ارزیابی خطر فلزات سنگین در خاک‌های اطراف شرکت صنایع فولاد خوزستان

نوع مقاله: مقاله پژوهشی

نویسندگان

1 گروه علوم و مهندسی خاک دانشگاه علوم کشاورزی و منابع طبیعی خوزستان

2 استاد خاکشناسی، دانشکده کشاورزی، دانشگاه کشاورزی و منابع طبیعی رامین، خوزستان، ایران

3 دانشگاه کشاورزی و منابع طبیعی رامین خوزستان

چکیده

سابقه و هدف: فلزات سنگین جزء آلاینده‌هایی هستند که با توجه به پایداری و دوام آن در محیط زیست، امروزه به یک معضل جهانی تبدیل شده اند. ورود این عناصر به زنجیره غذایی از روش های مختلف، تهدیدی جدی برای انسان و سایر موجودات می باشد. در اراضی کشاورزی واقع در اطراف مناطق صنعتی این تهدید جدی تر به نظر می رسد. لذا این پژوهش، با هدف ارزیابی خطر فلزات سنگین در خاک های اطراف شرکت صنایع فولاد خوزستان صورت گرفت.
مواد و روش‌ها: به منظور بررسی اثر کودهای آلی بر غلظت عناصر سنگین در گیاه اسفناج و گشنیز در خاک‌های آلوده طبیعی اطراف کارخانه صنایع فولاد خوزستان و محاسبه نسبت خطر (HQ) جهت ارزیابی سلامت غذایی این محصولات، آزمایشی فاکتوریل در قالب طرح پایه کاملاً تصادفی با سه تیمار فاصله از کارخانه صنایع فولاد (در سه سطح 100، 1000 و 10000 متر)، کود پیت (در دو سطح 0 و 3 درصد وزنی) و کود ورمی کمپوست (در دو سطح 0 و 3 درصد وزنی) با کشت دو گیاه آزمایشی اسفناج و گشنیز در سه تکرار انجام شد. مقدار عناصر روی، مس، نیکل، کادمیوم و سرب در نمونه های خاک به روش هضم با اسید (جهت برآورد مقدار کل)، عصاره گیری با DTPA و EDTA (جهت برآورد مقدار قابل دسترس) و در گیاه به روش خاکستر گیری تر انجام و با استفاده از دستگاه جذب اتمی اندازه گیری شد. نتایج مربوط به خاک و گیاه به ترتیب برای محاسبه شاخص آلودگی خاک و نسبت خطر مورد استفاده و ارزیابی قرار گرفتند.
یافته‌ها: نتایج نشان داد با افزایش فاصله از 100 متر به 10000 متر، مجموع مقدار کل فلزات سنگین در خاک حدود 75 درصد کاهش می یابد که مؤید نقش مستقیم کارخانه صنایع فولاد در آلودگی زمین‌های اطراف است. نتایج نشان داد کود های آلی با تاثیر بر تثبیت فلزات، خطر رها سازی آن‌ها به محیط زیست را کاهش می‌دهند. با مقایسه اثرات دو کود نتایج حاکی از آن است که اثر کود پیت نسبت به کود ورمی‌کمپوست در جذب سطحی عناصر و در نتیجه کاهش انتقال فلزات سنگین به گیاه بیشتر بوده و اما ورمی‌کمپوست در افزایش وزن تر و خشک گیاه موثر‌تر عمل کرده است. نسبت خطر محاسبه شده برای عناصر سرب و کادمیوم بیشتر از حد مجاز بود، اما در مورد سایر عناصر در شرایط فعلی خطری وجود ندارد که علت آن را می توان اثر ویژگی های خاک بر عدم انحلال پذیری ترکیبات حاوی فلزات سنگین دانست.
نتیجه‌گیری: با توجه به ارزش غذایی سبزیجات و اهمیت سلامت محصولات ارائه شده، استفاده از کودهای آلی جهت غنی سازی خاک ها علاوه بر افزایش کمیت، می تواند بر سلامت محصولات به ویژه در مناطق با تهدید آلودگی های زیست محیطی کمک نماید.

کلیدواژه‌ها


عنوان مقاله [English]

Risk Assessment of Heavy Metals in Soils around Khuzestan Steel Company

نویسندگان [English]

  • Mahboobeh lajmirorak Nejati 1
  • Nafiseh Rang Zan 1
  • Habibollah Nadian Ghomsheh 2
  • Bijan Khalilimoghadam 3
1 Department of Soil Science, Agricultural Sciences and Natural Resources University of Khuzestan
2 Department of Soil Science, Agricultural Sciences and Natural Resources University of Khuzestan
3 1Department of Soil Science, Ramin Agriculture and Natural Resources University of Khuzestan
چکیده [English]

Background and Objectives: Heavy metals are the pollutants that became a global problem because of their stability in environment. Each year on a global scale thousands of tons of heavy metals are release into the soil system. The most important pathway of exposure to human is daily intake of food. Accumulation of heavy metals in soil and cross the critical limit, make unsafe food which is menacing human health. The human body is adopted with essential elements such as iron, copper, manganese and zinc in special dose but high concentration of iron and manganese cause Parkinson's disease. High concentration of copper causes damage to the liver and high concentration of zinc causes malfunctioning of copper which has effect on immune system. Other metals such as lead and cadmium at any concentrations induced renal tumors, reduced growth and increased blood pressure, therefore, the risk of cardiovascular diseases for adults can be increased.This experiment was conducted to evaluate the non-carcinogenic risk assessment of heavy metals in spinach and coriander grown on metal contaminated soils which were collected from vicinity of Khuzestan Steel Company.
Materials and Methods: For this purpose, topsoil samples (0-15 cm) were collected from around of Khuzestan Steel Company according to prevailing wind direction (east-west). Exact sampling location was determined using GPS. Total metal content was determined using aqua-regia solution digestion method. EDTA and DTPA extractable metal also measured with standard methods. The experiment was laid out in factorial completely randomize designs with three treatments consist of distance (100, 1000 and 10000 meters), vermicompost (0, 3% w/w) and peat in (0, 3% w/w) with three replications. Seeds of spinach and coriander were sown in pots and harvested after 8 weeks. Total metal content in plants analyzed after digestion with di-acid mixture. According to toxic level of Zn, Cu, Cd, Pb and Ni hazard quotient was calculated.
Results: The results showed that organic manures stabilize metals and reduce the risk of their release into the environment. The effect of Peat on adsorption and reducing heavy metals transfer to plant was higher than vermicompost, whiles vermicompost was more effective in increasing fresh and dry weight of both of plants. By and large, heavy metals were reduced in soils as distance from factory increased. This is indicating the role of the factory to contaminate the surrounding land. Hazard quotient value in case of lead and cadmium were more than permissible limit but about others were acceptable which may be related to soil properties which are preventing heavy metals solution.
Conclusion: According to nutrition aspects of vegetables and importance of providing high quality food, application of organic manure in soil can be effective not only in increasing quantity of production but also in quality of them especially in case of polluted area.

کلیدواژه‌ها [English]

  • Contamination Index
  • Hazard Quotient
  • Spinach
  • Coriander
  • Organic Manure
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