Evaluation of the Efficiency of Biocompatible Polymer in Reducing Dust Storms in Laboratory Conditions

Dust storm is a great challenge worldwide, especially in Iran. West and southwest regions of Iran are more exposed to dust storms due to their geographical position and neighboring countries such as Iraq, Syria, Jordan, Yemen, and Saudi Arabia. Today, scientists have proposed different ways to control wind erosion and dust storm; for instance, construction of live and non-living windbreaks to decrease wind velocity near the ground or covering soil surface through natural or chemical materials to prevent soil particles removal by winds in different intensities. Chemical polymers are one of the most effective methods to reduce soil erosion and dust. In recent decades, using synthetic polymers such as polyvinyl acetate has been considered in order to increase aggregate stability and soil stabilization. These polymers bind the soil particles to make larger aggregates and consequently increase aggregate stability. Moreover, the investigation of different mulches efficiency is essential in dust storm control and sand dune fixation. Therefore, the aim of this project was evaluating the efficiency of biocompatible polymer to decrease dust storms in laboratory conditions.

This project was conducted near Mehran city (Mohsen Abad plain) in Ilam province in 2019. In order to perform soil physical and chemical analyses, soil sampling was randomly carried out from soil surface (0-30 cm) in different places in the study area. These analyses consist of soil texture, soil saturation moisture, soil pH, EC, lime, soil organic matter, and aggregate stability. Moreover, to evaluate polyvinyl acetate, soil loss by wind tunnel, compressive strength, penetration and impact resistance are tested on samples. In this regard, soil samples collected in the study area were poured in trays with 35× 35× 3 cm dimensions. By considering four levels of polymer (C1=1, C2=1.5, C3=2, and C4=2.5 percent) with control (C0) in three replicates, 30 treatments were prepared. In order to evaluate polyvinyl acetate mulch, all tests consist of a wind tunnel simulator test, aggregate stability, permeability and impact resistance were performed after 28 days, and the results were studied. The data were analyzed by conducting one-way analysis of variance (ANOVA) and means comparisons were calculated by using Duncan test at significance levels of P ≤ 0.01 and P ≤ 0.05.

According to the results, the most and the least aggregate stability were observed significantly (P<0.05) in C4 treatment with 85 % and control with 18 %, respectively. The wind tunnel test showed that the highest soil loss belongs to control treatment (C0 =without mulch) with significant differences from other treatments. In terms of compressive strength, C4 treatment with 2.4 kg/cm2 had the highest compressive strength against the penetrometer device compared to other treatments. In addition, the result showed that by increasing the polymer concentration, the penetration rate of polyvinyl acetate polymer significantly decreased into the soil. Furthermore, increasing the polymer concentration, increased impact resistance compared to the control. In addition, based on the results, hit resistance rose by increasing polyvinyl acetate concentration so that the least and the highest hit resistance were observed for control treatment (C0: 3 cm penetration in the soil surface) and C4 (1.35 cm penetration in the soil surface) treatment, respectively.

One of the important soil physical properties is aggregate stability which can protect soil against erosion and erosive forces such as wind and rain. Based on the results of aggregate stability test, by increasing polyvinyl acetate concentration on soil surface, this factor improved significantly. Polymers bind primary soil particles together to form secondary particles or larger aggregates, which in turn increase aggregate stability. In soil conservation studies, wind tunnel simulation is used to monitor different mulch effects on wind erosion. In this study, the least soil loss is found when polymer is used, the reason can be explained by the fact that polyvinyl acetate cover soil surface and avoid wind contact with soil surface directly. Soil compressive strength depends on cementing agents directly and PVA in this study acted as a connection agent for soil particles. Based on the results, by increasing PVA amount, the compressive strength of the soil increased. Based on the given results of this research, polyvinyl acetate mulch from 2 to 2.5 concentration percent increases compressive strength and aggregate stability in laboratory conditions. Furthermore, this polymer attaches soil particles together and penetrates in the soil to increase compressive strength and influence dust storm control.  In general, polyvinyl acetate polymer can be used as a suitable mulch by creating a good physical and mechanical conditions in the soil. Nevertheless, it should be considered that these results have been obtained in the laboratory conditions. So, for application of PVA in the natural ecosystem such as arid land conducting further is research required.