Estimation of 90Sr content in wood of scots pine based on measurement surface flux density of beta-particles from stem bark

This paper presents an approach for indirect measuring of 90Sr activity concentration in stem wood of Scots pine`s live trees within the Chernobyl exclusion zone based on values of beta-particles surface flux density from stem bark at a thee height of 1.3 m above the forest floor that obtained by use STORA-TU RKS-01 radiometer-dosimeter under field condition. The similar express-methods often consider in scientific publications so as they allow to obtain probable levels of radiation contamination without taking samples for laboratory measurements. That in turn can be used to optimize sampling or for example in the case of the need to preserve the intact initial state of the biota during long-term in situ or/and in vivo observations. The empirical data for validation of the method have received on 13 experimental sites of artificial (plantation) even-aged stands which consist only of one woody species: Scots pine. The correlation analysis discovered statistical significant relation at p-value=0.05 between arithmetic averages of beta-particles surface flux density from stem bark of pine trees at the forest sites and 90Sr activity concentration in stem wood elements (sap wood, heartwood and all stem wood), and functional dependencies among these parameters are described by a simple linear equation with only one slope parameters (R2 = 0.90–0.96) whose predicted values for sap wood, heartwood, and all stem wood are (± standard deviation) 23.1±8.5, 42.3±10.3, and 26.8±6.8 Bq·cm2·min·(kg·pcs)-1, respectively. Moreover, the influence of biometric indicators of individual trees (diameter, height, age) on this pattern was not detected. However, the average diameter (DBH) of stands has the strongest influence among forest inventory indicators on the value of the 90Sr activity concentration ratio between sap wood and heartwood (r = 0.93), that is, the radial distribution of the studied radionuclide in stem wood of pine trees. The results of these studies should be confirmed by a larger collection of observations for Scots pine given the small sample size for her in this paper. Also, scientists are necessary to include empirical data for other major forest-forming woody species within the research region due to the importance of using express-methods of radioactive contamination levels estimation for the planning and optimization of forest management.

A rapid method for screening 90Sr activity in water and milk samples using Cherenkov radiation

Strontium-90 is one of the most dangerous fission products that enter the food chain. Because of its similar chemistry to calcium, it is deposited to bones posing a high risk for human health. 90Sr is a pure ^-emitter and decays to 90Y also a /3-emitter. The fast moving electrons emitted by the 90Y decay, produce Cherenkov radiation, which can be detected by a Liquid Scintillation Counter (LSC). Water and milk samples spiked with various concentrations of 9 0Sr/90Y in equilibrium were measured in a LSC (Tricarb 3170 TR/SL). The derived efficiencies were 50% for water samples and 13 % for milk samples. The minimum detectable activities (MDA) for measuring 90Sr in water and milk samples, without any pretreatment were calculated 240 mBq/L and 1 Bq/L respectively. The intervention levels for 90Sr contamination in water and milk samples, established by the European Union are 125 Bq/L and 75-125 Bq/L depending on age, respectively. The interference of 40K, which is present in milk due to its natural potassium content,was also investigated.

Distribution of the Fukushima-derived radionuclides in seawater in the Pacific off the coast of Miyagi, Fukushima, and Ibaraki Prefectures, Japan

The activities of artificial radionuclides in seawater samples collected off the coast of Miyagi, Fukushima, and Ibaraki Prefectures were measured as part of a monitoring program initiated by the Japanese Ministry of Education, Sports, Science and Technology immediately after the Fukushima Dai-ichi Nuclear Power Plant accident. The spatial and temporal distributions of those activities are summarized herein. The activities of strontium-90, iodine-131, cesium-134 and -137 (i.e. 90Sr, 131I, 134Cs, and 137Cs) derived from the accident were detected in seawater samples taken from areas of the coastal ocean adjacent to the power plant. No 131I was detected in surface waters (≤ 5 m depth) or in intermediate and bottom waters after 30 April 2011. Strontium-90 was found in surface waters collected from a few sampling stations in mid-August 2011 to mid-December 2011. Temporal changes of 90Sr activity in surface waters were evident, although the 90Sr activity at a given time varied widely between sampling stations. The activity of 90Sr in surface waters decreased slowly over time, and by the end of December 2011 had reached background levels recorded before the accident. Radiocesium, 134Cs and 137Cs, was found in seawater samples immediately after the accident. There was a remarkable change in radiocesium activities in surface waters during the first 7 months (March through September 2011) after the accident; the activity reached a maximum in the middle of April and thereafter decreased exponentially with time. Qualitatively, the distribution patterns in surface waters suggested that in early May radiocesium-polluted water was advected northward; some of the water then detached and was transported to the south. Two water cores with high 137Cs activity persisted at least until July 2011. In subsurface waters radiocesium activity was first detected in the beginning of April 2011, and the water masses were characterized by σt (an indicator of density) values of 25.5–26.5. From 9–14 May to 5–16 December 2011, the depths of the water masses increased with time, an indication that deepening of the isopycnal surfaces with time can be an important mechanism for the transport of radiocesium downward in coastal waters. During 4–21 February 2012, the water column became vertically homogeneous, probably because of convective mixing during the winter; the result was nearly constant values of radiocesium activity throughout the water column from the surface to the bottom (~200 m depth) at each station.

Distribution of the Fukushima-derived radionuclides in seawater in the Pacific off the coast of Miyagi, Fukushima, and Ibaraki Prefectures, Japan

The activities of artificial radionuclides in seawater samples collected off the coast of Miyagi, Fukushima, and Ibaraki Prefectures were measured as part of a monitoring program initiated by the Japanese government Ministry of Education, Sports, Science and Technology immediately after the Fukushima Dai-ichi nuclear power plant accident. The spatial and temporal distributions of those activities are summarized herein. The activities of strontium-90, iodine-131, cesium-134 and -137 (i.e. 90Sr, 131I, 134Cs, and 137Cs) derived from the accident were detected in seawater samples taken from areas of the coastal ocean adjacent to the power plant. No 131I was detected in surface waters (≤ 5 m depth) or in intermediate and bottom waters after 30 April 2011. Strontium-90 was found in surface waters collected from a few sampling stations in mid-August 2011 to mid-December 2011. Temporal changes of 90Sr activity in surface waters were evident, although the 90Sr activity at a given time varied widely between sampling stations. The activity of 90Sr in surface waters decreased slowly over time, and by the end of December 2011 had reached background levels recorded before the accident. Radiocesium, 134Cs and 137Cs, was found in seawater samples immediately after the accident. There was a remarkable change in 137Cs activities in surface waters during the first 7 months (March through September 2011) after the accident; the activity reached a maximum in the middle of April and thereafter decreased exponentially with time. Qualitatively, the distribution patterns in surface waters suggested that in early May 137Cs-polluted water was advected northward; some of the water then detached and was transported to the south. Two cores of the water with high 137Cs activity persisted at least until July 2011. In subsurface waters 137Cs activity was first detected in the beginning of April 2011, and the water masses were characterized by σt (an indicator of density) values of 25.5–26.5. From 9–14 May to 5–16 December 2011, the depths of the water masses increased with time, an indication that deepening of the isopycnals with time can be an important mechanism for the transport of 137Cs downward in coastal waters. During 4–21 February 2012, the water column became vertically homogeneous, probably because of convective mixing during the winter, the result being nearly constant values of 137Cs activity throughout the water column from the surface to the bottom (~200 m depth) at each station.