灌溉水质对土壤饱和导水率和入渗特性的影响

为研究淡水与微咸水降水头入渗的差异,采用矿化度为1.0 g/L的微咸水与去离子淡水,对滨海围垦区粉砂土与南京黄棕壤土进行了一维降水头积水入渗试验。试验结果表明,采用微咸水入渗可以增大2种土壤的入渗能力,且对黄棕壤土的影响更为明显。利用Philip入渗模型对试验数据进行拟合,结果表明,模型可以较为精确地描述2种土壤的微咸水降水头入渗过程,且模型对黄棕壤土入渗过程的拟合精度更高。土壤水分与盐分再分布过程中,在粉砂土上层,微咸水灌溉对盐分的淋洗效果与淡水灌溉相近,但在土壤深层微咸水灌溉使土壤的积盐量显著高于淡水。采用淡水灌溉的黄棕壤土,土壤表层脱盐、深层积盐;采用微咸水灌溉的土柱剖面均明显积盐,且因表层土壤孔隙结构被破坏,持水能力增强,使表层土壤与深层土壤均积累了较高含量盐分。

Influence of Water Quality on Soil Saturated Hydraulic Conductivity and Infiltration Properties

In order to investigate the differences in falling-head infiltration between fresh water and saline water, one-dimensional precipitation-head water infiltration column experiments were carried out for two soils, i.e., coastal saline-alkali soil and yellow-brown soil by using either fresh water or saline water with mineralization of 1.0g/L. The results showed that higher infiltration rates were obtained for saline water than for fresh water and the wetting front advance was faster for both soils. It indicated that saline water could enhance the infiltration capacity of the two soil types. This was especially so for the yellow-brown soil because it had better structure and was more readily affected by salt in saline water. The analysis of Philip infiltration modeling showed that the model was able to describe process of both saline and fresh water falling-head infiltrations in both soil types. However, the model predictions of measured yellow-brown soil data were poorer than those of saline alkali soil data. This was caused by soil sorptivity, which was a constant in the Philip model, and it could not describe the slight decrease in infiltration capacity, which occurred with increase of infiltration duration, as accurately for the yellow-brown soil as it could for the saline alkali soil. During the redistribution processes of water and salt, the salt leaching was similar under saline and fresh water infiltration in the upper levels of saline alkali soil columns because desalting was the main process occurred in those layers. However, salt accumulation was evidently greater under saline water infiltration than that under fresh water infiltration in layers closer to the wetting front. The salt content was increased in the upper layers while it was decreased in the deeper layers of yellow-brown soil under fresh water infiltration; but it was increased in all of layers under saline water infiltration; and the top and bottom layers both had the highest levels of saltiness, because the salt was retained specifically in the top soil layers due to the damage in the soil structure and the increase in water retention capacity, while it was leached from middle layers into lower layer to some extent.