摘要
黄河三角洲盐渍土改良具有重要的经济和社会意义。风化煤(0%、1%、3%、5%)添加到不同含盐量(1.0 mg·g^(-1)、7.5 mg·g^(-1)、35.3 mg·g^(-1))的滨海盐渍化土壤后,可降低土壤浸提液的钠吸附比(Sodium adsorption ratio,SAR)及Cl^-/SO_4^(2-)比,有助于减轻盐渍危害。7.5 mg·g^(-1)含盐量土壤在5%添加下SAR由7.81降为6.61,Cl^-/SO_4^(2-)由10.20降为8.25。风化煤中丰富的羧基等表面官能团及Ca^(2+),可通过三个作用过程改变盐渍化土壤溶液的离子组成,涉及:(1)风化煤固相Ca^(2+)与溶液Na^+离子的交换,从而降低土壤溶液中Na^+的浓度和危害;(2)溶液中Ca^(2+)与土壤交换性Na^+的置换,有助于土壤团聚体的形成和Na^+的淋洗;(3)溶液中的Na^+与风化煤中的溶解性有机质形成络合物,使Na^+的活度和植物有效性降低,间接起到减害作用。此外,钠吸附比和氯硫比可用于在实验室初步判断风化煤等物料用于盐渍土改良的潜力和效果。
【Objective】To ameliorate salt-affected soil in the Yellow River Delta for productive use is of great social and economic significance to the region. Trials have been conducted to use leonardite as a soil amendment for the purpose, but failed to get consistent results and probe in-depth into the causes. This research aimed to assess changes in salt composition of the soil solution in the salt-affected soil applied with leonardite, and reveal processes and mechanisms of the changes. 【Method】Three topsoil samples (S1, S2 and S3), different in salt contents (1.0, 7.5, and 35.3 mg·g^-1, respectively), were collected from a farmland in the Yellow River Delta. After being air dried and gently ground to pass a 100-mesh sieve, the samples were mixed, separately, with leonardite at 0%, 1%, 3%, and 5% in dosage and each treatment had two replicates. Then the mixtures were prepared separately into suspensions (solid: water = 1g: 5ml), which were shaken at 300 r·min^-1 for 7 d and then centrifuged at 3 000 r?min-1 for 10 min. The obtained supernatants (or soil extracts) went through a 0.45-μm filter and got ready for analysis of Ca^2+, Mg2+, K+, Na^+, Cl-, NO3-, and SO42- with ion chromatography. The leonardite used in the experiment was digested by HNO3-HClO4-HF for analysis of Ca^2+, Mg2+, K+, and Na^+, and its carboxyl and phenolic hydroxyl groups were determined with the titration method of the International Humic Substances Society. 【Result】The leonardite was found to contain Na^+ (1.66 mg·g^-1), K+ (1.07 mg·g^-1), Ca^2+ (19.97 mg·g^-1), Mg2+(1.60 mg·g^-1), carboxyl group (2.74 mol·kg^-1) and phenolic hydroxyl group (1.63 mol·kg^-1). In the soil solution, sodium adsorption ratio (SAR) decreased with leonardite increasing in spiking dosage, which was attributed to Ca^2+ release from and Na^+ adsorption to leonardite. In the treatment of adding 5% leonardite to soil S2 SAR reduced from 7.81 to 6.61. In analogy to SAR, Cl^-/SO4^2- molar ratio was proposed as a new indicator to reflect changes in anion compositions. It decreased from 10.20 to 8.25 in the treatment, which was a result of SO4^2- release from and/or Cl- retention by leonardite. The reduction of SAR and Cl-/SO4^2- ratio suggests that leonardite could lessen the toxic effects of Na^+ and Cl^- on plants. 【Conclusion】With Ca^2+ and abundant carboxyl groups it contains, leonardite could alter ion compositions in soil solution via: 1) ion exchange between Ca^2+ in leonardite and Na^+ in soil solution, reducing Na^+ concentration in the solution and its harmful effect; 2) replacement of Na^+ adsorbed on soil colloids by Ca^2+ released from leonardite, favoring formation of soil aggregates and leaching of Na^+;and 3)formation of complexes of Na^+ in solution with organic substances dissolved from leonardite, reducing Na^+ activity and toxicity. It is, therefore, proposed that SAR and Cl-/SO4^2- ratio be tested as indicators for fast laboratory assessment of suitability of soil amendments for use in salt-affected soils, which would help land managers choose proper soil amendments for use and avoid input of Na-rich organic materials, such as sodium humate, in salt affected soils.
作者
王洁
校亮
毕冬雪
韦婧
袁国栋
WANG Jie;XIAO Liang;BI Dongxue;WEI Jing;YUAN Guodong(Yantai Institute of Coast Zone Research,Yantai,Shandong 264003,China;University of Chinese Academy of Sciences,Beijing 100049,China;School of Environmental and Chemical Engineering,Zhaoqing University,Zhaoqing ,Guangdong 526061,China)
出处
《土壤学报》
CAS
CSCD
北大核心
2018年第6期1367-1376,共10页
Acta Pedologica Sinica
基金
国家重点研发计划项目(2016YFD0200303)
山东省重点研发计划项目(2016CYJS05A01-1)资助~~
关键词
盐渍土改良
风化煤
钠吸附比
氯硫比
减钠脱盐
Amelioration of salt-affected soils
Leonardite
SAR
Chloride/sulphate ratio
Desalinization and sodium deactivation
