Relation between process of oxidation of sulfur compounds and water content in a coastal muddy soil.

Research Project

Project/Area Number	02660238
Research Category	Grant-in-Aid for General Scientific Research (C)
Allocation Type	Single-year Grants
Research Field	農業土木
Research Institution	Okayama University
Principal Investigator	ADACHI Tadashi Okayama University, Faculty of Agric., Professor., 農学部, 教授 (20012007)
Co-Investigator(Kenkyū-buntansha)	天谷孝夫岡山大学, 農学部, 助教授 (80033265)
Project Period (FY)	1990 – 1991
Project Status	Completed (Fiscal Year 1991)
Budget Amount *help	¥1,900,000 (Direct Cost: ¥1,900,000) Fiscal Year 1991: ¥300,000 (Direct Cost: ¥300,000) Fiscal Year 1990: ¥1,600,000 (Direct Cost: ¥1,600,000)
Keywords	Acid sulfate soil / Muddy soil / Sulfur compound / Soil microorganism / Soil pH / Water content (pF) / 海成粘土 / 乾燥 / 土壌水分
Research Abstract	The relation between the process of oxidation of sulfur compounds and the water content(water moisture suction)in a coastal muddy soil was examined. The concentration of sulfuric ions increased with the progressing of oxidation of sulfur compounds containing in pyrite etc. and consequently the soil pH decreased in the coastal muddy soil. The treatment of salt removal enhanced the activity of microorganisms participating sulfur oxidation and formation of sulfuric ions. Actually, the soil pH decrease was occurred more greatly in the soil containing lower salt concentration. In spite of the difference of the soil pF values, the soil pH decreased from 7.6 to 3.0 - 4.0, after two years drying of the soil. Especially, the oxidation of sulfur compounds occurred at the pF values of 4.0 to 4.4 and the lowest pH was observed at the pF 2.8. Accordingly, we concluded that the decrease of soil pH in a coastal muddy soil was mainly occurred by microorganisms which oxidize sulfur compounds under the condition of higher-water than pF 3.0.