Elsevier

Environmental Pollution

Volume 215, August 2016, Pages 273-279
Environmental Pollution

Short communication
Natural and anthropogenic radioactivity in the environment of Kopaonik mountain, Serbia

https://doi.org/10.1016/j.envpol.2016.05.031Get rights and content

Highlights

  • Apart from K-40, radionuclides are not detected in cow milk.

  • Cs-137 is still present in the soil, grass, mosses and herbal plants.

  • The highest decrease in Cs-137 is observed at higher altitudes.

Abstract

To evaluate the state of the environment in Kopaonik, a mountain in Serbia, the activity concentrations of 4 K, 226Ra, 232Th and 137Cs in five different types of environmental samples are determined by gamma ray spectrometry, and radiological hazard due to terrestrial radionuclides is calculated. The mean activity concentrations of natural radionuclides in the soil are higher than the global average. However, with an exception of two sampling locations, the external radiation hazard index is below one, implying an insignificant radiation hazard. Apart from 40K, content of the natural radionuclides is predominantly below minimum detectable activities in grass and cow milk, but not in mosses. Although 137Cs is present in the soil, grass, mosses and herbal plants, its specific activity in cow milk is below minimum detectable activity. Amongst the investigated herbal plants, Vaccinium myrtillus L. shows accumulating properties, as a high content of 137Cs is detected therein. Therefore, moderation is advised in consuming Vaccinium myrtillus L. tea.

Introduction

Naturally occurring radionuclides in the environment represent the main source of the radioactivity exposure for humans and biota. Anthropogenic activities affect the distribution of natural radioactivity. Various applications of nuclear energy, coal combustion, production and application of phosphorus fertilizers, mining industry and formation of radioactive waste dumps contribute to redistribution of natural radioactivity. A military operation, undertaken by the North Atlantic Treaty Organization (NATO) against Yugoslavia in 1999, caused environmental contamination with depleted uranium of southern parts of Serbia (UNEP, 2002). During the NATO bombing, Kopaonik, among other locations, was under a heavy and prolonged attack, which resulted in the destruction of the terrain and disruption of the forest ecosystem (UNEP/UNCHS BTF, 1999).

Once in the environment, radioactive material can get incorporated into food as it is taken up by plants or ingested by animals (WHO, 2011). Plants with an ability to accumulate high concentrations of radionuclides have a potential to act as biomonitors and thus help to identify areas of radiation risk. A number of studies have shown that mosses, lichens and mushrooms are typical representatives of bioindicator plants for radionuclides present in the environment (Delfanti et al., 1999, Grdović et al., 2010, Mitrović et al., 2009, Steinnes and Njåstad, 1993, UNSCEAR, 2008). Mosses have some advantages compared to other bioindicator species: their accumulating capacity is higher than of other plants (Elstner et al., 1987); their ability to indicate quality of the air, water and soil, based on their presence, absence or floristic composition, is an important characteristic in facilitating their role as bioindicators of radioactive contamination (Grdović et al., 2010); and mosses entrap airborne particulates, both passively and actively, through an extra cellular ion-exchange (Knight et al., 1961). For these reasons, a comprehensive radioecological study needs to include moss samples.

Since transfer of radionuclides through food chain leads to humans via both plants and animals, our study also encompasses other environmental samples: soil, grass, cow milk and herbal plants. Radioactive contamination of animal feed, such a grass, hay and ensilaged crops, is a major route for animal contamination (Howard et al., 2001). Milk and dairy products are important foodstuff in human infant and adult diet, and it is necessary for them to be safe for human consumption. Beside animal products, herbal teas can also contribute to human contamination with radionuclides (Mitrović et al., 2015).

The goal of this paper is to determine the level of radioactivity in different environmental samples from Kopaonik. Apart from the artificial 137Cs (half-life 30 years), three naturally occurring radionuclides: 40K, 232Th and 226Ra are investigated. In addition, an analysis of 238U in the soil is performed.

Caesium-137 is a fission product, and it is a significant indicator of anthropogenic pollution in the environment. Mosses are good bioindicators of this radioisotope (Sawidis et al., 2009). However, it can also be detected in higher plants (Todorović et al., 2013). Radioactive contamination with radiocaesium occurred in Serbia after the 1986 nuclear accident in Chernobyl. A radioecological study, conducted in 1987 (Mićić et al., 1989), showed an increased level of radioactive caesium in the environment of Kopaonik.

Radionuclide 40K (half-life 1.248 × 109 years) is an isotope of potassium that is abundant in nature and is crucial for functioning of all living cells. Natural uranium is a mixture of three radioisotopes: 238U (99%, half-life 4.5 × 109 years), 235U (0.71%), and 234U (0.006%). Its most important daughter is 226Ra (half-life 1602 years), which decays to another important radioactive isotope – radon. Thorium-232 (half-life 1.405 × 1010 years) is less radioactive than uranium, but more abundant in nature. These radionuclides in the soil significantly contribute to the total dose of irradiation to population and environment (Fisenne, 1993).

Hence, in this paper, the radionuclides’ contents in the environmental samples are determined, and radiation hazard parameters are calculated to evaluate the state of the environment in Kopaonik. In attempt to assess a long-term impact of pollution events caused by human activities, our results are further compared with the results of two studies performed at the same location: Mićić et al. (1989) conducted a study in 1987, one year after the Chernobyl nuclear accident, and Esposito et al. (2002) investigated an influence of the NATO bombing in 1999.

Section snippets

Sampling site

Kopaonik is a mountain range in the south western part of the Republic of Serbia. The largest ski resort in Serbia, located around the Kopaonik slopes under the highest peak, Pančićev vrh (elevation 2017 m a.s.l.), and a national park, with its diverse plant and animal species, make Kopaonik a popular tourist destination. The climate of Kopaonik is subalpine and the annual average precipitation rate is up to 1000 mm.

Seven sampling locations were included in this study (Fig. 1): Brus (43.3842 °N

Results and discussion

The mean activity concentrations of radionuclides in the investigated samples are given in Table 2. The mean activity concentration of 40K, the dominant radionuclide in the soil, was 725 Bq kg−1. The mean activity concentrations of 226Ra and 232Th were 80 Bq kg−1 and 77 Bq kg−1, respectively. In all investigated soil samples, the artificial radionuclide 137Cs was detected (4.2–142 Bq kg−1). The locations of the radionuclides’ highest activity concentrations did not coincide: the 40K activity

Conclusion

Radioecological investigation in Kopaonik was conducted with an aim to assess the state of the environment, with a special emphasis on possible impacts of two events: the 1986 Chernobyl nuclear accident and 1999 NATO bombing.

In four sampling sites, the detected activity concentrations of 226Ra and 232Th were larger than the world average as a consequence of the local geological structure. The mean activity concentrations of natural radionuclides in the soil were higher than the global average,

Acknowledgment

This paper is a part of the research done within the projects “Climate changes and their influence on the environment: impacts, adaptation and mitigation” (No. 43007) and “Development of technology and products based on mineral raw materials and biomass for protecting the food resources” (No. TR31003) financed by the Ministry of Education, Science and Technological Development of the Republic of Serbia (2011–2016).

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