Abstract
Chemical reactions and physical and biological processes control the adsorption of Cd and Cu by soils. Heavy metal retention by soils can decrease their bioavailability in the soil-solution system. Cd and Cu adsorption were evaluated in in-surface and subsurface horizons of eight Brazilian soils: five Oxisols, two Alfisols and one Ultisol. The maximum adsorption estimated by the linearized Langmuir equation was correlated with some soil attributes. In the surface horizon, Cd maximum adsorption was positively correlated with total CEC, specific surface area, and clay, silt, “free” Fe and “total” Al (extracted by sulfuric acid) contents, while, in the subsurface horizon, the correlation was positive with effective CEC, pH, and “amorphous” Fe contents. Maximum Cd adsorption was also negatively correlated with sand contents in surface horizons. On the other hand, in the surface horizons, maximum Cu adsorption was positively correlated with percentage of Al saturation and clay, “total” and “amorphous” Al oxides contents; in subsurface horizons, it was correlated with pH and clay and “amorphous” Al oxides contents
Highlights
(1997), oito amostras tinham acidez alta ou muito alta, notadamente o LBw, o Latossolo Vermelho distrófico (LVd) e ambos os LVAd
SILVEIRA, M.L.A. et al Energia livre de reação de adsorção de cobre em Latossolos Ácricos, Sci. Agric., Piracicaba, v
Summary
Foram coletadas amostras superficiais e subsuperficiais (na maior expressão do B) de oito solos de importância econômica, geográfica e taxonômica: Latossolo Vermelho acriférrico – LVwf (Ribeirão Preto – 21°10' S, 47°48' W, altitude 546 m); Latossolo Bruno ácrico – LBw As amostras foram secas ao ar e passadas em peneira de plástico com abertura de malha de 2,0 mm de diâmetro, para a realização das análises químicas, físicas e mineralógicas dos solos. As isotermas de adsorção foram construídas para descrever a retenção do Cd e do Cu pelos solos, relacionando-se as quantidades desses elementos adsorvidos com as concentrações nas soluções de equilíbrio. A equação linearizada de Langmuir foi utilizada para obtenção dos valores de não simulou de maneira satisfatória os valores de Admáx. (eixo x) em função da (Ceq./ Cads) (eixo y), obtendo-se uma reta com declividade igual a 1/ Admáx, da qual se pode estimar a adsorção máxima e o parâmetro 1/ K. Foram também realizadas análises de regressão linear simples entre a quantidade adsorvida dos elementos, as propriedades químicas, físicas e mineralógicas dos solos e a adsorção máxima dos metais, estimada pela equação linearizada de Langmuir
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