Effects of three super-absorbents application (A۲۰۰, Perlites and Zeolite) on soil erosion and sediments of saturated soils

Abstract

Introduction

The water consumption in the world has increased due to population growth, increasing per capita water use, and irrigation. In these areas, the most part of water resources, originated from rainfall, are consumed by agriculture. Soil aggregate and soil structural improvement should decrease soil erosion and increase soil permeability. Superabsorbent was extensively used for soil improvement and decrease of runoff. The literature review indicates that most study about superabsorbent focused on the effect of these materials on control erosion, infiltration and runoff in non- saturation condition, whereas study about saturation condition was not investigated. Also increase infiltration component, rise the ability of the soil to store water for plant use, and decrease soil evaporation could reduce the need for supplemental watering, decrease runoff and growth the sustainability of the plants but soil erosion is also important due to its role as the area for maintain water and other fertilizers . In the recent years, an increasing interest for using of natural aluminosilicates such as zeolite, perlite and other super absorbent in the agricultural activity has been observed.  The main aim of this study was to investigate the impacts of three types of superabsorbent on soil erosion in the saturation condition in the laboratory condition.     

Material and Methods

In this study the effect of application of three superabsorbent polymers (A200 Perlite and Zeolite) on runoff sediment at four level 0 (control) 510 and 15%   and two slope (5 and 10%) was investigated in saturated soil. The study was carried out in laboratory plots (100*40 cm) in a completely randomized design. Plots fill with untreated (control) and the treated soil. In each experiment, constant water intensity was created .Treated soils were irrigated under same intensity and exited runoff and sediment were measured for 20 minute. Sediment was measured after evaporate of water in 105 degrees centigrade.

Results and discussion

To determine the effectiveness of three type of super absorbent on drained water at the saturation condition, the sample collected from treated and control soil were analyzed. According to results, a significant decrease was observed in sediment amount after application of super-absorbents, but sediment reduction for three type of superabsorbent was different. According to the results, application of superabsorbent polymers at level of 5 and 10% significantly decrease the amount of sediments (P<0.05). Whereas the amount of sediment was increase when the level of superabsorbent increased to 15%. The maximum reduction of measured sediment for studied superabsorbent were 0.98, 1.28, and 1.56 for A200, perlite and zeolite respectively. Also all superabsorbent decrease the amount of sediment comparing to control treatment, but the efficiency of A200 was better than other super-absorbents. According to results, sediment intensity was 1.2 and 2.6 gram per lit in the slope of 5 and 10% in non-treatment condition respectively. For both study slopes, the amount of sediment decrease significantly where the amount of A200 was increased. The amount of sediment was decreased to 0.3 and 0.4 gram per liter for slope of 5 and 10%, when the application A200 was 0.67%.  Measured sediment decreased to 0.5 and 0.1 gram per liter for 1.35% of superabsorbent.  But the amount of sediments was decreased to 1.7 and 2 gram per liter when A200 increased to 2%.In this condition, non-significant difference was observed between control and treated soil .  We can conclude that the limitation amount of these superabsorbents for soil erosion control in saturation condition is 10%. These results are reported by other researchers (Xe hibin et al., 2001). Debhi et al (2013) also indicated that also superabsorbent could decrease soil erosion, but the amount and efficiency of them should relate to soil and atmospheric condition.

Conclusion

Most of super-absorbents are naturally volcanogenic sedimentary mineral composed primarily of aluminosilicates. These minerals have a three dimensional crystal lattice, with loosely bound cations, capable of hydrating and dehydrating without altering the crystal structure. This provides a natural material with the ability to exchange ions, absorb gases and vapors, act as molecularscale sieves and catalyze reactions owing to fixed pore sizes and active sites in the crystal lattice. Such material should increase soil water retention via water absorption and water maintain. But in soil saturation condition, these water storage and swell of soil aggregate should lead to increasing of surface runoff and consequently increase of soil erosion and sediment.