Determination of toxic aluminum for wheat roots by potentiometry with fluorid ion selective electrode

Avaliou-se o método potenciométrico com o eletrodo seletivo de fluoreto (ESIF) para estimar as espécies tóxicas de Al às raízes do trigo em soluções pura e de solo e em solos ácidos tratados com doses de calcário. Comparou-se Al-ESIF com o método espectrofotométrico com a solução de ferron. O crescimento das raízes diminuiu exponencialmente com o aumento de Al-ESIF, cuja técnica detectou principalmente as espécies A13+, Al(OH)2+ e Al(OH)2+. A concentração de Al-ESIF nos solos sem calcário (pH 4,0) variou de 30 a 2100 x 10-6M e diminuiu com o aumento do pH até valores não detectáveis em pH > 5,6. Al-ferron foi superior ao Al-ESIF em todos os pH estudados. Os complexos de A1 em pH > 5,6 foram reativos com ferron, mas não com F-. -Al-ESIF apresentou a melhor estimativa das espécies tóxicas de Al às raízes do trigo.A potentiometric technique with fluoride ion selective electrode (FISE) was evaluated for its ability to estimate toxic Al species for wheat root growth in pure and soil solution, and in limed and unlimed treatments of selected acid soils. Al-FISE was compared with a spectrophotometric-ferron method. Root growth decreased exponentially with increasing Al-FISE. The dominant forms of Al-ESIF was estimated by Geochem as A13+, AlOH2+, and Al(OH)2+. Al--FISE concentration in unlimed soil solution ranged from 30 to 2100 x 10-6M and decreased with increasing soil pH. Al-ferron was greater than Al-FISE for all pH studied. Above pH 5.6 Al-FISE was undetectable but Al-ferron increased in soils high in dissolved organic carbon. Al complexes above pH 5.6 was reactive with ferron but not with F- ion. Al-FISE was better predictor of the toxic Al species for wheat root growth than Al-ferron