آلودگی خاک با فلزات سنگین، مسئلة مهمی است. این پژوهش با هدف بررسی غلظت فلزات سنگین (کادمیم، مس، آهن، منگنز، سرب و روی) در 102 نمونه خاک معدن سرب و روی کوشک شهرستان بافق در استان یزد انجام و غلظت به روش مربع لاتین تعیین شد؛ همچنین ارزیابی آلودگی خاک با استفاده از عامل آلودگی (CF)، غنیشدگی (EF) و شاخص زمینانباشتگی (Igeo) انجام شد.
نتایج نشان داد میانگین مقادیر کادمیم، مس، آهن، منگنز، سرب و روی در خاکهای منطقه بهترتیب 26/0، 39/0، 1/4، 3/5، 9/40 و 9/51 میلیگرم بر کیلوگرم است و در این بین، کادمیم، سرب و روی از حد آستانة ایران و جهان فراتر رفتهاند. در تمامی شاخصهای محاسبهشده، بیشترین مقدار به عنصر سرب مربوط بوده که دلیل آن، نوع سنگ مادری و زمینشناختی و فعالیتهای انسانی است.
تجزیه و تحلیل آماری چندمتغیره، مؤلفة اصلی و تجزیه و تحلیل خوشهای نشان داد فلزات سنگین بررسیشده در دو گروه طبقهبندی میشوند؛ گروه اول شامل عناصر مس، کادمیم، سرب و روی است که سرب و روی عمدتاً از آلودگیهای سنگشناختی و فعالیتهای انسانی ناشی از معدنکاری و ترافیک تأثیر میپذیرند؛ گروه دوم شامل منگنز و آهن است که این عناصر نیز از منابع سنگشناسی و انسانشناختی ناشی از فعالیتهای کشاورزی و کودهای شیمیایی تأثیر میپذیرند.
با توجه به اینکه خاک منطقة پژوهش علاوه بر عناصر سرب و روی به سایر فلزات سنگین نیز آلوده است، انجام پژوهشهای بیشتر در منطقه برای ارزیابی برنامههای راهبردی مدیریت منابع خاک ضروری است.
عنوان مقاله [English]
Evaluation of Heavy Metal Contamination in Soil Samples around the Lead-Zinc Mine of Kushk, Bafq, using Pollution Indicators and Principal Component Analysis
Soil is a major component of the biosphere that is exposed to pollutants such as heavy metals. Soil pollution by heavy metals is an important issue and heavy metals originate from the two main sources of natural resources and human inputs including mining, various industries, road transport, mineral and chemical fertilizers for agriculture, sewage sludge, and industrial wastes. Mining and mineral processing activities are the most important sources of potentially toxic elements entering the environment and pollute various parts of the environment (including water, soil, air, and vegetation sources). Along with population growth and industrial development, mining activities for metal extraction have also expanded and as a result, the environment around the mines has been more and more affected by metal pollutants.
Kushk Pb-Zn mine has been manually worked since 1940 and mechanized since 1964 and is located in a condensing and processing plant next to the mine. Mining waste is located on the margin of the mine deposited and can be spread downstream by wind or water. Because so far few studies have been conducted on the level and extent of pollution of soil sources around the lead and zinc mine, so the present study aims to evaluate the concentration of heavy metals (Cd, Mn, Cu, Fe, Pb, and Zn) and the extent of pollution and their environmental hazards were assessed in the study area.
Sampling was done in November 2018 and 102 soil samples were collected from the Kushk mine area and its surroundings. Sampling has been done inside and outside the mine up to a radius of about eight kilometers. The location of the samples was determined by the Latin square method. The Latin Square Method is an almost modern sampling method that is stratified or layered. Their concentration was measured using a German model atomic absorption spectrometer (Jena330). After reading the concentration by the atomic absorption spectrometer, the obtained data were analyzed by Excel and IBM SPSS Statistic 22 software. Also, to show the spatial distribution of pollution of different elements considered in the research, the IDW method was used to prepare the maps using Arc GIS 10.3 software. Also, soil pollution was assessed using the pollution factor (CF), enrichment factor (EF), and land accumulation index (Igeo).
This study evaluated six heavy metals in 102 soil samples (Cd, Mn, Cu, Fe, Pb, and Zn) conducted in the Kushk Pb-Zn mine in Bafq. The concentration of the studied heavy metals was in the order of Zn > Pb > Mn > Fe > Cd > Cu and only three elements of cadmium, lead, and zinc were above the alert threshold. The highest amount of elements was present in the southern part of the mine and near the mineral tailings and downstream of the road and sometimes on the road and machine traffic. The results showed the distribution of lead and zinc elements in the margins of the mine, especially in the margins of mineral tailings and downstream of the road. The reasons for this can be considered as the effect of wind and the existence of seasonal waterways in the transfer of these elements due to human activities such as mining and transportation to the mentioned points. Lead and zinc are gallons, so the amount of lead in the soil can indicate the geological origin of the contamination. The concentrations of copper, iron, and manganese for the soil in the study area were below the warning threshold. The results of the pollution indices used (except the Nemro index) indicated that the area was either not polluted or had little pollution. The Nemro index indicated that all elements (except copper) were severely contaminated. The lead was the highest element in all indicators, which can be said to be due to the type of parent rock and the geology of the region. On the other hand, the results of multivariate statistical analysis of heavy metals showed that vehicle and geological activities were the most important sources of zinc, lead, and cadmium contamination. Iron, copper, and manganese were mainly controlled by geological sources and parent materials, and manganese concentrations can be affected by fertilizers and agricultural soils. Due to the fact that the soil of the study area was contaminated with other heavy metals in addition to lead and zinc, so the need for more research in the area to evaluate strategic plans for soil resource management is necessary.