不同咸水梯次滨海盐土入渗过程及水盐分布特征

咸水冰融化入渗对重盐碱地具有明显的改良作用,而咸水冰融化是融水水质和水量的动态变化过程。为模拟咸水冰融化入渗滨海盐土过程,探讨咸水灌溉改良盐碱地的可行性,本研究设置了不同咸水梯次入渗滨海盐土的土柱试验,试验处理为:咸水梯次入渗(GSI)、咸水单一入渗(DSI)和咸水冰融化入渗(MSI),以淡水入渗(CK)为对照;其中咸水矿化度和水量分别为15g·L~(–1)和314.3mm。根据咸水冰融化过程中融水水质和水量的变化过程,GSI设置了4个矿化度和水量(S1:81 g·L~(–1)和25 mm;S2:19 g·L~(–1)和125.8 mm;S3:3 g·L~(–1)和94.3 mm;S4:0 g·L~(–1)和69.2 mm)的咸水连续入渗。结果表明:相同时间内,咸水处理的入渗深度和速度均大于CK;入渗初期,GSI的入渗深度和速率均高于DSI,且上一梯次咸水的入渗能显著提高下一梯次咸水的入渗率,后期GSI处理随着入渗咸水矿化度的降低,入渗率显著低于DSI。入渗后,0～40 cm土层土壤水盐含量由大到小依次为DSIGSIMSI,GSI和MSI土壤水盐分布一致,脱盐率分别为92.87%和91.38%,显著大于DSI的74.74%。以上结果明确了不同咸水梯次入渗滨海盐土的入渗特征,咸水梯次入渗可获得与咸水冰融化入渗一致的脱盐效果,这为后续模拟咸水冰融水入渗盐碱土过程提供了手段,同时也为咸淡水轮灌技术提供了理论依据。

Saline Water Infiltration Process and Water-salt Distributions in Coastal Saline Soil Relative to Concentration of the Saline Water

To irrigate fields of heavily salinized-alkalinized soil with water from melting saline ice is found to have an apparent soil ameliorating effect. Melting of saline ice is a dynamic process of meltwater in quality and quantity. To explore feasibilities of using saline water to irrigate fields of saline soil for soil amelioration, in this paper an experiment was designed to simulate infiltration process of water from melting saline ice into coastal saline soil. A soil column experiment was conducted in this study. The experiment was designed to have three treatments and a CK, i.e. gradient saline water infiltration (GSI), mere saline water infiltration (DSI), melting saline ice infiltration (MSI) and fresh water infiltration as control (CK). The saline water used in the experiment was set to be 15 g?L-1 in salinity and 314.3 mm in volume. Besides, according to the variation of meltwater in salinity and volume during the melting process of saline ice, four batches of infiltration were designed for Treatment GSI, with melted water different in salinity and volume (81 g?L-1, 19 g?L-1, 3 g?L-1 and 0 g?L-1 and 25 mm, 125.8 mm, 94.3 mm and 69.2 mm, respectively, for S1, S2, S3 and S4). The four batches of water were charged one after another when the previous batch totally infiltrated. Results show that infiltrating water went down deeper and faster in all the three treatments than in CK within the same time period, and in Treatment GSI than in Treatment DSI during the initial infiltration stage. In Treatment DSI, each batch infiltration significantly increased the next batch in infiltration rate for the first two batches, but for the last two, Treatment GSI fell significantly behind Treatment DSI in infiltration rate, owing to the lowering salinity of the infiltration water. At the end of the infiltration, the treatments were found following an order of DSI > GSI > MSI in water and salt content in the 0~40 cm soil layer; Treatment GSI and Treatment MSI were quite similar in soil water and salt distribution and reached up to 92.87% and 91.38% respectively in desalinization rate, which were apparently higher than 74.74% in Treatment DSI. The above findings have made clear the characteristics of the infiltration of saline water varying in salinity in coastal saline soil, and batch infiltration of saline water had an effect similar to that of infiltration of melting saline ice on desalinization, which provides an useful means to simulate infiltration process of meltwater, changing in salinity and volume with the saline ice melting, and a theoretical basis for the technology of irrigating saline soil with saline and fresh water alternative.