Potential acid sulfate soils(PASS) are drained for agriculture, resulting in the formation of active acid sulfate soils(AASS), which gradually evolve into post-active acid sulfate soils(PAASS). Various redox concentra...Potential acid sulfate soils(PASS) are drained for agriculture, resulting in the formation of active acid sulfate soils(AASS), which gradually evolve into post-active acid sulfate soils(PAASS). Various redox concentrations(precipitates, costings, and mottles) occur in these soils as a result of pedogenic processes including biological activity and effects of land management. Although several studies have determined the mineralogy and geochemistry of ASS,the mineralogy and geochemistry of redox concentrations occurring in a sequence of ASS through PASS to PAASS have not been investigated. This study examined the mineralogy and geochemistry of redox concentrations and matrices within 5 PASS, 8 AASS, and 5 PAASS in Thailand. The labile minerals were predominantly controlled by oxidation status and management inputs. The unoxidized layers of PASS, AASS, and PAASS contained pyrite and mackinawite.The oxidation of Fe sulfides caused acidification and accumulation of yellow redox concentrations of jarosite and Fe(hydr)oxides at shallow depths. As the soils became well developed, they were recognized as PAASS, and the jarosite and goethite transformed to hematite. As ASS were drained, Co, Mn, Ni, and Zn moved downward and were associated with Fe sulfides and Mn oxides in the unoxided layer. Concentrations of As, Cu, Cr, Fe, and V did not change with depth because these elements became associated with jarosite and Fe(hydr)oxides in yellow and red redox concentrations, as well as the root zone, in the partly oxidized layer of AASS and PAASS. Arsenic was associated with pyrite under reducing conditions.展开更多
基金The authors gratefully acknowledge the Royal Golden Jubilee Ph.D.Program under the Thailand Research Fund and Kasetsart University for financial support(No.PHD/0150/2552).We gratefully acknowledge assistance from Dr.Nattaporn Prakongkep from the Land Development Department,Kasetsart University,Thailand,Drs.Rathanon Jaroenchasri and Rachan Leotphayakkarat from the Department of Soil Science,Kasetsart University,Thailand,Drs.Michael Smirk and Kim Duffecy from the School of Earth and Environment,the University of Western Australia(UWA),and staff from the Centre for Microscopy,Characterisation and Analysis,UWA.
文摘Potential acid sulfate soils(PASS) are drained for agriculture, resulting in the formation of active acid sulfate soils(AASS), which gradually evolve into post-active acid sulfate soils(PAASS). Various redox concentrations(precipitates, costings, and mottles) occur in these soils as a result of pedogenic processes including biological activity and effects of land management. Although several studies have determined the mineralogy and geochemistry of ASS,the mineralogy and geochemistry of redox concentrations occurring in a sequence of ASS through PASS to PAASS have not been investigated. This study examined the mineralogy and geochemistry of redox concentrations and matrices within 5 PASS, 8 AASS, and 5 PAASS in Thailand. The labile minerals were predominantly controlled by oxidation status and management inputs. The unoxidized layers of PASS, AASS, and PAASS contained pyrite and mackinawite.The oxidation of Fe sulfides caused acidification and accumulation of yellow redox concentrations of jarosite and Fe(hydr)oxides at shallow depths. As the soils became well developed, they were recognized as PAASS, and the jarosite and goethite transformed to hematite. As ASS were drained, Co, Mn, Ni, and Zn moved downward and were associated with Fe sulfides and Mn oxides in the unoxided layer. Concentrations of As, Cu, Cr, Fe, and V did not change with depth because these elements became associated with jarosite and Fe(hydr)oxides in yellow and red redox concentrations, as well as the root zone, in the partly oxidized layer of AASS and PAASS. Arsenic was associated with pyrite under reducing conditions.
