Застосування лабораторної бета-радіометрії для кількісної індикації концентрації радіонуклідів в пробах рослинного походження

The aim is to improve the beta-radiometric method of quantitative indication of the content of 90Sr and 137Cs in the counters of plant samples. Material and methods. In the Chernobyl exclusion zone (ChEZ) in 2017, 2019, leaves of silver birch, black poplar, common reed, sedge were selected, which were dried, crushed, and used as calculating samples for beta radiometry and spectrometry. For measurements, a combined KRK-1 radiometer and a SEB 01-150 spectrometer beta-radiation energy were used. Results. Currently, in plant samples from the ChEZ, the following are widespread: natural 40K, the concentration of which is usually less than 1 % in relation to the concentration of technogenic radionuclides 90Sr+90Y and 137Cs, therefore, when measuring 90Sr and 137Cs, beta radiation of 40K can be ignored. The measurements were carried out without a spectral filter and using a thin molybdenum filter. Without filter – show the count rate of 90Sr+90Y and 137Cs radiation. The filter transmits 2–3.5 % of the low-energy beta radiation of 90Sr and 137Cs and more than 95 % of the high-energy 90Y. The ratio of the count rate of 90Y pulses with and without filter is 2.14. The 90Sr concentration in the samples was determined from the results of measurements of 90Y, and 137Cs – through the fraction of the counting rate, which remains after deducting 90Sr+90Y. Comparison of the concentration of radionuclides measured by the method of beta-radiometry and spectrometry showed no significant difference between the results obtained by the two methods. Conclusions. The beta radiometry method for 90Sr and 137Cs provides for measuring the counting rate of beta radiation from counting samples without a spectral filter and using a thin molybdenum filter. Based on the research results, a procedure for calculating the concentration of 90Sr and 137Cs in counting samples of plant leaves was developedЦель – усовершенствование бета-радиометрического метода количественной индикации содержания 90Sr и 137Cs в счетных образцах растений. Материал и методы. В Чернобыльской зоне отчуждения (ЧЗО) в 2017, 2019 отобраны листья березы повислой, тополя черного, тростника обыкновенного, осоки острой, которые высушивали, измельчали, и использовали в качестве счетных образцов для бета радиометрии и спектрометрии. Для измерений применены радиометр комбинированный КРК-1 и спектрометр энергии бета-излучения СЕБ 01-150. Результаты. В настоящее время в растительных образцах из ЧЗО распространены: природный 40К, концентрация которого обычно менее 1 % по отношению к концентрации техногенных радионуклидов 90Sr+90Y и 137Cs, поэтому при измерении 90Sr и 137Cs бета излучением 40К – можно пренебречь. Измерения проведены без спектрального фильтра и с применением фильтра из тонкого молибдена. Без фильтра – показывают скорость счета излучения 90Sr+90Y и 137Cs. Фильтр из молибдена пропускает 2–3,5 % низкоэнергетического бета-излучения 90Sr и 137Cs и более чем на 95 % – высокоэнергетического – 90Y. Отношение скорости счета импульсов 90Y с фильтром и без него составляет 2,14. Концентрацию 90Sr в образцах устанавливали по результатам измерения 90Y, а 137Сs – через долю скорости счета, что остается за вычетом 90Sr + 90Y. Сравнение концентрации радионуклидов измеренной способом бета-радиометрии и бета-спектрометрии показало отсутствие достоверной разницы между результатами полученными двумя методами. Выводы. Способ бета радиометрии 90Sr та 137Cs предусматривает измерение скорости счета бета-излучения счетных образцов без спектрального фильтра и с применением фильтра из тонкого молибдена. По результатам исследований разработана процедура вычисления концентрации 90Sr и 137Cs в счетных образцах листьев растенийМета – удосконалення бета-радіометричного способу кількісної індикації вмісту 90Sr та 137Cs в лічильних зразках рослин. Матеріал і методи. У Чорнобильській зоні відчуження (ЧЗВ) в 2017, 2019 р. відібрано листки берези повислої, тополі чорної, очерету звичайного, осоки гострої, які висушували, подрібнювали, та використовували в якості лічильних зразків для бета радіометрії та спектрометрії. Для вимірювань застосовано радіометр комбінований КРК-1 і спектрометр енергії бета-випромінювання СЕБ 01-150. Результати. В теперішній час у рослинних зразках з ЧЗВ розповсюджені: природний 40К, концентрація якого як правило менше 1 %, порівняно із концентрацією техногенних радіонуклідів 90Sr+90Y та 137Cs, тому при вимірюванні 90Sr та 137Cs бета випромінюванням 40К – можна знехтувати. Вимірювання проведені без фільтру та із застосуванням фільтру із тонкого молібдену. Без фільтру – показують швидкість рахування випромінювання 90Sr+90Y та 137Cs. Фільтр із молібдена пропускає 2–3,5 % низькоенергетичного бета-випромінювання 90Sr та 137Cs та більше ніж на 95 % – високоенергетичного – 90Y. Відношення швидкості рахування імпульсів 90Y з фільтром та без нього складає 2,14. Концентрацію 90Sr у зразках встановлювали за результатами вимірювання 90Y, а 137Сs – через частку швидкості рахування, що залишається за вирахуванням 90Sr+90Y. Порівняння концентрації радіонуклідів виміряної способом бета-радіометрії та бета-спектрометрії показало відсутність достовірної різниці між результатами отриманими обома методами. Висновки. Спосіб бета радіометрії 90Sr та 137Cs передбачає вимірювання швидкості рахування бета-випромінювання лічильних зразків без фільтру та із застосуванням фільтру з тонкого молібдену. За результатами досліджень розроблено процедуру обчислення концентрації 90Sr та 137Cs у лічильних зразках листків росли

Application of Laboratory Beta Radiometry for Quantitative Indication of Radionuclide Concentration in Plant Samples

The aim is to improve the beta-radiometric method of quantitative indication of the content of 90Sr and 137Cs in the counters of plant samples. Material and methods. In the Chernobyl exclusion zone (ChEZ) in 2017, 2019, leaves of silver birch, black poplar, common reed, sedge were selected, which were dried, crushed, and used as calculating samples for beta radiometry and spectrometry. For measurements, a combined KRK-1 radiometer and a SEB 01-150 spectrometer beta-radiation energy were used. Results. Currently, in plant samples from the ChEZ, the following are widespread: natural 40K, the concentration of which is usually less than 1 % in relation to the concentration of technogenic radionuclides 90Sr+90Y and 137Cs, therefore, when measuring 90Sr and 137Cs, beta radiation of 40K can be ignored. The measurements were carried out without a spectral filter and using a thin molybdenum filter. Without filter – show the count rate of 90Sr+90Y and 137Cs radiation. The filter transmits 2–3.5 % of the low-energy beta radiation of 90Sr and 137Cs and more than 95 % of the high-energy 90Y. The ratio of the count rate of 90Y pulses with and without filter is 2.14. The 90Sr concentration in the samples was determined from the results of measurements of 90Y, and 137Cs – through the fraction of the counting rate, which remains after deducting 90Sr+90Y. Comparison of the concentration of radionuclides measured by the method of beta-radiometry and spectrometry showed no significant difference between the results obtained by the two methods. Conclusions. The beta radiometry method for 90Sr and 137Cs provides for measuring the counting rate of beta radiation from counting samples without a spectral filter and using a thin molybdenum filter. Based on the research results, a procedure for calculating the concentration of 90Sr and 137Cs in counting samples of plant leaves was develope

The effect of soil on spatial variation of the herbaceous layer modulated by overstorey in an Eastern European poplar-willow forest

The tree species composition can influence the dynamics of herbaceous species and enhance the spatial heterogeneity of the soil. But there is very little evidence on how both overstorey structure and soil properties affect the spatial variation of the herb layer. The aim of this study is to evaluate the factors of the soil and overstorey structure by which it is possible to explain the fine-scale variation of herbaceous layer communities in an Eastern European poplar-willow forest. The research was conducted in the “Dnipro-Orils’kiy” Nature Reserve (Ukraine). The research polygon (48°30′51″N, 34°49″02″E) was laid in an Eastern European poplar-willow forest in the floodplain of the River Protich, which is a left inflow of the River Dnipro. The site consists of 7 transects. Each transect was made up of 15 test points. The distance between rows in the site was 3 m. At the site, we established a plot of 45×21 m, with 105 subplots of 3×3 m organized in a regular grid. The adjacent subplots were in close proximity. Vascular plant species lists were recorded at each 3×3 m subplot along with visual estimates of species cover using the nine-degree Braun-Blanquet scale. Within the plot, all woody stems ≥ 1 cm in diameter at breast height were measured and mapped. Dixon’s segregation index was calculated for tree species to quantify their relative spatial mixing. Based on geobotanical descriptions, a phytoindicative assessment of environmental factors according to the Didukh scale was made. The redundancy analysis was used for the analysis of variance in the herbaceous layer species composition. The geographic coordinates of sampling locations were used to generate a set of orthogonal eigenvector-based spatial variables. Two measurements of the overstorey spatial structure were applied: the distances from the nearest tree of each species and the distance based on the evaluation of spatial density of point objects, which are separate trees. In both cases, the distance matrix of sampling locations was calculated, which provided the opportunity to generate eigenvector-based spatial variables. A kernel smoothed intensity function was used to compute the density of the trees’ spatial distribution from the point patterns’ data. Gaussian kernel functions with various bandwidths were used. The coordinates of sampling locations in the space obtained after the conversion of the trees’ spatial distribution densities were used to generate a set of orthogonal eigenvector-based spatial variables, each of them representing a pattern of particular scale within the extent of the bandwidth area structured according to distance and reciprocal placement of the trees. An overall test of random labelling reveals the total nonrandom distribution of the tree stems within the site. The unexplained variation consists of 43.8%. The variation explained solely by soil variables is equal to 15.5%, while the variation explained both by spatial and soil variables is 18.0%. The measure of the overstorey spatial structure, which is based on the evaluation of its density enables us to obtain different estimations depending on the bandwidth. The bandwidth affects the explanatory capacity of the tree stand. A considerable part of the plant community variation explained by soil factors was spatially structured. The orthogonal eigenvector-based spatial variables (dbMEMs) approach can be extended to quantifying the effect of forest structures on the herbaceous layer community. The measure of the overstorey spatial structure, which is based on the evaluation of its density, was very useful in explaining herbaceous layer community variation