The more serious the silicone rubber’s aging, the smaller was the T2. The state of the composite insulator can be evaluated by using T2 and aging years simultaneously. With the actual degree of aging in the silicone rubber intensified, its tensile strength and elongation at break generally showed a downward trend.Composite insulators operate in harsh field environments all year round. Their various properties and states of aging require attention. It is important to study the performance changes of composite insulator sheds after aging to evaluate the life of insulators operating on grids. For this reason, 22 composite insulator sheds from different factories, with different voltage levels and different ages years were selected to conduct mechanical properties testing. The mechanical properties include hardness, tensile strength, and elongation at break, and were investigated by thermogravimetric (TGA) testing, surface morphology, and nuclear magnetic resonance (NMR) characterization. The changes in mechanical properties of high temperature vulcanization (HTV) composite insulator silicone rubber aged in the natural environment were analyzed, including the reasons for these changes. The results showed that the transverse relaxation time T Composite insulators have the advantages of negligible mass, high strength, good pollution resistance, and low maintenance workload . Their s2 increased, and oxidation occurred. The results of the TGA testing showed that the organic content in the sheds decreased, the inorganic content was exposed, and the proportion of remaining substances in the TGA analysis increased. The remaining substances were inorganic fillers, including Al2O3 formed after dehydration of aluminum trihydrate (ATH) and silica. Zhang et al. [The physical and chemical properties that characterize the electrical performance of composite insulators have been studied worldwide. For example, Mavrikakis et al.  tested tg et al.  studied g et al. ,7,8,9. Research has also been carried out on the physical and chemical characteristics that affect the mechanical properties of composite insulators. For example, Xie et al.  tested tIto et al. studied the mechanical and chemical properties of silicone rubber by applying artificial heating, irradiation, and other aging methods. The results show that the performance of the sheds had decreased, and the tensile fracture was mainly elastic deformation ,13. KhanInternationally, many tests have been carried out on the physical and chemical properties of composite insulators, and the variation rules of some characteristic parameters have been obtained. Due to the small sample size of insulators operating in the field, it is difficult to obtain insulators with different ages in the same environment. Furthermore, the process formulas of different factories are different. The research mechanism is limited to qualitative analysis. In the current study, based on composite insulators located in the test station for different durations of years, the mechanical properties of the sheds were tested for nuclear magnetic resonance, hardness, tensile strength, etc., combined with TGA and microscopic tests, to study the changes in the mechanical properties of composite insulator sheds under the same aging conditions. The research results provide scientific data support for further revealing the mechanical failure mechanism of composite insulator sheds.Composite insulator silicone rubber sheds have aged for different years without electrification at high altitudes in the natural environment of the XueFeng Mountains in Hunan Province. The composite insulators were produced in four different factories, denoted A, B, C, and D. The main components of the composite insulator sheds are methyl vinyl siloxane and inorganic fillers. The proportions of the fillers are different for composite insulators manufactured by different factories, therefore, the initial mechanical properties are different before the aging process begins. To meet the requirements of mechanical and electrical properties including different mechanical loads and creepage distances, different factories have manufacture insulators of different voltage levels. In the study sample there were 22 insulators with five voltage levels, 35 kV, 110 kV, 220 kV, 500 kV, and 800 kV, respectively. Among them, 9 had an aging period of 3.5 years and below, 8 had 3.5 to 8 years, and 5 had 8 years and above. All the composite insulators showed no damage or cracking to the sheds. In the following discussion, “a” indicates units of years of aging.NMR tests were carried out to explore the characteristic parameters of the physical and chemical properties of the composite insulator sheds with different operational ages. The NMR sensors used in the experiment are shown in 2 was obtained. The transverse relaxation time is the time required for the transverse magnetization vector to decay to 37% of the maximum value [2 can reflect the aging degree of the sample, the lower the T2, the greater the aging degree of the sample [2, and the magnetic field’s polarization causes the sample’s heating. The experimental data were measured at constant room temperature in a single session. In the NMR experiment, the CPMG (Carr–Purcell–Meiboom–Gill) pulse sequence was utilized to excite the sample, as shown in echo is the echo time, A180° and A90° are the 180° pulse amplitude and the 90° pulse amplitude, respectively.Before the test, samples were washed with absolute ethanol and dried in the shade for 24 h. Since the upper surface is affected by ultraviolet rays and numerous environmental factors, it can reflect the degree of aging more than the lower surface. NMR experiments were performed on the upper surface of the sample, and the transverse relaxation time Tum value . For a ge sample . Room teThe CPMG pulse parameters in the experiment were set as in An electronic shore hardness tester was utilized to measure the hardness of the composite insulator sheds. The test method corresponds with standard ISO 48-4 . The samThese tests were conducted according to the ISO 37 standard guidelines . The samThe test used AGX with a desktop electronic universal testing machine produced by SHIMADZU company, as shown in sT can be calculated according to Formula (1), and the elongation at break bE can be calculated according to Formula (2).sT is the tensile strength (MPa), mF is the tensile force at break (N), D is the width of the narrow part of the sample (mm), t is the thickness of the sample (mm), bE is the elongation at break (%), L0 is the initial test length of the sample (mm), bL is the test length of the sample at the moment of rupture (mm). Before the test, the thickness of the C section of the experimental length of the sample was measured. When measuring, the cross-section of the test sample was uniformly stressed, and the gripper movement speed was set to 500 mm/min. During the test, if the sample did not break in the narrow part, the result was discarded and another sample was retested. Each sample was measured three times, the tensile strength was calculated separately, and the final results were averaged. The tensile strength TGA is a simple technique for measuring change in weight with temperature. It provides decisive data for material and product design as well as information about aging stability. The TGA analyzer model used in this study was TGA/DSC1/1600LF. The TGA analyzer is shown in In this work, an environmental scanning electron microscope (SEM) was utilized to observe the micro-morphology of the composite insulator silicone rubber shed sample, which was viewed from all angles.The environmental scanning electron microscope was produced by Thermo Fisher. The accelerating voltage was 0.2~30 kV, the resolution 1 nm (30 kV)~3 nm (1 kV), and the magnification 6~2,500,000. Due to the insulating nature of silicone rubber, all the specimens were sputter-coated with a thin layer (15 nm) of gold.The main material of the composite insulator shed samples was polydimethylsiloxane (PDMS). When the silicone rubber ages on the composite insulator in the natural environment, ultraviolet rays break the chemical bonds with lower bond energy in the silicone rubber, such as Si-C bonds and C-H bonds. With further aging, the Si-O bond energy on the main chain decays, and the bond energy between the Si atom and the methyl or vinyl groups on the side chain changes accordingly, thereby affecting the H atom in the groups. The increase in cross-link density also reduces the mobility of H-containing groups. The quantity of H atoms in PDMS is high, and a large signal intensity can be obtained by using H as the resonance object. Nuclear magnetic resonance technology can reveal the H content and state in the silicone rubber by using the resonance characteristics of the H atom, to reflect the degree of aging.2 is the transverse relaxation time.The samples were tested by NMR according to the method described above. The CPMG echo signal image obtained from a particular test is shown in 2 are shown in The years of aging of the samples from each factory and the transverse relaxation time T(1)2 values of the composite insulator sheds decreased, and the two showed certain linearity. For example, the 35 kV sheds from factory A had aging periods of 1, 3.5, and 8 years, and their T2 values were 122.5 ms, 120.6 ms, and 118.7 ms, respectively, indicating a gradual decrease.With the increase in years of aging, the T(2)2 values were different at different voltage grades with the same aging periods from the same manufacturer. For example, factory A produced 35 kV and 110 kV sheds and with aging periods of 1 year their T2 values were 122.5 ms and 114.8 ms, respectively. The 110 kV and 220 kV sheds from factory C with aging periods of 6 years had T2 values of 111.7 ms and 122.1 ms, respectively.The sheds’ T(3)2 values. For example, factories B and C both produced 220 kV sheds which had an aging period of 6 years, with T2 values of 115.0 ms and 122.1 ms, respectively. Factories A, C, and D all made 110 kV sheds with aging periods of 6 years, and the T2 values of the three were 102.5 ms, 116.3 ms, and 125.0 ms, respectively.Sheds with the same aging period and the same voltage level from different factories had different T(4)2 value decreased with the aging period, i.e., the faster the aging speed.The aging speeds of sheds with the same voltage levels from different factories were different, as reflected in the linear fitting line showing different slopes. For example, the slopes of the fitting lines of the 110 kV sheds from factories A and C were 2.46 and 1.63, respectively. The greater the slope, the faster the T(5)2 values of sheds from different factories. The T2 value of sheds from factory D maintained a high level during the aging period, and the T2 of the sample aged for 10 years was 123.2 ms. The maximum value of T2 of the aged samples from factory B was 115.8 ms, and the aging period was 3.5 years. For factory C that value was 122.1 ms, and the aging period was 6 years.There were also differences in the overall TFrom the results in 2 of natural aged composite insulator sheds, and T2 gradually decreased with the increase in years of aging. The different insulator formulas and production processes of factories are reasons for the differences in T2 value and rate of decline. Therefore, the recorded years of aging cannot be used as the only reference standard. The transverse relaxation time T2 obtained from the tests and the recorded years of aging should be comprehensively considered to analyze the actual aging of samples, and the influence of different factories and voltage levels should also be considered.There was a positive correlation between years of aging and the transverse relaxation time TThe samples were tested for hardness according to the method described above. The details are shown in (1)2, the overall chemical structure did not change dramatically, and the actual degree of aging was not high. It can be speculated that the drop point may have been caused by different onsite sampling locations, according to the sheds’ leeward aspect, exposure of inner and outer positions to ultraviolet rays, etc. The severity of natural aging factors differed, resulting in diverse test results for the same sheds taken from different sampling positions.With the increase in years of aging, the hardness of composite insulator sheds generally showed an increasing trend. For example, the aging periods of the 35 kV sheds from factory A were 1, 3.5, and 8 years, and the hardness was 68.8, 70.8, and 78, respectively. The 110 kV samples from factory D showed an upward trend in general from 3.5 years to 10 years, and the hardness increased by 2.61%. The hardness of the samples from factory D with an aging period from 3.5 years to 6 years and the hardness of the 220 kV sheds from factory C decreased slightly. Combined with the high overall value of T(2)Sheds with the same years of aging and voltage levels from different factories had different hardness values. For example, factories A, C, and D all produced samples with voltage of 110 kV and an aging period of 6 years, with hardness 75.2, 83, and 76.5, respectively.(3)There were also differences in the overall hardness of the sheds from different factories. The hardness variation range of the sheds from factories B and D during the aging period was 2, and the ranges for A and C were 9.8 and 6, respectively. The effect of ultraviolet aging on the hardness of samples from factories A and C was more obvious.From the results in In general, the hardness of sheds increased with the increase in years of aging. Research analysis has indicated that, in the early stages of the aging period, ultraviolet light carrying photon energy severs the Si-C bonds and C-H bonds with lower bond energy in the sheds’ polymer material . Breakin2 and the recorded aging years. For example, data for the 500 kV sheds from factory B reflects the superiority of adding T2 as an aging index; the hardness of the sheds with aging time of 1 year and 10 years was 80.5 and 81.5, respectively. Although the years of aging varied, the hardness hardly changed, and T2 of the two were 114.1 ms and 113.7 ms, respectively. It can be seen from the NMR results that their actual degree of aging was almost the same, and the degree of cross-linking was equivalent.As mentioned above, the actual aging of the samples was be analyzed with consideration of TThe mechanical properties were tested according to the above method, and the relationship between the mechanical properties of the samples from each factory and the years of natural aging was analyzed and compared. The results are shown in (1)With the increase in years of aging, the tensile strength of composite insulator sheds generally showed a downward trend. For example, the years of aging of the 35 kV sheds from factory A were 1, 3.5, and 8 years, and the tensile strengths were 4.58 MPa, 3.88 MPa, and 3.79 MPa, respectively. For sheds from factory D, the tensile strength dropped from 6.77 MPa to 6.63 MPa with increased aging from 3.5 to 10 years.(2)The tensile strength was different in sheds of different voltage levels but from the same factory with the same aging period. For example, the 35 kV and 110 kV sheds aged for one year in factory A had tensile strength values of 4.58 MPa and 4.41 MPa, respectively. The 220 kV and 110 kV sheds aged 6 years from factory C had tensile strength values of 5.82 MPa and 4.89 MPa, respectively.(3)Sheds with the same aging period and voltage level from different factories had different tensile strengths. For example, the factories A, C, and D all produced samples with a voltage level of 110 kV and an aging period of 6 years, and their tensile strengths were 3.94 MPa, 4.89 MPa, and 6.44 MPa, respectively.(4)Sheds from different factories showed the same phenomenon of rapid performance decline in the early stages of aging. The tensile strength of the 35 kV sheds from factory A decreased by 15.2% and 2.3%, respectively, in the aging period of 1 year to 3.5 years and of 3.5 years to 8 years. The tensile strength of the sheds decreased faster when initially aged by natural factors. This phenomenon is reflected by the changing slope of the straight line in the figure. This phenomenon was also apparent in the 110 kV factory C and 220 kV factory B samples.(5)There were similarities and differences in the overall tensile strengths of sheds from different factories. For example, the measured minimum tensile strength of the sheds from factory D after aging is 6.44 MPa, which was much higher than the other three factories. The tensile strength of the sheds from each of the four factories showed the same phenomenon, generally higher at high voltage levels than at low voltage levels.From the results in 2 values of the three samples fluctuated by no more than 2.57%. Compared with the NMR results of the other samples, this group of samples maintained a very high T2 value. That is, in this natural environment, the degree of aging was not obvious in terms of increasing mechanical properties.In general, with the increase in years of aging, the overall tensile strength of the sheds decreased. It can be speculated that where the curve for factory D declines and then rises after aging, the effect may be caused by different sampling locations on site. With the increase in years of aging, the TDL/T 376-2010  stipulat2  are shown in The relationships between the tensile strength, elongation at break, and T2 decreased, the tensile strength generally showed a downward trend, and T2 was positively correlated with the tensile strength.From the fitting results in Analysis shows that under the irradiation of ultraviolet energy, the chemical bonds with lower bond energy are separated, manifesting as the decline of mechanical properties including tensile strength. With the increase in years of aging, the number of broken chemical bonds increases, the microscopic cross-linking of free radicals occurs, and the micro-dynamic process of fracture and cross-linking is reflected in an overall decrease in tensile strength at the macro level. With the increase in years of aging, the functional group components inside the silicone rubber and the elemental contents change. The backbone integrity is destroyed after aging, and the polarity degree increases. Its overall performance exhibits a decrease of mechanical properties. 2, the samples’ overall elongation at break showed a decreasing trend.According to the results in 2 were consistent when characterizing the mechanical properties of the samples. These two characteristic parameters should be combined during the monitoring and analysis of composite insulator sheds during aging.The above results show that the years of aging and TThe main components of composite insulator sheds are methyl vinyl siloxane (base glue) and inorganic fillers. The inorganic fillers are generally aluminum trihydrate (ATH) and silica. As an important additive, ATH can improve flame retardancy, electrical tracking resistance, corrosion resistance, electrical properties, and UV aging resistance of silicone rubber. The composite insulators manufactured by different factories contained different proportions of each component, some may add more inorganic filler in order to save costs, and the shed will show different resistance during the aging process. According to the above analysis, there were numerical differences in the test results of samples after aging from different manufacturers, and they followed the same pattern of change. Taking samples from factory C as an example, the TGA analysis curve of the samples in the 110 kV group is shown in 2 became smaller, the proportion of weight loss in the first and second stages decreased, and the proportion of remaining mass increased.It can be seen from the curves and graphs that different years of uncharged aging had an impact on the thermal gravimetric test results for the sheds. With the increase in years of aging, TThe specific TGA analysis data are shown in According to the analysis, the first stage of weight loss was mainly due to the dehydration of ATH in the inorganic filler of the sheds. This dehydration of the ATH is stated as:3) from combustion, as shown in the following (The more serious the aging, the more inorganic fillers are precipitated from the pores caused by the aging, and the decomposable amount after heating decreases. The weight loss in the second stage was mainly the thermal decomposition of PDMS. Similar to the previous stage, the more serious the aging, the less PDMS available for pyrolysis. Decomposition of PDMS may be caused by the release of the siloxane side chain (CHollowing :2O3 formed after dehydration of ATH and silica.The remaining substances are inorganic fillers, including AlATH in sheds has a spacing effect. The addition of ATH can limit the re-cross-linking of the broken chemical bonds of the silicone rubber, and the inorganic fillers are not affected by ultraviolet rays, so the more fillers, the less the shed surface is affected by radiation. Aging leads to the appearance of voids, and the inorganic fillers are exposed to the air and precipitate . The red2 decreases, the content of base rubber in the sheds gradually decreases, and the content of inorganic filler increases, which is consistent with the gradual decrease of tensile strength of C-1, C-2, and C-3.The above results show a correlation between the precipitation of inorganic fillers inside the silicone rubber shed and the decomposition of the base rubber under uncharged aging, with ultraviolet rays as the main aging factor. With the increase in years of aging, the value of TThe samples from factory C are taken as examples. The SEM test images of the samples of the 110 kV group are shown in 2 of C-2 were smaller than those of C-1. At the same time, the polymer materials in the cracks were directly exposed to the natural environment, and the degree of intermolecular cross-linking became larger, leading to further aging. The surface hardness of silicone rubber is closely related to the degree of intermolecular cross-linking; specifically, hardness increases with greater cross-linking density [In  density .With the increase in years of aging, deep pits of different sizes were observed on the surface of the C-3 sample, and the surface of the silicone rubber gradually changed from flat to rough, and holes appeared. After the number of holes increased, water easily entered the material, causing decreases in the mechanical properties of the silicone rubber.The bonding effect of inorganic fillers and silicone rubber matrix materials is not ideal, and an increase of filler ratio will reduce the bonding degree of the base rubber body, the mechanical strength, and the tensile strength . The eloNatural aging reduces the mechanical properties of silicone rubber insulator sheds. The main effect is that with the increase in years of aging, the surface of the material becomes harder, and the tensile strength decreases. The elongation at break value fluctuates, but generally shows a decreasing trend.2 of the sheds, measured by NMR testing, and the recorded years of aging, showing that the longer the aging period, the smaller was the T2. There was consistency in measuring the mechanical properties of sheds with years of aging and T2 as characteristic values.There was a certain linearity between the transverse relaxation time TNatural aging is mainly caused by environmental factors. The samples in this paper were mainly affected by snow, fog, and ultraviolet rays, from which ultraviolet energy damages the chemical bonds of the silicone rubber sheds. Microscopically, this process is a dynamic confrontation between chemical bond breaking and cross-linking. Macroscopically, the surface morphology of the sheds and the content of inorganic fillers are changed, thereby affecting the mechanical properties.Based on NMR technology and mechanical properties testing, this paper has taken the natural aged composite insulator shed as the research object, systematically analyzed and studied its mechanical properties after aging, and here draws the following conclusions:


With an increase in aging time, the proportion of particles of a size less than 0.1 mm decreases, and that of particles of size 0.1–0.5 mm increases. After 72 h of aging, the particle size proportion remains unchanged. Reasonable aging time can, thus, reduce the hydration reaction of lime, improve particle agglomeration effects, and reduce the crack development of the soil.The effect of aging on the internal mechanism of the dry shrinkage cracking of lime soil was studied from the perspective of macroscopic cracking phenomenon and microscopic composition change, and the reasonable aging time of lime soil was determined. Large numbers of cracks often occur in buildings constructed using lime soil, which impacts sustainable development and building environmental protection. This study explored the influence of aging time on the mechanical properties and shrinkage cracking of lime soil. The influence of aging time was evaluated using a triaxial compression test; using the dry–wet cycle, sieving, pH, and other tests, the influence of aging time on volume crack rate, expansion shrinkage rate, particle size distribution, and pH was analyzed. Scanning electron microscopy and X-ray diffraction experiments were used to analyze changes in the lime soil particle structure for different aging times and the formation of new substances. The results show that as aging time increases, the stress–strain curve of the soil softens significantly, shear strength deteriorates, and cohesion decreases. When the aging time is 6 h, the expansion rate and shrinkage rate at the center of the soil sample are the maximum. The volume fracture and expansion shrinkage rates decrease first, and then plateau with aging time, with the changes remaining stable after 72 h; these rate decreases are positively correlated with the change rate of pH. The formation of Ca(OH) Lime soil is a common building material for ancient buildings, mainly composed of lime, quartz sand, and clay ,2,3,4,5.In order to improve the properties of lime soil, the “aging” process was studied by a large number of scholars. The aging process is directly related to the hydration and reactivity of lime soil ,14,15. GAt present, the research mainly focuses on the effect of aging time on the activity of calcium hydroxide and its engineering application, but there is little research on the aging process law under the joint action of lime and soil. After lime and soil are mixed evenly and reacted with water, the internal physical and chemical changes continue, and lime soil aging takes a certain amount of time . Under tThe soil used in the test was exfoliated soil from a soil site in Henan Province a. The soSeven sets of samples were prepared with aging times of 6, 12, 24, 48, 72, 120, and 168 h, lime content of 20%, and moisture content of 20%. Through unconsolidated, undrained shear tests, dry–wet cycles, screening, pH evaluations, XRD, and SEM, the micro mechanism of the effects of aging time on the dry shrinkage cracking of lime soil were explored experimentally .Limit moisture content test: This test used the combined liquid and plastic limit tester to determine the liquid limit and plastic limit of silty clay in Henan Province, calculate the plasticity index, and judge the range of plastic state of silty clay. In this test, 300 g of air-dried soil samples with the optimum moisture content of 27.3% were taken. The moisture content of the prepared soil samples was the plastic limit, the middle value of liquid plasticity, and the liquid limit of the soil, so that the cone penetration depth was controlled at 3~5, 7~9, and 15~17 mm, respectively. They were placed into double-layer, fresh-keeping bags and left for 24 h. The liquid plastic limit was retested. If the penetration depth is not within the specified range, the test shall be reperformed. If the penetration depth is within 3 specified ranges, the test is deemed to be successful, and the liquid limit and plastic limit can be obtained. When the test results met the requirements, the soil samples were placed under the three conditions into the 105 °C oven, and their moisture content was measured to calculate the limit moisture content of silty clay;Aging of soil sample: The soil sample was dried, then the powder was extracted and passed through 2 mm sieve. A total of 3500 g of soil samples was evenly mixed with 700 g of lime, and 840 mL of distilled water was added for uniform mixing. A total of seven groups of samples were prepared. The prepared lime soil sample was placed into the standard oxidation tank , and aged for 6, 12, 24, 48, 72, 120, and 168 h. During the aging process, 30 g samples  were taken every 6 h to dry and measure the average moisture content, and water was added to maintain the initial moisture content of 20%;3 to prepare the triaxial samples of diameter 39.1 mm and height 80 mm. The unconsolidated, undrained triaxial shear test was carried out according to the standard for geotechnical test methods (GB/T50123-2019), and the shear rate used was 0.5 mm/min to measure the stress–strain relationship of the sample under confining pressures of 50, 100, and 150 kPa. To reduce the test errors, three parallel tests were conducted in each set of tests with four samples each time, of which three samples were used for triaxial shear under different confining pressures. Since the triaxial test was conducted by computer and acquisition system, the computer automatically recorded the stress value at the corresponding strain, and automatically generated the stress–strain curve and Mohr’s circle after the test started; then the internal friction angle and cohesion of the excavated sample were calculated.Triaxial compression test: The aged soil samples were proportioned according to the moisture content of 20% and dry density of 1.28 g/cm3, and the static compaction treatment carried out. The lime soil sample was dried in a temperature control oven set at 40 °C for 36 h; after drying, water was sprayed evenly onto the surface of the sample with a spray bottle of 800 mL, which was recorded as a dry–wet cycle  was taken, and a screening test was conducted on the samples with sieve hole diameters of 2, 1, 0.5, 0.25, 0.1, and 0.075 mm. The particle size information of aged lime soil samples was obtained;pH value test: The aged sample was dried, and 100 mL of distilled water was added to 20 g of the dried sample , and a pH818 precision pH meter was used to test the pH value of the supernatant after standing;Electron microscope test: The test instrument was a S570 scanning electron microscope. The aged samples were dried for electron microscope test, and the scanning electron microscope multiples were 500 times and 2000 times. The chemical reaction products and microstructure changes in the samples were observed;X–ray diffraction test: An X-ray diffraction test was conducted after the sample was dried. The test instrument was an X-ray diffractometer with model d8-advance, and the scanning incidence angle was 10–70°. The changes in chemical products in the sample were explored.2) was used for quantitative fracture analysis. Firstly, Image–pro plus6.0, Adobe PhotoShop, and other software were used to cut the image, correct the size, and remove the lime efflorescence interface. Then, MATLAB software (MATLAB 7.0) was used to compile the program for extracting the characteristic parameters of three-dimensional volumetric fracture rate, and the method of integration was used to solve the volume fracture rate of the sample through the three-dimensional level [S is the area of each pixel. S = 1, M is the maximum gray value of the image; M = 255, the gray level corresponding to the ith pixel of iD; and N is the total number of image pixels.Crack image processing and information extraction: In order to reduce the influence of sample boundary, the middle part of the sample 2 reacts with CO2 in the air to form CaCO3 crystals, which consumes part of OH− in the sample, and the pH value of the sample decreases. The decreasing rate of the pH value accelerates when the aging time is 72 h, and the decreasing rate is 0.11%. With the further extension of aging time, the content of Ca(OH)2 decreases gradually, the carbonation of CO2 in the air decreases, and the OH− consumed by CaCO3 crystallization is relatively limited, so the reduction rate of the pH value of the sample slows down, and gradually tends to be stable.The pH value test results are shown in The content of each particle size of samples with different aging times is shown in 2 produced by the CaO hydration reaction increases, and the volume crack rate resulting from the secondary hydration reaction decreases.2 is accelerated, and the expansion rate is reduced. The shrinkage of the sample reflects its water-holding capacity. 2 produced by the CaO hydration reaction. To further explore the internal mechanism of the effect of the pH value on lime soil cracking under different aging times, seven sets of samples with different aging times were selected for the XRD test to explore the formation and change law of the internal products of the samples. 2, CaCO3 crystals, and other substances. Quantitative analysis of the XRD results is carried out, and the analysis results are shown in (1)2 increases first, and then decreases. The CaO hydration reaction generates Ca(OH)2, which leads to the increase in the peak intensity of Ca(OH)2. Affected by carbonization reaction, Ca(OH)2 reacts with CO2 in the air, so that the peak intensity of Ca(OH)2 decreases, and the peak intensity of CaCO3 gradually increases. However, the diffraction peak intensity of the CaCO3 crystals is low, the content of CO2 in natural air is low, the carbonization reaction is slow, and the final carbonization products are limited [ limited ,38;(2)2, and the content of CaO decreases to 5.2%. When the aging time is extended to 72 h, the content of CaO decreases to 0.8%. If the aging time is extended further, the overall decreasing trend is not obvious, and the content changes remain within 0.05–0.73%;In the aging process, the content of CaO decreases with the increase in aging time. When the aging time is 6 h, a large amount of the CaO reacts with water quickly to form Ca(OH)(3)2 increases first, and then decreases with the extension of the aging time, and a peak value is obtained at 24 h. The change in the Ca(OH)2 content tends to remain stable at 72 h of aging, and even after the aging time is prolonged. The overall decrease trend is not obvious, and the change in Ca(OH)2 content is about 1.4–1.8%. The change trend of the pH value is consistent with that of Ca(OH)2.The content of Ca(OH)During aging, the change in the pH value of the sample is closely related to the amount of Ca(OH)2 just after the hydration reaction is disordered and irregular, and is prone to stress concentration. From the macroscopic point of view, the soil is easy to crack. With the increase in aging time The increase in aging time is at the expense of soil strength. With the increase in aging time, carbonization and agglomeration reactions occur on the soil surface. However, it is difficult for the agglomerates and particles to form cementation, which leads to the obvious deterioration in the micro mechanical properties and shear strength of the soil sample, including the obvious softening of the stress–strain curve, the serious loss of shear strength, and the attenuation of cohesion;(2)When the aging time is 6 h, the expansion rate and shrinkage rate at the center of the soil sample are the maximum. With the increase in aging time, the change in expansion and contraction rates at different positions gradually tends to be the same. The volume crack and expansion shrinkage rates first decrease, and then tend to stabilize with the increase in aging time. Compared with a sample aged for 6 h, the volume crack rate of the sample aged for 72 h decreases by 53%, the expansion rate decreases by 14.5%, and the shrinkage rate decreases by 10.5%. With the extension of aging time, the change rates of these three characteristic parameters are about 0–1% each;(3)2 and CaCO3 tend to be stable, the hydration reaction is completed, and the cracking potential is reduced. If the aging time is prolonged, the carbonization reaction causes the shear strength of the soil to decrease, and affects the durability of the soil;The decrease in volume crack rate and expansion shrinkage rate with aging time is positively correlated with the change rate of the pH value, and pH is the internal reason affecting soil cracking. The pH increases first, and then decreases with the increase in aging time. When the sample reaches the reasonable aging time, the pH of the sample shows an obvious decreasing trend. At this time, the changes in Ca(OH)(4)A reasonable aging time improves the particle agglomeration of lime soil. With an increase in aging time, the soil particles undergo obvious agglomeration, the proportion of particles of a size less than 0.1 mm decreases, and the proportion of particles of size 0.1–0.5 mm increases. After an aging time of 72 h, the particle size distribution remains almost unchanged.Through unconsolidated, undrained triaxial shear tests, dry–wet cycles, screening, pH evaluation, and other tests, the effects of different aging times on the mechanical properties and dry shrinkage cracking of lime soil are explored at the macro scale. Using SEM and XRD tests, the changes in the particle structure and formation of new substances at the micro scale are analyzed. The following observations are obtained from this study:


In this section we described the structure of the self-administered semiquantitative food frequency questionnaire used in the 5-year follow-up survey of the JPHC study, the computation algorithms, and the area-based mean intakes of nutrients and food groups in the subjects of the validation study. The FFQ consists of five sections: 1) semiquantitative frequency questions for rice and miso (fermented soybean paste)-soup, 2) those for alcoholic beverages, 3) those for vitamin supplements, 4) those for foods and beverages, and 5) questions on dietary and cooking behaviors. From the questions, intakes of nutrients and foods by food groups were computed. Although most of them were computed from the frequency and relative portion size indicated in the replies, together with the fixed portion size, a seasonal coefficient was added in the computation of vegetables and fruits. Only frequency of intake and fixed portion size were used for computation of beverages. Sugar and cream added in coffee and tea were computed from the frequency of coffee and tea intake. The intakes of cooking oil, cooking salt (sodium), and salt in noodle-soup were estimated from the questions of relative preference of oil, salt, and noodle-soup. The JPHC study group has developed a FFQ based on a data-based approach using 3-day dietary record data obtained from 335 subjects sampled from the 4 areas in the JPHC study, Cohort I,2 In this section, the questionnaire design of the FFQ and the computation algorithm are briefly presented together with the intake levels of main nutrients and food groups among the subjects of the validation study.Self-administered semiquantitative food frequency questionnaires (FFQ) have been used to assess nutrient and food intake levels of the subjects in large-scale epidemiologic studies from several countries.For computation of food and nutrient intake from the FFQ, we divided the 138 food items and 14 supplementary questions reported in the previous publication about FFQ development 2 into five sections: 1) semiquantitative frequency questions regarding rice and miso (fermented soybean paste)-soup, 2) alcoholic beverages, 3) supplements, 4) 135 foods, and 5) 13 questions regarding dietary and cooking behaviors.In the first section, questions on the relative size of the rice-bowl were asked in terms of 3 categories; small, medium-size, and large. The intake of rice was asked in terms of the number of bowls consumed, from less than 1, to 1, 2, 3, 4, 5, 6, 7-9, or 10 per day. Two additional questions about rice were asked: “Do you eat vitamin-enriched rice?”, and “Do you mix in other grains such as barley, foxtail millet, or Japanese barnyard millet?”. For miso-soup, the frequency of the intake was asked from almost never to 1-3 times/month, 1-2 times/week, 3-4 times/week, 5-6 times/week, or daily. The intake amount was asked in terms of the number of bowls from less than 1, to 1, 2, 3, 4, 5, 6, 7-9, to 10 per day. The relative salt content was also asked in terms of less salty, medium-salty, and salty.In the second section, frequency of alcohol drinking was asked using 6 categories from almost never to 1-3 times/month, 1-2 times/week, 3-4 times/week, 5-6 times/week, or daily. The usual intake amount was asked using the standard units (volumes) for each type of alcoholic beverage from 1, 2, 3, 4, 5-6, to 7 units per occasion. The standard units in Japan are the following: go  for sake, shochu  and awamori ; a large bottle of beer (633 ml); 1 glass (30 ml) for whisky; and 1 glass (60 ml) for wine.In the third section, the use of vitamin supplements was asked in terms of the frequency and duration of use, and separately for supplements with multi-vitamins, including beta-carotene, vitamin C, and vitamin E. The frequency was from 1-2 pills/week, 3-4 pills/week, 5-6 pills/week, 1 pill/day, 2-3 pills/day, to 7 pills/day. The duration of use was from < 1 year, 1-2 years, 3-4 years, 5-9 years, 10-19 years, to > 20 years.In the fourth section, the frequencies and relative portions or standard units were asked for 113 foods, and only frequency was asked for the 18 beverages. The food names and the standard portions/units were shown in 2In the fifth section on dietary and cooking behaviors, 13 questions were asked. These questions are described elsewhere in this supplement.Intakes of rice and miso from miso-soup were calculated from bowl size, frequency, and the number of bowls consumed per day. Standard bowl sizes were 140 grams for rice and 150 grams for miso-soup for both sexes. The portion of rice for a small bowl and a large bowl was 110 and 170 grams, respectively. In the category of rice, rice boiled with cooking water was used for food and nutrient computations, while for miso-soup, miso and cooking water were used. Cooking water was not considered in other food computations.For alcohol (ethanol), the following ethanol content was used for the calculation: 180 ml sake, 23 grams of ethanol; 180 ml shochu and awamori, 36 grams of ethanol; 30 ml whisky or brandy, 10 grams of ethanol; 60 ml wine, 6 grams of ethanol; and 633 ml beer, 6 grams of ethanol.For the computation of the total dietary intake covering all but the third section dealing with the use of vitamin supplements, we developed a composition table for 147 foods and beverages from food items and supplemental questions on the FFQ . The com3 For those foods, subjects were asked in the FFQ to report the consumption at the time of year when each food was most available. Seasonal coefficients were used to calculate the average yearly intake of such foods. The coefficients were determined based on the intake reported by the dietary records by season. Area was not considered in this computation. The equation may be stated:The significant seasonal variation reported for the intake of some nutrients such as vitamin C, is probably due to the seasonal variation in fruits and vegetables.i, Xi,ave is the mean intake of the study subjects for the whole year average estimated from a 28-day (4 season) DR, and Xi,max is the mean intake of the population for the intake in a 7-day (1 season) DR of the season with the highest consumption. Where SCi is the seasonal coefficient of food4 All supplement use and some nutrition-fortified beverages were excluded from the computations in this study because their composition tables were not available.The salt intake from cooking salt and salty seasonings such as soy sauce was estimated from the cooking methods most frequently used for meats, fish, and vegetables, the use of table salt and soy sauce, and the intakes of meats, fish, and vegetables. Intake of cooking oil and salt was estimated by the method used in the dietary history: the amounts of cooking oil and salt for 5 cooking methods  were estimated for 3 food groups , and multiplied by the individual intake of each food group according to the cooking methods most frequently used by the individual.5 Since the food composition table for cholesterol has numerous missing values,6 we developed a composition table for cholesterol substituting methods used for the development of the fatty acid food composition table.7The intakes of 16 nutrients for each food were calculated using the food composition table developed for the FFQ based on the Standard Tables of Food Composition in Japan, the 4th revised edition.5 Green and yellow vegetables were defined as 44 vegetables with 600 micrograms of carotene per 100 gram and 10 frequently used vegetables that contribute to the intake of carotene among Japanese, according to the definition by the Ministry of Health, Labor and Welfare. Additionally, mugwort (leaves) with 3600 micrograms of carotene per 100-gram food portion was included in the green and yellow vegetables because it could not be overlooked as a carotene source among the subjects in Okinawa in a previous survey.2 Salted pickled vegetables were defined according to the food group used in the National Nutrition Survey.8 In FFQ, sugar intake was assessed only for those for coffee and/or tea. Therefore, sugar from cooking was not included in the analysis, but the energy and nutrients derived from sugar for coffee and/or tea were included in the corresponding computations.The subjects of the present study were 215 persons (102 men and 113 women) with whom both the FFQ for the validation study and their complete dietary records (14-day records in Okinawa and 28-day records in the other 3 areas) were used for the analysis. The mean intakes for food groups and nutrients were calculated by sex and area, and compared by ANOVA. The definition of food groups was mainly based on the Standard Tables of Food Composition in Japan, the 4th revised edition.5 used in the computation and their weighting ratios were also described.2 The standard portion sizes, food codes, and their weighting ratios were also basically determined from the data set. The seasonal coefficients were determined from the relative intakes observed in each season in the dietary records of this validation study. We consider this paper to be rather unique in that it presents the questionnaire makeup along with its algorithm for the computation of food intake; nevertheless the validity heavily depends on it. Only food items and the standard portion sizes were described in some reports on the FFQ development  using the previous data obtained from the subjects in the study areas.10 Also in the data of this validation study, a significant seasonal variation was observed for these two nutrients, and their main food sources .11 Therefore, we asked the "frequency of intake for the most available season" for 48 vegetables and fruit. Then we estimated the intakes over the year using the seasonal coefficients: [intake of the most available season]/[intake over the year] obtained from the dietary records in this validation study. This method of using seasonal coefficients to improve the validity of the FFQ was efficient and feasible in our study because the DR data from 4 seasons were available. However, a more precise evaluation of its efficacy is needed to generalize the method. We also estimated intake of cooking oil and cooking salt, and intake of noodle-soup. They were estimated from relatively simple qualitative, rather than quantitative, questions. Because reliability may be compromised by this type of question (see reference 4The most outstanding characteristic of the FFQ may be its use of a seasonal coefficient. Most of the reports from Westem countries concluded that seasonal variation in food and nutrient intake is negligible. On the other hand, some Japanese studies suggested possible seasonal variation in intakes of some foods and, as a result, in some nutrients such as oranges, vitamin C and carotene.13 and cooking salts including salty seasonings have been major sources of sodium in a Japanese population.14 Therefore, the consideration of these foods seems important when these nutrients are investigated. However, the validity of the method remains to be examined, because the validity for sodium, for example, was relatively low when the 24-hour urinary excretion was used as the gold standard both in the present and previous studies.15,16 The validity and the reproducibility of the FFQ are reported in the other papers in this Supplement.17,18Cooking oils are major sources of n-6 polyunsaturated fatty acids,


Bunias orientalis L. + Bromopsis inermis L. + Galega orientalis Lam. 6–8 years old), spring barley Hordeum vulgare Leyss.—variety Sasha). Immobilization processes predominated in the soil under the sowed crops, it contributes to the preservation of soil organic matter . The highest transformation ratio of soil organic matter, i.e. increased conversion of plant residues into organic matter, was noted with applying nitrogen-phosphorus fertilizers (N60P60) under the barley. The combination of irrigation factors and the use of mineral fertilizers (N30-60P60) were contributed to the growth of the microorganisms’ population, the amplification of decomposition of cellulose, and improvement of nitrification capacity in the soil. The perennial irrigation of the meadow-chernozem soil and the application of intensive technology of cultivation of crops in crop rotation stimulated the growth of the microorganisms’ population and didn’t detriment the ecological state of the soil.The research was carried out on the territory of the Russian Federation in the forest-steppe region of the south Western Siberia (Omsk state), in the long-term (43 years) stationary experiment. Sprinkling was used for irrigation in the experiment. The number of different physiological groups of microorganisms, the cellulolytic activity of the soil, and nitrification capacity were determined under the sowing of an eight-field grain-grass crop rotation (perennial grasses ( At the same time, the microbiological regime of the soil most of all affects the efficiency of the use of fertilizers. Therefore, when the biological activity of soils is increased, the growth of yield increases too6. Long-term use of high doses of mineral fertilizers can cause the activation and growth of toxin-forming microbes7.Thus, excessive activation of the soil microflora can lead to negative ecological consequences: deterioration of biological and physicochemical properties of soil, mineralization of humus, increase of gaseous nitrogen losses during denitrification and nitrification, accumulation of nitrates in the soil, plants, and groundwater, destruction of the stratospheric ozone shield11.Mineral fertilizers, applied in moderate doses, activates the viability of microorganisms of various physiological groups. According to that, in soils, the number of aerobic and anaerobic nitrogen fixers, ammonifiers, cellulose-decomposing bacteria, actinomycetes, and fungi are increased12. The lack of moisture reduces the availability of mineral nutrition elements, including phosphorus, and changes the potential mechanisms of its replenishment in the soil solution13.The climatic conditions, especially the rainfall in the vegetation period have a significant impact on the plant development and their yeild14.Optimization of the water regime during irrigation causes changes in the agrochemical and biological properties of soils, which are enhanced by the application of fertilizers17.The water regime of the soil has a significant impact on the diversity of soil microorganisms and the enzymatic activity of loamy soils. Water scarcity causes changes in the relative abundance of certain types of bacteria. Microbial communities have a high susceptibility to drought in sandy soils and an important role of exogenous organic matter in protecting microbial activity during periods of drought18.During irrigation, the number of microorganisms, which mineralize nitrogen and carbon-containing compounds, increases in the soil microbial community , and this indicate an increase in mineralization of the organic matter process. At the same time, the number of fungi decreases21.Intensification techniques and inappropriate irrigation methods can lead to losses of soil organic matter (humus), contamination of groundwater and other degradation processes, as well as negatively affect crop yieldsBased on this, the research aimed to study changes in biological properties and direction of soil-microbiological processes in irrigated meadow-chernozem soil in variants with long-term application of mineral fertilizers, the effect of agricultural practices on the yield of crops, and the assessment of the ecological state of the soil.Bunias orientalis L. + Bromopsis inermis L. + Galega orientalis Lam. 6–8 years old), spring barley Hordeum vulgare Leyss.—variety Sasha; in variants of the experiment without fertilization and with a medium supply of mobile phosphorus —control and N60P60 for perennial grasses and barley with a high content of P2O5—more than 150 mg/kg (fertilized).The studies were carried out in 2015–2017 in an irrigated grain-grass crop rotation under crops: perennial grasses  m every 10 days and were carried out by the wide-coverage wheel sprinkler “Volzhanka” sprinkler machine. The irrigation rate was 300 m22.The soil was meadow-chernozem, medium-thick, medium-strength, heavy loamy with a humus content of 7% (according to Tyurin) in a layer of 0–0.045 m, the depth of groundwater is 2.5–3.0 m. Soil pH was neutral—7.0–7.2. In the layer of 2–4 m, the salt content varies by layers—from low to high salinity, sulfate-soda, or soda-sulfate chemismWater source—Om’ river . Mineralization of water in August was around 0.5 g/l, hydrocarbonate-chloride, calcium-magnesium chemism.22.The depth of groundwater occurrence in the stationary zone in the initial period of research changed from 4.5 to 5.5 m, in 2015–2017 yrs. 25–3.0 m. Mineralization of groundwater from steal to low- and medium-mineralized, hydrocarbonate-sulfate or sulfate-hydrocarbonate, sodium-magnesium chemism, pH within 7.1–8.5. The sum of exchangeable cations is 34.5–36.3 mEq/100 g of soil, the compound is dominated by calcium—93.8%, magnesium—6.1%, the proportion of sodium doesn’t exceed 1%, it’s a baselineThe initial supply of mobile phosphorus varied from low (according to Franceson) to medium (according to Chirikov), and the supply of potassium was high. The nitrate-nitrogen content was determined in the soil by the disulfophenol method—it varied from low to medium.3)—on the starch-ammonia agar (SAA). In case of differences of the yield level of variants, we considered the number of nitrifying microorganisms (a group of autotrophic (see autotrophs) microorganisms capable of obtaining energy for life through the oxidation of inorganic nitrogen compounds) on leached agar with the addition of double ammonium-magnesium salt of phosphoric acid, soil microscopic fungi on Czapek agar2.Samples were taken in sterile parchment bags for microbiological studies three times during the growing season. The samples were taken using 4–5 injections with a drill to a depth of 0–0.2 m. Counting of the number of microorganisms was carried out on the solid nutrient medium: the total number of saprophytic bacteria that decompose organic nitrogen-containing compounds in the soil—on the meat-peptone agar (MPA); microorganisms that consume nitrogen in mineral form , some higher actinomycetes (genus Actinomyces–Streptomyces) and filamentous fungi . Starch-ammonia agar (SAA) is a synthetic, solid, elective medium. On starch-ammonia agar, the number of microorganisms (bacteria and actinomycetes) assimilating mineral forms of nitrogen is revealed.Meat-peptone agar (MPA) is a nutrient-rich environment on which many heterotrophic microorganisms of various systematic and physiological groups develop: gram-negative, non-endospore-forming bacteria of the genera M) of organic matter was also calculated—the accumulation of humus substances in the soil LM = (MPA + SAA) * MPA/SAA23.To determine the direction of soil microbiological processes, the ratios of SAA/MPA mineralization coefficient and MPA/SAA immobilization coefficient were calculated. The coefficient of transformation . During the vegetation in 2016, 227 mm of precipitation fell at the norm of 197 mm (115% of the norm). In June-July, the amount of precipitation exceeded the norm by 74%. The temperature regime was increased. The hydrothermal coefficient in May–August was 1.09. In the growth of 2017, the air temperature was within normal limits with a lack of precipitation. The hydrothermal coefficient was 0.70, which indicates the dryness of the summer period. The largest amount of precipitation fell in July (66 mm—108%), during the growing season the amount of precipitation was only 144 mm (70% of the norm).Materials comply with the code of ethics for scientific publications.The application of mineral fertilizers on the irrigated soil stimulated the number of nitrifying bacteria and fungi to the greatest extent, by 27–52 and 77% respectively. The effect of mineral fertilizers on the soil microflora depended on the combined influence of factors of moisture and soil temperature, and the type of cultivated crop Table .Table 1B26.Optimization of mineral nutrition during the cultivation of perennial grasses on an irrigated background in 2015 and 2016 to the greatest extent stimulated the growth of the nitrifying bacteria number—61.6 and 72.6% to the control, respectively. An increase in the number of nitrifiers indicates an intensive process of nitrification in the soil, and the formation of nitrates—the main source of nitrogen fertilization for plants, therefore, indicates an improvement in the nitrogen nutrition of the cultivated crop. Soil moistening in June-July 2016, when, in addition to the norm, 87.7 mm of precipitation fell, contributed to an increase in the number of soil fungi (68.6–77.7 thousand CFU/g). In 2017, under the influence of fertilizers, the number of microorganisms on MPA and SAA significantly increased by 60 and 87% compared to control, respectively. An increase in the number of microorganisms in the soil of fertilized variants associated with the enrichment of mineral nutrition elements, an increase in the amount of root litter during the growing season, and a large number of residues after harvesting crops on fertilized plots26. Since the main function of fungi is the decomposition of plant organic residues in the soil, it can be assumed that on fertilized backgrounds the process proceeds more intensively due to an increase in the amount of decomposed substrate.On average, over three years of research, the application of fertilizers under perennial grasses on irrigation stimulated the number of nitrifying bacteria and fungi to the greatest extent, by 51.5 and 76.6% to the control. In the references, it was noted that an increase in the number of fungi can occur when the soil is acidified with fertilizers during their long-term useThe intensity of cellulose decomposition under perennial grasses did not differ significantly in the variants during the years of research. The difference between the variants was 2.3–11.0%. The cellulolytic activity was the highest (48.3–59.3%) in 2016, compared to 2015, 2017 yrs., which was associated with an increased temperature and heavy rainfall in June-July (163–187% of the norm).28. Apparently, for the same reason, the intensity of cellulose decomposition in the fertilized variant in comparison with the control tended to decrease. However, the number of microorganisms in the soil during the application of fertilizers was higher in comparison with the control, which accordingly influenced the total biological activity of the soil. The total biological activity of the fertilized variants under perennial grasses was 6–26% higher than the control, depending on the conditions during the years of research.The nitrification capacity of the soil in fertilized variants exceeded the control by 35.4% only in 2015; in subsequent years, the potential amount of nitrate-nitrogen was lower concerning the control on 17–24%. One of the possible reasons for it was a significant excess of the bluegrass component over the legume in the agrocenosis. In the control without nitrogen fertilizers, the share of the legume component was higher and the botanical composition of the grass mixture was more balanced. Under such conditions, the influence of perennial grasses on the biological properties of the fertilized soil in comparison with the control had a smaller positive effect. During the decomposition of bluegrass crops residues, the number and activity of microorganisms are lower and weaker than in leguminous plantsThe use of nitrogen-phosphorus fertilizers for spring barley under conditions of irrigation had a stimulating effect on the number of various groups of microorganisms Table .Table 2BIn 2015, the number of nitrifiers doubled in comparison with the control in a fertilized variant, in 2016–2017 yrs.—fungi by 107 and 52%, respectively. In 2017, the number of saprophytic bacteria on MPA increased by 78%, microorganisms on SAA increased by 100% (two times) concerning the control without fertilizers. On average, over the years of research, the application of mineral fertilizers significantly (by 66.6%) increased the intensity of cellulose decomposition in the soil, by 44.4%—nitrate accumulation in favourable conditions (soil nitrification capacity). At the same time, the total biological activity of the soil increased by 16%.30-60P60) for different crops had a stimulating effect on groups of soil microorganisms. In the average of the years of research, the number of nitrifying bacteria and fungi (by 52 and 76% to the control), and the number of saprophytic bacteria on the MPA and immobilizing NH3 on the SAA were extended (in 2017 year was 78 and 100% respectively).Thus, the long-term use of mineral fertilizers in stationary experiments in moderate doses (N3 mg/kg). Under natural conditions, the supply of plants with nitrogen depends on the intensity of the nitrification process.The application of mineral fertilizers had a positive effect on the nitrification capacity of the soil—the amount of nitrate-nitrogen, which is formed due to the internal nitrogen resources of the soil, which made possible the potential for providing plants with available nitrogen  and meat peptone agar (MPA). An increase in this ratio indicates the predominance of the mineralization process in the soil and the intensive use of soil nitrogen, while its decrease indicates an increase in humification processes. The microbiological processes’ intensity of nitrogen-containing compounds transformation in the soil was estimated by the coefficients of mineralization (SAA/MPA) and immobilization (MPA/SAA)29.The number of microorganisms on starch ammonium agar is associated with the consumption of mineral nitrogen. On average, over the years of research in the soil under crops, the processes of immobilization or fixation of nitrogen by microorganisms prevailed, the MPA/SAA ratio > 1. The soils under the pedoclimatic condition of Siberia have a high ability to fix the introduced mineral nitrogen, contributing to its preservation and accumulation in the zone of the root system. The continuous transformation of the immobilized nitrogen in the mineral products of decomposition allows us to provide plants with assimilable forms of nitrogen more evenlyM = (MPA + SAA) * MPA/SAA), which potentially reflects the intensity of the accumulation of humic substances in the soil, was under barley in variants with the application of mineral fertilizers . For the preservation of positive humus balance with using perennial grasses in crop rotations, especially bluegrass, on irrigated soils, it is necessary to apply organic fertilizersThe level of crop yields ultimately determines the effectiveness of the use of one or another agricultural technique. In 2015, the yield of crops in the crop rotation was higher in the variants with the use of fertilizers, an additional 2.97 t/ha of barley grain and 1.34 t/ha of dry matter of perennial grasses were obtained for two cuttings in comparison with the control . A similar connection of the crops yield with nitrification capacity was confirmed in 2017 (r = 0.68 ± 0.28). This was explained by the fact that in the process of nitrification, organic nitrogen-containing compounds under the action of microorganisms were mineralized to nitrate nitrogen, which was the main source of plant nutrition in SiberiaThus, long-term irrigation of meadow chernozem soil doesn’t decrease biological activities, and the use of intensive technology in crop rotation stimulated an increase in the number of soil microorganisms and their vital activity. Long-term irrigated meadow-chernozem soil with intensive cultivation of cereals (barley) had a high biological activity (up to 141% concerning the control), which positively affected the yield during the research years—2.78–4.69 t/ha and 1.72–2.02 t/ha on control.The total biological activity in the arable layer of meadow-chernozem soil during intensive cultivation of perennial grasses was 106–126%. With prolonged irrigation in meadow chernozem soil under crops, the processes of nitrogen immobilization by microorganisms prevailed—MPA/SAA > 1.Medium and strong correlations were established between indicators of the intensity of cellulose decomposition, the nitrification capacity of the soil, and the yield of cultivated crops  .Supplementary Information.


The possibility of removing metallic  impurities and non-metallic (such as [O] and C) impurities from technogenic hafnium through single and double refining in the conditions of electron beam melting (EBM) has been studied. The influence of thermodynamic and kinetic parameters on the degree of removal of these impurities from the base metal under vacuum conditions and within a temperature interval of 2500 K to 3100 K is defined. The relative volatility of metal impurities and the stability of the oxides and carbides present in the base metal are evaluated. The possibility for complete removal of Fe, Cr, Zn, [O], and C during EBM is shown. In the case of double refining, at a temperature of 2700 K for 20 min, the maximum degree of removal of Zr is 46.8%, the achieved highest hafnium purity is 99.004%, and the overall effectiveness of the refining of hafnium from impurities is 53%. There is a correlation between the degree of removal of Zr and the micro-hardness of the Hf ingots obtained after EBM. The weight losses vary in the ranges of 1.5–5.8% and 1–8% under the studied single and double refining processes, respectively. However, its production is too limited—no more than 70 t per year, with most of the commercial hafnium being produced by zirconium refining. The separation of these two metals during the main production process is extremely complicated due to the great similarity in their chemical properties , and C. The micro-hardness of the ingots obtained after recycling is determined.−3 Pa.The experiments for hafnium technogenic material melting were conducted in the “Physical problems of the e-beam technologies” laboratory of the Institute of Electronics, Bulgarian Academy of Sciences, using the e-beam melting furnace ELIT-60 with a beam power of 60 kW. The ELIT-60 installation  is equipped with one electron gun with an accelerating voltage of 24 kV and a vacuum melting chamber. The refined molten material solidifies in a water-cooled copper crucible with a moving bottom  and the The elemental composition of the waste Hf prior to the EBM (determined by ICP-OES) is given in b): 12 kW (T = 2500 K), 15 kW (T = 2700 K), 16 kW (T = 2800 K), and 17 kW (T = 2900 K). At the lowest operating temperature (2500 K), the refining time (τ) was 5 min, while at the higher melting temperatures, the refining duration was 5 min and 8 min.In the present study, single and double electron beam melting and refining (EBMR) of technogenic hafnium have been performed. In the single refinement, the experiments were carried out at the following beam powers  have been carried out during the double refining of the technogenic hafnium. The conditions of the experiments are determined on the basis of the results from the single refining. Test A includes initial refining (I-A) at T = 2500 K and τ = 5 min and second refining (II-A) at T = 2500 K and τ = 15 min. In test B, the first (I-B) and second (II-B) refining are performed at the same temperature (T = 2700 K) and refining time (τ = 8 min). Test C was performed at T = 2700 K and different refining durations: the first (I-C) at τ = 5 min and the second (II-C) at τ = 20 min. Test D includes initial refining (I-D) at T = 2900 K and τ = 5 min and second refining (II-D) at T = 3100 K and τ = 10 min.The temperature was determined by an optical pyrometer QP-31 using special correction filters. The chemical composition of the initial material and the samples after the e-beam melting was determined by ICP-OES, a CS analyzer, and an ONH analyzer. The baseline and final concentrations were controlled for the base metal Hf and for the impurities such as Zr, Fe, Cr, Zn, [O], and C.The thermodynamic analysis of the possible chemical interactions occurring during the refining of technogenic hafnium from metallic  and non-metallic impurities ([O] and C) under e-beam melting conditions was carried out on the basis of the Gibbs free energy (ΔG). The calculations were performed using the professional program for thermochemical calculations, HSC Chemistry ver.7.1, module “Reaction Equation”, taking into account the physical state of the substance . The thermodynamic characteristics of the relevant elements and substances such as enthalpy, entropy, and coefficients of specific heat capacity, necessary for the calculations, were taken from the program database. The indices (s), (l), and (g) mean that the substance is in a solid, liquid, or gaseous state, respectively during EBMR.−3 Pa and these parameters correspond to the actual processing conditions of melting and refining of technogenic hafnium in the electron beam installation ELIT-60.The calculations were made at temperatures of 2500 K, 2700 K, 2800 K, 2900 K, and 3100 K and an operating pressure in the vacuum chamber of 1 × 10The pressure in the vacuum chamber is constant and the main parameters that affect the removal of impurities are the temperature, the physical state of the impurities during refining , and the2, ZrO2, Cr2O3, FeO, and ZnO) and carbides  are shown in The melting and boiling temperatures of the studied metals , their oxides  changes into a liquid state at a temperature above 2700 K. At the highest operating temperature (3100 K), the oxides HfO2 and ZrO2 will also be in a molten state. Zinc is in a gaseous state within the entire operating temperature range, while ZnO changes from a liquid to a gaseous state at T = 2633 K. The melting temperatures of the hafnium and zirconium carbides are significantly higher—4255 K and 3805 K, respectively. These temperatures vary by about 30–40 K depending on the stoichiometric composition of the carbide  and C increase significantly, up to 65.6% and 62.8%, respectively.The lowest zirconium content (0.994%) in hafnium and the highest hafnium purity of 99.004% is achieved in test C  with a weight loss of 8%. The maximum degree of Zr removal is 46.8% and it is slightly higher than the result obtained during single refining (45.6%). Unlike zirconium, the degree of removal of [O] and C is more than 90%.In test D (with the highest operating temperature and double refining), the degree of removal of Zr decreases to 40.3%. The overall effectiveness of Hf refining is also reduced (47.4%).Based on the thermodynamic and experimental studies, a hypothesis is proposed to reduce the degree of removal of Zr and the complete removal of [O] and C at high operating temperatures. The thermodynamic analysis performed has shown that the following interactions can take place under temperatures above 2900 K under vacuum conditions:It can be seen that the end products from the chemical reactions taking place in the Hf-Zr-O-C system will be liquid hafnium and zirconium and a gaseous component CO(g).−3 Pa is −946 kJ/kgZr. It is negative and commensurate with ΔGT of the other reactions (11) and (12) (−1372 kJ/kgZr and −1667 kJ/kgZr). Removal of the gas stream (CO(g)) will facilitate the reaction in the direction of obtaining Hf(l) and Zr(l).The calculated value of the Gibbs free energy of the reaction (13) at a temperature of 3100 K and a pressure in the vacuum chamber of 10The results obtained so far completely confirm the conclusions made on the basis of the thermodynamic analysis of the behavior of the impurities present in technogenic hafnium. The low degree of removal of zirconium by evaporation in EBM conditions is due to the small differences in the vapor pressure of zirconium and hafnium within the studied temperature intervals and the ability to form Zr(l) during the reaction in the Hf-Zr-O-C system.2 of the hafnium specimens obtained after single and double refining are presented in The average values of micro-hardness measured according to Vickers (μHV) and the standard deviations at a load of 0.2 kgf/mmIt can be seen that the removal of impurities during EBM leads to homogenization of the sample and the reduction of its micro-hardness. The analysis of the results shows that after single refining, the lowest micro-hardness of the ingot (2378 MPa) is obtained at T = 2700 K and τ = 8 min. With double refining of hafnium at the same temperature and a longer refining time (20 min), the measured micro-hardness of the ingot decreases slightly (2321 MPa). With the further increase in temperature to 2900 K in single refining, the micro-hardness of the sample increases by ~9%, and with double refining and a higher temperature T = 3100 K, it increases by ~6%. The measured values of the specimens’ micro-hardness are in accordance with the degree of removal of impurities and the chemical composition of the samples after single and double refining.In the temperature range of 2500–3100 K in vacuum conditions, the evaporation of the impurities Zn, Fe, and Cr, whose vapor pressure is significantly greater than that of hafnium, is most likely. The Zr vapor pressure is slightly higher, but close in value to that of Hf and its evaporation is thermodynamically probable, but it will be accompanied by losses of the base metal.2(g), which are products from the chemical reaction between HfC and ZrC and ZnO, FeO and Cr2O3 oxides.The non-metallic impurities, oxygen and carbon, present in technogenic hafnium will most likely be removed in the form of CO(g) and COIt has been found that with single refining, the maximum degree of removal of Zr (45.6%) and the best purification of hafnium technogenic material (98.982%) is achieved at a temperature of 2700 K and a refining time of 8 min. With the increase in the temperature to 2900 K, the degree of removal of Zr decreases to 41.4%, which is due to both the very small difference in the vapor pressure between Zr and Hf as well as being due to the possible chemical reactions in the Hf-Zr-O-C system, which result in liquid zirconium.The results from the double refining of hafnium indicate that the degree of removal of zirconium slightly increases even with prolonged refining. The lowest content of zirconium in the tested material and hafnium with the highest purity of 99.004% is achieved at T = 2700 K for 20 min and the effectiveness of refining of technogenic hafnium is 53%.The lowest value of hafnium micro-hardness is obtained at the highest degree of zirconium removal.The possibility for removing metallic  impurities and non-metallic ([O] and C) impurities from technogenic hafnium during electron beam melting has been examined in the paper. Based on the thermodynamic analysis and experimental results from single and double refining in different technological modes, the following conclusions can be made:The results obtained confirm the significant similarity in the physical and chemical properties of the two metals (Hf and Zr), which hampers separation. The study showed that zinc, iron, chromium, oxygen, and carbon can be completely removed under the EBM of technogenic hafnium, and the maximum level of zirconium removal is 46.8%.


Thorough spatial and statistical analyses were undertaken to identify the pre- and during pandemic nitrogen dioxide concentrations. Complementarily, Spearman’s correlation test was performed with variables that impact air quality. The study results a fall in nitrogen dioxide concentration levels in 21 of the 24 metropolitan regions which was observed. The Spearman’s correlation coefficient between the nitrogen dioxide variation and the vehicle density was 0.485, at a significance level of 0.05. With these findings in mind, the paper advocates that while the pandemic has a significant negative consequence on the health of population globally, a series of measures that result in a new social organization directly interfere in the reduction of air pollution that contributes to the quality of the air we breathe.The Covid-19 pandemic has negatively disrupted the way our economy and society functions. Nonetheless, there have also been some positive externalities of the pandemic on the environment. This paper aims to evaluate the concentration of nitrogen dioxide in Brazilian metropolitan regions after the policies adopted to confront Covid-19. In terms of methodological approach, the study employs cross-sectional quantitative analyses to compare the period of 36 days, i.e., 12 March to 16 April—before (in 2019) and after (in 2020) the pandemic declaration. The data were obtained from the Sentinel 5-P low-Earth polar satellite concerning Brazilian metropolitan regions ( Due to Nonetheless, the recent changes in the diagnostic criteria of the disease have led to an increase in the rate of new cases and, every day, increasing numbers and challenges have been the subject of intense debate in the scientific community , thin particulate material , and increased ozone (O3) concentration in different regions of the globe , people declared they have noticed an improvement in the quality of the breathed air after the adoption of social isolation in their regions . In a complementary way, the study focused on evaluating the association of other variables that can directly impact the concentration of atmospheric NO2, such as the density of vehicles, especially of combustion engines, in the Brazilian metropolitan regions , whose purpose is to obtain information and services of air quality, ozone layer, and climate (TROPOMI 2018). The satellite is equipped with the tropospheric monitoring instrument (TROPOMI—Tropospheric Monitoring Instrument), an image spectrometer that covers ranges of ultraviolet (UV—ultraviolet), visible (VIS—visible), near infrared (NIR), and short-wave infrared (SWIR), using passive remote sensing techniques to measure, at the top of the atmosphere, the reflected and irradiated solar radiation of the Earth , nitrogen dioxide (NO2), sulfur dioxide (SO2), carbon monoxide (CO), methane (CH4), formaldehyde (HCHO), and aerosols  of Google Earth Engine, from where it is possible to obtain the mean and standard deviation of NO2 concentrations in the troposphere, also called Near Real-time High-resolution Imagery (NRTI), distributed by ESA and post-processed by the Google Earth Engine API. It is worth noting that daily climatic events, such as the presence of clouds, reduce the quality of images and can influence reading at the time of the satellite overpass. For this purpose, only satellite images with pixels of quality above 75% were used, that is, with the attribute “qa_value” greater than 0.75, in order to avoid erroneous interpretations affected by data quality , with 24 regions participating in the study.The maps of this 36-day average time were compared to maps from the same period in 2019 to assess the change in NO2 concentration variations were obtained, these data were compared with the population and vehicle densities of the metropolitan regions, in addition to the variation in the ozone (O3) concentration. The population data of the municipalities that make up the metropolitan regions were obtained on the website of the Brazilian Institute of Geography and Statistics (IBGE 2020), taking into account the population estimate of 2020, in order to obtain the ratio of inhabitants per kilometer square of each region.Once the NOThe density of vehicles in the metropolitan regions was calculated by the relationship between the fleet of licensed vehicles in the municipalities that make up the metropolitan region in April 2020 and the area of each metropolitan region. The fleet of licensed vehicle was obtained from the website of the National Transportation Department (DENATRAN 2020) of the Ministry of Infrastructure and the metropolitan region area was obtained from Institute of Applied Economic Research (IPEA) (IPEA 2020), in order to obtain the ratio of number of vehicles per kilometer square.3 was obtained by the same method used to define the concentration of NO2, previously described. To examine the monotonic association between the variables, the SPSS software was used, where Spearman’s correlation test was performed. The test was chosen in order to assess the strength of the correlation between the variables, and the association results generated were plotted in a table and interpreted at a significance level of 0.05 , which demonstrate the variation of NO2 in all metropolitan regions studied, and also in Table The results of the atmospheric concentration of NO2 in the comparison between the period of 2019 (left) and 2020 (right). This was the highest percentage reduction observed in the metropolitan regions that were object of this study.Baixada Santista metropolitan region, located on the coast of the state of São Paulo, showed a 48.7% reduction in the concentration of NO2 were limited to the urban and industrial nucleus of the cities of Cubatão and Santos, unlike the period of 2019, where the high concentrations were observed more than 40 km from these cities.As shown in Fig. 2 in the two periods studied. The map in Fig. Belém metropolitan region, located in northern Brazil, presented a little significant reduction of 2.6% in the concentration of NOIn Belo Horizonte metropolitan region, located in southeastern Brazil, the reduction observed was 11.3%, even though it was delimited in a polygon of larger scale. Then, we observe a significant reduction of 20% in the region of Campinas, which had high concentrations, in 2019, between Campinas and Americana, not observed in the period of 2020.Finally, the reduction is also substantial in the metropolitan region of Curitiba, located in the Southern region of Brazil, where there was a decrease of 17.5%.2. As shown in Table In the metropolitan region of Florianópolis, in southern Brazil, there was an expressive reduction of 30.3% in the concentration of NO2 concentration; however, this reduction of only 5.2% is overshadowed by the scale of the metropolitan region, which covers a polygon with thousands of square kilometers, as illustrated in Fig. 2, different from results observed so far.The metropolitan region of Manaus, located in the state of Amazonas, northern Brazil, showed a small reduction in atmospheric NO2 concentration, 26.6%. In this case, the substantial reduction was observed in both the mean concentration of NO2 and the standard deviation when comparing the results of 2019 and 2020.In the metropolitan region of Rio de Janeiro, located in the state of the same name and southeastern region of Brazil, there was a significant reduction in NOIn the metropolitan regions of Salvador and São Luís, both located in the northeast region, there was a reduction of 32.5 and 11.2%, respectively. Figure Finally, the metropolitan region of São Paulo, the largest in the country, also located in the southeast region, had the second largest percentage (37.9%) reduction among the metropolitan regions studied.2 in the compared periods was 21.6%. Figure 2, although there was a reduction, according to Fig. In the metropolitan region of Sorocaba, located in the state of São Paulo, the reduction of NO2.The metropolitan region of Teresina, located in the northeast, also showed low variation in the atmospheric concentration of NOA percentage reduction of 18.8% was observed in the Distrito Federal , in the Brazilian Midwest region. Although the reduction is significant, the concentration values are considered low in both periods, as shown in Fig. Finally, the metropolitan region of Cuiabá, also in the Midwest, registered an increase of 15.7% in 2020 compared to 2019, a movement in the opposite direction to that observed in most metropolitan regions. It is observed, however, that like Manaus MR, the MR scale can distort the results, since the urban center of Cuiabá occupies only a small fraction of the polygon.2 concentration (only reduction) in all metropolitan regions. The higher the reduction, the higher the intensity of green color.Figures 2 concentration in the Brazilian metropolitan regions evaluated.Table 2. Even in regions with no reduction, one can verify the effect of the scale of the metropolitan region on the result, as occurred in Cuiabá. Similarly, in Vitória MR, there was a significant reduction in the urban centers of Vitória and Vila Velha; however, the result was affected by the adjacent regions and not necessarily in inhabited areas, although within the metropolitan region.It is possible to observe that in 21 (87.5%) of the 24 metropolitan regions there was a reduction in the mean concentration of atmospheric NO2 in the comparison between the two periods was observed in most of the metropolitan regions. However, being a continental country, the Brazilian metropolitan regions have different socioeconomic characteristics, such as territorial extension, population, and number of vehicles circulating in the regions.The reduction of NO2 concentration and the population density (number of inhabitants per square kilometer), the density of vehicles (number of vehicles per square kilometer), and the variation in O3 concentration  in metropolitan regions.Table 2 variation and the vehicle density. This means that in the evaluated metropolitan regions, as the density of vehicles increases, a reduction in the concentration of atmospheric NO2 is expected. The existence of a positive moderate correlation was also verified for population density (Spearman’s Rho = 0.424). These are indications that point to the relevance of the contribution of combustion engines to air quality in metropolitan regions.At a significance level of 0.05, a moderate positive correlation (Spearman’s Rho = 0.485) was found between the NO3, as the p-value is above the 0.05 significance level, the association between variations in the concentration of NO2 and O3 was inconclusive, although the correlation coefficient shows a moderate negative correlation.Regarding O2 concentrations in 21 Brazilian metropolitan regions between March 12 and April 16, 2020, compared to the same period in 2019. Table 2 of 48.7% in the metropolitan region of Baixada Santista, a place with the greatest reduction, followed by the region of São Paulo (37.8%) and Salvador (32.5%). In São Paulo, the reduction observed in this study for the concentration of NO2 is in line with the results obtained by automatic air quality monitoring stations, which revealed a 25% reduction in concentration in March 2020 when compared to March from 2015 to 2019 . In this work was verified a small increase of 3.6% in the concentration of NO2 in the MR, confirming the insignificant variation observed by the environmental agency.In the state of Rio Grande do Sul, the State Foundation for Environmental Protection (FEPAM) issued a report concluding that there were no significant changes in the concentration of NO2.5 and PM10 in the periods of 20 March and 20 April in 2019 and 2020. There are two automatic monitoring stations in the metropolitan region of Belo Horizonte. The first showed a reduction of 31% in the concentration of PM10 and 45% in the concentration of PM2.5, while the second station pointed out a reduction of 10% for PM10 and 26% for PM2.5  in all metropolitan regions, that a reduction in concentration was observed and the population and vehicle fleet remained relatively stable during the period, it was possible to observe the indirect effects of population and vehicle density in the reduction of NO2 concentration. At a significance level of 0.05, the Spearman correlation coefficient found was 0.424 (population density) and 0.485 (vehicle density). The results indicate that there seems to be a dependency, albeit indirect, between the variables. This means that in those metropolitan regions where there are more vehicles per square kilometer there is a tendency for a more accentuated variation in the concentration of NO2. Higher vehicle densities may be related to a greater number of NO2 emitting hot spots, such as high-flow highways or roads and traffic jams.The study at hand also investigated the effects of population and vehicle density on the percentage variation of NO2 emission that, consequently, will interfere in other important health indicators.This measure of concentration of pollutants in the air can be an important public health factor, because as pollution levels decrease, there is a 6% reduction in mortality cases (39). Considering that the interaction of the human being with the environment that is lived produces an important part of emissions that lead to air pollution Derísio , the eviThis is because data from the WHO show that more than four million people died worldwide from respiratory diseases per year  pandemic showed a reduction in the emission of NO2 causes toxicity when there is long-term exposure, in the maintenance of air quality and the planet’s biodiversity, because the high level of this compound in the air leads to damage to nature due to its corrosive characteristic, causing acid rain which, when falling to the surface, alters the chemical composition of the soil and water, reaching food chains, destroying forests and crops.This study raises the government’s need to encourage public policies that enable a rational organization about economic activities and the preservation of the environment in the post-pandemic period, since such actions impact on the reduction of mortality rates from other diseases respiratory, since the increase in NO2 emission, such as accessible public transport, use of alternative energy sources, such as electricity, solar, biofuel, to maintain the health of the population.Therefore, this research leads to reflection on new strategies that are alternatives to the reduction of NO2 emissions has begun to falter. The pervasive disruptions from the Covid-19 pandemic have radically altered the trajectory of global CO2 emissions. Contradictory effects of the post-Covid-19 investments in fossil fuel-based infrastructure and the recent strengthening of climate targets must be addressed with new policy choices to sustain a decline in global emissions in the post-Covid-19 era.” As emphasized by Sarimin and Yigitcanlar , since we considered the WHO declaration of pandemic as the start date for the execution of the research in all regions. Nonetheless, there is a delay between that declaration and the restriction measures adopted by governments and regional agencies. Furthermore, investigation of a single air pollutant is a limitation, despite we also liked at the O3. Another limitation of this study is not to focus on the policy issues and prescribe public policy and actions to address the air pollution and climate change issues in Brazil. Nevertheless, our prospective research will focus on these limitations by considering NO2 and also other pollutants and investigating larger timeframes and conduct time series analyses and prescribe relevant policy actions.Besides the NO