مطالعه و بررسی عناصر سنگین موجود در خاک شهرستان های زابل و بیرجند

خاک به‌عنوان عنصر اساسی در اکوسیستم‌های زنده جهت حفظ حیات در کره زمین ضروری است. یکی از مهم‌ترین مشکلات محیط‌زیستی امروزه، آلودگی خاک است به خصوص در کشورهای در حال توسعه بسیار مشهود است. این مشکل همواره یکی از نقاط توجه مسئولین شهری و محیط‌زیستی بوده است. هدف از این تحقیق بررسی عناصر سنگین موجود در خاک شهرستان‌های زابل و بیرجند است. به‌منظور بررسی میزان غلظت فلزات سنگین و نیز وضعیت آلودگی خاک در مناطق مورد مطالعه، از نمونه‌برداری خاک به روش شبکه‌ای منظم استفاده شد. تعداد 90 نمونه خاک از دو شهرستان و با نمونه‌برداری از خاک سطحی (صفر تا 25 سانتی‌متر) برداشت شد. پس از عملیات نمونه‌برداری، نمونه‌ها به آزمایشگاه انتقال یافت و پس از خشک شدن، از الک دو میلی‌متری عبور داده شد. سپس نمونه‌ها توسط دستگاه icp-oes در آزمایشگاه مرکزی دانشگاه سیستان و بلوچستان تحلیل شدند. نتایج حاصل از بررسی همبستگی فلزات سنگین شهر بیرجند توسط ضریب پیرسون در نرم‌افزار r نشان داد عنصرهای مس، روی و آرسنیک بیش‌ترین همبستگی منفی را با دیگر فلزات سنگین دارند؛ اما سایر فلزات سنگین رابطه‌ مثبت با یکدیگر داشتند. نتایج ماتریس همبستگی پیرسون برای غلظت فلزات سنگین موجود در خاک شهر زابل نیز نشان داد که بین بیش‌تر عناصر همبستگی منفی وجود دارد و در سایر موارد همگی دارای رابطه‌ همبستگی مثبت هستند. شاخص زمین‌انباشتگی نشان داد منشا آلودگی شهر بیرجند با عنصر کروم و سرب بیش‌تر منابع انسانی دارد. هم‌چنین، منشا سایر عناصر که در محدوده‌ غیر آلوده قرار داشتند را می‌توان از پوسته‌ زمین دانست. از طرفی در شهر زابل شاخص زمین‌انباشتگی نشان از آلوده بودن خاک منطقه به نیکل است؛ لذا می‌توان نتیجه گرفت که این دو شهر در الگوی آلودگی فلزات سنگین متفاوت هستند و منشا آن به عوامل محلی، مانند فعالیت‌های صنعتی، ترافیک و مصرف سوخت باز می‌گردد و نیازمند اقدامات بیشتر جهت کنترل و کاهش آلودگی فلزات سنگین در هر دو منطقه است.

study and investigation of heavy elements in the soil of zabol and birjand cities

introduction one of the most significant environmental challenges today is soil pollution, which is particularly evident in developing countries. this issue has consistently been a focal point of urban and environmental officials. soil, as a fundamental component of living ecosystems, is essential for sustaining life on earth. in addition to its crucial role in the continuity of life, soils have a significant impact on evolution and even the formation of life. they serve as a primary source for generating societal wealth and play a vital role in development projects and community health initiatives. today, the accumulation of heavy metals and soil pollution in agricultural lands is recognized as one of the most vital issues in the field of environmental biology globally. this not only compromises the quality of agricultural products but also jeopardizes the sustainability of agricultural production. the entry of heavy metals into soil ecosystems occurs through human activities, and researchers believe that these pollutant sources may pose long-term risks to human health. this is because prolonged exposure to surface soils containing heavy metals can lead to serious health hazards through inhalation, ingestion, and skin absorption.materials and methods the study areas in this research include two counties: birjand in south khorasan province and zabol in sistan and baluchestan province. in this study, a systematic grid sampling method was used for soil sampling. a total of 90 samples were collected, with a distance of 200 meters between each sample on both sides of the road. the sampling depth was 0-25 cm. after sampling, the samples were transferred to the laboratory. finally, 12 elements (al, mn, fe, cr, zn, ni, ti, co, cd, cu, as, pb) were analyzed in the soil samples using the icp-oes instrument (varian 710-es model). then, three indices, including muller's accumulation index, contamination factor, cumulative pollution index, and enrichment factor, were used to assess the degree of contamination in the soil samples. the pearson correlation matrix in r software was also employed to examine the relationships between heavy metals present in the soil samples from the cities of birjand and zabol.results and discussion the levels of metals present in the soil of birjand (compared to their concentration in the earth's crust) indicated high concentrations of lead, nickel, cadmium, zinc, copper, and chromium, which are related to human activities. according to the results obtained from the analysis of background soil samples, among the measured metals in zabol city, the highest average concentration was found in aluminum and iron, while the lowest average concentration was observed in nickel. the results of the pearson correlation analysis for heavy metals in birjand city showed that copper, zinc, and arsenic had the highest negative correlation with other heavy metals, while the rest of the heavy metals showed a positive correlation with each other. the results of the pearson correlation matrix for the concentration of heavy metals in the soil of zabol city also showed that there is mostly a negative correlation between most elements, while in other cases, they exhibited a positive correlation. based on the accumulation index, it can be stated that the origin of pollution in birjand city due to chromium and lead is primarily anthropogenic. additionally, the origin of other elements that fall within the non-polluted range can be attributed to the earth's crust. on the other hand, in zabol city, the accumulation index indicates soil pollution with nickel.conclusion based on the results of the study in the two cities of zabol and birjand, it can be concluded that the pollution status of heavy metals in these two cities differs significantly. considering the correlation between heavy metals in soil samples from the cities of birjand and zabol, it was found that in birjand, copper, zinc, and arsenic had negative correlations with other heavy metals, while the rest of the heavy metals showed a positive correlation with each other. however, in zabol city, most elements showed negative correlations. nevertheless, the strongest positive correlations were observed between titanium and iron, titanium and manganese, arsenic and lead, and manganese and cobalt. these results indicate differences in the pattern of heavy metal pollution between the cities, which may be attributed to local factors such as industrial activities, traffic, and fuel consumption. overall, this study highlights the need for further actions to control and reduce heavy metal pollution in both cities.