نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشجوی دکتری گروه مهندسی علوم خاک دانشگاه تهران

2 استادیار پژوهشی پژوهشکده حفاظت خاک و آبخیزداری

3 استاد گروه مهندسی علوم خاک دانشگاه تهران

چکیده

در میان فرآیندهای مختلف تخریب اراضی، فرسایش خاک تهدیدیجدی برای منابع خاک و آب کشور است.  خصوصیات فیزیکی و شیمیایی خاک تأثیر مهمی بر تولید رواناب و رسوب دارند.  این تحقیق با هدف بررسی تأثیر برخی از این خواص در تولید رواناب، رسوب، و همچنین غلظت رسوب در شرایط صحرا انجام شد.  آزمایش­ها روی خاک­های منطقه گُل‌آباد اردستان با متوسط بارندگی سالیانه حدود 170 میلی‌متر اجرا شد.  به این منظور از یک باران­ساز قابل حمل در صحرا و در 9 واحد همگن از منطقه با 3 تکرار (جمعاً در 27 پلات آزمایشی) استفاده شد.  بارشی با شدت 35 میلی‌متر در ساعت به مدت 40 دقیقه روی پلات‌هایی با سطح یک متر مربع، شبیه‌سازی و نمونه‌های رواناب و رسوب در انتهای هر بارش جمع‌آوری شد.  همچنین برخی خصوصیات فیزیکی و شیمیایی شامل بافت خاک، سنگریزه در دو موقعیت (سطح و داخل خاک)، رطوبت اولیه و رطوبت در مکش های صفر، 03/0 و 5/1 مگاپاسکال، pH، EC، آهک و مادة آلی اندازه‌گیری شد.  نتایج حاکی از آن است که با افزایش میزان رس تولید رسوب و همچنین غلظت رسوب افزایش می­یابد در حالی که بخش شن، تولید رواناب و رسوب را کاهش می­دهد.  با افزایش سنگریزة سطحی و سنگریزة داخل خاک، رواناب به ترتیب افزایش و کاهش می­دهد.  سنگریزة سطحی نقش مهم­تری نسبت به سنگریزه داخل خاک نشان داد
به­طوری که افزایش آن افزایش تولید رسوب را نیز به دنبال داشت.  با افزایش رطوبت در مکش­های 03/0 و 5/1 مگاپاسکال، تولید رسوب و غلظت آن افزایش معنی­داری نشان داد.  افزایشpH باعث کاهش تولید رواناب شد.  آهک به دلیل تشکیل سلة سطحی، افزایش فرسایش را به دنبال داشت.  در مجموع، از میان خصوصیات بررسی­شده، توزیع اندازه ذرات مهم­ترین عامل در کنترل رواناب و رسوب در خاک­های مورد مطالعه معرفی شد.

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