淋溶条件下低分子量有机酸对淋出液及三峡库区典型土壤性质的影响

Effects of Low-Molecular-Weight Organic Acids on Leachate and Soil Properties of Typical Soils Under Leaching Condition in Three Gorge Reservoir Areas

[目的] 研究低分子量有机酸（草酸、柠檬酸、酒石酸）作用下淋出液及土壤（紫色潮土和灰棕紫泥）性质的变化，以期为三峡库区的环境管理提供参考和科学依据。[方法] 采用间歇式土柱模拟试验进行研究。[结果] 高浓度低分子量有机酸（≥50mmol/L）能够破坏灰棕紫泥的酸碱缓冲体系，当草酸、柠檬酸和酒石酸浓度≥50mmol/L时，灰棕紫泥土壤pH值均从8左右降到了4.11以下；而紫色潮土的缓冲性能较强，经淋溶后土壤pH值变化不大，仍然维持在6.84~8.71左右，与空白处理差异性不显著。另外，灰棕紫泥淋出液电导率变化较紫色潮土明显，高浓度低分子量有机酸处理下，灰棕紫泥淋出液电导率最高值达到了34.400mS；灰棕紫泥在3种低分子量有机酸淋洗下淋溶出离子量的大小顺序为：柠檬酸〉酒石酸〉草酸。[结论] 低分子量有机酸的酸解作用和络合作用是影响淋出液pH值、淋出液电导率和土壤pH值变化的主要原因，并能够参与紫色潮土和灰棕紫泥的化学和生物化学过程。低分子量有机酸的存在对三峡库区水环境恶化存在一定的风险。

[Objective] To provide references and scientific bases for environmental management of the Three Gorges Reservoir areas, the effect of three simple organic acids（oxalic acid, citric acid, tartaric acid） on the properties of leachate and soil（purple soil and grey-brown purple soil） were investigated. [Methods] leaching experiments were conducted using intermittent soil column in lab. [Results] Low-molecular-weight organic acids at high concentration（≥50 mmol/L） can upset the acid-alkaline buffer system of grey-brown purple soil. Either oxalic acid, citric acid or tartaric acid, when the concentration was higher than 50 mmol/L, pH value of grey-brown purple soil was observed declined from around 8 to lower than 4.11. Whereas, the buffer effect of purple soil behaved strong. soil pH value of it varied between 6.84 and 8.71 after leaching, no significant differences were observed with the contrast value of blank treatment. Electrical conductivity of grey-brown purple changed more obviously than the one of purple soil. In the treatments of high concentrations of low-molecular-weight organic acids, the highest electrical conductivity of grey-brown purple soil even reached 34.400 mS. The leached amount of ions by the three acids had a rank of citric acid〉tartaric acid〉oxalic acid. [Conclusion] The main reasons affecting pH value, electrical conductivity of leachate and soil pH value were acid splitting and complexing action of the low-molecular-weight organic acid. Meanwhile, the acid-participated chemical and biochemical processes of the purple soil and grey-brown purple soil were also important. The presence of low-molecular-weight organic acids has certain risk to water environment in the Three Gorge Reservior areas.