Publications by authors named "Yoko Ohtomo"

Arsenic contamination not only complicates mineral processing but also poses environmental and health risks. To address these challenges, this research investigates the feasibility of utilizing Hyperspectral imaging combined with machine learning techniques for the identification of arsenic-containing minerals in copper ore samples, with a focus on practical application in sorting and processing operations. Through experimentation with various copper sulfide ores, Neighborhood Component Analysis (NCA) was employed to select essential wavelength bands from Hyperspectral data, subsequently used as inputs for machine learning algorithms to identify arsenic concentrations.

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In Mondulkiri province, Cambodia, artisanal gold miners dump tailings and wastewater from gold processing into a tributary of the Prek Te River. In the rainy season, heavy metal concentrations in the tributary decrease below the WHO drinking water standard levels through natural attenuation; however, this does not occur in the dry season. To further understand the natural attenuation mechanism, detailed analyses of the wastewater from tailing and tributary water, tributary sediments, waste rock, and ore minerals were undertaken in both seasons.

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Article Synopsis
  • Microbial life in subseafloor sediments is crucial for the Earth's carbon cycle, but the effects of geodynamic processes on these organisms are not well understood.
  • Drilling into a submarine mud volcano revealed that around 90% of methane found there is produced by microbes, primarily at depths of 300 to 900 meters and temperatures between 16° to 30°C.
  • Smaller populations of highly active microorganisms, specifically methanogens and acetogens, were identified, suggesting that fluid movement from subduction processes enhances microbial activity and implies that mud volcanoes may play a larger role in methane production than previously thought.
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Abiotic formation of RNA was important for the emergence of terrestrial life, but the acknowledged difficulties of generating and stabilizing ribose have often raised questions regarding how the first RNA might have formed. Previous researchers have proposed that borate could have stabilized ribose; however, the availability of borate on the early Earth has been the subject of intense debate. In order to examine whether borate was available on the early Earth, this study examined metasedimentary rocks from the Isua Supracrustal Belt.

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Geological CO2 sequestration in unmineable subsurface oil/gas fields and coal formations has been proposed as a means of reducing anthropogenic greenhouse gasses in the atmosphere. However, the feasibility of injecting CO2 into subsurface depends upon a variety of geological and economic conditions, and the ecological consequences are largely unpredictable. In this study, we developed a new flow-through-type reactor system to examine potential geophysical, geochemical and microbiological impacts associated with CO2 injection by simulating in-situ pressure (0-100 MPa) and temperature (0-70°C) conditions.

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