|Budget Amount *help
¥1,000,000 (Direct Cost : ¥1,000,000)
Fiscal Year 1999 : ¥1,000,000 (Direct Cost : ¥1,000,000)
Acidification of terrestrial and aquatic environment would affect the surface chemical processes at the interface of water and sediment or soil particles. The behavior of aluminum has especially important environmental consequences. We have studied related three topics.
(1) Chemical weathering of rocks and minerals by acid :
Dissolution of elements, and resulting changes in the surface chemical composition, of rock (Japan Geological Survey Rock Standard : basalt-JB1a, feldspar-JF1, gabbro-JGb1 and dunnite-JPa1) and mineral (KィイD1-ィエD1, NaィイD1-ィエD1 and Ca-feldspar, and MgィイD1-ィエD1 and Fe-olivine) particles by 0.01 M nitric acid have been investigated. The surface chemical compositions were studied by X-ray photoelectron spectroscopy (XPS). From the rock and mineral surfaces, elements other than Si, in general, preferentially dissolved, leaving Si-enriched surface layers.
(2) Surface chemical composition of lake sediment :
Al/Si ratio in sediment particles determined by XPS varied for sedime
nts of Lake Tazawa and Kussharo where acidic river water has been introduced or flowing in. The ratio in the Lake Tazawa sediment core showed remarkable increase after the introduction of acidic river water. In the surface sediment of Lake Kussharo it related to the amount of extractable Al in the sediment, Al concentration in the surface of sediment particles thus reflects behavior of Al in lake water.
(3) Behavior of elements in the acidified water and soil environment of tea farm area :
Tea farm soils acidified under different application of nitrogen and other fertilizers, and soils under natural vegetation (control) were compared for elemental and surface chemical compositions of soil particles. The elemental distribution was governed both by soil acidification and by supply with fertilizer. For example, concentration of Ni, Co and Mn attributed to basic rocks was higher in the control soils, whereas K in the surface layer of the control soil particles was depleted as compared with those of tea farm soils although the bulk concentration did not differ much. Less