Environmental Erosion Research

fa بررسی تأثیر کاربری اراضی بر غلظت گرد و غبار و میزان هدررفت خاک در مناطق بیابانی (مطالعه موردی: عین خوش ـ دهلران، ایلام) An Investigation of Land-Use Effect on Dust Concentration and Soil Loss in Desert Areas: A Case of Ein Khosh-Dehloran, Ilam سناریوسازی و پیشی‌بینی وجوه مختلف فرسایش مستخرج از پایان‌نامه / رساله / طرح پژوهشی یکی از مهمترین بحران‌های زیست‌محیطی در مناطق خشک و نیمه‌خشک، پدیدهی مخرب بیابان‌زایی و فرسایش بادی است. وقوع طوفان‌های گرد و غبار ناشی از فرسایش بادی، فرآیندی است که باعث تخریب سرزمین می‌شود و می‌تواند به‌عنوان یک شاخص بیابان‌زایی قابل توجه قرار گیرد. این پژوهش به‌منظور بررسی میزان هدررفت خاک و غلظت گرد و غبار در کاربری‌های مختلف با استفاده از دستگاه‌های تونل باد وpro Microdust اجرا شدهاست. نتایج نشان داد شدت فرسایش بادی و میزان انتشار گرد و غبار با افزایش سرعت باد، از 2 به 16 متر بر ثانیه افزایش می‌یابد. همچنین با توجه به نتایج مشخص شد میزان این پارامترها در اثر فرسایش بادی در کاربری‌های مختلف، متفاوت است و در هر دو سری نمونه‌های دست‌خورده و دست‌نخورده، بیشترین و کمترین میزان فرسایش بادی و غلظت گرد و غبار به ترتیب در اراضی تپه ماسه‌ای، مرتع، جنگل دست کاشت کهور، کشاورزی و جنگل طبیعی کنار مشاهده شد. از طرفی در کاربری‌های مختلف، میانگین هدررفت خاک به میزان mg/cm2/min 03/0 و میانگین ذرات معلق به میزان mg/m3 27/0 در نمونه‌های دست‌خورده بیش از دست‌نخورده بود؛ زیرا در اثر نمونه‌برداری از ساختمان خاک به هم خورده، پایداری بین خاکدانه‌ها از بین میرود و خاک به‌راحتی در معرض بادبردگی قرار می‌گیرد. همچنین در اثر به هم خوردگی خاک، جرم مخصوص ظاهری نیز تغییر می‌کند؛ به گونهای که با افزایش جرم مخصوص ظاهری، کیفیت خاک کاهش می‌یابد. درنهایت با توجه به نتایج همبستگی و مؤلفه‌های Pc1  ـ که تأثیر کنترلی بیشتری بر فرسایش بادی دارد ـ می‌توان نتیجه گرفت مهمترین عواملی که در تولید گرد و غبار و فرسایش‌پذیری بادی خاک تأثیر دارند شامل رطوبت، بافت و ماده آلی خاک است و عواملی مانند نسبت جذب سدیم، شوری، تخلخل، منیزیم و آهک نیز اهمیت کمتری دارد. Extended abstract 1- Introduction The occurrence of dust storms caused by wind erosion is a process that causes the destruction of land and can also be considered as a desertification indicator (Xu, 2006). Generally, the formation of a dust storm depends on three factors: the presence of strong winds, a sensitive surface to wind erosion and unstable weather conditions (Xia and Yang, 1996). Humans play an important role in the formation of dust storms through changing land use in sensitive areas to sand storms. In the arid and semi-arid areas covered with tiny and unstable materials, land degradation may occur as a result of land use change caused by over-grazing and farming. As a result, wind erosion increases, leading to more sand storms (Xu, 2006). 2- Methodology For this research, first, using satellite imagery and land use map, the land uses in the study area that included the Ziziphus Nummularia natural forest, planted Prosopis Juliflora forests, agricultural land, sand dunes and rangelands were determined. After observing and accurately identifying the area, one week after the first rainfall, 15 undisturbed soil samples and 15 disturbed soil samples were collected from the area. After transferring the samples to the laboratory, the samples were exposed to dry air and then some physical and chemical properties of the soil were measured. Wind tunnel was used to determine the soil loss in different land uses, also the dust density determined using a Microdust pro device, which was installed in the outlet of the wind tunnel. This device measures dust concentrations in milligrams per cubic meter. So soil samples were simulated in 4 wind speeds including 2, 9, 16 m/s and wind erosion threshold velocity for 5 minutes. To determine the wind erosion threshold velocity, soil samples were placed in the wind tunnel. Then, by adjusting the wind speed that was possible by the inverter and using the accelerometer, the wind speed erosion threshold was measured in different land uses. In this way, the velocity has slowly increased, and the first particle that began to move was considered as the wind erosion threshold. In this study, the erosion rate was calculated from the ratio of the weight or volume of eroded soil to the sample surface. So, to determine the amount of soil loss, at the end of each experiment, the amount of sediment accumulated in the sediment trap was collected and weighed, and the soil loss was calculated based on the amount of soil erosion in grams per cm2 per minute. 3- Results Based on the results, there was no significant relationship between the dust concentration in the undisturbed and disturbed samples, but there was a significant relationship between soil loss in the undisturbed and disturbed samples. Comparison of the mean of suspended particles and the amount of soil loss in the both sample groups showed that the lowest and highest amount of suspended particles and soil losses was related to the Ziziphus Nummularia natural forest and sand dunes, respectively. According to the correlation results, there was a positive and significant correlation between wind erosion and SAR parameter (P <0.01), but there was a negative and significant correlation between the erosion and OC, Silt, SP and CS (P <0.01). Also, erosion had a negative correlation with EC, Mg, P and had a positive correlation with sand (P<0.05). The Principal Components Analysis (PCA) showed that three main components of wind erosion controller were Pc1, Pc2 and Pc3, whose quota were about 48.7%, 21% and 9.7%, respectively. 4- Discussion & Conclusions The results showed that by increasing the wind speed from 2 to 16 m/s, the intensity of wind erosion and dust concentration increased, but the amount of these parameters was various in different land uses. As in both sampling methods, these parameters had decreased from sandy hill, pasture land, planted Prosopis Juliflora forests, agriculture and Ziziphus Nummularia natural forest, respectively. In general, it can be said that in different land uses, the amount of soil loss and dust concentration in disturbed samples was more than undisturbed samples. Actually, since the soil structure is broken up during the sampling, the stability between the soil particles is lost and the soil is easily exposed to wind erosion. Also, due to the corrosion of the soil, the bulk density varies. As the bulk density increases, the soil quality will decrease (Harris et al, 1996). Finally, it was found that Pc1 components had more control over wind erosion. The components of Pc1 include EC, organic matter, Mg, lime, silt, saturation moisture content, porosity and compressive strength. These parameters have an effect on wind erosion, and cause erosion to be further reduced. دهلران, فرسایش بادی, کاربری اراضی, گرد و غبار,pro Microdust Dust, Wind erosion, Land use, Microdust Pro, Dehloran 1 20 http://magazine.hormozgan.ac.ir/browse.php?a_code=A-10-65-1&slc_lang=fa&sid=1 Marzieh Mirhasani مرضیه میرحسنی mirhasani239@gmail.com 10031947532846005014 10031947532846005014 No Ilam University دانشگاه ایلام Noredin Rostami نورالدین رستمی n.rostami@ilam.ac.ir 10031947532846005015 10031947532846005015 Yes Ilam University دانشگاه ایلام Masoud Bazgir مسعود بازگیر masoud.bazgir@gmail.com 10031947532846005016 10031947532846005016 No Ilam University دانشگاه ایلام Mohsen Tavakoli محسن توکلی mohtavakoli2003@yahoo.com 10031947532846005017 10031947532846005017 No Ilam University دانشگاه ایلام