Environmental Erosion Research

fa ارزیابی کارایی پلیمر زیست سازگار در کاهش طوفان‌های گرد و غبار در شرایط آزمایشگاهی Evaluation of the Efficiency of Biocompatible Polymer in Reducing Dust Storms in Laboratory Conditions مدیریت و کنترل اثرات فرسایش محیطی مستخرج از پایان‌نامه / رساله / طرح پژوهشی فرسایش بادی و طوفانهای گرد و غبار از پدیده‌های رایج مناطق خشک و نیمه خشک است و پیامدهای زیانبار گسترده‌ای را به همراه دارد. ایران نیز به دلیل قرار گرفتن در کمربند خشک و نیمه خشک جهان، مستعد فرسایش بادی است. بنابراین، مقابله با این پدیده‌ها به برنامه‌ریزی کوتاه مدت و دراز مدت نیازمند است. امروزه از پلیمرهای شیمیایی برای بهبود ویژگیهای فیزیکی و مکانیکی خاک و کنترل فرسایش آن استفاده میشود. در این تحقیق، عملکرد پلیمر زیست سازگار پلیوینیل استات برای تثبیت سطح خاک در یکی از مکان‌های مولد گرد و غبار بررسی شد. بعد از شناسایی یکی از مناطق مستعد و مولد گرد‌ و ‌غبار در منطقه مهران در استان ایلام، نمونه‌برداری از عمق 30-0 سانتی‌متری انجام شد. بعد از تجزیههای فیزیکی و شیمیایی خاک، غلظت‌های مورد استفاده از این پلیمر شامل شاهد 1، 5/1، 2 و 5/2 درصد بر روی این نمونه‌ها (سینی 35×35×3 سانتی‌متری) اجرا شد. با در نظر گرفتن چهار سطح پلیمر در سه تکرار، تعداد سی نمونه آزمایشی تهیه شد و در قالب طرح آماری کاملاً تصادفی، بعد از 28 روز آزمونهای مختلفی بر آن صورت گرفت؛ نظیر آزمون مقاومت فشاری، مقاومت به ضربه، ضخامت لایه و پایداری خاکدانه. نتایج نشان داد که با افزایش غلظت پلیمر، میزان نفوذ پلیمر پلیوینیل استات به خاک به طور معنی‌داری کاهش یافت. همچنین با افزایش میزان غلظت پلیمر، مقاومت به ضربه نیز نسبت به تیمار شاهد افزایش یافت. بیشترین و کمترین پایداری خاکدانه نیز به طور معنیداری (P<0.05) به ترتیب در تیمار 5/2 درصد با 85 درصد و شاهد با 18 درصد دیده شد. در مجموع، با ایجاد شرایط فیزیکی و مکانیکی مناسب در خاک میتوان از پلیمر پلیوینیل استات به عنوان یک خاکپوش استفاده کرد؛ هر چند استفاده کاربردی از آن به ویژه در عرصههای طبیعی، به پژوهشهای بیشتری نیاز دارد و با در نظر گرفتن مسائل زیست محیطی امکانپذیر است.   1- Introduction: 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. 2- Methodology 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. 3- Results 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. 4- Discussion & Conclusions 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.    ایلام, پایداری خاکدانه, تونل باد, خاک‌پوش, فرسایش بادی. Ilam, Aggregate stability, Wind tunnel, Mulch, Wind erosion. 217 230 http://magazine.hormozgan.ac.ir/browse.php?a_code=A-10-891-1&slc_lang=fa&sid=1 MASOUD Bazgir مسعود بازگیر m.bazgir@ilam.ac.ir 10031947532846007616 10031947532846007616 Yes Soil and Water Engineering Department, Faculty of Agriculture, Ilam University, Ilam گروه مهندسی خاک و آب، دانشکده کشاورزی، دانشگاه ایلام، ایلام Davood Namdar Khojasteh داود نامدار خجسته davoodnamdar@gmail.com 10031947532846007617 10031947532846007617 No Soil Science Department, Faculty of Agriculture, Shahed University, Tehran گروه علوم و مهندسی خاک، دانشکده کشاورزی، دانشگاه شاهد، تهران Manocheh Mohammad Hosseini منوچهر محمد حسینی mohamadhosseni1397@gmail.com 10031947532846007618 10031947532846007618 No Soil and Water Engineering Department, Faculty of Agriculture, Ilam University, Ilam گروه مهندسی خاک و آب، دانشکده کشاورزی، دانشگاه ایلام، ایلام Mahmood Rostaminia محمود رستمی نیا mrostaminya@yahoo.com 10031947532846007619 10031947532846007619 No Soil and Water Engineering Department, Faculty of Agriculture, Ilam University, Ilam گروه مهندسی خاک و آب، دانشکده کشاورزی، دانشگاه ایلام، ایلام Majid Abdouss مجید عبدوس 10031947532846007620 10031947532846007620 No Organic Chemistry Department, Faculty of Chemistry, Amirkabir University of Technology, Tehran گروه شیمی آلی، دانشکده شیمی، دانشگاه اصنعتی امیرکبیر، تهران