电渗析与酸淋洗模拟紫色土酸化的效果比较

为了比较电渗析与酸淋洗试验模拟紫色土酸化的效果,在重庆地区采集了不同pH(5.00和7.06)的2个紫色土,分别进行不同天数(1,2,5,7,10天)的电渗析和酸淋洗试验处理,并分析了试验处理前后土壤的酸度特征和交换性盐基成分含量变化。结果表明,在整个10天的淋溶处理过程中,2种紫色土的pH均无显著变化,说明紫色土具有一定的酸缓冲能力,短期的酸雨淋溶不能实现紫色土的严重酸化。而采用电渗析处理10天后,中性紫色土和酸性紫色土的pH分别降低3.4和1.1个单位。在整个电渗析处理过程中,土壤的交换性酸含量显著升高,盐基离子大量淋失。电渗析可以实现对紫色土的快速酸化处理。2种紫色土中,电渗析处理后中性紫色土的酸化程度大于酸性紫色土。这是由于中性紫色土的表面负电荷量更高,导致更多致酸离子吸附在土壤胶体表面,最终造成中性紫色土的酸化程度更加严重。因此,电渗析处理比酸雨淋溶处理对紫色土酸化效果更好,且可用于紫色土的酸化机理研究。进一步结合2种方法的技术可操作性,认为电渗析法是研究紫色土酸化问题的一种有效技术手段。

Effect of Electrodialysis and Acid Leaching on the Acidification of Purple Soil

In order to better understand the effects of electrodialysis and acid leaching treatments on the acidification process of purple soils, an acid purple soil with the pH value of 5.00 and a neutral purple soil with the pH value of 7.06 collected in Chongqing were treated by electrodialysis and acid leaching treatments for different days (1, 2, 5, 7 and 10 days, respectively). The variation of soil acidity and exchangeable base cations during these treatment processes were analyzed. The results showed that the pH values of both acid purple soil and neutral purple did not change significantly. This could be attributed to the high acid buffering capacity. The purple soils could not be acidified in a short-term acid rain leaching. Differently, after 10-day electrodialysis treatment, the pH values of acid purple soil and neutral purple soil decreased by 3.4 and 1.1, respectively. In the electrodialysis process, the soil exchangeable acidity increased significantly and the content of exchangeable base cations decreased greatly. It was indicated that electrodialysis could be used to rapidly acidify purple soil. The acidification degree of neutral purple soil after electrodialysis treatment was higher than that of acid purple soil. This was because the amount of negative surface charge of neutral purple soil was higher than that of acid purple soil, which caused that more acidic ions (H⁺ and Al³⁺) were adsorbed on the surface of neutral soil, correspondingly, resulting in the increased acidified degree of neutral purple soil. Therefore, compared to acid leaching treatment, electrodialysis treatment was a more effective way to acidify the purple soil in a short time. It also could help us to reveal the acidification mechanism of purple soil. After taking the feasibility of electrodialysis and acid leaching treatments into account, it was concluded that electrodialysis was an effective technique to study the acidification of purple soil.