تأثیر گوگرد بر فرایند گیاه‌پالایی اسفناج از خاکهای آهکی آلوده به کادمیم

نوع مقاله: مقاله پژوهشی

نویسندگان

1 دانش‌آموخته دکترای بخش علوم خاک، دانشگاه آزاد اسلامی واحد علوم و تحقیقات تهران

2 استاد، بخش علوم خاک دانشگاه شیراز، شیراز

3 استاد، بخش علوم خاک، دانشگاه آزاد اسلامی واحد علوم و تحقیقات تهران

چکیده

همزمان با افزایش آلودگی خاکها ناشی از کاربرد لجن فاضلاب و کودهای فسفره و نگرانی انتقال این عنصر به گیاهان و چرخه مواد غذایی، روشهای متعددی از جمله گیاه‌پالایی برای پاکسازی زمین‌های آلوده پیشنهاد شده است. از آنجا که آهک نقش مهمی در نگهداری کادمیم در خاکهای آهکی دارد بنابراین به‌نظر می‌رسد اکسایش گوگرد با تأثیر بر‌ این بخش بتواند راندمان فرایند گیاه‌پالایی و استخراج کادمیم را بهبود بخشد. برای مطالعه تأثیر گوگرد تلقیح شده با باکتری تیوباسیلوس (معادل صفر،‌2،‌ 4 و 6 تن در هکتار) در خاکهای آهکی آلوده به 40 میلی‌گرم کادمیم در کیلوگرم خاک، بر اکسایش گوگرد و غلظت کادمیم عصاره‌گیری شده با دی‌اتیلن تری‌آمین پنتااستیک‌اسید و فرایند گیاه‌پالایی توسط اسفناج در طی 50 روز رشد گیاه، آزمایش گلخانه‌ای انجام گردید. تغییر pH، قابلیت هدایت الکتریکی و مقدار سولفات اندازه‌گیری شده بیانگر فرایند اکسایش گوگرد بود. با این‌حال، به‌رغم عدم مشاهده تغییر در غلظت کادمیم عصاره‌گیری شده با DTPA، کاربرد گوگرد به‌طور متوسط غلظت این عنصر را نسبت به شاهد 71/6 درصد افزایش داد اما مقدار رشد گیاه متأثر از سمّیت کادمیم و شوری خاک کاهش یافت. بیشترین مقدار جذب و استخراج کادمیم در تیمار معادل 2 تن در هکتار گوگرد و با 63 درصد افزایش نسبت به شاهد اندازه‌گیری شد. به‌نظر می‌رسد به‌رغم کاهش رشد گیاه در تیمارهای آزمایشی، کاربرد گوگرد در این خاکها توانسته مقدار استخراج کادمیم و فرایند گیاه‌پالایی را بهبود ببخشد و بیشترین بهره‌وری در تیمار معادل 2 تن در هکتار گوگرد و با 63 درصد افزایش نسبت به شاهد اندازه‌گیری شد.

کلیدواژه‌ها


عنوان مقاله [English]

Effect of Sulfur Application on Spinach Phytoremedaiton Process of Cadmium in Contaminated Calcareous Soils

نویسندگان [English]

  • Ali Kasraian 1
  • Najafali Karimian 2
  • Ebrahim Pazira 3
1 Former Ph.D. Student of Soil Science, Science and Research Branch, Islamic Azad University (IAU), Tehran, Iran
2 Prof., Dep. of Soil Science, Shiraz University, Shiraz, Iran
3 Prof., Dep. of Soil Science, Science and Research Branch, Islamic Azad University (IAU), Tehran, Iran
چکیده [English]

Recently, cadmium (Cd) concentration has increased in croplands through sewage sludge and phosphorous fertilizers application. On the other hand, some special methods, like phytoremedation, were introduced in order to decrease soil contamination hazard. Calcium carbonate plays an important role in Cd solubility in highly calcareous soils. Sulfurs oxidation, by dissolving Cd carbonate fraction, may improve phytoremediation efficiency. An experiment was conducted to study the effects of S application (equivalent to 0, 2, 4 and 6 Mg S ha-1) on Diethylene Triamine Pentaacetic Acid  (DTPA) extractable Cd and also on Cd uptake and extraction by spinach (Spinacea oleracea L.) in calcareous soils which were contaminated by 40mg Cd kg-1. To ensure biological S oxidation, all S-treated samples were inoculated by Thiobacillus spp. and incubated for 50 days. The soil pH, EC and soluble sulfate were affected by S application and it clearly showed that S oxidation process was occurred in Cd treated soils. The most significant change for pH and sulfate were observed at 4 Mg S ha-1 and for electrical conductivity (EC) of soil it occurred at 6Mg S ha-1. Application of S had no effect on DTPA extractable Cd in soils whereas; its concentration increased 73.55% in average in plant tissue. Plant dry matter decreased significantly (about 63 percent) following Cd application. Although the highest rate of S oxidation was observed at 4 and 6 Mg S ha-1 tٰٰٰhe maximum Cd extraction (2.5µg Cd pot-1) was observed at 2 Mg S ha-1 . This may be due to adverse effect of Cd toxicity and increase of soluble salt resulted by S oxidation in higher level of S application.

کلیدواژه‌ها [English]

  • Cadmium
  • Sulfur
  • Phytoremediation
  • Spinach
  • Calcareous soils
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