Yoriko Yokoo
University of Tsukuba
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Featured researches published by Yoriko Yokoo.
Water Air and Soil Pollution | 2001
Yoriko Yokoo; Takanori Nakano; Masataka Nishikawa; Hao Quan
Aeolian particles originating from arid areas in China, termed Kosa, are considered to be a major source of non-sea-salt Ca, a dominant base cation, in acid precipitation in northeastern Asia. We extracted evaporite minerals (halite, gypsum, and carbonate) from the surface soil collected at eight desert and loess areas in northern China with water and acetic acid. Most 87Sr/86Sr ratios of the extracted fractions fell in a restricted range (0.7115 ± 0.0015) and differed from those of bulk soils and acid-insoluble minerals (0.712–0.717). The selective dissolution of the soil carbonates in the atmosphere is consistent with two facts: (1) their 87Sr/86Sr ratios are close to the maximum 87Sr/86Sr ratios of spring precipitation in Japan, when Kosa activity is marked; and (2) their mole ratios of Mg/Ca (0.15) and Sr/Ca (0.001) are almost identical to those of precipitation in China and Japan when Kosa activity is marked. The 87Sr/86Sr, Mg/Ca, and Sr/Ca ratios in the acid-soluble components can be used as indexes of Kosa aerosols in the precipitation of the northwestern Pacific.
Water Air and Soil Pollution | 2001
Takanori Nakano; Yoriko Yokoo; Ryo Anma; Junko Shindo
We investigated the vertical profile of element distributions in the soil column on a granite substrate at three sites on the island of Yakushima, a world natural heritage site in southwestern Japan, where stream acidification due to acid rain is of increasing concern. Statistical analysis shows that the elements in the granitic soil can be classified into three groups according to their mineralogical derivations: Group 1 (K, Mg, Mn, Rb, and Nb), group 2 (Fe, Ti, Zr, Cr, and Pb), and group 3 (Ca, Na, Sr, and P), which are related to the presence of K-feldspar and K-mica, Fe-Ti oxides, and plagioclase and apatite, respectively. The pattern of distribution of group-1 elements in the soil column differs slightly among the sites because of differences in the proportions of K-feldspar and K-mica, The organic surface soil is enriched in group-2 elements and shows a strong magnetic susceptibility, indicating the presence of biogenetic magnetite. At all sites, Ca and Sr are intensely depleted due to the selective dissolution of plagioclase. Ca depletion compared to the original granite reaches more than 90 % in the C horizon, resulting in a decreasing capacity for the neutralization of acid rain and an increasing contribution of atmospheric Ca to the surface soil and vegetation.
Water Air and Soil Pollution | 2001
Yoriko Yokoo; Takanori Nakano
Sequential leaching experiments using H2O, H2O2, NH4Cl, and HCl were performed on surface soils on an andesite substrate at four sites in the Kawakami mountainous area, central Japan. The solutions extracted from the dehydrated soil by H2O, H2O2, and NH4Cl have relatively constant ratios with respect to Ca, Mg, and Sr, while they have variable 87Sr/86Sr ratios depending on the site. The elemental ratios and Sr isotopes in the extracted solution are different from those of the soil minerals but identical to those of the soil solution and the plants. Sr isotopic data indicate that the residues after extraction from fine-grained minerals by NH4Cl and HCl are a mixture of acid-resistant minerals derived from bedrock and from arid areas in China. We suggest that there is a vital exchange of Sr and other cations between plants and the soil pool of exchangeable cations through the soil solution, while soil minerals, except chlorite, do not participate in the exchange reaction.
Chemical Geology | 2004
Yoriko Yokoo; Takanori Nakano; Masataka Nishikawa; Hao Quan
Atmospheric Environment | 2004
Takanori Nakano; Yoriko Yokoo; Masataka Nishikawa; Hideaki Koyanagi
Hydrological Processes | 2001
Takanori Nakano; Yoriko Yokoo; Masaru Yamanaka
Annual report of the Institute of Geoscience, the University of Tsukuba | 1996
Yoriko Yokoo; Takanori Nakano
Annual report of the Institute of Geoscience, the University of Tsukuba | 1998
Yoriko Yokoo; Takanori Nakano
Annual report of the Institute of Geoscience, the University of Tsukuba | 1996
Takanori Nakano; Yoriko Yokoo; Tadashi Tanaka
Japan Geoscience Union | 2016
Yoriko Yokoo; Syuhei Ito; Ki-Cheol Shin; Shota Kato; Takanori Nakano; Minoru Tokumasu
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National Institute of Advanced Industrial Science and Technology
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