| 摘要: |
| 【目的】探究再生水典型溶质Na+与淡水交替入渗条件下，红壤水力特性的响应特征及其微观孔隙演变规律。【方法】采用一维水平入渗试验，以土壤体积质量为1.30 g/cm3的典型红壤为研究对象，以自来水为对照（CK），设置2组单因素试验：NaCl质量浓度分别为1、3、5、10 g/L，咸淡交替频次分别为1、2、4、6次，系统测定土壤水盐分布、持水与导水能力，定量解析当量孔径分布特征。【结果】①不同NaCl质量浓度处理下土壤水力性质呈非单调响应，临界质量浓度介于3~5 g/L。当NaCl质量浓度为1、3 g/L时，红壤大孔隙比例增加，持水能力降低，非饱和导水率与水分扩散率较CK升高15%~25%；而NaCl质量浓度为5、10 g/L时，土壤微孔隙比例增大，其中，NaCl溶液质量浓度10 g/L处理田间持水率较CK提高12.67%，但导水率较CK降低20%~30%。②随着交替频次增加，土壤大孔隙比例持续增大，持水能力逐步衰减。交替频次为6次时，大孔隙比例较CK增加116.63%，田间持水率下降16.82%，重力水含量增加115.63%。③NaCl质量浓度为10 g/L时，α较CK降低53.6%，表明土壤特征孔径减小；交替频次为6次时，α较CK增加221.4%，表明土壤特征孔径增大。【结论】NaCl溶液-淡水交替入渗引起的红壤水力特性演变存在质量浓度阈值效应与交替频次累积退化特征。为降低红壤结构退化及水分快速流失风险，在本试验条件下，建议将NaCl溶液质量浓度控制在3 g/L以下，并严格限制交替灌溉频次；该建议应用于实际再生水灌溉前仍需开展田间验证。 |
| 关键词: 红壤 水力特征 孔隙分布 交替作用 再生水 |
| DOI：10.13522/j.cnki.ggps.2026124 |
| 分类号: |
| 基金项目: |
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| Effects of alternating irrigation with NaCl solution and freshwater on hydraulic properties and pore structure of red soils |
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Wang Hui, Hu Bo, Kong Qianqian
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1. College of Water Resources & Civil Engineering, Hunan Agricultural University, Changsha 410128, China;
2. Engineering Research Center of Precision Irrigation Control for Irrigation Districts in Hunan, Changsha 410128, China
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| Abstract: |
| 【Objective】Red soils are widely distributed in subtropical regions and are characterized by strong weathering, low fertility and sensitivity to changes in soil structure and hydraulic properties. The increasing use of reclaimed water for irrigation on red soils raises concerns over the potential effects of dissolved solutes, particularly Na+, on their pore structure and water transport properties. The objective of this study was to investigate changes in the hydraulic properties and pore structure of red soil under alternating infiltration with freshwater and NaCl solutions used to represent the effect of Na+ as a typical solute in reclaimed water. 【Method】A one-dimensional horizontal infiltration experiment was conducted using a typical red soil packed to a bulk density of 1.30 g/cm3, with tap water as the control (CK). Two sets of single-factor treatments were established: NaCl concentrations of 1, 3, 5, and 10 g/L at one alternation cycle, and alternation frequencies of 1, 2, 4, and 6 cycles at a fixed NaCl concentration of 3 g/L. Soil water and salt distributions, water-retention and hydraulic-conductivity characteristics, and equivalent pore-size distribution were determined.【Result】①Soil hydraulic properties responded nonmonotonically to NaCl concentration, with a transition occurring between 3 and 5 g/L. At 1 and 3 g/L, the proportion of macropores increased and water-retention capacity decreased, while unsaturated hydraulic conductivity and soil-water diffusivity were 15%-25% higher than those of CK. At 5 and 10 g/L, the proportion of micropores increased. At 10 g/L, field capacity was 12.67% higher and hydraulic conductivity was 20%-30% lower than those of CK. ②Increasing alternation frequency increased the proportion of macropores while reducing water-retention capacity. At six alternation cycles, compared with CK, the proportion of macropores increased by 116.63%, gravitational water content increased by 115.63%, and field capacity decreased by 16.82%. ③When NaCl concentration was 10 g/L, alternating irrigation decreased the van Genuchten parameter α by 53.6% relative to CK, indicating a decrease in characteristic pore size. When alternation frequency was 6 cycles, alternating irrigation increased the parameter α by 221.4% relative to CK, indicating an increase in characteristic pore size. 【Conclusion】The hydraulic response of red soil under alternating infiltration showed a NaCl concentration threshold and cumulative deterioration as alternation frequency increased. Increasing alternation frequency promoted macropore development but facilitated water leaching, indicating a deterioration in soil water-retention capacity. To mitigate the risk of soil structural degradation and excessive water leaching, under the conditions of this experiment, the NaCl solution concentration should be maintained below 3 g/L and the alternation frequency should be strictly limited; field validation is required before applying this recommendation to reclaimed-water irrigation. |
| Key words: red soil hydraulic characteristics pore size distribution alternating infiltration reclaimed water |
