Estudio de la adsorción de Cu y Zn en andosoles de las Islas Canarias. II

Abstract

A comparative study of the curves of adsorption of Cu and Zn (surface horizons) was carried out on 13 andosoil profiles of the Canary Islands. The adsorption of Cu and Zn, as a function of the depth of the profile, was studied; the maximum capacity of adsorption of each horizon being calculated in two ways: one by blocking previously with KCL 1N, and the other without using the KCL 1N splutioon. The different factors which could affect these adsorptions were also studied. It was found that the shape of the curves, and the values of maximum adsorption were very similar within cach of the different groups of andosoils in the study. When the different groups of andosoils are compared great differences appcar, especially in the younger soils (vitrandepts) as against the rest of the groups, there being observed, in general, a decreased in the maximum values of adsortion, on passing from yhe younger to the older soils. We found that, in general, the adsorption of Cu and Zn decreases with the depth of the profile. The values of adsorption of Cu and Zn are always higher in the case of the samples not treated with KCl 1N. We found from the statistical study, carried out on relating the adsorption of Cu and Zn with other properties of the soil (% total carbon, % humic acids, % clays, % amorphous oxides of the Fe and Al, and the total capacity of exchange) that: The organic material conditions, to a certain degres, the adsorption of Cu and Zn. The lack of correlation between the % of clay and the adsorption of Cu and Zn, indicates to us the heterogeneity in the composition of this fraction. The significant correlations between the total capacity of cationic exchange, and the values of adsorption of Cu and Zn indicate a posible cationic exchange by means of which the Cu and Zn is retained in some positions of exchange corresponding to the measurements for the capacit6y of cationic exchange. A significant correlation was found on relating the values of the adsorption of Cu and Zn, which suggests to us the existence of same analogous mechanisms of adsorption for both cations, although acting more intensely on the Cu.