The radiation indicators of rock dumps, ground and surface water, atmospheric air and residential air, as well as alluvial soils of technogenic landscapes of the South Elkon uranium-ore region in the territory of South Yakutia were studied. It has been shown that the most active dumps in their radiation parameters are close to radioactive ores, while the exposure dose rate here is 1600-2150 µkR/h, the effective specific activity of natural radionuclides is 20441-23640 Bq/kg, and the uranium content is 1637-1888 mg /kg. Ranking of the studied dumps according to the degree of radiation hazard showed that only 2 dumps out of 31 (6,4 %) belong to the category of safe, 13 (41,9 %) - to the category of potentially hazardous, and 7 and 9 (22,6 % and 29,0 %) - respectively categories of dangerous and especially dangerous. In the mountainous terrain, cold and humid climate of the study area, these rock dumps, unevenly distributed over an area of about 500 km2 of mountain-taiga landscapes, are the main source of radioactive contamination of air, ground and surface water, and soil cover. At the same time, the maximum values of uranium and radon content in the studied surface and groundwater, respectively, were 8,0 and 32,2·10-5 g/l, as well as 112 and 3090 Bq/l. In the studied technogenic zones, there is a direct relationship between the intensity of pollution of surface waters and alluvial soils drained by them, formed in the floodplains of these watercourses. Key words: rocks, soils, surface and underground waters, air, radiation parameters, technogenic pollution.

The radioecological situation of the mothballed geological survey site at the Elkon Plateau deposit in the Aldan Highlands was assessed by field radiometry. It was found that the extraction of a huge mass of radioactive rocks to the surface from underground mine workings (adits, mines) has significantly increased the area with an elevated background radiation of 1.0–12.0 µSv/h and more. The studies have shown that under conditions of anthropogenic contamination, the determining factors of migration, distribution, and accumulation of natural radionuclides in soils, besides their chemical properties, are humid climate, genetic features of radioactive ore, presence of permafrost rocks, soil-forming processes, and organic matter content. In the existing conditions of mountain taiga landscapes, the intensity of wind dispersion of radionuclides from dumps is significantly lower than that of hydrogenic dispersion. Active leaching of uranium from the dump rocks led to a dramatic disturbance of the radioactive equilibrium between radium and the parent radionuclide towards its excess in the soils of the Akin Creek Valley. Prolonged uncontrolled environmental impact of radioactive dumps contributed to the accumulation of uranium and radium in soils to levels of low- (14 252–66 836 Bq/kg) and medium-activity (102 294–601 987 Bq/kg) solid radioactive waste. At present, the problem of environmental contamination with natural radionuclides in the Elkon uranium ore mining district remains extremely urgent and requires close attention of nature conservation specialists.

An assessment of the radioecological situation of the preserved geological exploration site at the Elkon Plateau field in the Aldan Highlands was carried out using field radiometry. It was found that the removal of a huge mass of radioactive rocks to the surface from underground mine workings (tunnels, mines) significantly increased the area with an increased radiation background - 1,0-12,0 mSv/h or more. Studies have shown that in conditions of man-made pollution, the determining factors of migration, distribution and accumulation of natural radionuclides in soils, in addition to their chemical properties, are: a humid climate, genetic features of radioactive ore, the presence of permafrost rocks, soil formation processes and the content of organic matter. Under the prevailing conditions of mountain-taiga landscapes, the intensity of wind scattering of waste from dumps is significantly lower than that of hydrogenic. The active leaching of uranium from the rocks of the dumps led to a sharp disturbance in the soils of the Akin Creek valley of the radioactive equilibrium between radium and the parent radionuclide towards its excess. Prolonged uncontrolled exposure of radioactive dumps to the environment contributed to the accumulation of uranium and radium activities in soils to levels of low (14252-66836 Bq/kg) and medium-active (102294-601987 Bq/kg) solid radioactive waste.

Впервые проведена комплексная оценка радиационной и экологической обстановки на 9-ти золоторудных месторождениях Куранахского рудного поля (КРП), а именно «Северное», «Порфировое», «Центральное», «Южное», «Первухинское», «Боковое», «Дорожное», «Дэлбэ» и «Канавное». При проведении исследований использовался комплексный подход, основанный на применении геоэкологических, радиоэкологических и геохимических методов исследования в сочетании с экспрессными и точными методиками полевых и лабораторных работ. Показано, что гамма-фон на исследуемой территории изменяется в пределах от 7 до 26 мкР/ч и не превышает фоновые величины, характерные для карбонатных и терригенных осадочных пород. В мелкоземе пород отвалов и карьеров концентрации 40К варьируют в пределах 0.6-10.1 мг/кг, 238U – 0.8-12.3, а 232Th – 0.5-10.8 мг/кг и в целом соответствуют таковым, характерным для осадочных горных пород. Эффективная удельная активность радионуклидов в мелкоземе горных пород изменяется от 38 до 386 Бк/кг. Помимо оценки радиоэкологической обстановки на исследуемой территории, нами также изучалось общее экологическое состояние природной среды в районе КРП. Здесь также отмечается многофакторное антропогенное и техногенное воздействие на природные ландшафты. В частности показано, что в данном районе 47 % общей площади территории природных ландшафтов нарушено геолого-разведочными и добычными работами. В общем по результатам проведенных исследований радиоэкологическая обстановка в исследуемом районе в настоящее время оценивается как благоприятная, а эколого-геологическая может быть охарактеризована как напряженная, а в отдельных случаях даже как кризисная.

— The results of the field radiometric survey of the mined monazite Vasil’evka placer in southern Yakutia are presented. It is shown that the natural background radioactivity of soils of the surveyed area mainly depends on the features of its geological structure and, to some extent, on landscape-geocryological conditions. The rate of equivalent dose of gamma radiation on the soil surface of the studied plot varies in a wide range (from 0.04 to 0.50 µSv/h or more), depending on changes in the concentrations of 40 K, 238 U, and 232 Th in soils. Radiogeochemical features of soils in the studied area are well displayed on radiometric maps by isolines of the dose rate and radionuclide contents. The concentrations of 40 K, 238 U, and 232 Th are minimal in a peat-bog soil and a high moor on the interfluves composed of crystalline schists and gneisses and are maximal in podburs and alluvial soils formed on the products of weathering of granitoid rocks and monazite-bearing alluvial deposits in the Vasil’evka River valley. The studied soils are characterized by low mean concentrations of 40 K and 238 U, corresponding to their background values in soils of Yakutia. The mean concentration of 232 Th in the studied soils is increased as compared to the geochemical background. In addition to the composition of soil-forming rocks, the content and distribution of radionuclides in soils are significantly affected by soil-forming processes, chemical properties of elements, and technogenic impact. According to the effective specific activity of radionuclides, the studied soils correspond to the first, second, and third classes of building materials. Soils and enriched sands in some parts of technogenic landscapes are assigned to low-radioactive industrial waste according to the specific activity of thorium and require disposal. Their use as building materials from the identified areas of natural thorium concentration in alluvial deposits has serious limitations.

This article describes the features and migration patterns of natural long-lived heavy radionuclides 238U and 226Ra in the major components of the environment including rocks, river waters, soils, and vegetation of permafrost taiga landscapes of Southern Yakutia, which helped us to understand the scale and levels of their radioactive contamination. Different methods have been used in this study to determine the content of 238U and 226Ra in various samples, including gamma-ray spectrometry, X-ray spectroscopy, laser excited luminescence, and emanation method. It was determined that the main source of radioactive pollution of soil and vegetation cover, as well as surface waters in these technogenic landscapes, are the dumps of radioactive rock that were formed here as the result of geological exploration carried out in this area during the last third of the 20th century. The rocks studied were initially characterized by a coarse, mainly stony gravelly composition and contrasting radiation parameters, where the gamma radiation exposure rate varied between 1.71 and 16.7 µSv/h, and the contents of 238U and 226Ra were within the range 126–1620 mg/kg and 428–5508 × 10−7 mg/kg, respectively, and the 226Ra: 238U ratio was 1.0. This ratio shifted later on from the equilibrium state towards the excess of either 238U or 226Ra, due to the processes of air, water, and biogenic migration. Two types of 238U and 226Ra radionuclides migration were observed in studied soils, namely aerotechnogenic and hydrotechnogenic, each of which results in a different intraprofile radionuclide distribution and different levels of radioactive contamination. In this study, we also identified plants capable of selective accumulation of certain radionuclides, including Siberian mountain ash (Sorbus sibiricus), which selectively absorbs 226Ra, and terrestrial green and aquatic mosses, which accumulate significant amounts of 238U.

Инвентаризационные крупномасштабные карты почвенно-растительного покрова важны для охраняемых территорий, особенно в условиях возрастающего техногенного пресса. Цель наших исследований заключается в составлении карт почвенно-растительного покрова Якутского Ботанического сада на ландшафтной основе с использованием ГИС-технологий для обеспечения рационального природопользования и мониторинга экологического состояния. Сегодня использование ГИС-технологий позволяет реализовать интегральное картографирование биоразнообразия посредством создания масштабно-согласованного ряда ландшафтных и тематических карт почвенно-растительного покрова. Использование ГИС-технологий позволило составить карты, характеризующие основные природные условия: ландшафтно-типологическое строение, почвы и растительность в масштабе 1:10 000. Методология создания картографических моделей основана на анализе состава и структуры почвенно-растительных комплексов в границах ландшафтных контуров, предварительно выделенных по топографической карте масштаба 1:2 000. Базовая ландшафтная карта позволяет отобразить более общие закономерности на уровне групп типов урочищ. Составление ландшафтной основы на этом уровне позволяет генерировать различные тематические карты, необходимые как для оценки структуры почвенно-растительного покрова, так и в целом для оценки экологической обстановки. Составление почвенной карты на ландшафтной основе предполагает разработку параллельной сравниваемой схемы типологических ландшафтных единиц и типологических единиц структуры почвенного покрова. Картографические модели растительного покрова, созданы по принципу отображения распределения комплексов растительности, под которыми понимается сочетание (комбинация) фитоценозов и группировок растений, сопряжённо сосуществующих в границах ландшафтных контуров определенной размерности. На основе практического применения ГИС-технологий выявлены закономерности в пространственном распределении ландшафтов, почв и растительности. Разработанные карты почвенно-растительного покрова позволяют анализировать и оценивать природоохранную ценность и биогеографическую специфику территории Якутского Ботанического сада, определять приоритетность и эффективность охраны отдельных видов и экосистем, планировать природоохранные мероприятия. Large-scale inventory maps of soil and vegetation cover are important for protected areas, especially in the context of increasing technogenic pressure. The purpose of our research was to map the soil and vegetation cover in Yakutsk Botanical Garden on a landscape basis using GIS technologies to ensure environmental management and monitoring of the ecological status. Today, the use of GIS technologies makes it possible to implement integrated mapping of biodiversity through the creation of a large-scale coordinated series of landscape and thematic maps of soil and vegetation cover. The use of GIS technology allowed us to produce maps describing basic natural conditions of the landscape-typological structure of the soil and the vegetation in the scale 1:10 000. The methodology for the creation of cartographic models was based on the analysis of the composition and structure of soil-plant complexes within the boundaries of landscape contours, pre-selected topographic map scale 1:2 000. The basic landscape map allows displaying more general patterns at the level of groups of types of tracts. The establishment of a landscape base at this level allows for the generation of various thematic maps, both for the assessment of land cover structure and for the assessment of the environmental situation in general. The compilation of a soil map on a landscape basis involves the development of a parallel comparative scheme of typological landscape units and typological units of the structure of the soil cover. Cartographic models of vegetation cover, created on the principle of mapping the distribution of vegetation complexes, which refers to the combination of phytocenoses and groups of plants, coexisting in the boundaries of landscape contours of a certain dimension. On the basis of practical application of GIS-technologies regularities in spatial distribution of landscapes, soils and vegetation were revealed. The developed maps of soil and vegetation cover allow analyzing and evaluating of the environmental value and biogeographic specificity of the territory of Yakutsk Botanical Garden, to determine the priority and effectiveness of the protection of individual species and ecosystems, to plan environmental activities.

We examine the geographical features in the distribution and the radiation parameters of radioactive rock dumps in the Elkon uranium ore area on the territory of South Yakutia. It is pointed out that the dumps under study are geomorphologically located on the Elkon horst which is a protrusion of crystalline basement rocks, towering over the territory of the Aldan highlands. It is found that most of these dumps lie within streambeds and in the bottoms of mountain rivers of the zone of hypergenesis and, geochemically, they are influenced by steep-slope topography, a cold humid climate and mountain-taiga vegetation dominating land cover. It is shown that these rock dumps were formed in the last third of the 20th century, during a large-scale and intense geological exploration for radioactive raw materials in this area. Radiation parameters of the dumps under study, such as the gamma radiation exposure dose, the content of 238U, 232Th and 40K, as well as the effective specific activity of these radionuclides were determined. It is found that the most active rock dumps, in their radiation parameters, approach radioactive ores. The dumps under study were ranked according to the degree of radiation danger to the population on the basis of the particular values of the gamma radiation exposure dose and effective specific activity of these radionuclides. It is established that the main source of radioactive contamination of soil and vegetation cover and the surface waters in the Elkon uranium ore area on the territory of South Yakutia are 40 rock dumps which are unevenly distributed in the total area of about 500 km(2) of the mountain-taiga permafrost landscapes. It is determined that more than half of these dumps, in their radiation parameters, are classified as hazardous and specially hazardous.

GaInPAs/InP heterostructures grown by low pressure (0.1 bar, 600 oC) metal-organic chemical vapor phase deposition were investigated. The thicknesses of grown GaInAsP layers were about 1 µm. For the epitaxial layers Ga1-xInxP1-yAsy) with average compositions of x = 0.77 – 0.87 and y = 0.07 – 0.42 the variation of V group elements content y with the epilayer depth were revealed, weher the compositions of V-group elements were changed up to Δy = 0.1 atomic fractions in V group elements sublattice. In most cases, y change occurs in a GaInAsP region up to 200 nm thick adjacent to the InP. In some cases, y changes throughout the whole GaInPAs layer thickness. Fo the epitaxial layers with a satisfactory crystal perfection the less was the mismatch between the substrate and the GaInPAs epitaxial layer, the smaller was the value of Δy. For GaInPAs layers characterized by a low degree of crystal perfection and a high lattice mismatch between GaInAsP and InP layers, the value of Δy was about zero. These data let us suggest that the incorporation of atoms of the V group in the epitaxial layer strongly depends on elastic deformation of the growing monolayer, that is mismatched with the underlying crystal surface.

Quantum photoresponse yield of a silicon XUV avalanche photodiode prototype with 1.5‑mm-diameter active region has been studied in the 320–1100 nm wavelength range. It is established that the proposed avalanche photodiode has the external quantum efficiency above 20 electron/photon in the 580–1000 nm range at a reverse bias voltage of 485 V.

The sensitivity at wavelengths in the range 400–1150 nm, dark current, and dynamic characteristics of an silicon avalanche photodiode with an active region 1.5 mm in diameter that we developed have been examined. It has been shown that the avalanche photodiode has the following set of characteristics: sensitivity 80–85 A/W at wavelengths of 900–1010 nm, dark current 1.5 nA, and leading and trailing edges shorter than 2.5 ns at a reverse bias voltage of 350 V.

Изучены радиационные параметры отвалов горных пород зоны Южная в Эльконском ураново-рудном районе на территории Южной Якутии, содержание и распределение урана, радия и радона в поверхностных водах, а также U в почвах техногенных ландшафтов на различном удалении от источников радиоактивного загрязнения. Показано, что наиболее активные отвалы по радиационным параметрам приближаются к радиоактивным рудам, при этом мощность их экспозиционной дозы (МЭД) составляет 1600-2150 мкР/ч, эффективная удельная активность (Аэфф) – 20441-23640 Бк/кг, а содержание урана – 1637-1888 мг/кг. Ранжирование изучаемых отвалов по степени радиационной опасности показало, что 12 отвалов из 31 (39%) относятся к категории безопасных, 6 (19%) – к категории потенциально-опасных, а 5 и 8 (16% и 26%) – соответственно к категориям опасных и особо опасных. В условиях горного рельефа, холодного и гумидного климата исследуемой территории данные отвалы горных пород, неравномерно размещенные на площади около 500 км 2 горно-таежных ландшафтов, являются основным источником радиоактивного загрязнения почвенно-растительного покрова и поверхностных вод. При этом максимальные значения содержания урана, радия и радона в изученных поверхностных водах соответственно составляют 180·10 -7 г/л, 4.7·10 -12 г/л и 256.8 Бк/л, что в 100, 8 и 198 раз превышает их фоновые концентрации в водах естественных ландшафтов. В исследованных техногенных зонах отмечается прямая зависимость между интенсивностью загрязнения поверхностных вод и дренируемых ими аллювиальных почв, формирующихся в поймах данных водотоков.

Silicon XUV avalanche photodiode prototype quantum yield have been explored with an active area of 1.5 mm in a 320 – 1100 nm spectral range. Quantum yield of a 20 electron per photon have been reached in 580 – 1000 nm spectral range with bias 485 V.

This study aims at investigating the allocation conditions of rock dumps in the South zone located in the Elkon uranium mine region (the Southern Yakutia), and also at determining their radiation parameters as sources of technogenic contamination of the soil-vegetation cover and surface waters, and assessing the danger of these dumps for people. In this study, the generally accepted geographical methods were used, including comparative geographical and geochemical methods, as well as a combination of various radiometric research methods. The radiation parameters of the rock dumps of the South zone of the Elkon uranium mine region, the content and distribution of uranium, radium and radon in surface waters, as well as 238U content in technogenic soils at different distances from radioactive contamination sources were studied. It was found that the most active dumps, in terms of their radiation parameters, are located close to the radioactive ores, with the EDR of 1600-2150 R/h, effective specific activity - 20441-23640 Bq/kg, and uranium content of 1637-1888 mg/kg. The ranking of the studied dumps according to the degree of radiation hazard showed that 12 out of 31 dumps (39%) belong to the safe category, 6 (19%) belong to the category of potentially dangerous, and 5 and 8 (16% and 26%) were classified as dangerous and very dangerous respectively. In the conditions of the mountainous terrain, cold and humid climate of the studied area, these rock dumps, which are unevenly spread in mountain and taiga landscapes over the area of about 500 km2, are the main source of radioactive contamination of soil and vegetation cover and surface waters. The maximum contents of uranium, radium and radon in the studied surface waters were 18010-7 g/L, 4.710-12 g/L and 256.8 Bq/L respectively, which are 100, 8 and 198 times higher than their background concentrations in waters of natural landscapes. In the studied technogenic zones, a direct relationship was registered between the pollution intensity in surface water and that in the drained alluvial soils formed in the floodplains of these watercourses.

Sensitivity in 400 – 1150 nm spectral range, dark current and dynamic characteristics have been tested of a developed silicon avalanche photodiode with an active diameter of 1.5 mm. Developed Si APD possesses: photosensitivity 80-85 A/W in 900 - 1010 nm spectral range, 1.5 nA dark current, rise and fall time less than 2.5 ns with a bias voltage of 350 v.

Gradual variation of the content y of Group-V components by Δy of up to 0.08 across the thickness (600–850 nm) of an epitaxial layer has been observed for Ga1 – xInxAsyP1 – y solid solutions (x = 0.86, y = 0.07–0.42) produced on InP by metal-organic vapor-phase epitaxy under lowered pressure, although the composition of the gas mixture, temperature, and pressure were maintained invariable in the course of the growth process. For different gas mixture compositions, the value of Δy and the manner of its variation were different. An analysis of the data obtained demonstrated that Δy is due to the deformations that appear in a growing layer because of the lattice mismatch with the substrate.

The spatial distribution patterns of climatic changes in Yakutia are considered. For 26 meteorological stations of Yakutia we calculated the linear trend coefficients of climatic characteristics: air temperature (mean annual, January and July temperatures) and the mean annual amount of atmospheric precipitation from 1966 to 2016. Maps of climate change trends were compiled from linear trend coefficients. A spatial analysis of the zonal (regional) peculiarities of the climate of Yakutia has been carried out. An increase in air temperature was established for the 50-year period under consideration. It was found that the annual values of the air temperature trend are positive and, on average, a characteristic trend change interval is 0.3 to 0.6 °C/10 yr. Most of the meteorological stations recorded trends of air temperature with maximum values in winter and minimum values in summer. It was determined that the values of the trends in annual precipitation show different directions, and positive trends occur on more than 70% of the territory of Yakutia. Their maximum corresponds to the mountain-taiga regions of Southern Yakutia. Negative trends in precipitation with values of up to–15 mm/10 yr. are observed in tundra landscapes. The findings show that different regions of Yakutia respond differently to climate change. The trend of an increase in mean annual temperature is largely due to the rise in temperatures during the winter months. The rise in air temperature in Yakutia may be part of global warming. Over the last 50 years there has been an increase in the amount of precipitation in Yakutia as a whole.