غلظت کل و قابل جذب فلزات سنگین و ارزیابی شاخص های آلودگی در خاک های شهرستان زنجان

نوع مقاله : مقالات پژوهشی

نویسندگان

مرکز تحقیقات و آموزش کشاورزی و منابع طبیعی استان زنجان

چکیده

به‌منظور برآورد میزان آلودگی خاک، غلظت کل و قابل جذب فلزات سنگین در 144 نمونه تهیه شده از عمق 15-0 سانتی متری خاک‌های اطراف شهرستان زنجان اندازه گیری شد. سپس شاخص های ارزیابی میزان آلودگی (زمین انباشتگی، فاکتور غنی سازی و نسبت قابل جذب) محاسبه و نقشه‌های پراکنش فلزات سنگین به روش عکس فاصله تهیه شد. مقادیر میانه غلظت کل فلزات (با عصاره گیر تیزاب سلطانی) برای کادمیم، مس، سرب و روی به ترتیب برابر 5/0، 5/22، 14 و 3/82 و مقادیر میانه غلظت قابل جذب (استخراج شده با DTPA) آن ها به ترتیب برابر 1/0، 9/0، 6/1 و 2/3 میلی گرم بر کیلوگرم خاک اندازه گیری شد. صدک نودم شاخص زمین انباشتگی نشان داد حداقل 10 درصد نمونه ها آلوده به فلزات روی، سرب و کادمیم هستند. از نظر شاخص فاکتور غنی سازی، آلودگی با منشأ درازمدت مشاهده نشد. بالا بودن نسبت قابل جذب فلزات سرب و روی نشان داد منشأ آلودگی آن ها یکسان بوده و از منابع جدید آلاینده به خاک ها وارد شده اند. تمام شاخص‌های ارزیابی آلودگی با ماده آلی خاک ها همبستگی مثبت (به‌جز نسبت قابل جذب کادمیم) داشتند. بنابراین ماده آلی عامل اصلی کنترل‌کننده این شاخص‌ها شناخته شد. شاخص‌های زمین انباشتگی روی، کادمیم و سرب و نسبت‌های قابل جذب روی و سرب نیز با اسیدیته خاک ها همبستگی منفی نشان دادند. درنتیجه در طول فصولی از سال قابلیت جذب فلزات سنگین در خاک افزایش می‌یابد.

کلیدواژه‌ها


عنوان مقاله [English]

Total and Available Heavy Metal Concentrations and Assessment of Soil Pollution Indices in Selected Soils of Zanjan

نویسندگان [English]

  • M. Taheri
  • M. Esmaeili Aftabdari
  • T. Khoshzaman
  • M. Tokasi
  • M. Abbasi
Agricultural and Natural Resources Research Center of Zanjan Province
چکیده [English]

Introduction: Soil is a hardly renewable natural resource. Although soil degradation, caused by either human activities and natural processes is a relatively slow procedure, but its effects are long lasting and most often, irreversible in the time scale of man's life. Among the most significant soil contaminants resulting from both natural and human sources, heavy metals are more important due to their long- term toxicity effects. For evaluating soil's enrichment rate by heavy metals, a wide and full study of soils background values, including total and available fractions of heavy metal contents should be done. Zanjan province has some great mines and concentrating industries of lead and zinc especially in Angoran, Mahneshan. Unfortunately produced waste materials of these industries spread over the adjacent areas. Investigations showed that accumulation of some heavy metals in vegetables and crops planted in this region had occurred. Therefore, performing some investigations in these polluted areas and assessing pollution rate and heavy metals distribution in arable lands had prime importance. Our goals were: 1) determining the total and available amounts of Cu, Pb, Zn and Cd in the soils of arable lands in polluted areas of Zanjan city, 2) producing the distribution map for the metals mentioned above and 3) calculating pollution indices in the soils.
Materials and Methods: The study area was in south west of Zanjan city. For soil sampling, a 1 Km by 1 Km grid defined in ArcGIS software on landuse layer and totally 144 points that placed on agricultural lands, due to our goals, were sampled. For sampling, in a 5m radius around the point we collected some subsamples from depth of 0 - 15 cm, and after mixing the subsamples, finally a 1Kg soil sample prepared and sent to the laboratory. Sampled soils were air dried and were passed through a 2mm sieve. Soils organic matter (OM) content and texture were determined by Walkely-Black and Bouyoucos hydrometer methods, respectively. Soils pH were determined by glass/calomel electrode in saturation paste, EC by EC-meter in saturation paste extract, and calcium carbonate equivalent (lime) by reverse titration method. Total and available amounts of Zn, Cu, Cd and Pb were extracted by Aqua- Regia method (wet oxidation by chloridric acid and nitric acid with the 3:1 ratio) and by DTPA extracting solution, respectively. After extracting and filtering liquid samples, metal concentrations were measured by atomic adsorption method using GBC avanta P. Statistical analysis by SPSS and indices calculation by Excel were performed, and distribution maps were prepared by Inverse Distance Weighting method in ArcGIS software. For evaluating pollution rate, Geoaccumulation index, Enrichment factor and Availability Ratio indices were calculated and interpreted.
Results and Discussion: The textures of soil samples were loam, clay loam and sandy loam. The OM contents of almost soils were less than 2 percent. Lime was less than 25 percent and acidity of soils were neutral to slightly alkaline. Soils salinity were less than 2 dS/m except a few samples. Accordingly, these soils were suitable for agriculture and there were no limitation due to evaluated properties. Median values for the total concentrations of Cd, Cu, Pb and Zn (extracted by Aqua Regia) were 0.5, 22.5, 14 and 82.3 mg/Kg of soils, respectively, and for available fraction (extracted by DTPA) were 0.1, 0.9, 1.6 and 3.2 mg/Kg of soils that were much lower than measured total values. According to 90th percentile of geoaccumulation index, at least 10 percent of samples had been polluted with Zn, Pb and Cd. Enrichment factor revealed no long term pollution. Availability ratios of Pb and Zn were relatively high, showing there exists unique and recent pollution source for them. All pollution indices showed positive correlations with OM content of soils (except for availability ratios of Cd, which had negative correlation). Therefore, OM content of soils were respect to control these indices. Geoaccumulation index of Zn, Cd and Pb, and availability ratios of Zn and Pb showed negative correlations with soil pH. Therefore, in some seasons of the year, their availabilities will increase in soil.
Conclusion: The results showed that Cu content in soils were not in the critical limit but Cd, Pb and Zn content in soils were greater than standard levels and reclamation procedures for remedy of these soils must be done. The high values of the heavy metals in available fraction inthe soils increased the risk of bioaccumulation in microbial and biotic tissues. In areas where there are high content of available form of heavy metals in soils, it could be an index of new contamination in soils by heavy metals. According to geoaccumulation index of Cd, Zn and Pb, there are some contaminated points around waste depositition areas near Zanjan city. These points are in the direction that wind could effectively transport the particles of wastes to urban area. Enrichment factor (EF) showed that at least there were a few points polluted by Cd, Zn and Cu, although EF values were generally low. The leaked wastes of Zinc and lead industries had been spread in deposited areas caused difficulties in determining background values for the selected metals.

کلیدواژه‌ها [English]

  • Heavy metals
  • Pollution indices
  • Geoaccumulation index
  • Enrichment factor
  • Availability ratio
1- Afyuni M., Rezaee Nejad Y., and Khayyambashi B. 1998. Effect of sewage sludge on yield and heavy metal uptake of lettuce and spinach. Journal of crop production and processing, 2 (1): 19 - 30. (in Persian)
2- Amini M., Afyuni M., and Khademi H. 2007. Modeling cadmium and lead balances in agricultural lands of Isfahan region, central Iran. Journal of Science and Technology of Agriculture and Natural Resources, Water and Soil Science, 10 (4):77 - 90. (in Persian)
3- Bouyoucos G. H. 1951. A recalibration of the hydrometer method for making mechanical analysis of soils. Agronomy Journal, 43: 434–438.
4- Chen M., and Ma L. Q. 2001. Comparison of Three Aqua Regia Digestion Methods for Twenty Florida Soils. Soil Science Society of America Journal, 65: 491 – 499.
5- Chester R., Nimmo M., and Keyse S. 1996. The influence of Saharan and Middle Eastern desert-derived dust on the trace metal composition of Mediterranean aerosols and rainwaters: an overview. p. 253–273. In S. Guerzoni and R. Chester (ed.) Impact of desert dust across the Mediterranean. The Netherlands: Kluwer.
6- Dousis P., Anastopoulos I., Gasparatos D., Ehaliotis C., and Massas I. 2013. Effect of time and glucose-C on the fractionation of Zn and Cu in a slightly acid soil. Communications in Soil Science and Plant Analysis, 44. doi:10.1080/00103624.2013.748123.
7- Ezeh H. N., and Chukwu E. 2011. Small scale mining and heavy metals pollution of agricultural soils: The case of Ishiagu mining district, south eastern Nigeria. Journal of Geology and Mining Research, 3(4): 87 - 104.
8- Farahmandkia Z., Mehrasbi M. R., Sekhawatju M. S., Hasanalizadeh A. Sh., and Ramezanzadeh Z. 2010. Study of heavy metals in the atmospheric deposition in Zanjan, Iran. Iran's Journal of Health and Environment, 2 (4): 240 - 249. (in Persian with English abstract)
9- Fostner U., and Muller G. 1981. Concentration of trace metals and polycyclic aromatic hycarbons in river sediments: geochemical background, man’s influence and environmental impact. Geojournal, 5: 417–432
10- Giannakopoulou F., Gasparatos D., Haidouti C., and Massas I. 2012. Sorption behavior of cesium in two Greek soils: effects of Cs initial concentration, clay mineralogy and particle size fraction. Soil and Sediment Contamination, 21(8): 937–950.
11- Grubinger V., and Ross D. 2011. Interpreting the results of soil tests for heavy metals. University of Vermont, USA. Available at: http://www.uvm.edu/vtvegandberry/factsheets/interpreting_heavy_metals_soil_tests.pdf. (visited 7 December 2014).
12- Kabata-Pendias A. 2011. Trace elements in soils and plants (4th ed.). Boca Raton: CRC.
13- Karami M., Afyuni M., Rezaee Nejad Y., and Khosh Goftarmanesh A. 2009. Cumulative and residual effects of sewage sludge on zinc and copper concentration in soil and wheat. Journal of Science and Technology of Agriculture and Natural Resources, Water and Soil Science, 12 (46): 639 - 654. (in Persian)
14- Kaur R., and Rani R. 2006. Spatial characterization and prioritization of heavy metal contaminated soil-water sources in peri-urban areas of national capital territory (NCT), Delhi. Environmental Monitoring and Assessment, 123: 233–247.
15- Khodakarami L., Soffianian A., Mirghafari N., Afyuni M., and Golshahi A. 2012. Concentration zoning of chromium, cobalt and nickel in the soils of three sub-basin of the Hamadan province using GIS technology and the geostatistics. Journal of Science and Technology of Agriculture and Natural Resources, Water and Soil Science, 15 (58): 243 - 254. (in Persian)
16- Koçak M., Mihalopoulos N., and Kubilay N. 2007. Chemical composition of the fine and coarse fraction of aerosols in the northeastern Mediterranean. Atmospheric Environment, 41: 7351–7368.
17- Koulousaris M., Aloupi M., and Angelidis M. O. 2009. Total metal concentrations in atmospheric precipitation from the Northern Aegean Sea. Water, Air, and Soil Pollution, 209: 381–403.
18- Li Z., Ma Z., Jan van der Kuijp T., Yuan Z., and Huang L. 2014. A review of soil heavy metal pollution from mines in China: Pollution and health risk assessment. Science of the Total Environment, 468-469: 843 - 853.
19- Lim T. T., Tay J. H., and Teh C. I. 2002. Contaminant time effect on lead and cadmium fraction in a tropical coastal clay. Journal of Environmental Quality, 31: 806–812.
20- Lindsay W. L., and Norvell W. A. 1978. Development of a DTPA soil test for zinc, iron, manganese and copper. Soil Science Society of America Journal, 42: 421–428.
21- Loska K., Wiechula D., and Korus I. 2004. Metal contamination of farming soils affected by industry. Environment International, 30: 159–165.
22- Lu A. X., Zhang S., and Shan X. Q. 2005. Time effect of the fractionation of heavy metals in soils. Geoderma, 125: 225–234.
23- Massas I., Ehaliotis C., Gerontidis S., and Sarris E. 2009. Elevated heavy metal concentrations in top soils of an Aegean island town (Greece): total and available forms, origin and distribution. Environmental Monitoring and Assessment, 151: 105–116.
24- Massas I., Ehaliotis C., Kalivas D., and Panagopoulou G. 2010. Concentrations and availability indicators of soil heavy metals; the case of children's playgrounds in the city of Athens (Greece). Water, Air, and Soil Pollution, 212(1–4): 51–63.
25- Massas I., Kalivas D., Ehaliotis C., and Gasparatos D. 2013. Total and available heavy metal concentrations in soils of the Thriassio plain (Greece) and assessment of soil pollution indexes. Environmental Monitoring Assessment, 185: 6751 - 6766.
26- Muller G. 1969. Index of geoaccumulation in sediments of Rhine River. GeoJournal, 2: 108–118.
27- Nelson D. W., and Sommers L. E. 1982. Total carbon, organic carbon and organic matter. In A. L. Page et al. (ed.) Methods of soil analysis Part 2. 2nd ed. Agron. Monogr. 9. ASA and SSSA. Madison, WI.
28- Netherlands Ministry of Housing, Physical Planning and Environment (Netherlands MHPPE). 2000. Annexes circular on target values and intervention values for soil remediation. The Netherlands: MHPPE.
29- Srinivasa Gowd S., Ramakrishna M., and Govil P. K. 2010. Assessment of heavy metal contamination in soils at Jajmau (Kanpur) and Unnao industrial areas of the Ganga Plain, Uttar Pradesh, India. Journal of Hazardous Materials, 174: 113–121.
30- Stockman U., Minasny B., and McBratney A. B. 2014. How fast does soil grow? Geoderma, 216: 48-61.
31-US EPA. 2002. Supplemental guidance for developing soil screening levels for superfund sites. Office of Solid Waste and Emergency Response, Washington, D.C. Available at: http://www.epa.gov/superfund/health/conmedia/soil/index.htm, (visited 7 December 2014).
32- Wilcke W., Muller S., Kanchanakool N., and Zech W. 1998. Urban soil contamination in Bangkok: heavy metal and aluminum partitioning in topsoils. Geoderma, 86: 211– 228.
33- Yaylali-Abanuz G. 2011. Heavy metal contamination of surface soil around Gebze industrial area, Turkey. Microchemical Journal, 99: 82–92.
CAPTCHA Image