به‌کارگیری روش‌های ساختاری ژئوشیمیایی فرکتال و آمارۀ U جهت تعیین مناطق آلوده به عنصر سرب مرتبط با فعالیت‌های معدنی در منطقۀ ایرانکوه

نوع مقاله : مقاله پژوهشی

نویسندگان

1 گروه مهندسی عمران، دانشکدۀ فنی و مهندسی، دانشگاه محقق اردبیلی، اردبیل، ایران

2 گروه مهندسی معدن، دانشکده فنی و مهندسی، مجتمع اموزش عالی گناباد، گناباد، ایران

3 دانشکده مهندسی معدن، دانشگاه صنعتی اصفهان، اصفهان، ایران

چکیده

شناسایی عناصر سمی و آلاینده و تعیین مناطق آلودگی اطراف فعالیت‌های معدنکاری از مسائل ضروری در آلودگی‌های زیست‌محیطی معادن است. فلزات سمی می‌توانند از طریق گردوغبار، آب و فعالیت‌های انسانی به‌طور گسترده در اطراف معادن توزیع شوند. در این مطالعه، تعیین ابعاد آلودگی فلز سرب در محیط اطراف معدن سرب و روی ایرانکوه موردبررسی قرارگرفته است. بدین منظور تعداد 137 نمونه از خاک محدودۀ اطراف معدن از عمق صفر تا سی سانتی‌متری برداشت‌ شده است. آلودگی‌های زیست‌محیطی به‌ویژه عناصر سرب و روی که در مناطق کشاورزی جنوب معدن ایرانکوه پراکنده شده‌اند نگرانی‌هایی را ایجاد کرده است. جهت تعیین مناطق آلوده و تشخیص جوامع ژئوشیمیایی عنصر سرب در قسمت‌های جنوبی این معدن، روش‌های فرکتالی عیار–مساحت و طیف توان–مساحت همراه با روش مدل‌سازی آمارۀ فضایی U در قالب روش‌های ساختاری ژئوشیمیایی مورداستفاده قرار گرفته است. روش فرکتالی طیف توان–مساحت یک روشی جدید در حوزه مطالعات زیست‌محیطی است که جوامع فرکانسی عنصر آلاینده را موردبررسی قرار می‌دهد. این روش جوامع فرکانسی سرب را در 4 کلاس فرکانس بالا، نسبتاً بالا، متوسط تا پایین و پایین تقسیم‌بندی کرد. کلاس فراوانی متوسط تا پایین به‌خوبی توانست محدوده آلودگی را نشان دهد. نتایج مدل‌سازی فرکتالی عیار–مساحت نشان داد که گستردگی آلودگی در منطقه تا مناطق کشاورزی و مسکونی هرچند با غلظت اندک وجود دارد. هاله‌های پراکندگی آلودگی زیست‌محیطی به‌دست‌آمده از این روش برای عنصر سرب با واقعیت‌های میدانی بیشتر مطابقت دارد. این روش توانست دو الگوی مقادیر آنومال آلودگی و زمینه را برای داده‌های تخمینی عنصر سرب با اطمینان بیشتری تخمین بزند. روش آمارۀ فضایی U جوامع بالاتر را به‌درستی در محدودۀ استخراجی و محل سد باطله تعیین می‌کند، اما جامعۀ میانی که غلظت این عناصر را در محدودۀ زمین‌های کشاورزی و مسکونی نشان می‌دهد، دارای گستردگی هالۀ کمتری نسبت به روش‌های دیگر است و با مشاهدات میدانی کمتر مطابقت دارد. همچنین به دلیل وجود عامل باد به‌عنوان یکی از عوامل مهم در پخش مواد از سد باطله به سمت غرب، به نظر می‌رسد تثبیت ذرات سطحی در سد می‌تواند یکی از اولویت‌های پیشنهادی در منطقه باشد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Application of geochemical structural methods to determine lead-contaminated areas related to mining activities

نویسندگان [English]

  • Mirmahdi Seyedrahimi-Niaraq 1
  • hossein Mahdiyanfar 2
  • Ahmad Reza Mokhtari 3
1 Dept. of Civil Engineering, Faculty of Engineering and Technology, Mohaghegh Ardabili University, Ardabil, Iran
2 Dept. of Mining Engineering, Faculty of Engineering and Technology, Gonabad Higher Education Complex, Gonabad, Iran
3 Dept. of Mining Engineering, Isfahan University of Technology, Isfahan, Iran
چکیده [English]

Summary
In this study, the determination of lead –contaminated areas around the Pb-Zn Irankooh mine located in Iran has been investigated using S-A and C-A fractal models and U statistical method. The S-A fractal method is a new method in the field of environmental studies that detects the frequency communities of the polluting element. The results of C-A fractal modeling showed that there is a range of pollution in the agricultural region and residential area. The U-spatial statistics method correctly determined the contaminated communities in the extraction area and the tailings dam location.
Introduction
Distinguishing between anomalous and background communities and determining the threshold of geochemical communities are usually done by structural and non-structural methods. The U spatial statistical method is one of the structural methods for geochemical anomaly separation, which is known for its high capabilities in determining geochemical anomalous areas in mineral exploration. In this investigation, U statistics, S-A, and C-A fractal methods have been used for modeling Pb-contaminated areas.
Methodology and Approaches
The geochemical distribution maps have fractal dimensions. Fractal dimensions of the anomaly and the background will be different from each other, which are used to separate the anomaly from the background. The S-A fractal method has been performed on the geochemical data in the frequency domain. The geochemical log-log diagram of the power spectrum values and cumulative areas is delineated, and straight lines are fitted on the diagram to show the trends of fractal populations. The U-spatial statistics method is a kind of moving averaging method that changes the dimensions of the window in which the averaging takes place at any specific point. Therefore, for each particular point, several U statistic values are calculated using the surrounding points, thus the spatial relationship of the samples is completely considered. 
Results and Conclusions
In this study, the Pb contaminations resulting from the distribution of this element in the surrounding areas of the Irankuh mine have been investigated. The C-A, S-A fractal, and U statistics methods were performed for pollution anomaly mapping. Four geochemical communities with different dimensions were obtained using C-A fractal method. The higher fractal dimensions are associated with Pb contamination of mining activities or human impacts and are known as anomalous communities. The communities with lower fractal dimensions are considered as background. The results of the fractal method show that the source of contamination has originated from the mine area and dispersed in the surrounding areas. The S-A fractal method separated the frequency signals in 4 geochemical communities. The population 2 including medium to low-frequency signals properly determined the contamination locations. The geochemical community with high concentrations correctly determined the contamination districts around the mining activities and tailings dam using U modeling. The middle community showed the agricultural and residential lands have a smaller contamination halo than other methods.

کلیدواژه‌ها [English]

  • Pollutant elements
  • U Spatial statistics method
  • Determination of pollution areas
  • C-A Fractal model
  • S-A Fractal model
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