result and other geological investigation information are usually displayed separately, which are not able to provide a comprehensive interpretation. However, geological modelling technique provides a solution for these limitations.In this study, a conglomerate and sandstone distributed site in Taoyuan city, Taiwan, was applied for hydrogeological model establishment, flow simulation, and particle tracking calculation by FracMan software. Furthermore, regional investigation data including geological map, resistivity imaging profile (RIP), geological drilling, and hydrogeological simulation result, were applied to SKUA-GOCAD and integrated into a three-dimensional geological model, which provided comprehensive interpretations. At last, the lithology distribution model built by SKUA-GOCAD was applied to FracMan for another case simulation. This result was compared with the previous result simulated with simplified geological model, showing that how much geological modelling can help hydro-geological simulation. 
Climate change will increase Cd accumulation in spinach leaves
Authors: Muehe Marie , Pienkowska Aleksandra , Glöckle Alexandra , Sánchez Natalia , Khadela Shitalben , Richter Paul-Georg , Merbach Ines , Herzberg Martin , Reitz Thomas
Published: March 2024

Metal contamination in agricultural soils poses a notable environmental and health concern. When available in soils, metals can be assimilated and accumulated by crops, emphasizing the potential for human exposure to elevated metal levels through the consumption of contaminated agricultural produce. Our recent research shows that future climate change conditions of +4°C, doubled atmospheric CO2, and reduced soil moisture [1] increases the mobility of the heavy metal Cd in agricultural soils [2]. It remains uncertain whether this climate-augmented Cd bioavailability in agricultural soils transfers into the food chain.To address this gap in knowledge, we cultivated four varieties of spinach (Spinacia oleracaea) in four soils with diverse geochemistry and heavy metal contents. Spinach, chosen as a model for leafy crops prone to heavy metal accumulation in edible parts, boasts a global production volume of 63 billion kg in 2021 [3]. Under anticipated climatic conditions with +3°C, +300 ppmv CO2 and 10% less water [1], three out of four spinach varieties yielded more edible biomass compared to today’s climate typical for spring spinach with 20°C daytime temperature and 50% water holding capacity. The non-essential heavy metal Cd and the micronutrient Zn proved most responsive to the imposed future climatic conditions, exhibiting increased accumulation in the edible part. Factors such as soil-root transfer and root to shoot translocation will be discussed to elucidate the climate-induced rise in Cd and Zn contents in spinach leaves beyond soil Cd mobility.Our findings offer significant insights into forecasting future spinach production and quality, applicable to other leafy vegetables, and underscore the importance of addressing combined climate and heavy metal contamination issues to sustain food quality. [1] IPCC, 2021. Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change.[2] Drabesch et al., submitted, Climate induced microbiome alterations increase Cd bioavailability in agricultural soils.[3] UN Food and Agriculture Organization, 2023. Spinach production in 2021; Crops/Regions/ World/Production Quantity/Year from pick lists.
Statistical Study on the Azimuthal Mode Number of Pc5 ULF Wave in the Inner Magnetosphere
Authors: Tong Xin , Liu Wenlong , Zhang Dianjun , Sarris Theodore , Li Xinlin , Zhang Zhao , Yan Li
Published: March 2024

The azimuthal mode number, m, of ULF waves is a significant contributing factor for radiation belt electron energization, because it determines the conditions for resonant interaction between waves and particles. Based on multi-point magnetic field measurements of GOES satellites from January to September of 2011, we statistically analyze the distributions of the characteristics of m of Pc5 ULF waves. In the dayside, the local peaks in the distributions of wave power spectra density locate at ~10 and ~13 MLT for m < 0 (westward propagation) and m > 0 (eastward propagation) waves respectively, suggesting the waves generally propagate anti-sunward. In the nightside, the local peaks are at 22~23 MLT for both m < 0 and m > 0 waves, suggesting possible relation to substorm activities. Further investigation shows that, with increasing solar wind activities, the enhancements of dayside peaks are primarily contributed by m ≤ 3 waves, whereas the enhancements of nightside peak are contributed by both m ≤ 3 and m > 3 waves. With increasing AE index, the enhancements are more significant for the nightside peaks comparing to dayside peaks, and for m > 3 waves comparing to m ≤ 3 waves. The results of this study provide inputs for further investigation on the radial diffusion coefficient of radiation belt electrons with considering mode number information.
Enhancing Large-Scale Hydro-Climate Services Through a Regionalized Machine Learning Approach
Authors: Du Yiheng , G. Pechlivanidis Ilias
Published: March 2024

Local observations can drive machine learning (ML) based post-processors for improving hydrological model accuracy and reliability, and further ensuring that model outputs represent the local hydrological conditions. However, post-processing large-scale hydrological models is not straightforward and remains particularly challenging in ungauged basins. This study presents an ML-based post-processing approach which allows streamflow regionalization based on the hydrological characteristics of the river systems. We employed Long Short-Term Memory (LSTM) models to tailor the simulated streamflow obtained from the E-HYPE hydrological model to local observations across the pan-European domain. Here, we took advantage of the European hydrologically similar regions identified in Pechlivanidis et al. (2020), while LSTM was trained to map the simulated and observed runoff for each hydrologically similar cluster. The catchments in each cluster were divided into training and testing datasets under a K-fold cross validation approach. We compared the raw and post-processed simulations using different evaluation metrics capturing general bias (Mean Absolute Error), high flows (Nash-Sutcliffe Efficiency; NSE), and low flows (log-NSE). The results indicate that the regionalized LSTM approach enhances the hydrological model performance, evidenced not only at the stations incorporated within the training set, but also at those excluded from the training set. Overall, this study highlights the potential of ML in post-processing hydrological model outputs, especially in ungauged basins, setting a promising framework for AI-enhanced large-scale hydro-climate services. ReferencesPechlivanidis, I. G., Crochemore, L., Rosberg, J., & Bosshard, T. (2020). What are the key drivers controlling the quality of seasonal streamflow forecasts? Water Resources Research, 56, e2019WR026987. https://doi.org/10.1029/2019WR026987
Geological features of methane vents in the East Siberian Sea, the Arctic Ocean
Authors: Hong Jong Kuk , Kang Seung-Goo , Choi Yeonjin , Rhee Tae Siek , Kim Sookwan , Kim Younggyun , Jin Young Keun
Published: March 2024

The Eastern Siberian Sea is known for the presence of subsurface permafrost and for emitting significant amounts of methane close to the coastline. The thawing of permafrost accelerates the release of methane and carbon dioxide, contributing to increased greenhouse gas concentrations in the atmosphere. In 2021 and 2023, a multidisciplinary survey aboard the Korean icebreaker Araon was conducted on the continental shelf of the East Siberian Sea. The survey area lies more than 500 km away from the nearest coastline and falls within international waters. During the survey, areas with high methane concentration were identified on the shallow continental shelf, at depths ranging from 50 to 70 meters, utilizing underway CH4 measurements. These zones extend in a northwest-southeast direction. Multiple surveys were conducted to pinpoint gas seepage zones and delineate subsurface structures. The EK80 scientific echosounder proved instrumental in locating the gas vents, as it displayed methane gas eruptions clearly, resembling pillars in the imaging. The shallow sedimentrary structure of the lower part of the gas vent, observed  by the SBP survey, revealed high-amplitude reflections at a shallow depth (~5 m) below the seafloor. At the gas expulsion sites, seismic profiles show numerous vertical faults within the shallow sedimentary layers and scatterings in the water column caused by the methane emission from the seafloor. Backscattered images from the side-scan sonar clearly depict gases emitting from the vents and moving upward in the water column. These gas vents were found to have about 10 meters in diameter.
Soil Shrinkage Characteristics of Peat and Other Organic Soils 
Authors: Seidel Ronny , Dettmann Ullrich , Tiemeyer Bärbel
Published: March 2024

Shrinkage is the volume reduction of a soil due to desiccation and decreasing pore pressure. This is important for the determination of volume based physical and hydraulic soil properties in the laboratory e.g., bulk density, volumetric moisture and water retention functions. Furthermore, it leads to changing surface elevation and crack formation at the field scale.There are two types of shrinking soils, clayey soils and organic soils, which are defined here as soils having a soil organic carbon content (SOC) above 7.5%. Clayey and organic soils differ strongly in their shrinkage behavior.  Furthermore, only few shrinkage studies differentiate between different organic soils. Parameters of existing shrinkage models are fully empiric and not directly linked to soil properties as dry bulk density, SOC, botanical composition and degree of decomposition.To determine the soil shrinkage characteristics (SSC i.e., relationship between moisture ratio and void ratio) of a variety of organic soils, we determined sample volumes with a three-dimensional (3D) structured light scanner at different moisture states from full saturation to dryness. We sampled 33 horizons (n = 4 replicates each) covering a wide range of botanical composition, development stages and degree of decompositions. Desiccation was performed by suction plates up to pressure heads of -200 hPa, followed by evaporation and oven-drying at 105°C. Volume and height of the 3D models created this way were determined by 3D graphic software and R, respectively. The volumetric moisture was determined by weighing the sample before and after scanning. Afterwards, volume and volumetric moisture were converted to moisture ratio and void ratio with the volume of solid particles. Due to small differences in particle volume between the replicates, both, moisture and void ratio were normalized by dividing them by the value at saturation. This normalization led to congruent results for the replicates.The shape of the SSCs strongly depended on the botanical composition and degree of decomposition. Peat consisting of slightly decomposed Sphagnum remains showed a supernormal shrinkage phase, i.e., volume reduction exceeds lost water volume at the dry end of the SSC and a relatively large range where volume reduction is (much) smaller than lost water volume, i.e., subnormal or structural shrinkage phase, at the wet end. The latter behavior was also shown by amorphous top soils. With increasing degree of decomposition or complete absence of Sphagnum remains the SSC flattened and tended to show a (near-) normal shrinkage phase, i.e., volume reduction equals lost water volume.The results showed that rigid Sphagnum remains strongly influence the shrinkage behavior of organic soils by stabilizing the matrix during desiccation until the large pores collapse rapidly when soil moisture and tension undercut a certain level. The SSC of organic soils without rigid fibers were more similar to SSCs of clayey soils.
On the Prevalence of Lower-Hybrid Wave-Induced Electron-Scale Current Sheets related to Kelvin-Helmholtz Vortices during Southward IMF
Authors: Blasl Kevin Alexander , Settino Adriana , Nakamura Rumi , Nakamura Takuma , Hasegawa Hiroshi , Vörös Zoltan , Hosner Martin , Panov Evgeny , Schmid Daniel , Volwerk Martin , Roberts Owen Wyn , Liu Yi-Hsin
Published: March 2024

Numerous spacecraft missions, theories and numerical modelling have studied the Kelvin-Helmholtz instability (KHI) excited at the Earth’s magnetopause at different scales. Important insights into particle transport and mixing as well as energy conversion related to the KHI were obtained from these studies and linked to processes such as magnetic reconnection and plasma turbulence.Recently, Blasl et al. (2022, 2023) and Nakamura et al. (2022 a, b) reported the first observations of the KHI during southward Interplanetary Magnetic Field (IMF) conditions from the Magnetospheric Multiscale (MMS) mission together with fully-kinetic Particle-In-Cell simulations designed for this event. The unprecedented resolution of the MMS mission together with large-scale kinetic simulation runs enabled a multi-scale study of the KHI. Their results showed the onset and evolution of secondary instabilities such as the Rayleigh-Taylor Instability responsible for globally deforming the vortex structures as well as the Lower-Hybrid Drift Instability (LHDI) leading to plasma mixing along the spine region of the vortices. Additionally, at 1 out of the 11 KH wave crossings they reported the observation of an electron-scale reconnecting current sheet at the interface between this mixing region and the magnetospheric plasma, as suggested by simulation results.In this study, we revisit this previously reported MMS KH event during southward IMF and study the remaining 10 vortex structures in detail. Especially, we will characterize the signatures of LHDI-induced plasma mixing from both simulations and observations at different evolutionary stages and discuss the prevalence and signatures of small-scale current sheets at these vortex structures. First results suggest the coexistence of vortex structures at different evolutionary stages in this KH event, which will be discussed in detail. A short discussion on the influence of the IMF on this mechanism will be given at the end of the presentation.
Developing a novel decision support tool for improving O3 air quality through strategic precursor gas emission controls
Authors: Lee Hyung Joo
Published: March 2024

In many parts of the world, ambient O3 levels have increased despite regulatory efforts to improve O3 air quality. The unexpectedly increasing O3 levels are largely attributed to a lack of understanding about O3 chemical regimes. The O3 mitigation strategies related to precursor gas emission controls have not adequately considered the O3 chemical regimes (NOx-limited or VOC-limited conditions). This study develops a novel approach to identifying the spatiotemporal variations of O3 chemical regimes collectively using ground and satellite data to support the decision-making of precursor gas emission controls. Using ground NO2 and O3 concentrations measured in both the Seoul Metropolitan Area (SMA) of the Republic of Korea and the LA County of California, U.S. for May 2018-April 2021, a mixed effects model is employed to generate daily relationships between NO2 and O3 concentrations. Positive and negative relationships between NO2 and O3 concentrations provide strong evidence of NOx-limited and VOC-limited conditions, respectively. Satellite data on TROPOspheric Monitoring Instrument (TROPOMI) HCHO/NO2 ratios represent relative NOx-sensitivity or VOC-sensitivity (i.e., higher and lower ratios indicating increasing NOx-sensitivity and VOC-sensitivity, respectively). The modeling and satellite approaches are complementary to each other because (1) the model does not account for VOC concentrations due to a lack of VOC measurements and (2) TROPOMI HCHO/NO2 alone does not provide the threshold level of separating NOx-limited from VOC-limited conditions. The monthly slopes of NO2 concentrations against O3 concentrations are highly correlated with monthly TROPOMI HCHO/NO2 both in the SMA (0.75) and LA County (0.87). Threshold levels distinguishing NOx- from VOC-limited conditions are defined by the TROPOMI HCHO/NO2 values when the NO2 slopes are equal to 0. In the SMA and LA County, the threshold levels are 3.0 (95% CI= 2.6-3.4) and 1.4 (95% CI= 1.3-1.6), respectively. During the study period, the O3 chemical regime is mostly VOC-limited in the SMA (35 out of 36 months), meaning that NOx emission controls can worsen O3 air quality until the O3 chemical regime reaches NOx-limited conditions. In the SMA, VOC emission controls can help reduce the O3 levels. On the other hand, in LA County, the O3 chemical regimes transition from VOC-limited to NOx-limited conditions during the warm seasons and vice versa during the cool seasons, depending on the seasonality of NOx and VOC emissions. The O3 mitigation strategies in LA County can be the most effective with season-specific emission controls. This study offers a novel method for determining the most effective strategy of precursor gas emission controls and informing decision-making to enhance O3 air quality.
Towards efficient and standardised large-scale monitoring of peatland habitats through fine-scale drone-derived vegetation mapping
Authors: Steenvoorden Jasper , Limpens Juul
Published: March 2024

Northern peatlands provide key climate regulating services by sequestering and storing atmospheric carbon as peat, but they also harbour highly specialized plant and animal species. Yet, 50% of peatlands in the European Union are currently degraded. To understand the effect of recent restoration efforts on habitat suitability and peat accumulation rate, there is a need to develop and refine efficient and standardised methods that can effectively target the multiple ecosystem services that peatlands provide. Given the spatial characteristics of peatlands, as well as the direct link between vegetation structure and peatland functioning, vegetation mapping with unmanned aerial vehicles or drones is ideal for such tasks.For this study, we collected very-high-resolution drone imagery (2.8cm) of five Irish peatlands (ranging between 35–124 ha) in September 2022. We then used Random Forest classifiers to map fine-scale vegetation patterns (microform and plant functional type) in all peatlands using the resulting remote sensing products. Hereafter we subdivided and labelled each peatland into 20x20m grid cells using polygon-shaped field-based ground truth maps of peatland, and classified large-scale peatland habitats (ecotopes, and status or Active versus Degraded Raised Bog) with Support Vector Classifiers while using the proportions of microforms and plant functional types and topography as input datasets. Lastly, we assessed model performance and mapping accuracy between models trained on a singular peatland to those trained using a pooled ground truth dataset from the four other peatlands to evaluate the spatial transferability of habitat mapping over multiple peatlands.Our results highlight that model performance for fine-scale vegetation patterns were consistently high (>90%) for all peatlands. Subsequent classifications of peatland habitats were also relatively consistent for singular peatlands with overall model performances of 73.0% and 89.3% for ecotopes and status respectively. Nevertheless, we observed notable reductions in overall model performances of 11.0% and 6.2% using pooled ground truth datasets. Inconsistencies in classification models resulted largely from artificial landscape features created by restoration, sun and shading, variation in plant phenology, suboptimal elevation models, and development of a gridded ground truth dataset from an original polygon-shaped and field-based map.Our findings highlight that fine-scale vegetation patterns and peatland habitats can be classified accurately and consistently on the scale of whole peatlands using drone-derived imagery products and machine learning classifications. Our study provides comprehensive and novel insights into the multiple requirements for accurate vegetation mapping on which future drone studies can build to further optimize and standardise monitoring of vegetation dynamics in a wide variety of peatlands and peatland types of contrasting eco-hydrological integrity.
Which dataset should be used to get building footprint and height worldwide ?
Authors: Bernard Jérémy , Wurtz Jean , Masson Valéry , Bocher Erwan
Published: March 2024

The building size and distribution has a big impact on atmospheric properties such as wind speed, air temperature, air pollution, etc. This impact may be quite different depending on the lattitude and the climate where a city is located. Nowadays, climate simulations performed over city territories consider average building properties (building height, distance between buildings, etc.) over one to several hundred meters grid cells. However, it is difficult to find a homogeneous building dataset that would be used over the world to observe the effect of a same building organisation between two regions of the world located at a different lattitude or in a different climate zone.This work is dedicated to the evaluation of several building datasets (OpenStreetMap, BING, Global Human Settlement, etc.) that are available over several continents. The building footprint and height of each dataset are compared to local reference data for different parts of the world. The objective is to identify which dataset would be preferable to use depending on its quality and availability.
Cluster Observation on the Latitudinal Distribution of Magnetic Pc5 Pulsations in the Inner Magnetosphere
Authors: Yan Li , Liu wenlong , Zhang dianjun , Sarris Theodore E , Li Xinlin , Tong Xin , Cao Jinbin
Published: March 2024

Ultralow frequency (ULF) waves in the Pc5 band are ubiquitous in the inner magnetosphere and can impact radiation belt dynamics by interacting with electrons through drift or drift-bounce resonance. In this paper, based on ∼ 19 years of Cluster measurements, we perform a comprehensive study of the three-dimensional distribution of poloidal, toroidal, and compressional ULF waves from L = 4 to 10, for magnetic latitudes (MLAT) up to Ultralow frequency ±50°, and in all magnetic local times (MLT). The distribution of the Pc5 ULF wave power is found to vary greatly as a function of L and MLT. For all L and MLT sectors, wave power of the poloidal and toroidal modes of the magnetic field increase with increasing MLAT, while the compressional mode decreases with increasing MLAT. The dawn–dusk asymmetries of wave power in poloidal and toroidal modes are more pronounced at higher MLAT. Furthermore, the wave power for Kp > 2 is approximately 2.93, 3.21, and 3.42 times greater than the wave power for Kp ≤ 2, respectively for compressional, poloidal and toroidal components. The information on the latitudinal distributions of ULF waves presented in this paper is important for future investigations on the radial diffusion process of radiation belt electrons with non-90° pitch angles while they bounce away from the magnetic equator.
Increased millennial-scale monsoonal circulation amplitude across the mid-Pleistocene transition revealed via speleothem records
Authors: Niu Xiaowen , Wang Jian , Kang Le , Zhang Haiwei , Cheng Hai , Li Youwei
Published: March 2024

The Asian summer monsoon (ASM) represents a significant and expansive element within the global climate system. While speleothem δ18O records offer robust characterization of millennial-scale ASM variations over the last 640 ka (thousand years), limited data exists regarding the ASM's behavior preceding the U-Th dating limit of approximately 640 ka. This includes periods such as the mid-Pleistocene Transition (MPT, ~800-1200 ka) and the pre-MPT era. In this study, we present two meticulously calibrated high-resolution speleothem δ18O records sourced from central China. These records span three distinct periods: 640–615, 690–660, and 1,360–1,310 ka BP ( thousand years before present, the present defined as 1950 CE). The absolute dating of these records is accomplished via laser ablation and isotope dilution U-Pb methods. Our meticulous tuning aligns these records with the summer insolation (690–660 and 1,360–1,310 ka BP) and the preceding record (640–615 ka BP). Our findings indicate a close association between millennial-scale weak ASM occurrences and North Atlantic stadials and Antarctic warming events within the period of 685–675 ka BP, similar to previously established connections within the last 640 ka. Furthermore, millennial-scale ASM variations occurred prior to the MPT, specifically during the period of 1360–1310 ka BP, albeit with relatively smaller amplitudes in comparison to those observed after the MPT in the last ~690 ka. We hypothesize that reduced freshwater forcing in the North Atlantic and/or altered freshwater routing to the Gulf of Mexico through the Mississippi drainage system might have resulted in a less pronounced weakening of the Atlantic Meridional Overturning Circulation (AMOC) before the MPT, thereby leading to smaller amplitudes in millennial-scale ASM variations observed during 1360–1310 ka BP.
An analytic method for optimizing hydropower installed capacity expansion size in hydro-solar-wind hybrid system
Authors: Wu Chen , Liu Pan , Cheng Qian , Yang Zhikai , Liu Zheyuan
Published: March 2024

The worldwide renewable energy installed capacities have increased rapidly, aiming to secure power supply and replace fossil fuels. However, challenges persist in optimizing the size of hydropower installed capacity expansion (HICE) in hydro- solar-wind hybrid system. In this study, an analytic method is proposed to determine the optimal hydropower installed capacity expansion size based on the relationship between HICE and generation, as well as the relationship between HICE and energy-loss. Firstly, an optimization function for HICE is proposed using the net present value method. Then, function assumptions are made and validated for the relationship between HICE and generation (HICE-generation function) and the relationship between HICE and energy loss (HICE-energy-loss function). Finally, the optimal sizes of HICE derived from the numerical and analytical methods are compared. A case study in the Yalong River basin in China reveals that: (1) the proposed HICE-generation and HICE-energy-loss functions can quantitatively characterize the relationship between HICE and generation and energy loss; (2) the proposed analytical method could yield the optimal HICE size without the need for a simulation process and heavy computational burden; and (3) it provides an optimal HICE size of 1210 MW with a relative error of only 5.5% compared to the numerical solution. Therefore, the proposed analytical method can be an effective tool for the planning and management of large hybrid energy systems.
First experiences of correlation between erosion and chemical weathering at basin scale. The case study of Niccone stream (Central Apennines, Italy)
Authors: Donnini Marco , Marchesini Ivan , Benigni Augusto , Dionigi Marco , Cappelletti David Michele , Selvaggi Roberta , Cencetti Corrado
Published: March 2024

Rivers' sediments can be classified as dissolved (ions transported in solution), suspended (small particles like clay and silt transported by the fluid's flow) and bedload (largest particles like sand, gravels and pebbles transported along the river bed). It is well known by the literature that chemical weathering of carbonate and silicate minerals consumes atmospheric CO2, enriching the dissolved load. In the “short-term” (
Propagation of whistler-mode waves in the magnetic duct caused by the compressional component of ULF wave oscillation
Authors: Tachi Koki , Katoh Yuto
Published: March 2024

Whistler-mode waves play crucial roles in radiation belt dynamics, facilitating the acceleration of electrons from kiloelectron volts to megaelectron volts energy range and the loss of radiation belt electrons via wave-particle interaction. Recent studies suggest the important role of the duct propagation of whistler-mode waves for the radiation belt dynamics because the resonant energy increases to the relativistic energy in the high latitude region where ducting whistler-mode waves can reach. While the density duct caused by electron density structure has been studied for decades, it is evident from the dispersion relation that the refractive index is affected not only by the cold electron density but also by the magnetic field. We study the propagation of whistler-mode waves in ULF wave-derived magnetic ducts by two-dimensional ray-tracing simulations in the dipole coordinate system. We assume a magnetic duct structure at L=6 by considering the dipole field and a waveform of ULF wave oscillation with compressional and poloidal components. The refractive index fluctuations of the duct are calculated from the background field fluctuations caused by modeled compressible amplitudes associated with poloidal oscillations in the fundamental mode. The duct's shape is determined using a Gaussian function, and the rate of change of the magnetic field and the duct width are given parametrically. The refractive index structure is modeled every eighth of a ULF wave period, and the propagation of upper/lower-band frequency whistler-mode waves is simulated. Depending on the wave phase of the modeled ULF wave, the background magnetic field increases or decreases with each ULF phase, generating a depletion or enhancement duct. The simulation results show duct propagations, while the frequency where ducting of whistler-mode waves observed switches because the duct structure shifts with each phase of the modeled ULF wave. The duct width corresponds to the spatial scale of high-m ULF waves. A larger spatial scale can be expected if the ULF-induced plasma density variations are included. Furthermore, the duct propagation in other harmonics is also confirmed. This study reveals the characteristics of whistler-mode wave propagation by magnetic ducts due to ULF waves.
Identification of plant, bacterial and fungal necro mass markers in soil organic matter via ultrahigh resolution mass spectrometry
Authors: Stumpf Konstantin , Simon Carsten , Lechtenfeld Oliver
Published: March 2024

Soil organic matter (SOM) plays a central role in the global carbon cycle, influencing for example soil fertility, biodiversity, and erosion. Recent theories predict that SOM is a blend of plant metabolites and their breakdown products, perpetually undergoing recycling and transformation driven by soil organisms such as fungi and bacteria. However, our understanding of SOM remains incomplete due to its complex chemical composition. Particularly, we lack distinct metabolite information for the majority of these compounds or sources, hampering the analysis of SOM structure, it’s genesis, as well as mechanistic understanding of soil processes. Non-targeted analysis by ultrahigh resolution mass spectrometry, foremost Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS), has substantially advanced our understanding of organic matter complexity in soils and allows to gain a representative picture through the use of liquid chromatography (LC). To address the above knowledge gaps, we employed LC-FT-ICR-MS for the investigation of three primary types of necromass (maize litter, bacterial and fungal necromass) extracts, as well as aqueous SOM extracts obtained from arable topsoils (2 – 20 cm depth). Water-soluble SOM fractions can be seen as a transition state between higher molecular weight structures in soils like bio- or necromass and its decomposition end products like carbon dioxide or methane.We employed an LC methodology capable of separating dissolved organic matter (DOM) across a broad polarity spectrum, including highly polar compounds that are typically lost during commonly employed solid-phase extraction. Our results show significant differences between farmyard manure-amended (FYM) and unamended (UF) soil DOM according to its nominal carbon oxidation state (NOSC), saturation and molecular mass, that are most prominent for the highly polar fraction of SOM. We assigned intricate markers derived from bacterial, fungal or plant necromass that indicated higher potential necromass contribution to FYM than UF soil DOM, in line with higher microbial activity in these soils. We found that necromass markers contribute most to the CHNO formula class in soil DOM, thereby explaining structural differences between FYM and UF samples.The outcomes of our research represent an initial stride towards the identification of novel molecular markers intrinsic to soil DOM, its thermodynamic properties and N content. In the long term, these techniques will enable not only the detection of shifts in the molecular composition of soil DOM during substrate decomposition but also the recognition of alterations in structural motifs that are associated with specific necromass types. This advancement holds promise for enhancing our understanding of soil DOM dynamics and therefore may hold important implications for soil and ecosystem management.