Department of Soil Science, Tarbiat Modares University, P.O. Box 14115-336, Tehran, Iran.
Chemosphere. 2010 Aug;80(7):733-9. doi: 10.1016/j.chemosphere.2010.05.025. Epub 2010 Jun 12.
Boron (B) availability is regulated by its equilibrium concentration that in turn is buffered by adsorption and desorption reactions. Ionic strength, pH, OM content, and the type and amount of minerals are the major factors affecting B sorption reactions. To evaluate the influence of calcium carbonate equivalent (CCE) and ionic strength on B chemical behavior, its adsorption and desorption isotherms were measured in eight calcareous soils differed in CCE (0-85%). Adsorption and desorption data were described by the Langmuir and the Linear adsorption equations, respectively. No statistically significant relation was found between model parameters and soil properties. However, in comparison, soils with higher reactive particles (clay and OM) and higher pH adsorbed more boron. Removing CCE from a soil sample (CCE=18%) lowered B adsorption maximum by 35%. In contrast, increasing electrolyte concentration (0.01 M NaCl) to 0.1 and 0.5M caused to increase B adsorption maximum by 30% and 75%, respectively. At the equi-molar concentration, CaCl(2) increased B adsorption stronger than NaCl. The positive effect of ionic strength was attributed to a better screening of surface charges and compaction of double layer thickness. Desorption data were deviated from adsorption isotherms only at equilibrium concentrations smaller than 2 mM. Analysis of boron solution speciation and adsorption-desorption data revealed that B is mainly adsorbed as spectroscopically proved outer-sphere complex in the studied soil samples. The experimental data and model prediction could be used to manage B bio-availability and to optimize remediation processes in calcareous soils.
硼（B）的有效性受其平衡浓度控制，而平衡浓度又受吸附和解吸反应缓冲。离子强度、pH 值、有机质含量以及矿物的类型和数量是影响 B 吸附反应的主要因素。为了评估碳酸钙当量（CCE）和离子强度对 B 化学行为的影响，在 8 种不同 CCE（0-85%）的石灰性土壤中测量了其吸附和解吸等温线。吸附和解吸数据分别采用 Langmuir 和线性吸附方程进行描述。模型参数与土壤特性之间未发现有统计学意义的关系。然而，相比之下，具有更高反应性颗粒（粘土和有机质）和更高 pH 值的土壤吸附更多的硼。从土壤样品中去除 CCE（CCE=18%）会使硼的吸附最大值降低 35%。相比之下，将电解质浓度（0.01 M NaCl）分别提高至 0.1 和 0.5 M 会使硼的吸附最大值分别增加 30%和 75%。在等摩尔浓度下，氯化钙比氯化钠更能增强硼的吸附。离子强度的积极影响归因于更好地屏蔽表面电荷和压缩双电层厚度。解吸数据仅在平衡浓度小于 2 mM 时才偏离吸附等温线。对硼溶液形态和吸附-解吸数据的分析表明，B 主要以光谱证明的外球络合物形式吸附在研究的土壤样品中。实验数据和模型预测可用于管理 B 的生物有效性并优化石灰性土壤中的修复过程。
