模拟酸雨对森林红壤中铝的溶出及不同土层酸度变化的影响

为进一步探明酸沉降对森林红壤及生态环境的影响，模拟长沙地区降水酸度及离子组成，采用浸泡试验对两种森林红壤活性铝的释出及土壤理化性质的变化进行了研究。结果表明，模拟酸雨浸泡初期，土壤活性铝的释出量随浸泡次数的增加而增加，原始土壤pH值愈低，活性铝释出愈多；强酸度、高离子浓度（AR4）模拟酸雨对土壤中活性铝的溶出量远大于基础酸雨（AR3）及弱酸、低离子浓度酸雨（AR2）和对照酸雨（AR1）。模拟酸雨酸度愈大，对土壤pH值的影响愈明显，不同土层间，以A层土壤pH值下降最明显，B、C层土壤则下降较小。模拟酸雨模拟浸泡土壤25年后，土壤阳离子交换量均有不同程度下降，有机质含量高，原土壤阳离子交换量大的土壤下降幅度也大。

Effects of simulated acid rains on Al release and acidity changes in different horizons in forest red soils

In order to explore effects of acid deposition on forest red soils, the ecology and environment, a batch experiment was conducted with four simulated acid rain solutions to study Al release and changes of soil physical and chemical prosperities in two forest red soils in Changsha area. The results showed that the release of active Al increased with increasing volume of simulated acid rain solutions at the beginning of the experiment, and more active Al was released from the soil with a lower pH value. The total release of active Al from the soils was much greater for AR4 with high acidity and high ion concentrations than that for AR3 (similar to the real local precipitation), AR2 (with low acidity and low ion concentrations), and AR1 (distilled water as a control). Decreases in soil pH depended mostly on the acidity of simulated acid rain solutions, and the higher the acidity, the lower the soil pH. Among the different soil horizons, decreases in soil pH were more significant in horizon A than in horizons B and C for the same acid rain. After a simulated batch experiment corresponding to 25 years, cation exchange capacity (CEC) in the tested soils declined to different degrees, and this decline was greater for the soil with originally higher organic matter and higher CEC.