中国农业科学 ›› 2018, Vol. 51 ›› Issue (7): 1325-1333.doi: 10.3864/j.issn.0578-1752.2018.07.010

• 土壤肥料·节水灌溉·农业生态环境 • 上一篇    下一篇

电渗析法研究紫色土、黄壤和砖红壤的酸化特征

程永毅,李忠意,白颖艳,刘莉   

  1. 西南大学资源环境学院,重庆 400716
  • 收稿日期:2017-07-31 出版日期:2018-04-01 发布日期:2018-04-01
  • 通讯作者: 李忠意,E-mail:zhongyili@swu.edu.cn
  • 作者简介:程永毅,E-mail:chengyin046@126.com
  • 基金资助:
    国家自然科学基金(41701256)、中央高校基本业务专项资金(XDJK2016C191和XDJK2017D207)、重庆市项目博后资助(Xm2016076)

Acidification Characteristics of Purple Soil, Yellow Soil and Latosol with Electrodialysis Method

CHENG YongYi, LI ZhongYi, BAI YingYan, LIU Li   

  1. College of Resource and Environment, Southwest University, Chongqing 400716
  • Received:2017-07-31 Online:2018-04-01 Published:2018-04-01

摘要: 【目的】研究紫色土、黄壤和砖红壤在快速酸化过程中的酸化特征。【方法】将3种供试土壤在15 V·cm-1的外加直流电压梯度下进行连续30次,每次8 h的电渗析。并通过测定电渗析前后土壤的酸度指标、盐基离子含量以及在电渗析过程中土壤所释放的盐基离子含量来分析土壤的酸化特征。【结果】电渗析法可在短时间内实现土壤的快速酸化,3种土壤的pH均降低至4.5以下的强酸化水平。电渗析后,3种土壤的交换性酸、交换性H+和交换性Al3+含量显著增加。紫色土、黄壤和砖红壤的交换性酸含量分别从3.35、0.23和0.76 cmol(+)·kg-1增加至18.9、7.0和5.8 cmol(+)·kg-1,可见紫色土的酸化程度最为严重。土壤酸化后,水溶性和交换性K+、Na+、Ca2+和Mg2+含量降低,其中Ca2+、Mg2+的降低幅度较大。酸化导致土壤的交换性盐基总量和盐基饱和度下降,紫色土、黄壤和砖红壤的盐基饱和度从电渗析前的96.8%、82.6%和47.3%降低至电渗析后的20.5%、11.8%和12.2%。尽管紫色土的交换性酸含量远大于黄壤和砖红壤,但交换性盐基离子总量和盐基饱和度也大于黄壤和砖红壤。由于各土壤的交换性Ca2+和Mg2+含量大于交换性K+和Na含量,且相对于K+和Na,Ca2+和Mg2+与带负电的土壤颗粒间具有更强的静电引力,因此在酸化过程中,一价盐基离子K+和Na在3种土壤中均表现为快速释放,而二价盐基离子Ca2+和Mg2+表现出缓慢释放和波动释放的规律。3种供试土壤,随着土壤发育程度增加,土壤的潜在酸化风险下降(紫色土>黄壤>砖红壤),但土壤的盐基饱和度表现出紫色土>黄壤≈砖红壤。可以看出,紫色土的酸化特征表现出这种明显的“双面性”,由于紫色土具有较高的CEC值,导致土壤酸化后的交换性酸含量显著高于黄壤和砖红壤,使酸化紫色土上生长的植物存在较高的铝毒害风险;同时,由于紫色土丰富的矿物组分能够对盐基离子进行及时补充,紫色土酸化后仍含有相对较高的盐基离子含量和盐基饱和度,保证了植物生长对盐基养分离子需求,也能在一定程度上缓解紫色土的进一步酸化。【结论】电渗析法可用于模拟土壤的快速酸化过程;土壤的表面负电荷量和复盐基离子能力是决定土壤酸化特征的关键因素;紫色土具有异于地带性土壤黄壤和砖红壤的“双面性”酸化特征。

关键词: 电渗析, 酸化特征, 紫色土, 黄壤, 砖红壤

Abstract: 【Objective】The soil will be saturated by the ions of H+ and Al3+ under the process of electrodialysis. Theoretically, the acidification characteristic of soil can be studied with the method of electrodialysis. 【Method】Purple soil, Yellow soil and Latosol were selected to undergo the electrodialysis at a potential gradient of 15 V·cm-1. The electrodialytic times were 30 times and the duration of each electrodialytic time was 8 hours. The acidification characteristics of three kinds of soil were characterized by the measurements of soil exchangeable acidity, base cations before and after the electrodialysis and the release regulation of base cations in the process of electrodialysis. 【Result】The results showed that the tested soils could be acidified quickly with electrodialysis in short time. The pH value of each soil was less than 4.5, which meant the soils were strongly acidified. After electrodialysis, the contents of exchangeable acidity, exchangeable H+ and exchangeable Al3+ increased significantly. The contents of exchangeable acidities of Purple soil, Yellow soil and Latosol increased from 3.35, 0.23 and 0.76 cmol(+)·kg-1 to 18.9, 7.0 and 5.8 cmol(+)·kg-1,respectively. On the contrary, the content of water soluble and exchangeable base cations, especially Ca2+ and Mg2+, base exchange capacity and base saturation decreased. For example, the contents of base saturation of Purple soil, Yellow soil and Latosol decreased from 96.8%, 82.6% and 47.3% to 20.5%, 11.8% and 12.2%,respectively. The acidified Purple soil had higher content in soil exchangeable acidity and base saturation. Because the contents of Ca2+ and Mg2+ were higher than K+ and Na+ and the electrostatic force between Ca2+/Mg2+ and negatively charged soil surface is strong. In the process of electrodialysis, the monovalent base cations K+ and Na were released from the soil very quickly. However, the divalent base cations Ca2+ and Mg2+ were released from the soil slowly and wavily. The exchangeable acidity content of Purple soil was significantly higher than that of Yellow soil and Latosol because of the high content of cation exchange capacity (CEC), which increased the risk of Al3+ toxicity of plant in the acidified Purple soil. Meanwhile, the contents of base cations and base saturation of Purple soil were higher than that of Yellow soil and Latosol, because the cations in Purple soil could be supplied from the decomposition of soil minerals. The high content of base cations in the Purple soil ensured the demand of base cation for plant growth and alleviated the further acidification of soil. 【Conclusion】Therefore, the electrodialysis could be as an useful tool to research the acidification characteristics of soil. The acidification characteristic of soil was affected by the content of negative charge on the surface of soil and the soil’s renewed ability of base cations. Compared to Yellow soil and Latosol, the Purple soil had a dual effect on the process of acidification.

Key words: electrodialysis, acidification characteristic, Purple soil, Yellow soil, Latosol