Vertical profiles of Cs-137 in soil of the Matua Island ( the Central Kuril Islands, Russia) in 2017

<p>The 2011 Fukushima-Daiichi nuclear power plant (FDNNP) accident resulted in the atmospheric releases of large quantities of man-made radionuclides. According to [1], Matua Island, located at a distance of more than 1000 km from FDNPP, was also subjected to minor radioactive contamination. Matua Island, 52.6 sq.km, a recent volcano with the highest point of 1446 m a.s.l. is located in the center of the Kuril Islands Arc. Volcanic soils are formed on stratified gravelly-stony tephra more than 60 cm thick, underlain by thin layers of volcanic slags. The latest catastrophic eruption which changed the landscape of the island occurred in 2009.</p><p>Studies of the vertical distribution of the Cs-137 in soils were carried out on four landscape catenas. The length of the catenas from the sea shore deep into the island ranged from 700 m (maximum height a.s.l.  70 m) to 3.3 km (height a.s.l.  450 m).</p><p>Soil core samples were taken in  summer 2017 at a depth of tephra, which was located at a depth of 10 to 25 cm. Soil was sliced into separate layers with a step of 2 to 5 cm.</p><p>The measurement activity concentrations of the Cs-137 in the soil samples were carried out on a low-background gamma spectrometer Canberra Industries.  The counting time  was fixed not less than 24 h to ensure that the statistical measurement error is small.</p><p>Cs-134, the «Fukushima” fallout marker, due to the decay, was not detected. Therefore, it is difficult to accurately assess the Cs-137 contribution from the FDNNP accident from a global fallout.</p><p>The vertical distribution of Cs-137 is characterized by extreme heterogeneity, which reflects both the primary fallout conditions and the landscape conditions of the likely lateral redistribution. For сatena 1 with a length of 1 km and an altitude  of 400 m, the number of pickets (P0, P1, etc. – the numbering of pickets goes downhill), the specific activity of Cs-137 (Bq/kg) and the depth of the layer (cm) are given as follows: P0-27 Bq/kg (2-4 cm); P1 - 64 Bq/kg (6-8 cm); P2 – 70 Bq/kg (8-10 cm); P3 - 53 Bq/kg (4-6 cm); P4 - 15 Bq/kg (0-5 cm).  Similar spatial  heterogeneity of the specific activity of Cs-137 and its depth penetration was also found for catena 3 with a length of 1250 m and a height of 75 m (the numbering of pickets goes up the slope): P1-137 Bq/kg (17-20 cm); P2-76 Bq/kg (0-5 cm); P3 - 35 Bq/kg (0-4 cm); P4 - 43 Bq/kg (3-6 cm); P6 – 24 Bq/kg (5-10 cm).</p><p>The distribution of Cs-137 in individual soil layers was used to evaluate the empirically found shapes of the vertical profiles of radionuclide concentration. Cs-137 is believed here to be a  very valuable tracer  that  can be used to test  variability of vertical geochemical migration in Matua  landscapes.</p><p>[1]. Ramzaev V.P., Barkovsky A.N., Gromov A.V., Ivanov S.A., Kaduka M.V. Fukushima fallout in Sakhalin Region, Russia, part 1: <sup>137</sup>Cs and <sup>134</sup>Cs in grassland soils. Radiation Hygiene, 2018, Vol. 11, No. 1, pp. 25-42.</p>

Application of GPR sounding at the examination of fortification objects on Matua Island, Kuril Islands

Matua Island is of volcanic origin and was formed by Sarychev Peak volcano. The island is a place of a specific anthropogenic landscape. Its structure was substantially changed by fortification constructions and other military objects. Analogues of such a landscape weren't described in scientific literature, thus, perhaps, it may be considered unique for Russia and it merits more detailed and indepth review. Results of ground penetration radar (GPR) survey of soil-pyroclastic cover of the island's southeastern part are presented, which include also an investigation of certain subsurface military objects, the greater part of which is unexplored. It's established that existence of objects, various soil disturbances, downwrappings, anthropogenic or natural faults can be located by some radiophysical indicators — details of the reflected pulse, disturbance of pulse lineups, numerous phase shifts and repeated rereflections. It is shown that elaborated methods and increased power GPR with 50—250 MHz antennas to be applied can effectively solve these tasks on complex multilayer and moist volcanic soils.

he NBC Defence Troops Specialists` Expedition to Matua Island in the Kuril Chain

In May 2016 a special expedition by Russia’s Defence Ministry and Russian Geographical Society was organized in order to explore the island of Matua located near the centre of the Kuril Islands chain. By the beginning of World War II the island has been turned into the veritable fortress by the Japanese. There were certain reasons to suggest that the island could be used by the Japanese military for the development, production and stockpiling of weapons of mass destruction. Because of that an NBC control group, formed from the specialists of several scientific research institutions of the Radiological, Chemical and Biological Defence Troops of the Armed Forces of the Russian Federation was included in the joint team. The tasks of the group were to reveal and evaluate the NBC environment on Matua Island, to provide the protection of the personnel and the mitigation of any possible NBC contamination of the terrain and the Japanese military installations on the island. The group was also supposed to check the operational characteristics of NBC reconnaissance equipment and to conduct biological analysis at high northern latitudes without any fixed-site laboratories. The expedition has been working on the island from April 20 until June 29, 2016. The survey of the fortifications and engineering constructions on Matua Island, as well as the analysis of the contents of several chemical tanks and bottles, found on the island, revealed the absence of any evidence of the production of chemical, biological and nuclear weapons on Matua at the time of the Japanese military presence until August 1945. The analysis of the environmental samples (soil and water), taken at the locations of the surveys, and of the biological samples, taken from the organs of several mouse-like rodents, caught near the expedition camp, did not reveal any causative agents of infectious and particularly dangerous diseases. The radioactive contamination, residual radiation and gamma-rays were not detected on the territory of the island.