Effect of pH on Saturated Hydraulic Conductivity and Soil Dispersion1
Effect of pH on Saturated Hydraulic Conductivity and Soil Dispersion1
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DOI：
10.2136/sssaj1984.03615995004800010009x
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发表时间：
1984
影响因子：
2.9
通讯作者：
D. Suarez;J. Rhoades;R. Lavado;C. Grieve
中科院分区：
文献类型：
--
作者：
D. Suarez;J. Rhoades;R. Lavado;C. Grieve
交换性钠对土壤导水率（K）的不利影响是众所周知的，但目前仅使用钠度和总电解质浓度来评估灌溉水的适宜性。在干旱地区，高钠度通常与高溶解碳酸盐和高 pH 值相关，但在潮湿地区，高钠度可能与低 pH 值相关。为了评估 pH（作为自变量）对 A" 的影响，在 pH 6、7、8 和 9 下制备具有相同 SAR 和电解质水平的溶液。在堆积密度为 1.5 Mg m' 的柱中以恒定通量测定饱和 A' 值。在 pH 9 时，蒙脱石和高岭石土壤的饱和 K 值低于 pH 6 时的值。对于有机碳较低的蛭石土壤 且含泥量较高时，pH变化并未引起较大的K差异。 A" 的减少 1 来自美国盐度实验室、USDA-ARS、美国盐度实验室（Riverside, CA 92501）的贡献。1982 年 12 月 16 日收到。1983 年 9 月 9 日批准。2 分别由地球化学家、土壤科学家和植物生理学家提供。 R. Lavado 的永久地址是 Institute de Geomorfologia y Suelos, La Plata, Argentina。使用电解质含量较高的水时不可逆。 K 实验的结果与色散的光传输测量结果基本一致。尽管阴离子吸附达到或低于检测限，并且阳离子交换容量 (CEC) 仅轻微依赖于 pH，但土壤中 pH 对 A" 影响的差异可能是由于可变电荷矿物质和有机物质的数量差异造成的。附加索引词：钠吸附率、电解质浓度、光传输。Suarez、D.L.、J.D. Rhoades、R. Lavado 和 CM. Grieve。 1984. pH 对饱和导水率和土壤分散性的影响。土壤科学。苏克。上午。约翰福音 48:50-55。高水平的交换性钠对土壤导水率 (K) 的不利影响已得到充分证实。在给定的土壤可交换钠百分比 (ESP) 下钾的开始减少 SUAREZ 等人：pH 对饱和水力电导率和土壤分散性的影响 51 随总电解质浓度和土壤性质的变化而变化（Quirk 和 Schofield，1955 年；McNeal 和 Coleman，1966 年；Frenkel 等人，1978 年；Shainberg 等人，198la）。尽管进行了这些研究以及许多其他研究，但对于给定土壤，仍无法准确预测 ESP 和电解质浓度的确切水平，在该水平下 K 会发生减少。在已发表的实验室色谱柱研究中，中性或弱酸性氯化物 盐溶液（pH=6.0）通常在二氧化碳分压（Pco2）接近大气压（10”kPa）的情况下使用。当存在 CaCO3 时，柱中水的 pH 值可能为：上部为 6.0，下部为 7.5 至 8.0。干旱和半干旱土壤的地下通常是石灰质的。这种环境中的钠质土壤通常与高 pH 值和高溶解碳酸盐和碳酸氢盐浓度有关。对于此类土壤，pH 值可能超过 10，但在地表附近更可能在 8 至 9.5 的范围内。在酸性条件下也可能出现钠质土壤（每种溶液的 pH 值为 1.3 L）通过色谱柱。通过将 CO2 气体鼓泡到 5 L Pyrex 溶液储罐中，将 pH 6 的溶液保持在 pH 6。储罐底部的出口管放置在与蠕动泵相同的高度，以消除泵送操作过程中的 CO2 脱气。在脱气之前，在 U 形管中测量渗滤液的 pH 值。 发生。通过原子吸收分析进水和出水溶液中的 Ca、Mg、Na 和 K，通过酸滴定分析碱度，通过 AgCl 滴定分析 Cl（Rhoades 和 Clark，1978）。实验结束时，将柱分成 1 厘米的部分并分析可交换阳离子。为了比较的目的，K 数据被缩放到初始 K(K,) 值 使用 100 mmolc L"、SAR 20 溶液或 500 mmolc L~、SAR 40 溶液测定。基于 Bonsall 土壤、SAR 40、pH 9 处理的六次重复，确定 250、100、50 和 25 溶液的 log K/Kt 标准偏差为 0.08、0.18、0.19 和 0.11 mmol，；L”，分别。
The adverse effects of exchangeable sodium on soil hydraulic conductivity (K) are well known, but at present only sodicity and total electrolyte concentration are used in evaluating irrigation water suitability. In arid areas, high sodicity is often associated with high dissolved carbonate and thus high pH, but in humid areas high sodicity may be associated with low pH. To evaluate the effect of pH (as an independent variable) on A", solutions with the same SAR and electrolyte level were prepared at pH 6, 7, 8, and 9. Saturated A' values were determined at constant flux in columns packed at a bulk density of 1.5 Mg m'. At pH 9, saturated K values were lower than at pH 6 for a montmorillonitic and a kaolinitic soil. For a vermiculitic soil with lower organic carbon and higher silt content, pH changes did not cause large K differences. Decreases in A" were 1 Contribution from the U.S. Salinity Laboratory, USDA-ARS, U.S. Salinity Laboratory, Riverside, CA 92501. Received 16 Dec. 1982. Approved 9 Sept. 1983. 2 Geochemist, Soil Scientists, and Plant Physiologist, respectively. The permanent address of R. Lavado is Institute de Geomorfologia y Suelos, La Plata, Argentina. not reversible on application of waters with higher electrolyte levels. The results from the K experiments were generally consistent with optical transmission measurements of dispersion. Although anion adsorption was at or below detection limits and cation exchange capacity (CEC) was only slightly dependent on pH, differences in pH effects on A" among soils are likely due to differences in quantities of variable-charge minerals and organic matter. Additional Index Words: sodium adsorption rate, electrolyte concentration, optical transmission. Suarez, D.L., J.D. Rhoades, R. Lavado, and CM. Grieve. 1984. Effect of pH on saturated hydraulic conductivity and soil dispersion. Soil Sci. Soc. Am. J. 48:50-55. T ADVERSE EFFECTS of high levels of exchangeable sodium on the hydraulic conductivity (K) of soils are well established. The onset of reduced K at a given soil exchangeable sodium percentage (ESP) SUAREZ ET AL.: EFFECT OF pH ON SATURATED HYDRAULIC CONDUCTIVITY AND SOIL DISPERSION 51 varies with total electrolyte concentration and soil properties (Quirk and Schofield, 1955; McNeal and Coleman, 1966; Frenkel et al., 1978; Shainberg et al., 198la). Despite these and numerous other studies, the exact levels of ESP and electrolyte concentration at which reductions in K will occur for a given soil still cannot be predicted accurately. In published laboratory column studies, neutral or slightly acidic chloride salt solutions (pH =; 6.0) were normally used with a carbon dioxide partial pressure (Pco2) near atmospheric (10"kPa). The pH values of water in the columns were likely =: 6.0 in the upper portion and 7.5 to 8.0 in the lower portions when CaCO3 was present. Arid and semiarid soils are usually calcareous in the subsurface. Sodic soils in this environment are generally associated with high pH and high dissolved carbonate and bicarbonate concentrations. With such soils, pH values can exceed 10 but are more likely in the range of 8 to 9.5 near the surface. Sodic soils may occur also under acid conditions (pH 1.3 L of each solution was passed through the column. The pH 6 solutions were maintained at pH 6 by bubbling CO2 gas into the 5-L Pyrex solution reservoir. An exit tube at the bottom of the reservoir was placed at the same height as the peristaltic pump to eliminate CO2 degassing during the pumping operation. The pH of the leachate was measured in the U tubes before degassing could occur. Influent and effluent solutions were analyzed for Ca, Mg, Na, and K by atomic absorption, alkalinity by acid titration, and Cl by AgCl titration (Rhoades and Clark, 1978). At the conclusion of the experiment, the columns were separated into 1-cm sections and analyzed for exchangeable cations. For purposes of comparison, the K data were scaled to the initial K(K,) values determined with the 100 mmolc L", SAR 20 solution, or 500 mmolc L~, SAR 40 solution. Based on six replications on the Bonsall soil, SAR 40, pH 9 treatment, log K/Kt standard deviations of 0.08, 0.18, 0.19, and 0.11 were determined for solutions of 250, 100, 50, and 25 mmol,; L", respectively.