Release of Basic Cations in Red Soil under Simulated Acid Rain and Buffering Mechanism

The effects of simulated acid rain on releasing base cations of red soil were studied with leaching experiments.Results show that there are two main buffer mechanisms in the red soil,e.g.cations exchange and mineral weathering.The release of base cations was significantly governed by acidic deposition of acid rain. With increasing input of H~+,the red soil buffering for acid rain will change from primary ion exchange to mineral weathering mechanism.Strong acidic rain causes more mineral weathering in red soil.Under the different acidic leaching,the releasing capacities of base cations leveled off,and the sensitivity on the acidic leaching followed as: Ca~(2+)Mg~(2+)(K~+)Na~+.It also has been found that there are a good linear relationship between the released Ca~(2+) and Mg~(2+),and(n(Ca~(2+)))/(n(Mg~(2+))) increases with increasing pH and leaching volume of acid rain.In contract,the source and releasing mechanism of Na~+ resulted from mineral weathering at strong acidic condition are different from those for K~+,Ca~(2+) and Mg~(2+).