Reactive Elements Research Articles

Coupling thermodynamic modelling with experimental study to reveal the evolutionary relationship of pore solutions, products, and compressive strength for lunar regolith simulant geopolymers

Alkali-activation is a highly promising approach for the in situ resource utilisation (ISRU) of lunar regoliths. However, the considerable variation in the composition of lunar regolith simulants can complicate the optimal design of geopolymer mixture ratios, necessitating an in-depth analysis of composition–performance correlations. This study proposes a calculation method that couples thermodynamic modelling with an experimental study to reveal the evolutionary relationship between the pore solution, product formation, and compressive strength. The results indicate that the modulus and dosage of the alkali activator can substantially change the relative content of reactive elements in the pore solution and affect the product type and content. Among these, [Si] and [Al] in the pore solution and gel production are key factors affecting the compressive strength of geopolymers. Understanding these composition–performance relationships is critical for offering essential guidance for performance-based, on-demand material design and optimisation.

Resistive Heating and Thermal Decomposition of an Additively Manufacturable Electrically Conductive Explosive

AbstractThe ability to transmit electrical signals through high explosive charges without using dense metal conductors could enable continuous monitoring of explosive charges with internally embedded sensors. With the sensor materials themselves being energetic, the impact on the intended detonation performance of the charge can be minimized. Embedded sensors enable real time, in‐situ measurements of conditions relevant to ageing assessments. Additionally, dynamic material property sensing can provide detonation performance data, enabling measurement of dynamic shock position. One proposed method to allow for electronic signal transfer through high explosives is to use electrically conductive explosive composites consisting of an electrically conductive polymer binder mixed with high explosive crystals. These conductive energetic pathways also serve as independently reactive elements and can provide additional functionality via dynamic sensor removal through resistive heating and subsequent decomposition. This work discusses the resistive heating of a previously developed, poly (3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) based, electrically conductive extrudable explosive composite. Experimental samples of the conductive explosive material were subjected to a range of direct current applications and the resulting heating and decomposition of the material is discussed.

An array of paired folded-end dipoles for whole-brain imaging at 9.4 T

PurposeTo improve transmit B1+ field homogeneity and longitudinal coverage of a human head RF array coil, we developed a novel eight-element transceiver (TxRx) array using composite elements based on paired folded-end dipoles. MethodsThe developed array consisted of eight pairs of coupled folded-end dipoles. Only one dipole in each pair was driven during transmission, while the other was passively coupled with the active one. The distribution of the transmit B1+ field was numerically optimized by changing the overlap between the dipoles and the value of the reactive lumped element placed in the middle of the passive dipole. ResultsThe proposed array of paired folded-end dipoles substantially improved the B1+ homogeneity and longitudinal coverage over the entire brain including the brain stem compared to a single-row folded-end dipole array. The improved whole brain coverage was demonstrated both numerically and experimentally. ConclusionAs a proof of concept, we developed and characterized both numerically and experimentally a prototype of a single-row eight-element 9.4 T array for human brain imaging consisting of composite array elements based on paired passively-coupled folded-end dipoles. The array improved the transmit magnetic field distribution due to the laterally elongated field pattern created by one active and one passive dipole per channel. As a result, the provided coverage was substantially better than that of an 8-element dipole array consisting of long folded-end dipoles. For the first time, an image of the entire human brain at 9.4 T, covering the brain stem up to the fourth vertebra, was obtained using a simple single row eight-element array.

A new concept of structural smart fabric activated by shape memory alloys

Abstract This work presents the development, prototyping and validation of a new concept of structure called Structural Smart Fabric (SSF). An SSF is a chainmail fabric composed by interconnected elements, called cells, which can be stiffened by reactive elements, such as those made by Shape Memory Alloy (SMA). Exploiting the shape memory functionality, SSFs are capable of sensing and reacting to external stimuli. Based on this concept, in this study we propose an SSF that integrates SMA wires into a 3D-printed chainmail structure. The shape memory effect of these wires is used as an actuating mechanism that, at high temperature, tightens the adjacent cells together and provides increased structural stiffness. In this study, finite element simulations were initially conducted to enhance the comprehension of the SSF’s mechanical behaviour. The influence of the initial cell spacing on the SSF stiffness and the wire stress profiles was evaluated during bending loading, as well as the evolution of contact pressure profiles between adjacent cells. This numerical approach enabled to tune the design of the SSF prototypes which were successively manufactured using Selective Laser Sintering (SLS) additive manufacturing technology with PA12. After the integration with the SMA wires, the SSF prototypes were tested under a 3-point bending configuration at different temperatures. The results revealed a remarkable increase in structural stiffness at elevated temperatures compared to ambient conditions. This study set the basis for a deeper understanding of SSF's unique capabilities and potential applications in fields where adaptive and responsive structures are required.

DEVELOPMENT OF A HUMAN-SPECIfiC 3D IN VITRO PAEDIATRIC CEREBELLAR TUMOUR MODEL USING DECELLULARISED BRAIN AUTOPSY TISSUE

Abstract AIMS Group-3 medulloblastoma (MB) is a paediatric cerebellar tumour with a dismal prognosis. Our objective was to establish a 3D in vitro model termed ‘tumoursphere matrix’ to recapitulate physiologically-relevant communication between tumour cells and reactive brain elements, aiming to discern differential gene expression in cancer cells upon co-culture with astrocytes and human brain extracellular matrix (ECM). METHOD Non-disease human autopsy brain was decellularised to generate ECM and extensively characterised to show DNA reduction, ECM ligand retention and compatibility with different cell lines. D283, D341 and D425 cells were co-cultured with primary human cerebellar astrocytes within a PEGDA hydrogel containing decellularised ECM. Following 7 days of culture, co-cultured cells were separated using fluorescence activated cell sorting to generate individual cell populations for transcriptomic analysis. RESULTS ECM characterisation showed a significant reduction in cellular material whilst retaining ECM ligands. Reduction of DNA content to 174 ng/mg was corroborated by an absence of nuclei in immunohistochemical staining. Colorimetric assays indicated collagen and glycosaminoglycan retention in decellularised ECM, and immunofluorescence confirmed retention of fibronectin, laminin and hyaluronic acid. Detection of all ECM ligands was cross-validated by Orbitrap-Secondary Ion Mass Spectrometry. Primary human cerebellar astrocytes, D283, D341 and D425 cells were cultured as spheroids within the ECM/PEGDA hydrogel for 7 days with no significant decrease in cellular viability. Cytokine and Human Matrix Metalloproteinase (MMP) Antibody Arrays showed retained cytokine and MMP expression in all three cell lines in the presence of ECM material. CONCLUSION We have developed a bespoke 3D model which can co-culture cells for over 7 days, whilst recapitulating the in vivo tumour environment. RNA sequencing on all 3 cell lines in mono and co-culture is currently in progress to identify differentially expressed genes in medulloblastoma cells upon astrocytic and brain ECM crosstalk. We hypothesise that biochemical signalling underlying this communication network will reveal putative therapeutic vulnerabilities.

On mitigating reactive jamming with dynamic resource allocation in optical IRS and UAV-assisted FSO-based networks

Free space optics (FSO) offers a promising opportunity to enhance next-generation network’s capacity with its unlicensed spectrum and wide bandwidth. However, jamming attacks, coupled with inherent anomalies in the FSO-based channel, threaten the performance of these networks. This is especially problematic for security-sensitive applications that demand a resilient communication infrastructure. To address this issue, optical intelligent reflecting surfaces (IRS) and unmanned aerial vehicles (UAVs) can provide promising solutions. This work introduces an efficient approach for mirror element assignment in UAV-assisted FSO-based networks, aimed at mitigating reactive jamming attacks while satisfying users’ quality-of-service (QoS) requirements. To ensure network reliability, we formulate an optimization problem that enhances overall network performance by simultaneously allocating resources such as mirror elements with awareness of jamming attacks. The formulated optimization problem is a binary linear programming problem, which is generally NP-hard. To address this, we introduce a batch-based sequential fixing linear programming procedure called the Reactive Jamming-Aware Mirror Element Allocation (RJA-MEA) scheme. This scheme optimally assigns mirror elements to satisfy the users’ rate demands. In this paper, the performance of the RJA-MEA scheme is compared with reference schemes such as Reactive Jamming Unaware-Mirror Element Allocation (RJU-MEA), Reactive Jamming-Aware Equal Mirror Element Allocation (RJA-EMEA), and Reactive Jamming Unaware-Equal Mirror Element Allocation (RJU-EMEA) schemes. The simulation results reveal that the proposed RJA-MEA scheme surpasses existing reference schemes, thereby significantly improving the overall network sumrate performance.

A scalar method for measuring the reactive element in microwave and millimeter-wave bands

This paper introduces a novel scalar method to determine the value of reactive elements by only measuring the amplitude value of the reflection coefficient. The methodology is illustrated using a Smith Chart, integrating reactive elements in series or parallel with a standard resistance element, and deriving a corresponding equation. Simulation results closely align with theoretical predictions. This approach extends beyond reactive elements, applying universally to π/T-network circuits. It obviates the need for Vector Network Analyzers (VNA) in measurement, reduces equipment requirements, and holds substantial importance for measuring diverse types of reactive microwave elements.

Comprehensive study of the effect of Hf and Ta co-doped MCrAlY bond coat on the high-temperature properties of thermal barrier coating

The MCrAlY bond coat is modified by reactive element (RE) Hf and refractory element Ta, and the high-temperature oxidation resistance of the thermal barrier coating (TBC) before and after the modification are investigated by comparative experiments. The experiments use high-velocity oxygen-fuel (HVOF) to prepare NiCoCrAlY and NiCoCrAlYHfTa bond coats on the surface of GH4099 high-temperature alloy, and then yttrium stabilized zirconia (YSZ) ceramic layers are prepared on the surface of the bond coat by atmospheric plasma spraying (APS), and cyclic oxidation is carried out in air at 1050 °C until failure. It is shown that the oxidation lifetime of the modified TBC reached 1992 h, which is one time higher than that of the unmodified TBC. The doping of Hf and Ta elements reduces the growth rate of the oxide layer, and these diffuse externally and combine with the internally diffused O to form HfO2 and Ta2O5 in the thermally grown oxide (TGO) layer, thereby improving the adhesion and mechanical properties of the oxide layer. In addition, the bond strength and thermal shock resistance of the TBCs are significantly improved after doping with Hf and Ta elements, which prolongs the lifetimes of the TBCs. In this paper, the morphology, structure, and properties of the modified TBCs are characterized to investigate the mechanism of the oxidation lifetime extension.

Reactivity of a plagioclase concentrate from the South African Bushveld Igneous Complex via extractive acid leaching vs. extractive roasting-leaching processes

This study compared the reactivity of a plagioclase concentrate subjected to two processes: (1) direct acid leaching and (2) thermochemical treatment with ammonium sulfate followed by leaching. The sample was prepared from coarse-grained pyroxenite rock retrieved from the Bushveld Igneous Complex, South Africa. It contained 78% plagioclase (labradorite), 9% orthopyroxene (enstatite) and 13% quartz. The elements contained in the concentrate were categorized into three groups based on their susceptibility to direct acid extraction after 6 h of leaching. Group 1 consisted of the highly reactive main elements of plagioclase (Al, Ca and Na, with extraction efficiencies of 95%, 89% and 81%, respectively). Group 2 included elements predominantly present in enstatite (Mg and Fe with extraction efficiencies of 41% and 55%, respectively). Group 3 was composed of slowly extractable Si (25%) from mostly plagioclase. Increasing the duration of direct acid leaching to 24 h had no effect on the extraction of Group 1 elements, whereas the extraction of Mg and Fe (Group 2) increased to >60%, and that of Si (Group 3) increased from 25 to 80%. The latter correlated with the nearly complete disappearance of the plagioclase blueprint in the XRD pattern of the residues generated after 24 h of leaching. In contrast, plagioclase had limited reactivity with ammonium sulfate during thermochemical treatment. Direct acid leaching of plagioclase-rich tailings can therefore generate leachates to be used as precursors for the preparation of value-added products, such as silica nanoparticles via a sol–gel route and calcium aluminate nanoparticles via solution combustion.

Morphology Control of Nanoporous Gold Through Selective Dissolution of Au–Ge Eutectic Microstructures

The synthesis of nanoporous gold (np‐Au) through the conventional method of dealloying a more reactive element from AuTherma alloys has been extensively studied and applied in various fields, particularly catalysis. Herein, a novel approach to creating droplet‐like np‐Au through the selective dissolution of Au–Ge eutectic microstructures is explored. This work reveals that adjusting the undercooling of the eutectic melt during solidification allows for the tuning of pore and ligament sizes. It is demonstrated that this undercooling can be modified, either directly or indirectly, by adjusting either the cooling rate or the heterogeneous nucleation site density of the eutectic melt. The findings, aligned with the model based on classical theory for eutectic solidification, elucidate the connection between the tuning of pore and ligament sizes in the eutectic microstructure and the undercooling of the eutectic melt. Importantly, it is established that this phenomenon is applicable across a variety of compositions, including hypereutectic, eutectic, and hypoeutectic. The ability to regulate pore and ligament size in single crystals of np‐Au droplets offers a novel approach to synthesizing catalytic np‐Au crystals with enhanced mechanical and thermal stability compared to conventional methods.

Hydrothermal solidification of siliceous and calcareous wastes into building materials: A generic mix design framework

The presence of inactive components in siliceous and calcareous wastes tends to cause a misunderstanding in their mix design for hydrothermal solidification. The contents of typical reactive elements (i.e. Caact, Siact and Alact) in raw materials are quickly determined by simulating hydrothermal conditions. A generic mix design framework is proposed, which utilizes the molar ratio of Caact/Siact as the controlling parameter. The framework was demonstrated through a series of studies, which involved the production of granular materials using a mixture of clayey soil with slaked lime, as well as the production of compacted cylinders using a mixture of clayey soil with either slaked lime or calcium carbide slag. Experimental results showed that the hydrothermal samples achieved their maximum strength when the molar ratio of Caact/Siact in raw materials approached the theoretical Ca/Si molar ratio (i.e. 0.83) in tobermorite, provided that the molar ratio of Alact/(Alact + Siact) remained below 21%.

Cost-effective methods of fabricating thin rare-earth element layers on SOC interconnects based on low-chromium ferritic stainless steel and exposed to air, humidified air or humidified hydrogen atmospheres

Most oxidation studies involving interconnects are conducted in air under isothermal conditions, but during real-life solid oxide cell (SOC) operation, cells are also exposed a mixture of hydrogen and water vapor. For this study, an Fe–16Cr low-chromium ferritic stainless steel was coated with different reactive element oxides – Gd2O3, CeO2, Ce0.9Y0.1O2 – using an array of methods: dip coating, electrodeposition and spray pyrolysis. The samples underwent oxidation experiments carried out over 100 h in three different atmospheres at 800 °C: air, an air/H2O mixture, and an Ar/H2/H2O mixture. The influence of different atmospheres on the corrosion of the Fe–16Cr steel was determined via oxidation kinetics studies; the corrosion product was evaluated using X-ray diffraction, scanning electron microscopy and area-specific resistance (ASR) measurements. All coated samples exhibited lower parabolic oxidation rate constants than bare steel and most also had lower ASR. The applied modifications were found to be sufficiently effective to allow the investigated low-chromium steel to be considered for application as an interconnect material for SOCs.

Effect of reactive elements in MCrAlX bond coat for durability improvement of thermal barrier coatings

The effects of reactive elements (RE) in MCrAlX alloy (M: Metals, X: RE) as the bond coat for thermal barrier coatings durability were investigated by both experimental evaluation and density functional theory (DFT) calculations. Cyclic oxidation tests showed that the lifetime of the sample with Y, Hf, and Si as RE displayed approximately twice of the sample with Y only. Furthermore, the interface energies between oxide (α-Al2O3) and bond coat with various RE (Si, Sc, Ti, Y, Zr, Hf, La, and Ce) were calculated by DFT. DFT results indicate that Hf and Si doping effectively reduce the interface energy.

APPLICATION OF A NEURONETWORK FOR DETERMINING THE TYPE OF ELEMENTS OF A SYMMETRICAL COMPENSATION DEVICE OF AN UNSYMMETRICAL SYSTEM WITH A ZERO WIRE

In article the possibility of using neural networks in the field of increasing the energy performance of a four-wire power supply system with an uneven load in the phases is being investigated. An uneven load in the phases causes asymmetry of currents in the network and contributes to the increase in the current in the neutral wire, which has an extremely negative effect on both the supply itself and its consumers. To eliminate asymmetry and reduce the current in the neutral wire, you can connect a symmetrical compensating device. Such a device is a set of reactive elements, the parameters of which are determined by search optimization. To determine the type of the required element, the defined parameters are recalculated. That is, the solution of such a problem consists of two component sub-problems – structural and parametric synthesis. This approach provides a high accuracy of calculations, but has a significant drawback: the calculations are cumbersome. In order to simplify the solution of the synthesis problem, it makes sense to determine the type of elements using neural networks, which will significantly reduce the time and resources spent on calculating the values of the parameters of the symmetrical compensating device. The subject of the article is the study of the possibility of using neural networks to predict the types of reactive elements of the symmetrical compensating device. During of the study, the parameters and type of neural network were determined, which provide the most accurate prediction of the topology of the structure of the symmetric-compensating device. The input parameters of the neural network were formed from sets consisting of eight parameters – resistances and inductances of the transmission lines and the neutral wire. The target matrix was formed from a set of data sets consisting of six elements containing information on the types of elements connected (0 – capacitor, 1 – inductance) between phases and between phases and the neutral wire. During research, the results of a quasi-solution were obtained, the values of which turned out to be commensurate with the accurate calculations for determining the structure of the symmetrical compensating device of the power supply system with a zero wire. This indicates the high quality of the developed neural network. Applying the minimax strategy to the received results provides an opportunity to reduce the received values to 0 and 1 to ensure clarity of the results obtained by the neural network.

Transfer of Self‐Sustained Reactions between Thermally Coupled Reactive Material Elements

System engineering requires the implementation of assembly methods allowing the formation of functional elements according to a desired system design. This is possible by joining prefabricated elements on a desired place in the system or by forming functional materials at wanted locations. Both approaches need temperature treatment. A typical system in part consists of materials restricting the use of annealing procedures above 300 °C. For this reason, higher‐temperature operations have to be localized to the point of use and transferred to the next reactive element. A further requirement is the reduction of the thermal budget of the localized joining process implementing ultrashort heat treatment operations. Reactive metallic multilayer offers the combined possibility of implementing a localized heat source and the formation of a functional intermetallic alloy. The article demonstrates the feasibility of a heat and reaction transfer chain in a topological structured pattern consisting of localized reactive multilayer materials under conditions of their gasless combustion. For the used Ni/Al multilayer material system, the critical (obstacle thickness) dimensions for the reaction and heat transfer are determined using a high‐speed camera and pyrometer measurements.

Reactive spontaneous infiltration and spreading wetting of graphite by Cu–aTi (a = 17, 34, 68 at. %) alloys at 1100 °C

Alloying with reactive elements, such as Ti, enhances the ability of Cu melts to wet graphite. However, our understanding of the reactive wetting and kinetic mechanisms of the Cu–aTi/C system at high temperatures is still controversial. The reactive spontaneous infiltration (RSI) of Cu–aTi alloys (a = 17, 34, 68 at. %) into porous graphite and the spreading wetting (SW) on dense pyrolytic graphite were examined to elucidate the effect of the Ti content on the RSI and SW mechanisms and kinetics. The reactive wetting behaviors were investigated using a modified sessile drop method, and the interfacial microstructures, elemental distributions, and phase compositions of samples were characterized using instrumental techniques. With increasing Ti content, TiCx became depleted in carbon and experienced a morphology change. The mechanisms of RSI and SW were controlled by the synergistic effects of Ti content and TiCx. By fitting the time-dependent variation of the relevant parameters (contact angle, spreading radius, infiltration volume, and infiltration depth) for the two substrates at the same Cu–aTi alloy content using reaction- and diffusion-limited models in the reactive wetting system, we found that the kinetics of these two processes were controlled by similar mechanisms.

Harmonic modelling and control of dual active bridge converter for DC microgrid applications

Due to the intermittent power availability from renewable sources, the bidirectional DC-DC converter (BDC) must integrate with the energy storage system for bidirectional power flow. Among many BDCs, the Dual Active Bridge (DAB) converter is the most promising because of the system's power handling capacity and efficiency. DAB bidirectional DC-DC converter is a topology with the advantages of a decreased number of devices, soft-switching commutations, low cost, and high efficiency. This work describes the guidelines for designing a DAB converter for small DC microgrid applications. It is shown that the judicial selection of reactive elements leads to soft switching for all the switches in the converter in varying load conditions. A guideline for the controller design is given and the operations are validated through the simulation. A harmonic modelling technique has been implemented to model the DAB converter based on an efficient closed-loop regulator. A solar PV system has also been implemented here with a SEPIC converter that is used as an interfacing element between the PV system and the load bus. At last, a DC Microgrid is simulated in a PSIM environment to showcase its various modes of operation. It is shown that the battery bank can support variable loads independently through the DAB converter. In inadequate solar power generation, load power demand is shared between the battery and PV system. In case of deep discharge of the battery, the PV system can charge the battery through a DAB converter.

Microstructure evolution and oxidation resistance properties of oxide dispersion strengthened FeCrAl alloys at 1100 °C

Oxide dispersion strengthened (ODS) FeCrAl alloys were prepared by mechanical alloying (MA) and spark plasma sintering (SPS) technology. To reveal the high temperature oxidation properties, ODS FeCrAl alloys were exposed to dry air for various times (1h, 4h, 10h, 20h, 45h, 70h, and 100h) at 1100 °C to investigate the microstructure evolution. The results illustrated that a flat and adherent alumina scale was gradually thickened on the alloy substrate with the increase of the oxidation time. In particular, it was observed that large-size reactive element (RE) oxides were inclined to be associated with cavities close to the gas interface and these cavities were progressive evolution to be larger-size pores with longer exposure time, while tiny RE oxides were not dispersed with cavities after 100h oxidation. In addition, α-Al2O3 with a double-scale structure were mainly composed of inner columnar grains and outer equiaxed grains, as well, the growth of α-Al2O3 scales illustrated that the oxidation rate decreased with oxidation reaction proceeding. For one thing, Ti segregation along grain boundaries (GBs) near the gas interface decreased the outward diffusion of the Al ions to weaken the oxidation rate. Furthermore, the gradual coarsening of columnar grains near the alloy substrate implied a longer diffusion path of O atoms, thereby accounting for slower oxidation process. To sum up, ODS FeCrAl alloys with thinner oxide thickness demonstrated the superior oxidation resistance than other materials, which would make it one of the promising candidate structural materials applicated in accident-tolerant fuel (ATF) cladding materials.

Phosphorus: Chronicles of the epistemology of a vital element.

It was in the philosopher's stone quest that the alchemist Hennig Brand isolated chemiluminescent white phosphorus (P), Greek for "light bearer", from urine in 1669. By 1771 phosphorus was isolated from bone, and in 1777 it was identified by Antoine Lavoisier as a highly reactive element that exists predominantly in nature as ionic phosphate (PO43-) and in solution as phosphoric acid (H3PO4). Early 20th century studies revealed phosphorylated biomolecules as essential components of replicative nuclear material (RNA, DNA), a metabolic source of energy (ATP), and structural components of cellular membrane (phospholipid bilayer). Life on earth began as organophosphates of a self-replicating RNA that evolved into DNA and acquired a membrane to form the original eukaryotes, which eventually joined to form multicellular organisms of the deep sea. Tissue mineralization during transition from the ocean to land generated the endoskeleton, the largest phosphorus stores of evolving vertebrates. Subsequent studies of phosphate homeostasis elucidated its complex regulatory system based on the interaction of the kidney, small intestine, bone, and parathyroid glands, orchestrated by hormones (PTH, calcitriol, FGF23, Klotho), and carried out by phosphate-specific transporters (SLC34 and SLC20 families) all to ensure adequate phosphate for survival and health. Paradoxically, kidney replacement therapy in the 1970s, by prolonging the lives of millions of individuals with kidney failure, revealed the hazards of phosphorus excess. "Phosphorus the light bearer" has become in the eyes of many nephrologists "Phosphorus the cardiovascular toxin".

Review of the sources and behaviors of plutonium isotopes in the atmosphere and ocean

Plutonium, as well as fission products such as 137Cs, had been released into the earth environment in 1945 after the first atmospheric nuclear explosion of plutonium bomb in the desert of New Mexico (USA, July 16) and later over Nagasaki (August 9), followed then by many other explosions. Thus, plutonium cycling in the atmosphere and ocean has become a major public concern as a result of the radiological and chemical toxicity of plutonium. However, plutonium isotopes and 137Cs are important transient tracers of biogeochemical and physical processes in the environment, respectively. In this review, we show that both physical and chemical approaches are needed to comprehensively understand the behaviors of plutonium in the atmosphere and ocean. In the atmosphere, plutonium and 137Cs attach with aerosols; thus, plutonium moves according to physical and chemical processes in connection with aerosols; however, since plutonium is a chemically reactive element, its behavior in an aqueous environment is more complicated, because biogeochemical regulatory factors, in addition to geophysical regulatory factors, must be considered. Meanwhile, 137Cs is chemically inert in aqueous environments. Therefore, the biogeochemical characteristics of plutonium can be elucidated through a comparison with those of 137Cs, which show conservative properties and moves according to physical processes. Finally, we suggest that monitoring of both plutonium and 137Cs can help elucidate geophysical and biogeochemical changes from climate changes.