تعیین مهمترین شاخص‌های مقاومت سله و تاثیر آن بر کنترل فرسایش بادی در کانون‌های گردوغبار خوزستان

بررسی حاضر به‌منظور تعیین برخی ویژگی ‌های سله و ارتباط آن با کنترل فرسایش بادی در کانون‌های گردوغبار خوزستان انجام شد. برای انجام این پژوهش، تعداد 18 نمونه سله هرکدام شامل سه نمونه فرعی از عمق cm 5 تا 0 از کانون‌های گردوغبار استان خوزستان برداشت شد، پس از هوا خشک شدن از الک mm2 عبور داده شد. سپس متغیرهای ph ،ec ،caco3 ،cec ،esp ،ca ،k ،mg ،po43، بافت، رطوبت اولیه، چگالی ظاهری سله‌ها اندازه‌گیری شد همچنین میزان حساسیت خاک به تشکیل سله با به‌کارگیری شاخص‌های پایداری خاک، سله بندی خاک، مقاومت فشاری، مقاومت برشی ارزیابی شد و از شاخص‌های میانگین وزنی قطر خاکدانه و میانگین هندسی قطر خاکدانه‌ها برای بررسی میزان پایداری خاکدانه‌ها بهره گیری شد. همچنین برای بررسی تاثیر این سله‌ها بر میزان کنترل فرسایش بادی نمونه‌هایی برای آزمایش تونل باد برداشت شد و مقدار بادبردگی و سرعت آستانه فرسایش بادی آنها تعیین شد. برای بررسی صحت و دقت مدل‌های رگرسیونی از آماره‌های rmse، rse، ame و 2 r استفاده شد. نتایج بررسی ساختار سله‌ها با میکروسکوپ الکترونی روبشی نشان داد که بیشتر سله‌های موجود در کانون‌های گردوغبار از نوع رسوبی می‌باشند همچنین مطابق با یافته‌های بررسی حاضر برای ارزیابی حساسیت خاک به تشکیل سله در کانون گردوغبار شرق اهواز شاخص مقاومت فشاری، در کانون گردوغبار جنوب شرق اهواز شاخص پایداری و در کانون گردوغبار امیدیه، ماهشهر و هندیجان شاخص مقاومت برشی شناخته می‌شود از مقایسه سرعت آستانه فرسایش بادی و مقدار هدررفت خاک در سله‌‌‌ سطحی و نیز نمونه‌های تخریب‌شده آن چنین نتیجه گرفته می‌شود که در سله‌های سطحی هر کانون میزان فرسایش بادی از حالت تخریب‌شده آن کمتر است.

determining the most important indicators of surface crust resistance and their effect on wind erosion control in dust storm sources in khuzestan

introductionin most arid and semi-arid areas, the soils have a compact surface layer that is denser and less permeable than the underlying layers. these layers are referred to as surface coating when they are wet, and when they dry, they are referred to as surface crust. surface crust can be divided into physical, chemical, and biological crusts depending on the nature of formation. physical and biological soil crusts are the most significant types of soil crusts in arid and semi-arid regions. two types of the physical crust are structural and depositional. natural events, such as raindrops and the drying process, are the primary causes of the formation of surface crust. the process involves the creation of hard, thin layers on the surface of the soil. the thickness of the surface crusts is typically between 1 mm and 5 cm. many researches have described different theoretical mechanisms for the formation of surface crusts in soil and reported their effective role in controlling wind erosion. the formation of crust in soil involves multiple stages, and the reaction of the soil surface to raindrop energy is divided into two main parts, as it was demonstrated. the first part involves the splashing of soil particles by raindrops’ impact. a layer with a thickness of approximately 0. 1 mm is produced in this instance. the second component is composed of fine soil particles that penetrate the soil pores with water and cause the formation of a layer that is 2 mm thick. according to a study, soil loss control is not affected by the crust cover beyond 30%. there is a linear relationship between soil loss and surface crust coverage, as the surface crust cover develops gradually, soil loss differs between soil types. material and methodsduring field surveys of dust storm sources in khuzestan, it was observed that there are surface crusts that are strong enough to act as a barrier against wind erosion in certain locations. the suggestion was made to investigate the type and general characteristics of these surface crusts. the purpose of this study is to examine the general characteristics of these surface crusts and their effect on wind erosion control. the study was conducted by randomly obtaining 18 surface crust samples, each containing three sub-samples from a depth of 0 to 5 cm from the dust storm sources of khuzestan province. after being air dried, they were then passed through a sieve of 2 mm. the factors of ph, ec, caco3, cec, esp, ca, mg, po3-4 texture, initial moisture, and apparent density of the surface crusts were measured. the soil’s sensitivity to crust formation was assessed by using soil stability index, crusting index, pressure resistance, and shear resistance. the stability of soil aggregates was assessed using the mean weight diameter and geometric mean diameter indices. soil samples were collected and tested in a wind tunnel to examine the impact of these surface crusts on wind erosion control and the amount of soil loss and the speed of wind erosion were assessed. an orbital wind tunnel device was utilized for this purpose. trays with soil were placed on the bottom of the tunnel in this manner. after the wind blew (speeds of 15, 10, 25 m/s) by measuring the difference in the weight of the tray before and after the wind blowing, the amount of erosion was calculated from a certain surface. then, the threshold speed for wind erosion was determined. statistical analysis was carried out using spss 26 software. the kolmogorov-smirnov test was used to verify data normality. then, the data sets were entered into a step-by-step regression as independent components to determine their relationship with the index of crust formation and stability of soil aggregates, as well as the effect of crusts and stability of soil aggregates on the amount of wind erosion.