Sulfate sorption by acid forest soils: 4. kinetics and effects of temperature and moisture1
1984
SINGH, B. R.
I investigated the kinetics of sulfate adsorption and the effects of temperature and moisture on sulfate sorption of two acid forest soils. Sulfate adsorption in both soils was time-dependent and showed an excellent fit, accounting for more than 99% of the variation, by a two-constant rate equationwhere x = adsorbed sulfate, Co = initial sulfate concentration, Ka = rate coefficient, t = time, and 1/m = constant. The average rate coefficients of sulfate adsorption over a period of 1152 h were 0.462 and 0.167 h for the iron-podzol and brown-earth soils, respectively. Thus the relative rate was faster in the iron podzol than in the brown earth. The rate of sulfate adsorption was faster initially (up to 4 h), but decreased drastically with increased time.Sulfate adsorption over a period of 1152 h in both soils showed the best fit, accounting for more than 99.9% of the variation, by a multiple-order kinetic equationwhere x and t are the same as in the rate equation, and K and n are constants.Sulfate adsorption in both soils increased over a temperature range of 4 to 24°C, but it decreased when the moisture content of the soils was raised from 5 to 100% on an oven-dry weight basis.The percentage of sulfate desorbed decreased with increase in time and temperature, but it increased with increased moisture content.These results indicate that longer contact between soil and sulfate ions and higher temperature will result in immobilization of atmospherically deposited sulfate in these soils, whereas increased moisture content will result in mobilization of sulfate and cations.
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