Study on Surface Alteration of Silicate Minerals during Chemical Weathering
| Project/Area Number |
13680613
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Environmental dynamic analysis
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| Research Institution | National Institute for Environmental Studies |
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Principal Investigator |
SEYAMA Haruhiko National Institute for Environmental Studies, Environmental Chemistry Division, Researcher, 化学環境研究領域, 主任研究員 (40142096)
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| Co-Investigator(Kenkyū-buntansha) |
TANAKA Atsushi National Institute for Environmental Studies, Environmental Chemistry Division, Researcher, 化学環境研究領域, 主任研究員 (80171734)
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| Project Period (FY) |
2001 – 2002
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| Project Status |
Completed (Fiscal Year 2002)
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| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2002: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 2001: ¥2,200,000 (Direct Cost: ¥2,200,000)
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| Keywords | Silicate Mineral / Weathering / Acid Dissolution / XPS / SIMS / Surface Analysis |
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| Research Abstract |
To examine the dissolution mechanism of silicate minerals in acidic solution, x-ray photoelectron spectroscopy was applied to plagioclase samples (Na_<0.5>Ca_<0.5>Al_<1.5>Si_<2.5>0_8) treated with 5x10^<-2>, 5x10^<-4> or 5x 10^<-6> mol l^<-1> H_2SO_4 for 3 h, 1 day and 1 week. The atomic abundances of Na, Ca and Al relative to Si in the surface layer of acid-leached (5x10^<-2> mol l^<-1> H_2SO_4) plagioclase decreased with increasing reaction time. From the preferential leaching of Na, Ca and Al, and the chemical shifts of the Si 2s and O 1s spectra, the formation of hydrous silicon dioxide on the mineral surface was deduced. The surface chemical composition of plagioclase changed in the same manner during dissolution by H_2SO_4 at a low concentration (5x10^<-4> mol l^<-1>), although the magnitude of the decrease in surface concentrations of Na,. *a and Al was lower, suggesting the formation of a thinner altered surface laye. However, after dissolution in 5x10^<-6> mol l^<-1> H_2SO_4, the relative surface abundance of Al was slightly higher than that of the untreated sample. The depth profile of the naturally weathered biotite also showed the formation of a thin altered surface layer slightly enriched in Al and Si, and was different from that of the icid-leached biotite in the laboratory. The mechanism of chemical weathering depends on the weathering solution reacting with minerals. The surface enrichment of Al and Si may result from the depression of Al leaching (retention of aluminosilicate structure) and/or the precipitation of hydroxide containing Al and Si caused by the weathering solution with a moderate pH value.
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Report
(3 results)
Research Products
(14 results)
