Solubility of Al, Cr, Cu and Zn in Soils from a Finnish Acid Sulphate Soil Area

Publisher Website
Google Scholar
Abstract
Soil material of 67 acid sulphate soils (A.S. soils) and 32 non-A.S. soils was collected from Ap horizons of cultivated fields at Tupos in Liminka on the northwestern coast of Finland. The soil samples were dissolved with aqua regia in order to estimate the total concentrations of Al, Cr, Cu and Zn. The labile fractions of these elements were extracted with 0.5 M ammonium acetate-0.5 M acetic acid-0.02 M Na2-EDTA (abbreviated AAAc-EDTA) at pH 4.65 and with 1 M KCl. Only 1–3% of total Al and Cr was soluble in the AAAc-EDTA solution, while as much as 20–40% of total Cu and Zn was dissolved by this extractant. Further, 1 M KCl extracted only 3–5% of Cu and Cr, about 25% of Al and 100% of Zn soluble in the AAAc-EDTA solution. The total content of the elements in the soil did not correlate with the soil pH(H2O), which ranged from 3.65 to 6.90. Instead, the negative correlation between soil pH and the quantities extracted with KCl and AAAc-EDTA was statistically highly significant, with the exception of the quantities of Cu extracted with AAAc-EDTA. Upon decreasing soil pH, the solubility of Cu and Cr was elevated relatively less than that of Al and Zn. The elevated concentrations of the easily soluble fractions of the elements in A.S. soils suggest more intense weathering in the A.S. soils than in the non-A.S. soils. The present results indicate the importance of acidification in increasing the solubility of Al, Cu, Zn and Cr in the soil.