Adsorption And Desorption Of SO₄～(2-) And NO₃～- In Three Hunan Soils

To Study the characteristics of adsorption and desorption of S042- and /or NO3- in Hunan soil and the effects on soil acidification, the three tested soils were treated with different concentrations of (NH4)2SO4 and /or NH4NO3 solutions and different pH value solutions through a continuous batch experiment under laboratory conditions. The conclusions are summarized as follows:The three tested soils have a strong ability to absorb sulfate and /or nitrate, which can delay soil acidification process in a short time. Adsorption amounts of SO42- in the three soilsincrease with increasing soil depth when SO42- concentrations are low. SO42- and NO3-adsorption amounts in the soils in the co-adsorption experiment of SO42- and NO3- are less than those in single SO42- or NO3- adsorption experiment when sulfate and/or nitrate concentrations are the same, indicating that SO42- interacts competitively with NO3- in theco-adsorption of SO42- and NO3-. In the three soils, red soil has the highest adsorption capacity of SO42-, followed by yellow-red soil, and adsorption capacity of yellow soil is the lowest; however, the lowest NCV adsorption is found for red soil, yellow-red soil is in the middle, and yellow soil has the highest adsorption.The desorption ratios of SO42- and/or NO3- at the same soil horizons increase with increasing adsorption amounts when these soils are treated with solutions of the same pH values, and decrease with decreasing solution pH values when these soils are treated with different pH value solutions. The SO42- desorption ratios of red soil and yellow-red soil decrease with increasing soil depth and those of yellow soil increase with increasing soil depth when these soils are treated with solutions of the same pH values. The desorption ratios of NO3-at different soil horizons from the three soils are different when these soils are treated with solutions of the same pH values.Base cations from the A horizons of the three soils are very easily lost. Yellow soil has the highest leaching ratios of base cations . and soil has almost the same leaching ratios as yellow-red soil. All RCL values in the soil solutions are low. and effects of the solution A13+ on vegetation are probably lightly.