Abstract
The process of sulfide oxidation in acid sulfate soils (ASS) is complex, involving the formation of numerous oxidation products. In this study the sulfide oxidation process was examined in 2 ASS materials over a period of 36 days using laboratory incubation experiments. Both ASS materials experienced substantial sulfide oxidation and acidification during incubation. The oxidation of pyrite was the primary cause of acidification in these ASS materials. Although a decrease in magnetic susceptibility (χ) over the initial 4 days of incubation suggested the rapid oxidation of ferromagnetic iron monosulfide greigite (Fe3S4), the total acid volatile sulfur (S AV) fraction increased in concentration by an order of magnitude over the initial 8 days of incubation. Oxygen (O2) concentration profiles indicated the presence of anoxic conditions in the centre of the incubating materials even after 16 days of exposure to the atmosphere enabling S AV formation to occur. The oxidation of the SAV fraction did not result in substantial acidification. A large proportion of the water-soluble iron released by sulfide oxidation was precipitated as iron oxides and hydroxides. Sulfate (SO42-) was the dominant sulfur species produced from sulfide oxidation in both ASS materials, although water-soluble SO42- was a poor indicator of the extent of sulfide oxidation. The sulfoxyanion intermediates, thiosulfate (S 2O32-) and tetrathionate (S4O 62-), were detected only in the early stages of incubation, with minimal amounts being detected after the initial 4 days. The relative abundance of these 2 intermediate sulfur species appeared to be dependent on the soil pH, with S4O62- dominating S2O32- in the more acidic ASS material (i.e. pH <6) as has been observed in previous studies. The diminishing presence of sulfoxyanion intermediates as oxidation progressed was indicative that ferric ion (Fe3+) and bacterial catalysis were driving the oxidation processes. While these sulfoxyanion intermediates only constituted a small percentage of the reduced inorganic sulfur (RIS) fraction, they accounted for up to 9.3% of the total soluble sulfur fraction. Elemental sulfur (S0) was not an important sulfide oxidation product in the ASS materials examined in this study.
| Original language | English |
|---|---|
| Pages (from-to) | 449-458 |
| Number of pages | 10 |
| Journal | Australian Journal of Soil Research |
| Volume | 42 |
| Issue number | 4 |
| DOIs | |
| Publication status | Published - 2004 |
| Externally published | Yes |
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The process of sulfide oxidation in some acid sulfate soil materials. / Ward, N. J.; Sullivan, L. A.; Fyfe, D. M.; Bush, R. T.; Ferguson, A. J.P.
In: Australian Journal of Soil Research, Vol. 42, No. 4, 2004, p. 449-458.Research output: Contribution to journal › Article
TY - JOUR
T1 - The process of sulfide oxidation in some acid sulfate soil materials
AU - Ward, N. J.
AU - Sullivan, L. A.
AU - Fyfe, D. M.
AU - Bush, R. T.
AU - Ferguson, A. J.P.
PY - 2004
Y1 - 2004
N2 - The process of sulfide oxidation in acid sulfate soils (ASS) is complex, involving the formation of numerous oxidation products. In this study the sulfide oxidation process was examined in 2 ASS materials over a period of 36 days using laboratory incubation experiments. Both ASS materials experienced substantial sulfide oxidation and acidification during incubation. The oxidation of pyrite was the primary cause of acidification in these ASS materials. Although a decrease in magnetic susceptibility (χ) over the initial 4 days of incubation suggested the rapid oxidation of ferromagnetic iron monosulfide greigite (Fe3S4), the total acid volatile sulfur (S AV) fraction increased in concentration by an order of magnitude over the initial 8 days of incubation. Oxygen (O2) concentration profiles indicated the presence of anoxic conditions in the centre of the incubating materials even after 16 days of exposure to the atmosphere enabling S AV formation to occur. The oxidation of the SAV fraction did not result in substantial acidification. A large proportion of the water-soluble iron released by sulfide oxidation was precipitated as iron oxides and hydroxides. Sulfate (SO42-) was the dominant sulfur species produced from sulfide oxidation in both ASS materials, although water-soluble SO42- was a poor indicator of the extent of sulfide oxidation. The sulfoxyanion intermediates, thiosulfate (S 2O32-) and tetrathionate (S4O 62-), were detected only in the early stages of incubation, with minimal amounts being detected after the initial 4 days. The relative abundance of these 2 intermediate sulfur species appeared to be dependent on the soil pH, with S4O62- dominating S2O32- in the more acidic ASS material (i.e. pH <6) as has been observed in previous studies. The diminishing presence of sulfoxyanion intermediates as oxidation progressed was indicative that ferric ion (Fe3+) and bacterial catalysis were driving the oxidation processes. While these sulfoxyanion intermediates only constituted a small percentage of the reduced inorganic sulfur (RIS) fraction, they accounted for up to 9.3% of the total soluble sulfur fraction. Elemental sulfur (S0) was not an important sulfide oxidation product in the ASS materials examined in this study.
AB - The process of sulfide oxidation in acid sulfate soils (ASS) is complex, involving the formation of numerous oxidation products. In this study the sulfide oxidation process was examined in 2 ASS materials over a period of 36 days using laboratory incubation experiments. Both ASS materials experienced substantial sulfide oxidation and acidification during incubation. The oxidation of pyrite was the primary cause of acidification in these ASS materials. Although a decrease in magnetic susceptibility (χ) over the initial 4 days of incubation suggested the rapid oxidation of ferromagnetic iron monosulfide greigite (Fe3S4), the total acid volatile sulfur (S AV) fraction increased in concentration by an order of magnitude over the initial 8 days of incubation. Oxygen (O2) concentration profiles indicated the presence of anoxic conditions in the centre of the incubating materials even after 16 days of exposure to the atmosphere enabling S AV formation to occur. The oxidation of the SAV fraction did not result in substantial acidification. A large proportion of the water-soluble iron released by sulfide oxidation was precipitated as iron oxides and hydroxides. Sulfate (SO42-) was the dominant sulfur species produced from sulfide oxidation in both ASS materials, although water-soluble SO42- was a poor indicator of the extent of sulfide oxidation. The sulfoxyanion intermediates, thiosulfate (S 2O32-) and tetrathionate (S4O 62-), were detected only in the early stages of incubation, with minimal amounts being detected after the initial 4 days. The relative abundance of these 2 intermediate sulfur species appeared to be dependent on the soil pH, with S4O62- dominating S2O32- in the more acidic ASS material (i.e. pH <6) as has been observed in previous studies. The diminishing presence of sulfoxyanion intermediates as oxidation progressed was indicative that ferric ion (Fe3+) and bacterial catalysis were driving the oxidation processes. While these sulfoxyanion intermediates only constituted a small percentage of the reduced inorganic sulfur (RIS) fraction, they accounted for up to 9.3% of the total soluble sulfur fraction. Elemental sulfur (S0) was not an important sulfide oxidation product in the ASS materials examined in this study.
KW - Acid volatile sulfur
KW - Acidification
KW - Chromium reducible sulfur
KW - Pyrite oxidation
KW - Soil incubation
KW - Tetrathionate
KW - Thiosulfate
UR - http://www.scopus.com/inward/record.url?scp=3242696372&partnerID=8YFLogxK
U2 - 10.1071/SR03135
DO - 10.1071/SR03135
M3 - Article
VL - 42
SP - 449
EP - 458
JO - Australian Journal of Soil Research
JF - Australian Journal of Soil Research
SN - 0004-9573
IS - 4
ER -