Boron and Zinc Transport Through Intact Columns of Calcareous Soils

M. MAHMOOD-UL-HASSAN; M. S. AKHTAR; G. NABI

摘要

Leaching of boron (B) and zinc (Zn) can be significant in some pedomorphic conditions, which can cause contamination of shallow groundwater and economic losses. Boron and Zn adsorption and transport was studied using 8.4 cm diameter ×28 cm long intact columns from two calcareous soil series with differing clay contents and vadose zone structures:Lyallpur soil series, clay loam (fine-silty, mixed, hyperthermic Ustalfic Haplargid), and Sultanpur soil series, sandy loam (coarse-silty, mixed, hyperthermic Ustollic Camborthid). The adsorption isotherms were developed by equilibrating soil with 0.01 mol L-1 CaCl2 aqueous solution containing varying amounts of B and Zn and were fitted to the Langmuir equation. The B and Zn breakthrough curves were fitted to the two-domain convective-dispersive equation. At the end of the leaching experiment, 0.11 L 10 g L-1 blue dye solution was also applied to each column to mark the flow paths.The Lyallpur soil columns had a slightly greater adsorption partition coefficient both for B and Zn than the Sultanpur soil columns. In the Lyallpur soil columns, B arrival was immediate but the peak concentration ratio (the concentration in solution at equilibrium/concentration applied) was lower than that in the Sultanpur soil columns. The breakthrough of B in the Sultanpur soil columns occurred after about 10 cm of cumulative drainage in both the columns; the rise in effluent concentration was fast and the peak concentration ratio was almost 1. Zinc leaching through the soil columns was very limited as only one column from the Lyallpur soil series showed Zn breakthrough in the effluent where the peak concentration ratio was only 0.05. This study demonstrates the effect of soil structure on B transport and has implications for the nutrient management in field soils.

机译：硼（B）和锌（Zn）的浸出在某些人形条件下可能很重要，这可能导致浅层地下水污染和经济损失。使用直径为8.4 cm×28 cm长的完整完整柱，研究了硼和锌的吸附和迁移，这些柱来自两种钙质土壤系列，具有不同的粘土含量和渗流带结构：Lyallpur土壤系列，粘土壤土（细粉质，混合，高热Ustalfic Haplargid）和Sultanpur土壤系列，砂壤土（粗粉质，混合，高温Ustollic Camborthid）。吸附等温线是通过用0.01 mol L-1 CaCl2水溶液平衡土壤来开发的，该水溶液包含不同量的B和Zn，并拟合到Langmuir方程中。将B和Zn突破曲线拟合到两域对流扩散方程。在浸出实验结束时，还将0.11 L 10 g L-1蓝色染料溶液应用于每根色谱柱以标记流路.Lyallpur土壤色谱柱对B和Zn的吸附分配系数均比Sultanpur土壤稍高列。在Lyallpur土柱中，B到达是立即的，但峰值浓度比（达到平衡/浓度的溶液浓度）低于Sultanpur土柱。两根柱子累积排水约10 cm后，B在Sultanpur土柱中突破。废水浓度的上升很快，峰值浓度比接近1。锌通过土壤柱的淋溶非常有限，因为Lyallpur土壤系列中只有一根柱在峰值浓度比仅为0.05的废水中显示锌的突破。这项研究证明了土壤结构对B运移的影响，并且对田间土壤的养分管理具有重要意义。

Boron and Zinc Transport Through Intact Columns of Calcareous Soils

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