Alteration of exchangeable cation distribution and associated chemical changes in acidifying surface mined soils

Abstract

Two mining areas of different ages, one area mined in 1972 and the other in 1977, were sampled in June and July of 1978. Twenty-five 100 cm cores were taken from each area and subdivided into 10 cm segments. Material from each segment was analyzed for pH, SO(,4)-S, and total-S, while half the total of samples from each core were analyzed for CEC, base saturation percentage, and water extractable cations. General trends show lower pH, base saturation, and total-S in the 1972 minesoil, as well as higher SO(,4)-S and water extractable cations. The variability of the data is extremely high as indicated by the coefficients of variability (CV), greater than 200% for some of the sulfur data. The effectiveness of the regression equations calculated to describe changes with depth and age is reduced by this variability, but the equations still suggest the presence of a weathered zone to the 20 cm depth in the 1977 minesoil. Calculations of the minimum sampling density required to estimate the property means range from a low of 35 samples per mining area to estimate pH within (+OR-)0.5 units to over 400 samples to estimate SO(,4)-S within (+OR-)100 ug/g soil. ....