Soil/

1
Aluminum Cycle
References
Acid Rain
Al/Mining Industry
Parent Material Al-silicates
Nonsilicates feldspar gibbsite
(Al(OH)3 mica variscite AlPO4
2H2O kaolines basaluminite
Plant Available Al Al3 AlOH2 Al(OH)2 Al(OH)4-
Al-organic chelates Al13 polymers
Acidification/Acid Hydrolysis pH lt 5.5
Soil/ Organic Matter
Al 3 H2O Al(OH)2 H
weathering
Alkaline Accumulation pH gt 7
bound Al
Accum. adsoprtion
Water sources Oceans Lakes Aquifers
Poor management
Plant loss
Neuorotoxcity embryotoxicity
Crops Plants


Rhyzotoxicity Phytotoxicity
Accumulation Adsorption
Short, thick roots
Agriculture
Water Purification
Animals
Forests
Humans
Alum (AlPO4)
Bradford, 2000
-yellowing of needles -possible death
Food Water consumption
-neurotoxicity -embryotoxicity
2
References
More on Aluminum
Forms taken up by plants
Toxicity symptoms in plants

Hydrolysis Reactions

No deficiency symptoms
Soluble Al species
Toxicity in humans
pH and Al availability
Mobility in Soil

Aluminum as a nutrient

Precipitated Forms
Anions that ameliorate toxicity
Toxic Forms
Toxicity in animals
3
Forms taken up by plants
Al3 Al(OH)2 Al(OH)2
4
Form taken up by plants
Mass flow at low pH (lt 5.5) Otherwise immobile in
soil
5
Toxic Forms
Al3, aluminum hydroxides A13 hydroxy-polymer
6
Toxicity symptoms of plants
Phytotoxicity (monomeric Al forms) Limited root
branching and rooting depths. Browning of root
tips. Inhibited shoot growth is believed to be
a direct result of impaired root growth.
Aluminum indirectly induces nutrient deficiencies
of N, P, K, Ca, and Mo as a result of decreased
plant uptake.
Rhyzotoxicity (polymeric Al forms) Impaired
germination of seeds.
7
Toxicity in humans
- Neurotoxicity - Impaired motor functions -
Possible aggravation of Alzheimer disease and
parkinsonism
8
Toxicity in animals
- Forest die-backs in North America and
Europe - particularily red spruce, various firs,
pines, sugar maple - Al accumulator plants
are toxic to herbivores - Embryotoxicity for
oysters. - Neurotoxicity for mammals.
9
Aluminum as a nutrient in plants
- Very low Al levels benefit some plants
tea some hydrophytes
ferns azaleas
rhododendrons - Otherwise need for Al is unknown

10
Effects of pH on availability
- Availability of inorganic complexes of Al is
greatest at low pH (lt 5.5)
- Organic complexes of Al are released at high
pH (gt 7.0)
11
Soluble species
Al3 pH lt 5.5

Al(OH)2 pH 4.7 6.5 Al(OH)2 pH
6.5 8.0
Al(OH)4- pH gt 8.0

12
Hydrolysis Reactions
Al3 H2O AL(OH)2
H2O Al(OH)2 OH-
Al(OH)2 Al(OH)2 OH- Al(OH)3
H
13
Precipitant forms
AlPO4 Al2SiO5 Al(OH)3
Al2(OH)6 (gibbsite)
14
Amelioration anions
PO43- F- SO42- hydroxides organic carboxylates

15
References Bertsch, P.M., and Bloom, P.R.,
1996. Aluminum. In Methods of Soil Analysis.
Part 3, Chemical Methods, 517 550. D.L.
Sparks et al. (Eds.). Soil Science Society of
America, Inc. Madison, Wisconsin, 1996 Brady,
N.C. and R.R. Weil. 1996. The Nature and
Properties of Soil. 11th Edition. Prentice
Hall. Upper Saddle River, New Jersey.
Carver, B.F. and J.D. Ownby. 1994. Acid soil
tolerance in wheat. In Adv. Agron. 54117-173.
Hargrove, W.L. 1986. The solubility of
aluminum-organic matter and its implication in
plant uptake of aluminum. Soil Sci. 142
179-181.
16
Lewis, T.E. (Editor). 1989. Environmental
chemistry and toxicity of aluminum. 1989, Lewis
Publishers, Inc., 344 P. Sparling, D.W. and
Lowe, T.P. 1996. Environmental hazards of
aluminum to plants, invertebrates, fish and
wildlife. Rev. Environ. Contam. Toxicol., 145
1-127. Srivastava, P.C. and U.C. Gupta. 1996.
Trace Elements in Crop Science. Science
Publishers, Inc. Lebanon,New Hampshire. Strid,
H. 1996. Aluminum toxicity effects on growth and
on uptake and distribution of some mineral
nutrients in two cultivars of spring
wheat Authors Danielle Bradford (2000), Olga
Kachurina, and Alan O'Dell