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Acid Sulfate Soils
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PresentationBy Narioka, H.
Acid Sulfate Soil in rice production for Negara Brunei Darussalam
in 2011
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Problem Recognition and Problem Soils
Hajime NARIOKA, Professor
Laboratory of Terrestrial Soil and Water,Division of Environmental Science and Technology, Graduate School of Bioresources, Mie University1577 Kurimamachiya-cho, Tsu-shi,Mie 514-8507, JapanPhone/Fax. +81 59 231 9574e-mail: narioka@bio.mie-u.ac.jp
Acid Sulfate Soil in rice production for Negara Brunei Darussalam
22 Feb. 2012
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Study
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5A.S.S. team
6A.S.S. field
7A.S.S. field
8Setting of groundwater observation system
9Setting of groundwater observation system
10Setting of groundwater observation system
11Pond which was affected excessively of A.S.S.
12Jarosite and crack on the surface at rice field
13Jarosite and crack on the surface of rice field
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Training items(at field investigation)
1) "Safety First"2) Existence of ASS by "watch, hear, smell, touch,
think"3) Mechanism of ASS4) Rice field structure5) Role and importance of irrigation and drainage6) Field investigation method7) Experienced soil layer structure of rice field8) Thought about "improvement of ASS problem“9) “The Team-work” and each confidence
What is the problem (soil)?
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What is the problem (soil)?
－Poor SoilsPoor soils refer to low potential soil productivity.Potential soil productivity is the maximum
productivity shown by soil that is optimum in factors for biological production, including drainage, inclination conditions, and their combination
－Problem SoilsThere are a variety of soils; some soils have
serious problems when utilized.These soils are less productive and unsuitable even
for the growth of crops because of the presence of extremely specific chemical, physical and biological properties.
Typical problem soils are peat soil, saline soils alkaline soils and acid sulfate soils.
Globally, Vertisol, Planosol, heavy clay alluvial soil, as well as strong weathering soil in the tropical zone are also considered to be problem soils.
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Important information for research:
“Topology and Soil Profiles”
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Topology
Important information
－Natural resources －Land use－Topology－Field (in situ)－Environment
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Soils
Important items－Poor Soils－Problem Soils
Exercise－Saline Soil－Acid Sulfate Soil－Peat Soil- Vertisols
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Soil Profiles
Ⅰ Ⅱ Ⅲ ⅣPeat Soil Saline Soil Saline Soil Acid Sulfate Soil
in the wood area in the hazard area21
Case of Problem Soils- Acid Sulfate Soils- Saline Soils- Vertisols
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Acid Sulfate SoilsCase of Problem Soils
Acid sulfate soils are covered 43.6% of Africa, 38.2% of Southeast Asia and 16.6% of South Asia. The area of acid sulfate soils reaches about 12 million hectares worldwide, most of which is located in tropical mangroves in Africa and Southeast Asia. The acid sulfate soils zone in Southeast Asia is considered to be potential farmland,but is not farmed because of its strongacidity.
Acid sulfate soils oxidizes when sulfate oxides in the soil are supplied oxygen due to land draining, leading to the formation of sulfuric acid and subsequent strong acidification of the soil to pH 3 or lower. 23
Saline soils are distributed in the semi-arid, arid, coastal and poor-draining zones in the world.
Definition by the U.S. Department of Agriculture (USDA)：－Electric Conductivity (ECsat; saturated extract) ≧ 4 mS/cm－Exchangeable Sodium Percentage (ESP) ＜ 15%－pH ＜ 8.5
Saline SoilsCase of Problem Soils
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VertisolsCase of Problem Soils
Black Cotton Soil (Africa and India), Regur (India), Gray and Brown Soils of Heavy Texture (Australia) etc.
This requires material with a high shrink-swell potential plus alternate wetting and drying.
Vertisols are very slowly permeable, once the cracks swell shut, and slow infiltration is a problem in irrigation.
They have a low plant-available water-holding capacity, but a relatively high total water-holding capacity. Because of their low permeability, once they havewet-up, Vertisols are good for paddy (wet) rice culture, because entrapped (diked) water does not leak away. 25
Strategies
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Strategy (1)
(Important information and items are understood and developed into the strategy)
－Investigation/Research－Administration(government policy)
－Civilian Activity(civilian productivity)
－Living Persons(human life)
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Strategy (2)1．Time scale and spatial
scale2．Topological information
(landform, coastline and water boundary)
3．Policy in the country (viewpoint to the problem)
4．Meaning of"Development, Protection and Conservation"
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Strategy (3)
(The necessary information)
－Map (soil, soil profiles, land use, vegetation, topological, etc.)
－Remote sensing, GIS etc.－Soil researcher－Professional of the Soil
Investigation－Soil Science－Soil Conservation－Consideration of
"Development, Protection and Conservation" 29
Plan Formulation forImprovement/Conservation
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Procedure for approaching
1．Policy (viewpoint to the problem)
2．Time scale and spatial scale
3．Land resources (landform, coastline and water boundary)
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Necessary information (1)
－Map (soil, soil profiles, land use, vegetation, topological, etc.)
－Remote sensing, GIS etc.
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Necessary information (2)
－Soil researcher
－Soil investigater
－Soil scientist
－Engineer
－Designer
Research forland use
1. Check point
(1)Soil properties
(2) Water condition
(3) Land classification in consideration of topography and social
Research forland use
2. Strategiesa) Drainage and dry field farming
by control of groundwaterb) Rice field production by
irrigation and flood controlc) Mixed cultivation by control of
groundwater leveld) Land condition which pyrite is
oxidized or note) Local community in regional
participationf) others
Research forland use
3. OK? or NG?Development, Conservation,Protection
※Estimation is not easy for "Peat Soil and Acid Sulfate Soil“
※Mechanism in the field of Acid Sulfate Soil is unexplained
Acid Sulfate SoilsProcess and Strategy
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Reports
1)Department of Agriculture(2008): Soils and Land Suitability of the Agricultural Development Areas, Soil Fertility Evaluation/Advisory Service in Negara Brunei Darussalam Volume 1, Contract: LTN/6/31/2003(10)
2)Department of Agriculture(2008): Soil Management in the Agricultural Development Areas, Soil Fertility Evaluation/Advisory Service in Negara Brunei Darussalam Volume 2, Contract: LTN/6/31/2003(10) 38
Soil Profiles
Ⅰ Ⅱ Ⅲ ⅣPeat Soil Saline Soil Saline Soil Acid Sulfate Soil
in the wood area in the hazard area 39
What is “ASS”?
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Acid Sulfate Soil
Characteristics
(1) Strong acidity (pH3）
(2) Oxidation of deposition below water surface or mud (local lake or sea)
(3) These are called “Acid Sulfate Soil”(ASS) by origin material
(4) There is easy to be ASS in the Geologic period
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Mangrove area
※ ASS in the world is distributed around 12,000,000ha.
※ Most of ASS area is in Mangrove area.
※ ASS area in Southeast Asia is “Potential farmland”.
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Mechanism of A.S.S.
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Why is “A.S.S.”
Generation of Acid Soil has two process.
(1)Accumulation process of sulfide
(2) Sulfuric acid process by oxidation.→Physical, Chemical
and Biological process
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Accumulation process of sulfide(1)
Process:Marine and Volcanic
Original materials:Pyrite（FeS2）
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Sulfuric acid process by oxidation(2)
※ Oxidation of Sulfide≦ pH3
↓
※ Generation of Sulfuric Acid
↓※ Pyrite（FeS2）
Chemical and BiologicalOxidation
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FeS2Pyrite
SO42- H+
Fe3+
O2FeS2+7/2O2+H2→Fe2++2SO4
2-+2H+
FeS2+2Fe3+→3Fe2++2SO0
S0
O2
化学的酸化
Fe2+1/4O2+H+→Fe3++1/2H2O微生物的酸化 (T. ferrooxidans)化学的酸化
Fe2+
Fe2+
Fe3+
2S0+3O2+2H2O→2SO42++4H+
化学的酸化
SO42- H+ Fe2+
SO42-
O2
微生物的酸化 (T. thiooxidans and T. ferrooxidans )
H+
Fe3+3H2O→Fe(OH)3+3H+加水分解
パイライト酸化の終了・土壌酸性化の停滞後，土壌の中和過程へ移行
Fe(OH)3Ferrihydrite
Fe3+
pH4加水分解・有機配位子の酸化
3Fe(OH)2++2SO4
2-→K+KFe(SO4)2(OH)6
KFe3(SO4)2(OH)6Jarosite
？
α-Fe2O3Hematite
脱水・再配列
α-FeOOHGoethite
脱水・再配列
pH≧4加水分解
加水分解？
FeSO4・7H2OMelanterite
FeSO4・4H2ORozenite
脱水
FeSO4・H2OSzomolnokite
風化
Fe2+Fe3+4(SO4)6(OH)2・20H2O
Copiapite
酸化
溶解
溶解・酸化
蒸発
2S0+12Fe3++8H2O→12Fe2++2SO42++16H+
酸化初期では重要な酸化剤
酸化初期では重要な酸化剤
FeS2Pyrite
SO42- H+
Fe3+
O2FeS2+7/2O2+H2→Fe2++2SO4
2-+2H+
FeS2+2Fe3+→3Fe2++2SO0
S0
O2
化学的酸化
Fe2+1/4O2+H+→Fe3++1/2H2O微生物的酸化 (T. ferrooxidans)化学的酸化
Fe2+
Fe2+
Fe3+
2S0+3O2+2H2O→2SO42++4H+
化学的酸化
SO42- H+ Fe2+
SO42-
O2
微生物的酸化 (T. thiooxidans and T. ferrooxidans )
H+
Fe3+3H2O→Fe(OH)3+3H+加水分解
パイライト酸化の終了・土壌酸性化の停滞後，土壌の中和過程へ移行
Fe(OH)3Ferrihydrite
Fe3+
pH4加水分解・有機配位子の酸化
3Fe(OH)2++2SO4
2-→K+KFe(SO4)2(OH)6
KFe3(SO4)2(OH)6Jarosite
？
α-Fe2O3Hematite
脱水・再配列
α-FeOOHGoethite
脱水・再配列
pH≧4加水分解
加水分解？
FeSO4・7H2OMelanterite
FeSO4・4H2ORozenite
脱水
FeSO4・H2OSzomolnokite
風化
Fe2+Fe3+4(SO4)6(OH)2・20H2O
Copiapite
酸化
溶解
溶解・酸化
蒸発
2S0+12Fe3++8H2O→12Fe2++2SO42++16H+
酸化初期では重要な酸化剤
酸化初期では重要な酸化剤
図１ パイライトの酸化と関連鉱物の生成過程概要 (参考：Nordstrom,1982および日本化学学会,1999)
Pyrite（FeS2）
Process of Oxidation
Jarosite
Pyrite
Thiobacillus ferrooxidans
Thiobacillus thiooxidans & Thiobacillus ferrooxidans
Most suitable temperature “Thiobacteria”: 15-25 ℃
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Field of A.S.S.
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Southeast Asia:Peat soil and A.S.S.
1. Peat soil, flooding and shallow groundwater level
2. Natural environments (groundwatert, soil and wildlife etc.)
3. Local economy and social
4. Farmland development (suitable land use, drainage control, suitable cultivation, suitable management etc.)
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Problems excavation of A.S.S.
1. Physical and chemical viewpoint of the soil
(1) Affected by the flood with high groundwater level
(2) Rapid subsidence of surface soil(3) Toxic organic matter for crops production(4) Surface soil is acidified when pyrite layer is
oxidized(5) Lack of inorganic fertility (artificial manure),
and disproportion of effect of fertilizer(6) Groundwater situation and soil environment
is changed(7) others 50
Problems excavation of A.S.S.
2. Environmental conservation and management
(a) Control of peat soil subsidence and groundwater flow
(b) Water control/management: drainage and irrigation
(c) Suitable cultivation system(d) Control of microbe and harmful insect(e) Evaluation of environmental influence, and
geographical investigation(f) Evaluation of social demand(g) Suitable land classification(h) others 51
Ridge/LeveeIrrigate-water
Plow-soil
Hard-pan
Subsoil
Soil layer structure (in Japan) of a typical rice field
deeper
15～20cm
10cm
Soil Hardness(Yamanaka)≧24mm
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Seasonal changes of soil surface conditions in Japan
a) well-drained in region with low rainfallb) poorly drained in region with high rainfall
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Percolation in saturated and unsaturated subsoils in Japan
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Thank you.ありがとうございました。
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