Soil/ Organic Matter Al/Mining Industry Alkaline Accumulation pH > 7 Al 3+ + H 2 O Al(OH) 2+ + H + Short, thick roots Rhyzotoxicity Phytotoxicity Crops & Plants Forests -yellowing of needles -possible death Accumulation Adsorption -neurotoxicity -embryotoxicity Food & Water consumption Water sources Oceans Lakes Aquifers Neuorotoxcity embryotoxicity Aluminum Cycle weathering Parent Material Al-silicates Nonsilicates feldspar gibbsite (Al(OH) 3 mica variscite AlPO 4 * 2H 2 O kaolines basaluminite bound Al Plant Available Al Al 3+ AlOH 2+ Al(OH) 2 + Al(OH) 4 - Al-organic chelates Al 13 polymers References Bradford, 2000 Acid Rain Acidification/Acid Hydrolysis pH < 5.5 Alum (AlPO 4 ) Water Purification Humans Animals Agriculture Poor management Plant loss Accum. & adsoprtion

More on Aluminum Forms taken up by plants Mobility in Soil Toxic Forms No deficiency symptoms Toxicity symptoms in plants Toxicity in humans Toxicity in animals Aluminum as a nutrient pH and Al availability Soluble Al species Hydrolysis Reactions Precipitated Forms Anions that ameliorate toxicity References

Al 3+ Al(OH) 2+ Forms taken up by plants

Mass flow at low pH (< 5.5) Otherwise immobile in soil Form taken up by plants

Al 3+, aluminum hydroxides A 13 hydroxy-polymer Toxic Forms

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. Toxicity symptoms of plants

- Neurotoxicity - Impaired motor functions - Possible aggravation of Alzheimer disease and parkinsonism Toxicity in humans

- 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. Toxicity in animals

- Very low Al levels benefit some plants: tea some hydrophytes ferns azaleas rhododendrons - Otherwise need for Al is unknown Aluminum as a nutrient in plants

- Availability of inorganic complexes of Al is greatest at low pH (< 5.5) - Organic complexes of Al are released at high pH (> 7.0) Effects of pH on availability

Al 3+ 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 Soluble species

Al 3+ + H 2 O AL(OH) 2+ + H 2 O Al(OH) 2+ + OH - Al(OH) 2 + Al(OH) OH - Al(OH) 3 + H + Hydrolysis Reactions

AlPO 4 Al 2 SiO 5 Al(OH) 3 Al 2 (OH) 6 (gibbsite) Precipitant forms

PO 4 3- F - SO 4 2- hydroxides organic carboxylates Amelioration anions

References: Bertsch, P.M., and Bloom, P.R., 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 The Nature and Properties of Soil. 11 th Edition. Prentice Hall. Upper Saddle River, New Jersey. Carver, B.F. and J.D. Ownby Acid soil tolerance in wheat. In Adv. Agron. 54: Hargrove, W.L The solubility of aluminum-organic matter and its implication in plant uptake of aluminum. Soil Sci. 142:

Lewis, T.E. (Editor) Environmental chemistry and toxicity of aluminum. 1989, Lewis Publishers, Inc., 344 P. Sparling, D.W. and Lowe, T.P Environmental hazards of aluminum to plants, invertebrates, fish and wildlife. Rev. Environ. Contam. Toxicol., 145: Srivastava, P.C. and U.C. Gupta Trace Elements in Crop Science. Science Publishers, Inc. Lebanon,New Hampshire. Strid, H 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