نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشجوی کارشناسی ارشد علوم مهندسی خاک دانشکده کشاورزی دانشگاه صنعتی اصفهان

2 استادیار خاکشناسی دانشکده کشاورزی دانشگاه صنعتی اصفهان

3 استاد خاکشناسی دانشکده کشاورزی دانشگاه صنعتی اصفهان

چکیده

میزان خطرآفرینی فلزات سنگین خاک برای گیاهان و سایر موجودات زنده در ارتباط با تغییرات اشکال شیمیایی و زیست‌فراهمی آنها در خاک می‌باشد. بنابراین درک بهتر توزیع فلزات در اشکال مختلف شیمیایی خاک نیازمند تحقیقات بیشتری است. به منظور بررسی اثر فعالیت ریشه و کود سبز یونجه (2% جرمی) بر تغییرات اشکال شیمیایی سرب، روی، مس و نیکل در خاک، آزمایشی گلخانه­ای با استفاده از سیستم رایزوباکس بر روی یک خاک آلوده به سرب و روی انجام گرفت. آزمایش با دو سطح کود سبز (صفر و 2 %) و 4 ناحیه با فاصله از ریشه، در سه تکرار و در قالب طرح اسپلیت پلات انجام شد. برای تعیین اشکال شیمیایی فلزات سنگین از روش عصاره‌گیری متوالی تسیر استفاده شد. نتایج نشان داد کود سبز به طور معنی­دار pH خاک را 2/0 واحد کاهش و کربن آلی محلول خاک را در ریزوسفر ذرت به مقدار بیش از دو برابر افزایش داد و بخش­های تبادلی و وابسته به مواد آلی و همچنین زیست­فراهمی فلزات سنگین را در خاک به طور معنی­دار افزایش داد. کربن آلی محلول خاک در ریزوسفر دارای بیشترین و در توده خاک دارای کمترین مقدار بود و مقدار pH در ریزوسفر 4/0 واحد کمتر از توده خاک اندازه­گیری شد. بخش اکسیدی فلزات با فاصله از ریشه روند افزایشی را نشان داد که احتمالاً به علت تبدیل بخش اکسیدی به شکل­های دیگر می­باشد. افزودن کود سبز به خاک باعث کاهش سرب اکسیدی و افزایش زیست­فراهمی سرب در ریزوسفر شد که ممکن است تبدیل بخش اکسیدی به بخش­های زیست­فراهم را تأیید کند. نتایج تجزیه گیاه نشان داد که افزودن کود سبز به خاک باعث کاهش غلظت سرب، روی و مس و همچنین کاهش جذب سرب و مس در شاخساره ذرت شد.

کلیدواژه‌ها

عنوان مقاله [English]

Effect of Green Manure on Chemical Forms of Some Heavy Metalsin Soil by Distance from Rhizosphere of Corn

نویسندگان [English]

  • Yaser Azimzadeh 1
  • Mehran Shirvani 2
  • Hossein Shariatmadari 3

1 MSc Student of Soil Science College of Agriculture Isfahan University of Technology

2 Assistant Professor of Soil Science College of Agriculture Isfahan University of Technology

3 Professor of Soil Science College of Agriculture Isfahan University of Technology

چکیده [English]

Environmental risk of heavy metals is associated with the changes of their chemical forms and bioavailability in soil. Therefore, distribution of metals in chemical forms in soil need to be more studied. To investigate the effects of alfalfa green manure (2% w/w) and root activity on chemical forms of lead, zinc, copper and nickel in a lead-zinc contaminated soil, a greenhouse experiment was conducted using rhizobox systems in a split plot design, with 3 replications, two levels of green manure (0 and 2%) and 4 zone by distance from root. Sequential extraction procedure (Tessier) was also carried out to differentiate the chemical forms of heavy metals in the soil samples. Results showed that the green manure addition enhanced dissolved organic carbon concentration (DOC) and reduced pH of the soil. It also increased exchangeable, organic matter-bound fractions and bioavailability of the metals. The highest and lowest values of DOC were found in rhizosphere and bulk soil respectively. The pH value in the rhizosphere was 0.4 times lower than in the bulk soil. Oxide fraction of metals increased with distance from the root that maybe related to the change of oxide fraction to other forms. Addition of green manure to the soil increased oxide fraction and bioavailability of lead in the rhizosphere that maybe approve the change of oxide form to more bioavailable forms. The results of plant analysis showed that green manure addition reduced the concentration of lead, zinc and copper and also reduced the uptake of lead and copper in shoots of corn.

کلیدواژه‌ها [English]

  • Heavy metals
  • sequential extraction
  • green manure
  • Rhizosphere
  • rhizobox
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