Effects of Simulated Acid Rain on Soil Acidification and Base cations Release of Four Types of Typical Soils from the Three Gorges Reservoir Region

The releasing characteristics and mechanism of base ions in four types of typical soils(yellow soil,grey-brown purplish soil,red-brown purplish soil,red purplish soil),which were collected from the Three Gorges Reservior Region,are studied by simulated acid rain leaching of soil columns equipment indoor.The results indicate that acid rain caused the acidification of four types of typical soils and the pH values of the teste soils decrease with the decline of acid rain pH.In general,the higher the pH value and CEC content of the soil are,and the smaller soil acidification is affected by acid rain.The electric conductivity(EC) of the leachates first increased,and then decreases.An EC peak occurres during all leaching processes,with the shape of the peak obviously different.Acid rain led to the loss of base ions,the reduction of base saturation degree,and the decline of the buffering capacity of the teste soils.Leached nutrients from the tested soils decreased in the order: Ca2+Mg2+Na+K+.