土壤结构调理剂PAM对复垦铁尾矿砂物理性状的影响

聚丙烯酰胺(polyacrylamide,PAM)是一种常见的土壤结构调理剂,但在尾矿复垦中却少有应用。该文通过室内土柱模拟试验,采用干混法在铁尾矿砂中加入PAM,设置0%(对照)、0.05%、0.10%和0.20%共4种质量浓度PAM,观测PAM对铁尾矿砂物理性状的影响。结果表明:1)除总孔隙度之外,对照与混合PAM尾矿砂的容重、毛管孔度和毛管持水量差异显著(P0.05)。2)随着尾矿砂毛管水上升高度增加,PAM质量浓度越大,含水率下降的趋势越缓慢,但含水率的变异性却越大,变异系数从1.22%(10 cm)增大到7.13%(40 cm)。3)PAM会极显著抑制尾矿砂毛管水上升高度(P0.01)但PAM质量浓度不同,抑制程度不同。据此可将上升曲线分为3个阶段:第1阶段,0~5 min,上升高度相似阶段;第2阶段6~25 min,上升高度分异阶段;第3阶段30~420 min,上升高度变化规律相对稳定阶段。毛管水上升高度随时间变化呈现幂函数增加趋势,上升速率随时间变化呈现幂函数减小趋势。4)在自然通风状态下,72小时内不同PAM质量浓度尾矿砂的含水率均持续降低,纯尾矿砂含水率的降低幅度最大,从37.53%减少到35.60%;PAM质量浓度为0.20%的尾矿砂含水率降低幅度最小,从37.40%减少到36.67%。因此,PAM的合理使用能够有效改善尾矿砂的物理性状和水分运移,为无土区的植被恢复创造适宜的生长条件。

Effect of soil structure conditioner PAM on physical properties of iron tailings in reclaiming

Abstract: Polyacrylamide (PAM) is a common soil structure conditioner, but it is seldom applied in the reclaiming of iron tailings. In order to study the improvement effect of PAM on dry iron tailings, and promote the vegetation restoration on soilless mining area, PAM was added to iron tailings to form 4 mass contents of 0% (control), 0.05%, 0.10% and 0.20% respectively using dry mixing method. The physical properties of mixture were observed and measured by simulating water transporting in soil columns with 10 cm diameter. The results showed: 1) The physical properties of iron tailings added with PAM had some improvement compared to the control, and in the order of PAM mass contents of 0.05%, 0.10% and 0.20%, the bulk density decreased by 1.82%, 3.03% and 4.85%, the total porosity increased by 2.75%, 4.50% and 7.25%, and the capillary porosity increased by 13.39%, 25.03% and 27.54%, respectively. There was significant difference (P<0.05) between the control and the tailings added with PAM. 2) As capillary water rose from 0 to 40 cm in the soil column, the volumetric water content of iron tailings under 4 PAM concentrations all tended to decline. The higher the PAM mass content of iron tailings, the slower the declining trend of volumetric water content with rising height, but the variation coefficient of tailings volumetric water content under 4 PAM mass contents got bigger and bigger from 1.22% to 7.13% with the height rising from 10 to 40 cm. 3) The rising heights of capillary water under 4 PAM mass contents were 25, 14.3, 14.5, and 14.4 cm respectively after the test lasted for 420 min, among which the difference was extremely significant (P<0.01). But in the rising process, the inhibition ability of different PAM mass contents on capillary water was changeable, so the rising process was divided into 3 stages: Stage 1 (0-5 min), similar rising height for different PAM mass content; Stage 2 (6-25 min), the rising height under 4 PAM mass contents showed obvious difference in the same rising time; Stage 3 (30-420 min), relative stable change of rising height for different PAM mass content. In the whole rising process of capillary water, the rising rate of the control was significantly higher than that added with PAM, but the difference of rising rate under 3 PAM mass contents was not significant. The accumulative rising height of capillary water increased with the time following the power function; the rising rate of capillary water decreased with the time following the power function. 4) In the condition of natural ventilation, the water content of iron tailing under different PAM mass contents reduced continuously, but the extent of reduction was different; the water content change of the control was the sharpest, from 37.53% to 35.60%, and the water content change for 0.20% PAM was minimum, from 37.40% to 36.67%. Therefore, PAM can improve the physical properties of iron tailings, inhibit water loss and create appropriate growth environment for vegetation restoration. The reasonable use of PAM is very beneficial to soilless ecological rehabilitation and erosion control.