Multi-Criteria Analysis of Soil Radioactivity in Čačak Basin, Serbia
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MULTI-CRITERIA ANALYSIS OF SOIL RADIOACTIVITY IN ČAČAK BASIN, SERBIA M. PAPIĆ1, M. VUKOVIĆ2, I. BIKIT3, D. MRĐA3, S. FORKAPIĆ3, K. BIKIT3, Đ. NIKOLIĆ2 1Faculty of Technical Sciences, Čačak, University of Kragujevac, Svetog Save 65, Čačak, Serbia, E-mail: [email protected] 2Technical Faculty Bor, University of Belgrade, Vojske Jugoslavije 12, Bor, Serbia, E-mail: [email protected]; Email: [email protected] 3Faculty of Sciences, University of Novi Sad, Trg Dositeja Obradovića 6, Novi Sad, Serbia, Email: [email protected]; Email: [email protected]; Email: [email protected]; Email: [email protected] Received March 11, 2014 The paper looks at the method of presenting and comparing soil radioactivity on different locations. Activities of natural radionuclides 238U, 226Ra, 232Th, 40K and anthropogenic 137Cs in arable land of Čačak basin were measured. Some 30 soil samples collected from different locations, i.e. the vicinity of the West Morava river, both urban and industrial areas of the town and rural region were analysed. Samples were taken from 0–30 cm depth. According to the values of the Shapiro-Wilk’s test (0.05 significance level), contents of 238U, 232Th and 40K were within the limits of normal distribution, while 226Ra and 137Cs were not. As espected, statistically significant positive correlation (p<0.01) was found between all the natural radionuclides. The analysed sites were ranked using the PROMETHEE method, and the results were presented in graph using the GAIA plane. The ranking involved five criteria which represented the overall activities of each of the radionuclides. The ranking inferred that Ljubić Polje location was the one with the lowest radioactivity, while, in contrast, the location of Trnavska Baluga showed the highest radioactivity level. As regards presence of radionuclides in soil, the comparative study of urban (industrial) and rural areas did not imply any significant differences among the locations. The results of the present study were discussed and compared with related values from several sources found in the literature. Generally, the study infers that soil in Čačak basin has not showed increased levels of radioactivity. Key words: soil, radioactivity, the absorbed dose rate, multi-criteria analysis, PROMETHEE/ GAIA. 1. INTRODUCTION Soil is usually defined as the upper layer of the Earth’s crust, formed by mineral particles, organic matter, water, air, and living organisms [1]. Its depth can vary from a few millimeters to several meters, and it is present in the larger part of the Earth’s surface as a narrower or wider layer called the pedosphere [2]. Rom. Journ. Phys., Vol. 59, Nos. 7–8, P. 846–861, Bucharest, 2014 2 Multi-criteria analysis of soil radioactivity in Čačak Basin 847 Soil contamination is one of the most serious problems in the world, with long term consequences on human life [3]. One of the most important aspects of soil contamination is its radioactivity which is based on the presence of radioactive elements or radionuclides. Radioactivity can be distinguished as natural and anthropogenic. Natural radioactivity refers to natural radionuclides which can regularly be found in the earth’s crust. In most places on the earth, the natural radioactivity varies only within narrow margins, but in some places there are wide deviations from normal levels because of the abundance of minerals with high radioactivity [4]. The main contribution to external exposure comes from gamma-emitting radionuclides present in trace amounts in the soil, mainly potassium (40K) and the uranium (238U) and thorium (232Th) families [5]. Radiation energy of the elements above accounts for some 98% of the total radiation of natural radioactive elements. Anthropogenic radioactivity of soil relies on anthropogenic radionuclides of various chemical elements which are the result of human intervention, in terms of the use of nuclear energy for military and apart from military purposes. Of all the anthropogenic radionuclides studied so far, cesium (137Cs) has been the predominant one. It is one of the most widespread and also among the most dangerous radionuclides for both humans and other living organisms, given its long disintegration period (30.2 years) and high energy radiation level. The overall background radiation caused by the natural radionuclides above can be expressed by using the absorbed dose of radiation at 1m above ground (D) which is calculated by coefficients of 0.462, 0.604 and 0.0417 (nGy/h)/(Bq/kg) for the content of 238U (226Ra), 232Th and 40K respectively [5]. However, this method does not provide a more comprehensive insight into the radioactivity of a particular location as it does not include the presence of some other radionuclides. The objective of this paper was to assess and rank the sampling locations in terms of the presence of the most significant natural and anthropogenic radionuclides in the alluvial soil [6–13] on the territory of Čačak. The ranking which involved five criteria (activities of 238U, 226Ra, 232Th, 40K and 137Cs) was done using the PROMETHEE (Preference Organization Method for Enrichment Evaluation) multi-criteria decision making method. The GAIA (Geometrical Analysis for Interactive Assistance) plane was used for the graphical representation of results. A comparative analysis of results of related studies performed by other authors was also provided in the paper so as to obtain a more comprehensive insight into the issue. 848 M. Papić et al. 3 2. MATERIALS AND METHODS 2.1. STUDY AREA The town of Čačak is located in western part of central Serbia with the municipalities of Gornji Milanovac to the north, Požega to the west, Lučani to the southwest and south, and Kraljevo and Knić to the east (Figure 1). It is the administrative center of the Moravica District. The geographic coordinates of the municipality are 20° 07'–20° 38' east longitude and 43° 44'–44° 01' north latitude. Morphologically, the Čačak basin is a tectonic depression formed in the Oligocene by the lowering movement of two longitudinal faults. The surface area of the Čačak basin towards the Kraljevo narrowing is over 270 km2. The basin lies at an elevation of 200 to 300 m. The pedological composition of the Čačak territory is diverse. The most common soil types are alluvial soil, vertisols, cambisols, and parapodzol. Alluvial soil is formed from deposits made by rivers, and it can be found in the Čačak basin all along the West Morava river. It belongs to fertile soils, particularly in mid – and low river courses. It is composed of river sediment, silt, sand and gravel deposited during floods. It is highly rich in organic matter and is easy to work [14]. Fig. 1 – Location of town Čačak, Serbia. Such soil diversity provides the conditions for highly developed biological diversity. Hence, this is the region with probably the most diverse agricultural production on the territory of entire Serbia. Based on the data of the Republic Institute for Statistics, the surface area of the Čačak municipality is 636 km2, whereby urban, forest and agricultural areas cover 45 km2 (7%), 158 km2 (25%) 4 Multi-criteria analysis of soil radioactivity in Čačak Basin 849 and 433 km2 (68% or 44.060 ha), respectively. Areas covering fields and gardens, orchards, vineyards and pastures follow with 26.935 ha, 6.930 ha, 5.456 ha and 4.609 ha, respectively. Based on the number of people employed in various agricultural activities, agriculture is the primary branch of economy [15]. According to the 2002 census, the town of Čačak (the municipality of Čačak, at the time of census) had the population of 117.072, with 73.152 and 43.920 people living in the urban and rural areas respectively [16]. Favourable geographic and climate setting and fertile West Morava basin allowed for the development of different branches of agriculture. The Čačak region has a long tradition of fruit growing, stock farming, vegetable growing and fruit- planting material production, which ensure a solid foundation for further investment in the development of agriculture. This hilly region is known for fruit production, while in fertile Morava basin vegetable and cereal crops are grown. The glasshouse production is also developed in lowlands [17]. Table 1 shows names of places and coordinates of the sampling sites examined. The exact position of each sampling site was recorded using Global Positioning System (GPS). These locations, extending from Pakovraće and Prijevor in the north west to Mrčajevci and Mršinci in the south east, form the agriculturally important region of central Serbia. Table 1 Sampling locations Coordinates Altitude Location Place [N] [E] [m] 1. Parmenac 43° 53' 50.2404" 20° 17' 40.3044" 246 2. Pakovraće 43° 54' 2.361" 20° 15' 58.4238" 253 3. Riđage 43° 53' 50.0526" 20° 16' 45.0942" 281 4. Beljina 43° 53' 37.8018" 20° 19' 22.4106" 243 5. Ljubić Kej 43° 54' 5.2266" 20° 20' 12.7068" 237 6. Prijevor 43° 53' 55.773" 20° 17' 27.7434" 246 7. Prijevor 43° 54' 9.8748" 20° 17' 11.364" 247 8. Prijevor 43° 54' 25.4298" 20° 16' 25.4202" 250 9. Prijevor 43° 54' 2.7396" 20° 16' 22.695" 246 10. Suvi Breg 43° 54' 1.0542" 20° 19' 7.2372" 240 11. Stančići 43° 52' 56.1288" 20° 26' 34.8756" 223 12. Mojsinje 43° 52' 57.648" 20° 27' 40.6044" 228 13. Donja Gorevnica 43° 52' 22.8864" 20° 29' 7.0656" 223 14. Mrčajevci 43° 51' 1.44" 20° 31' 21.36" 212 15. Mrčajevci 43° 49' 50.3394" 20° 30' 7.4874" 211 16. Kukići 43° 49' 56.7726" 20° 28' 23.106" 226 850 M. Papić et al. 5 Table 1 (continued) 17. Mršinci 43° 48' 47.2752" 20° 29' 24.2478" 224 18.