Strong explosive eruptions of volcanoes throw out mixtures of gases and ash from high-pressure underground reservoirs. Investigating these subsurface reservoirs may help to forecast and characterize ...an eruption. In this study, we compare seismic tomography results with remote sensing and petrology data to identify deep and subaerial manifestations of pre-eruptive processes at Bezymianny volcano in Kamchatka shortly before its violent explosion on December 20, 2017. Based on camera networks we identify precursory rockfalls, and based on satellite radar data we find pre-eruptive summit inflation. Our seismic network recorded the P and S wave data from over 500 local earthquakes used to invert for a 3D seismic velocity distribution beneath Bezymianny illuminating its eruptive state days before the eruption. The derived tomography model, in conjunction with the presence of the high-temperature-stable SiO
polymorph Tridymite in juvenile rock samples , allowed us to infer the coexistence of magma and gas reservoirs revealed as anomalies of low (1.5) and high (2.0) Vp/Vs ratios, respectively, located at depths of 2-3 km and only 2 km apart. The reservoirs both control the current eruptive activity: while the magma reservoir is responsible for episodic dome growth and lava flow emplacements, the spatially separated gas reservoir may control short but powerful explosive eruptions of Bezymianny.
Interspecific differences in arsenic bioaccumulation and organ distribution (muscle, liver, kidney and gills) in three predator fish (creole perch, rainbow trout and brown trout) from a Patagonian ...lake impacted by volcanic eruptions were studied. Arsenic in fish organs were compared analyzing: 1) temporal (before and after volcanic eruption) and spatial (near and far from the volcano) influence of Puyehue-Cordón Caulle volcanic complex activity on arsenic concentrations; 2) the influence of growth (as total length), organ type and their interactions over arsenic accumulation; and 3) arsenic speciation and total arsenic relationship with carbon to nitrogen ratios (C:N), as a proxy of lipid presence, in fish muscle. In general, total arsenic concentrations in creole perch organs were 2–7 times higher than those recorded in the corresponding organs of salmonids. Arsenic was preferentially accumulated in liver and kidney in the three fish species. The influence of the volcanic activity over arsenic concentrations was more evident in creole perch: organs from creole perch captured closest to the volcano exhibited higher arsenic concentrations. Temporal variations were not so consistent. No clear relationship between arsenic and fish length was observed. Positive and linear relationship between arsenic in all pair of organs was found in creole perch, while rainbow trout showed a quadratic relationship between muscle and the remaining organs, indicating different arsenic assimilation-elimination relationships between organs and fish. The arsenic liver:muscle ratio in the three fish species was greater than 1, suggesting some level of arsenic stress. Arsenobetaine (AB) and dimethylarsinic acid (DMA) were the dominant arsenic species in muscle of these fish, having creole perch 3–4 times higher AB than rainbow trout. A positive relationship between C:N ratio and total arsenic concentrations was found, with higher C:N in creole perchs near the volcano. In terms of food safety, no inorganic arsenic compound were detected, therefore arsenic levels in fish from Lake Nahuel Huapi does not represent any health risk to consumers.
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•Arsenic concentration in four tissues from three predator fish were compared.•Concentrations were higher in benthivorous fish tissues and near the volcanic source.•Arsenic concentrations were higher in liver and kidney.•Only arsenobetaine and dimethylarsinic acid were detected in fish muscle.•C:N ratios of fish were positively related to arsenic concentrations.
Previous literature on natech (Natural hazard-triggered TECHnological) disasters argue prevailing difficulties in establishing collective response and sharing common knowledge amongst different and a ...variety of stakeholders. We aim to describe such challenges using a case study and examine the relationship amongst the actors. Our case study focused on the 2018 Mt. Anak Krakatau eruption and the tsunami triggered by it. In this disaster, one of the largest industrial zones in Indonesia was partially affected. Our study largely explains the results based on some series of discussions with private companies and representatives of the residents collected in 2019 (from February to July). We also referred to the publicly available information, which relevant agencies in the Government of Indonesia issued. Although there were no physical damages in the factories and no causalities, staff in many facilities were worried about the situation and the surrounding residents were also scared how things would be going. The residents were not able to behave in collectively organized manner, because they faced with a lack of the synthesized and coordinated information and instructions. The residents were fully aware of the risk of natech disaster, but such awareness was not necessarily connected with reasonable risk perception and organized behaviours. Relevant organizations complied with their own protocols, but it did not necessarily bring better consequences. The meteorological agency disseminated information in their limited capacity. The volcano monitoring agency paid the limited focus on the volcano and its adjacent sea area. The national and local disaster management agencies tried to integrate technical information, but it took time. The companies carefully gathered information, but their priorities initially went to their internal response, including taking care of the families of their employees. These findings indicate that efforts were done in the right course separately and it is hard to achieve harmonized response under great uncertainty during a crisis.
We consider the problem of memory consumption by a real-time GPU-accelerated graphical application. A history of a resource is defined for a particular frame to be the final contents of such a ...resource at the end of the previous frame. When organizing a graphical application using a frame rendering graph approach, it makes sense to implement automatic serving of resource history read requests of nodes. In absence of history resource requests, allocating resources for a fixed frame graph is the classic problem of dynamic storage allocation (DSA). In this paper, we formulate a generalization of DSA that enables memory reuse for resources with history requests and provide a practical approximate algorithm for solving it.
The nitrogen reduction reaction was investigated on the surfaces of 18 different stable transition metal sulfides using density functional theory calculations. YS, ScS, and ZrS were modeled in the ...rocksalt structure with the (1 0 0) facet; TiS, VS, CrS, NbS, NiS, and FeS in NiAs‐type structure with the (1 1 1) facet; and MnS2, CoS2, IrS2, CuS2, OsS2, FeS2, RuS2, RhS2, and NiS2 in pyrite structure for both the (1 0 0) and (1 1 1) orientations. As the first step towards determination of sulfides that are less prone to hydrogen evolution, the competition between adsorption of NNH and H (for the associative mechanism), and between adsorption of N and H (for the dissociative mechanism) on these surfaces was considered. The catalytic activity through both the associative and dissociative mechanisms was explored and the overpotential required for electrochemical ammonia formation is reported. The scaling relations and volcano plots were constructed with free energy of adsorption of NNH or N on the surface as the descriptor. RuS2 was observed as the most active sulfide that could catalyze nitrogen reduction to ammonia at potentials around −0.3 V through the associative mechanism. NbS, CrS, TiS, and VS are also promising candidates for both the associative and dissociative mechanisms with overpotentials for nitrogen reduction around 0.7–1.1 V.
Artificially natural: Density functional theory is used to evaluate electrocatalytic synthesis of ammonia at ambient conditions on the surface of transition metal sulfides as cathode catalyst. The proposed catalysts, inspired by the nature and following the nitrogenase mechanism, can be a promising alternative for CO2‐free, decentralized, and sustainable production of fertilizers.
Abstract
Dominica, one of the most magmatically active islands of the Lesser Antilles through its four active volcanoes, is likely host under its central part, below Morne Trois Pitons–Micotrin, to a ...well-established transcrustal mush system. Pre-eruptive spatiotemporal magma dynamics are examined for five, explosive, pumiceous eruptions of this volcano in the last 24 kyrs through a combined Crystal System Analysis and intracrystalline Fe–Mg interdiffusion timescales modelling approaches. Before all eruptions, two magmatic environments of close compositions have interacted. These interactions began ~ 10–30 years prior to the four smaller of these eruptions, with more sustained mixing in the last decade, accelerated in the last 2 years. This contrasts with the largest pumiceous eruption, involving deeper magmas, with magma interaction starting over roughly a century but with various patterns. This suggests a possibility that increasing reactivation signals could be registered at the surface some years before future eruptions, having significant implications for volcanic risk mitigation.
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•Ultrathin TiO2 shell was coated on chalcogenide nanorod as a protecting layer.•The synthesis relies on kinetic control for layer-by-layer deposition of TiO2.•The heterostructure ...enables superior activity and stability of solar H2 evolution.•Charge transfer is controlled by type-II band alignment and tunneling effect.
It has been a subject of intensive research on avoiding photocorrosion of sulfide photocatalysts while retaining their activity for visible-light-driven photocatalysis. Herein, using Cd0.9Zn0.1S (CZS) nanorod as an example, we report an effective strategy based upon conformal coating of an ultrathin pinhole-free TiO2 shell, with controllable thickness from 2 to 7 nm, on the nanorod as protecting layer. The synthesis relies on the use of a syringe pump for kinetic control, by which, TiO2 can grow on the surface of CZS in a layer-by-layer mode. The core–shell heterostructures were found with excellent photocatalytic performance toward solar hydrogen production from a Na2S-Na2SO3 aqueous solution. The reaction can stably proceed for 200 h without notable decay of the hydrogen evolution rate. A volcano-type relationship between the mass activity and the shell thickness was gained either in the presence of a cocatalyst or not. The heterostructure with a shell thickness of 2 nm presented the highest H2-evolution activity with a quantum efficiency of 19%. However, the one with a shell thickness of 7 nm, instead, was found to be more active, with a quantum efficiency reaching 44%, when 1 wt% NiSx cocatalyst was introduced. It is believed that photogenerated electrons transfer from CZS to TiO2, while the holes vanish via quantum-tunneling-induced recombination with the electrons. This work suggests that sulfide photocatalysts with desirable efficiency and corrosion resistance could be achieved by introducing conformal atomic TiO2 layers.
Pyroclastic density currents (PDCs) are among the most hazardous of all volcanic processes in terms of high speeds and unpredictable extent. While concentrated PDCs are usually topographically ...confined, the dilute counterpart (ash cloud) is able to overrun topographic barriers, with unexpected trajectories posing a high risk for human settlements around the volcano. Here, for the first time, the temperature of an ash could, for a PDC originated during the 11 July, 2015 Volcán de Colima eruption, is determined, without pre-installed instruments, based on the degree of charcoaling of trees affected by the ash cloud. Temperature estimations were performed using Reflectance analysis and microtomography images processing of pine wood charred fragments. The combination of these two independent and well-established methods to organic matter charred in a volcanic environment constitutes a pioneering attempt for the indirect temperature estimation of dilute pyroclastic density currents (PDCs). Charcoal fragments were sampled at different heights along tree trunks outstanding from the PDC deposit. Both the temperatures obtained from charcoal analyses (reflectance and microtomography) and observation of damages to the tree trunks allowed to distinguish: (i) a lower Zone A, which extends 150-180 cm above the top of the PDC deposit, where trunks show peeled bark and multiple lithic impacts; temperature values are equal or slightly higher than the underlying deposit for the entire length of the valley; (ii) an upper Zone B, developed above 150-180 cm from the top of the PDC deposit, where trees are only burned without any block impact marks; temperature estimations for Zone B are comparable with the PDC deposit temperature range from proximal to distal areas. The temperature data indicate that the 11 July, 2015 Colima PDC event, the ash cloud was always thermally coupled with the under-running concentrated flow for the entire length of the ravine, explaining the observed strong vertical uplift of the ash cloud and the substantial absence of ash cloud detachments along flow. A corollary of our study is that, should a detachment have occurred, the ash cloud surge would have had initial temperatures as high as the one carried by the high concentration part of the PDC. A major outcome of our study is that the temperature estimation of ash clouds bears important implication in terms of hazard assessment for pyroclastic density currents along narrow valleys that usually cut the steep slopes of stratovolcanoes.
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