The acid precipitates have been acidyfying soil. The acidification can make aluminium in soils dissolve in hydrosphere such as soil water, groundwater, river water, lake water etc., of the buffer capacity for acid exceeds a certain limit. When present in high amount, aqua aluminium ion exhibits toxic effects against plants. The species that have generally been considered more toxic are the monomers such as Al(H_2O)_6^<3+>, Al(H_2O)_5OH^<2+> and Al(H_2O)_4(OH)_2^+. However, aluminium complexes with organic ligands are less phtotoxic than the aquaaluminium ion and its hydrolytic products. Therefore, a detailed understanding of the aluminium binding properties of organic ligands has particularimportance for umderstanding the phytotoxicity of aluminium.
In this study, the interaction between aluminium ion and some organic ligands (iminodiacetic acid, quinolic acid, tiron, salicylic acid, phthalic acid, chelex-100 and Bio-Rad cation exchange resins) ware investigated by ^<13>C and ^<27>Al NMR.It was found that the complex formation for aluminium ion with the organic ligands under acidic conditions strongly depended on the chelate effect. In other words, monodatate complexes were not formed but chelate complexes were preferably formed. Moreover, the stability of the chelate complexes was in order 5>6>7 membered rings.