Concentrations of 137Cs and 40K radionuclides and some heavy metals in soil samples from the eastern part of the Main Ridge of the Flysch Carpathians
The aim of the study is to present the results of determination of radioactivity of artificial 137Cs and natural 40K and certain heavy metals in soil samples collected from the eastern part of the Main Ridge of Carpathians, including the Beskid Niski Mts and the Bieszczady Mts. The evaluation of level of radionuclides was based on the bulk density analysis of the soil. A valuable finding of the study was a good linear correlation between the level of 137Cs concentration and bulk density of the soil as well as an inverse correlation between radioactivity of natural 40K and tested soil density. This might indicate though a high competitiveness of these elements between each other. Moreover, a good correlation between the concentrations of artificial element 137Cs and Pb has been also observed in soil samples collected from the Beskid Niski Mts. In most cases, the level of artificial 137Cs was lower comparing to an average 137Cs concentration established for soils in Poland.
Keywords137Cs 40K Soil Heavy metals Gamma spectrometry
The natural environment is exposed to various chemical contaminants, including the radioactive elements. Some of these radioactive elements are long-lived naturally occurring radionuclides. These radionuclides have always been present in the Earth’s crust and atmosphere. There are approximately 60 natural radionuclides and one of the most abundant elements in the Earth’s crust is 40K that remains to this point in time. Another source of radioactivity has a cosmogenic origin and it is the result of interaction between certain gases in the Earth’s atmosphere and cosmic rays . Besides such sources of naturally occurring radiation exposure, the natural environment may be subjected to radioactive contamination caused by human activity. The main sources of anthropogenic radioactive material were (and still are) nuclear weapons tests conducted in the atmosphere, the accidents of nuclear power plants, and either the processing or storage of nuclear fuel and large amounts of nuclear waste [2, 3, 4]. An example of the world’s worst civilian nuclear disaster was spreading into the atmosphere of Central and Eastern Europe a massive amount of radiocaeasium due to the explosion and fire at the Chernobyl power plant in April 1986.
The current state of knowledge concerning radioactivity on the whole area of Polish mountain’s soils is still not comprehensive. Though, to address this knowledge gap, a radioactivity study was carried out from 2011 to 2012 by the Department of Coal Chemistry and Environmental Sciences. The experimental area covered the eastern regions of the Main Ridge of the Flysch Carpathians Belt (the areas including the Beskid Niski Mts and the Połoniny part of the so-called Tarnica Mt in the Bieszczady Mts). The survey was conducted with the sampling and analysis of 27 soil samples in terms of spatial distribution of 137Cs and natural 40K and certain heavy metals including Cu, Zn, Cd and Pb. Data presented herein provide an update of a national evaluation regarding radioactivity in soils in the southern part of Poland since 2000, which included monitoring carried out in the Central Carpathians (the Tatra Mts) [5, 6, 7, 8] and part of the East Carpathians area (the Chornohora Mts) .
Sampling and methods
To collect the soil samples, 27 sampling locations were selected. Sampling was started in June 2011. The measurements of the gamma emitting radionuclide activity as well as the concentrations of certain heavy metals were performed on soil samples collected from the surface horizons of soil above 500 m ASL. The experimental area includes the Połoniny Caryńska and Wetlińska Mts, “Gniazdo Tarnicy” (Rozsypaniec, Halicz, Krzemień, Tarnica, Tarniczka Mt) in the Bieszczady Mts and the Beskid Niski Mts (specifically, Jaworzyna Krynicka, Spalone and Wołowiec close to Zawoja stream). Detailed positional data of the selected sampling points were established by a Garmin GPS Map 76CS satellite navigation system.
Sampling method and preparation of the samples
Soil samples were collected by the use of a cylidrical sampler that provides “soil cores” (10 cm height, 10 cm diameter). Those cores were cut into three segments that represented different soil layers starting from the soil surface: 0–3, 4–6, 7–10 cm (samples: a, b and c, respectively). That procedure allowed collection of 3 samples from each sampling point. The samples were dried at 105 °C to constant weight (for about 3 days), then the bulk density was determined and the samples were sieved (mesh diameter = 2 mm). The samples were prepared and stored prior to measurements in polyethylene containers.
Gamma spectrometric analysis
Detailed location of the sampling points given for the Beskid Niski Mts and activities of 137Cs and 40K presented in Bq per mass units or per surface units together with soil samples bulk density
Activity, dry mass
Altitude m ASL
Bulk density g/cm
Jaworzyna Krynicka 49°25′15″ N 20°53′12″E
Near Waholowski Wierch 49°24′38″ N 22°02′30″E
On the way to Tokarnia 49°25′41″ N 22°02′29″E
Near Tokarnia 49°25′16″ N 22°03′13″E
On the way to Wilcze Budy 1 49°26′30″N 22°00′37″E
On the way to Wilcze Budy 2 49°26′53″N 21°59′43″E
On the way to Puławy Górne 49°28′45″N 21°56′25″E
Before intersection the trail Red and green on the way to Skibice 49°28′32″N 21°56′21″E
On the way to Skibice and the Kozie Żebro Mt (about 45 min.) 49°28′27″N 21°56′36″E
The entrance to Kozie Żebro 49°27′52″N 21°12′40″E
On the way to Rotunda from Regietów 49°28′16″N 21°13′36″E
On the way to PopoweWierchy 49°30′12″N 21°15′51″E
On the way to Wołowiec near the stream Zawoja 49°30′23″N 21°19′11″E
Detailed location of sampling points given for the Bieszczady Mts and activities of 137Cs and 40K presented in Bq per mass units or per surface units together with soil samples bulk density
Altitude m ASL
Bulk density g/cm3
Smerek Mt 49°11′07″N 22°28′45″E
Połonina Wetlińska 3 49°09′26″N 22°33′05″E
Połonina Wetlińska 2 49°09′58″N 22°31′41″E
Połonina Wetlińska 1 49°10′06″N 22°31′06″E
Połonina Caryńska 2 49°08′18″N 22°36′09″E
Połonina Caryńska 1 49°08′07″N 22°36′26″E
TarnicaMt 49°04′37″N 22°43′30″E
Tarniczka Mt 49°04′46″N 22°43′24″E
Krzemień Mt 49°05′07″N 22°44′22″E
Krzemień Mt 49°04′52″N 22°44′51″E
Halicz Mt 49°04′43″N 22°45′59″E
Halicz Mt 49°04′21″N 22°46′08″E
Rozsypaniec Mt. 49°03′45″N 22°46′12″E
Rozsypaniec Mt 49°03′22″N 22°46′06″E
the radioactivity of 137Cs in the upper core part (up to 10 cm) [Bq/m2];
the concentration of 137Cs per mass unit [Bq/kg] in each of tested soil layers (samples a, b, c).
Atomic absorption spectrometry (AAS) analysis
Sieved and homogenized soil samples were wet digested in the microwave system (Anton Paar Multiwave 3000, Switzerland) with concentrated HNO3 and HClO4 (Merck, Germany). After digestion, the samples were transferred into quartz crucibles and the excess of reagents was evaporated on a hot plate and the residue was transferred quantitatively to volumetric flasks. Quadruple distilled water was used for glassware preparation and sample dilution. Quantitative determination of Zn and Cu was performed using flame technique at standard conditions (AAS spectrometer Perkin Elmer, Model 3110, USA) and concentrations of Cd and Pb were determined using electrothermal technique (AAS spectrometer with Zeeman background correction, Perkin Elmer 4100 ZL, Germany). Graphite furnace parameters were optimized using the Method development program to obtain high sensitivity and precision of measurements for each of the elements determined by means of ET AAS technique. Uncertainties of the elements quantitative determinations (RSD data presented in Table 2) were not higher than Cu 5.4 %, Zn 2.6 %, Cd 5.6 %, Pb 4.7 %. The accuracy of the analytical procedure was estimated by the use of the certified reference material (IRMM BCR-280, Lake Sediment). Satisfactory accuracy and precision was achieved.
Results and discussion
The surface horizons of soil consist of organic matter in various stages of humification, lying directly on the weathered rocks flysch substrate initial soils -Lithic Leptosols or as the level of accumulation in Rankers –Umbric Leptosols, Cambic Leptosols (Skeletic) and Dystric Cambisols . In this survey, the material belonging to initial and poorly formed types of soil was analyzed. It forms the specific structure of the soil cover occurring above the 500 m ASL. The soils are rocky outcrops of initial soils—Lithic Leptosols and Rankers Cambic Leptosols. On the Pleistocene regolith—initial soils were formed Hyperskeletic Regosols. Characteristic properties of all mountain soils including the soils of three searched areas of the Carpathians (Tatra Mts and Charnohora Mts) are as follows: decreasing pace of organic matter decomposition linked to the increase of altitude above the sea level and the presence of ectohumus horizons in the depths. The organic matter of those horizons shows similar chemical properties regardless the parent rock. Thus, there are similar forms of ectohumus both in the initial soils (Lithic Leptosols), rankers (Umbric Leptosols), rendzinas (Rendzic Leptosols)and in Podzols . Below this level, there is little stale bedrock (typically sandstones) or weathering hyperskeletic regolith of flysch rocks.
Heavy metals level in soils of the Beskid Niski Mts area
In Fig. 6a changes of the elements (being the constituents of inorganic material) concentrations in relation to the soil sampling point number are presented. The sampling point elevation ASL of the sampling points differed only a little in the considered geographical region (see Tab. 1).
The concentration fluctuations observed for Zn and Cu in tested soil samples were similar for both elements (Table 2; Fig. 6b). It indicates that these elements predominantly originate from natural sources (mother rock erosion) and that mineral composition of Flysch Carpathian Belt in sampling area is more or less homogenous. The changes of the anthropogenic origin elements i.e. Pb and 137Cs (presented in μg/g for Pb and activity Bq/kg units for 137Cs) with percentage of organic matter in tested soils were showed in Fig. 6a. The fluctuations in the concentration of Pb and137Cs were related to the organic matter content and can indicate Pb and Cs immobilization in organic matter. The findings were clearly visible in the sampling points no 7,8 and 9—the level of elements increased with the amount of organic matter (Table 2; Fig. 6a).
The content of 137Cs, 40K and certain heavy metals in soils collected from the eastern Carpathians areas was found to be greatly variable: The Beskid Niski Mts area—from 25 Bq/kg (364 Bq/m2) for the Waholowski Peak (605 m,sampling point 1) to 1,127 Bq/kg (8,463 Bq/m2) for the Kozie Żebro Mts (758 m, sampling point 8); The Bieszczady Mts area—from 143 Bq/kg (1,385 Bq/m2) for the Połonina Wetlińska 2 (1,206 m ASL, sampling point 15) to 609 Bq/kg (3,505 Bq/m2) for the Halicz Mt (1,250 m ASL, sampling point 23).
Radioactive cesium activity in the mountain soils showed the tendency to decrease with increasing density of the soil due to high amount of the organic matter. The humus, as the main component of the sorption complex, was responsible for the immobilization of 137Cs ions.
Our results confirmed strong competitive-sorption behavior of 137Cs and 40K in the soil sorption complex.
The work was supported by the NCN Grant No. N N304 17040 and the AGH University of Science and Technology Grant No. 188.8.131.52.
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