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Soil/ Organic Matter

Aluminum Cycle. References. Acid Rain. Parent Material Al-silicates Nonsilicates feldspar gibbsite (Al(OH) 3 mica variscite AlPO 4 * 2H 2 O kaolines basaluminite. Al/Mining Industry. Plant Available Al Al 3+ AlOH 2+ Al(OH) 2 +

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Soil/ Organic Matter

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  1. Aluminum Cycle References Acid Rain Parent Material Al-silicatesNonsilicates feldspar gibbsite (Al(OH)3 mica variscite AlPO4* 2H2O kaolines basaluminite Al/Mining Industry Plant Available Al Al3+ AlOH2+ Al(OH)2+ Al(OH)4- Al-organic chelates Al13 polymers Acidification/Acid Hydrolysis pH < 5.5 Soil/ OrganicMatter Al 3+ + H2O Al(OH)2+ + H+ weathering Alkaline Accumulation pH > 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 (< 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 (< 5.5) - Organic complexes of Al are released at high pH (> 7.0)

  11. Solublespecies • Al3+ pH < 5.5 • Al(OH)2+ pH 4.7 – 6.5 • Al(OH)2+ pH 6.5 – 8.0 • Al(OH)4- pH > 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. 54:117-173. 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

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