Dissolved Nitrogen Content Research Articles

Key Soil Abiotic Factors Driving Soil Sickness in Lycium barbarum L. Under Long-Term Monocropping

Sustainable cultivation of Lycium barbarum L. (L. barbarum) in northwest China faces challenges due to soil sickness. While previous studies have explored variations in L. barbarum’s root-associated microbiota, the impact of soil properties on its growth performance and plant–soil feedback remains unclear. This study investigated changes in soil properties across topsoil (0–20 cm) and subsoil (20–40 cm) in primary L. barbarum cultivation regions of northwest China, evaluating seedling growth and plant–soil feedback through pot experiments. Results revealed significantly higher fresh shoot weights in seedlings cultivated in topsoil compared to subsoil, with plant–soil feedback showing an inverse trend. Redundancy analysis indicated positive correlations between both fresh weight and plant–soil feedback with electrical conductivity and dissolved nitrogen content, while negative correlations were observed with soil pH at both depths. Notably, dissolved organic carbon content negatively correlated with fresh weight and plant–soil feedback in topsoil, suggesting a potential relationship between continuous single-species plant litter input and soil sickness under monocropping conditions. These findings indicate that long-term input of a single plant litter type, rather than chemical fertilization, may primarily contribute to L. barbarum soil sickness in northwest China, providing valuable insights for developing sustainable cultivation practices for growing L. barbarum.

Enhancing sugar beet yield and quality in Northeast China: Investigating the synergistic impact of sugar mill filter mud and biochar on black soil

In this study, different ratios of sugar beet sugar factory filter mud and biochar in different proportions were used to assess the effect of incorporating filter mud into the field on soil quality and its influence on two distinct sugar beet (Beta vulgaris) varieties: high-yielding KWS9147 and high-sugar KWS1176. The experiment was conducted in 2022 at the Hulan Campus of Heilongjiang University in Harbin City, Heilongjiang Province, China. Eight treatments were employed, including CK1 (no filter mud or biochar application), CK2 (20 t/ha biochar), T1 (16.67kg/ha filter mud), T2 (16.67 t/ha filter mud + 20 t/ha biochar), T3 (33.33 t/ha filter mud), T4 (33.33 t/ha filter mud + 20 t/ha biochar), and T5 (50kg/ha filter mud). For sugar beets, parameters such as the SPAD value(Soil and Plant Analyzer Development, represents the relative content of chlorophyll), disease resistance (root rot and brown spot), tuber yield, and sugar content were evaluated. Soil analysis included nitrogen content, available potassium content, available phosphorus content, and soil sucrase, urease, and phosphatase activities. Results indicated that the combined application of 16.67 t/ha filter mud and 20 t/ha biochar had a positive impact on the growth indices, tuber yield, sugar content, effective phosphorus, and quick-acting potassium content in KWS1176. In contrast, for KWS9147, the most favorable effect was achieved with the application of 16.67 t/ha filter mud. This treatment improved plant leaf growth, increased tuber yield and sugar content, reduced root rot incidence, elevated alkaline dissolved nitrogen content in the inter-root soil, and enhanced soil phosphatase activity. Biochar application did not contribute significantly to these improvements. Therefore, returning sugar mill sludge to the field demonstrated its potential to enhance soil quality, promote the yield of sugar beet varieties, and improve resistance to root rot while also providing an eco-friendly solution for managing environmental issues related to sludge accumulation.

The various effect of cow manure compost on the degradation of imazethapyr in different soil types

Adding compost to soil is an effective strategy to promote the degradation of organic pollutants and reduce ecological risks. However, the effect of compost on the degradation of imazethapyr (IMET) in different soil types is not clear. To address this issue, a pot experiment was conducted, and high-throughput sequencing and mass spectrometry technology were used to identify the influence of cow manure compost on the degradation efficiency of IMET in black soil and saline-alkali soil and the role of key microorganisms. The results showed that adding compost to black soil increased the degradation rate of IMET by 12.58% and shortened the half-life by 53.37%, while in saline-alkali soil, the degradation rate of IMET decreased by 6.99% with no significant change in the half-life. High-throughput sequencing results showed that adding cow manure compost (mass ratio of 4%) significantly increased the abundance of bacterial families capable of degrading organic pollutants in black soil, but had an inhibitory effect on this bacterial community in saline-alkali soil. Redundancy analysis (RDA) results showed that total organic carbon (TOC), alkali-hydrolyzable nitrogen (AN), ammonia nitrogen (NH4+-N) and nitrate nitrogen (NO3−-N) were the main factors driving microbial community variation. Mass spectrometry analysis indicated that IMET generated three metabolites during the degradation process. Sphingomonadaceae and Vicinamibacteraceae could accelerate the breaking of side-chain alkyl groups, while Chitinophagaceae could cause the rearrangement of the imidazole ring structure, gradually metabolizing IMET into small organic molecules. The application of appropriate cow manure compost can promote the development of IMET-degrading bacteria by adjusting the organic carbon and dissolved nitrogen content in black soil. In the future, the quantitative effects of organic fertilizer application on the IMET degradation process in different soil types should be further analyzed, and microbial isolation and purification should be used to enhance the ability of microorganisms to degrade herbicides.

Implication of dissolved nitrogen dynamics of urban rivers using multivariate regression and structural equation modeling

AbstractThe river's functional balance varies according to flow regimes and nutrient distribution. Watercourses can receive water from different point and nonpoint sources, which discharge high nitrogen load in rivers generated from domestic and industrial effluents and agricultural runoff. The excessive concentration of nitrogen load affects the riverine ecosystem by attenuating dissolved oxygen balance and disturbing the water quality. A study has been conducted to determine the nitrogen dynamics and their impact on the water quality of the Delhi stretch of Yamuna River, India, which is highly influenced by anthropogenic activities. Multivariate linear regression (MLR) was performed to gain insight into nitrogen dynamics, and structural equation modeling was applied to determine the direct (primary) and indirect (secondary) relation between the water quality parameters and the subsequent impact on water quality. Dissolved inorganic nitrogen (DIN) was measured using ammonia, nitrate, and nitrite, and total Kjeldahl nitrogen was estimated to reflect the dissolved organic nitrogen (DON). The variation in dissolved nitrogen (organic and inorganic) signifies high negative flux on the river's organic content, causing further degradation of river water quality. MLR predicted a high correlation between predicted and observed DIN at the Income Tax Office (ITO) (92.5%) and Nizamuddin (94.37%) and DON at ITO (93.49%) and Nizamuddin (95.28%). The high concentration during the lean period deteriorates the water quality tremendously and suggests that the variation in dissolved nitrogen content should be monitored carefully to maintain the river's water quality dominated by the organic load.

Effect of cooling rate on non-metallic inclusion formation and precipitation and micro-segregation of Mn and Al in Fe–23Mn–10Al–0.7C steel

The present study assesses the influence of the cooling rate on the morphology, composition, number density, size distribution of inclusions, and microsegregation of elements in Fe–23Mn–10Al–0.7 steel. The results indicate that with the increase of cooling rate from 5.1 K/s to 14.51 K/s, the total number density of inclusions increases from 28 mm−2 to 32 mm−2, with no change in the type of inclusions, the average size of MnS inclusion decreases from 9.57 μm to 5.21 μm. The precipitation and growth of MnS inclusion are predicted according to the coupled model, matching well with the experimental results. Furthermore, it is observed that AlN inclusion formed in the liquid steel can float up to the surface of the liquid steel, reducing the dissolved nitrogen content in the steel. As the cooling rate increases, the size and density of AlN inclusions on the liquid steel surface decrease. Combining the lattice mismatch of inclusions and the pushing and engulfment behavior of inclusions, the effect of cooling rate on the MnS precipitation for Al2O3 and AlN is analyzed. Moreover, under different cooling rates, Al segregation is very remarkable and it is low in interdendritic regions but high in dendrite stems.

Is microbial biomass measurement by the chloroform fumigation extraction method biased by experimental addition of N and P?

The chloroform fumigation extraction (CFE) method determines microbial biomass carbon (MBC) or nitrogen (MBN) by calculating the increase in extractable carbon (C) or nitrogen (N) due to microbial lysis during chloroform fumigation. In China, many studies have focused on the impacts of N and phosphorus (P) addition on soil MBC and MBN in forest ecosystems, where substantial atmospheric N deposition has strongly acidified soils. The addition of nutrients may alter the extraction process applied in the CFE method, potentially influencing the MBC and MBN determined by the CFE method independently of the actual microbial biomass. In this study, we tested whether the MBC and MBN determined by the CFE method were biased by the experimental addition of N and P in strongly acidified Chinese forest soils by adding N and P to the soils immediately before chloroform fumigation, which should not affect the actual microbial biomass. P addition significantly elevated the dissolved organic carbon (DOC) content, especially after fumigation, while N addition significantly reduced the dissolved nitrogen (DN) content. The added N was subtracted using blank samples without soil. However, the altered DOC and DN contents did not affect the MBC and MBN contents determined by the CFE method. In conclusion, our study suggests that the CFE is a relatively robust method to test the impacts of nutrient addition on microbial biomass in the strongly acidified soils of Chinese forests. We also suggested that: (i) even if a fertilization experiment results in an elevated DOC content following P addition, it does not necessarily indicate a stimulation of DOC production by microbes; and (ii) the soil adsorption capacity or the strength of microbial N uptake during the extraction procedure applied in the CFE method may affect the determination of MBN by influencing the DN extraction efficiency.

Prediction of nitrogen behaviour in the AOD process by a time-dependent thermodynamic model

ABSTRACT In this work, a time-dependent thermodynamic AOD process model, TimeAOD3™, is proposed to be used as a prediction model at practice to reach the desired nitrogen level to lower the cost and carbon footprint. The model is developed from an existing model and integrated with Thermo-Calc®. The modelling results suggest a fairly good prediction when compared with production-scale heats. The relative error of dissolved nitrogen content during and after decarburisation is −0.05 < RE < 1.36 and −0.23 < RE < 0.29, respectively. Besides, most modelled dissolved N% are higher than the measurement during decarburisation. This is probably owing to the formation of high turbulence flow and CO gas bubble which can flush the dissolved nitrogen out of the bath at practice. Moreover, dissolved C%, Cr% in bath and Cr2O3%, CaO%, MgO% in slag, as well as bath temperature are also compared and studied.

Analysis of Water Quality and Exchange Flux of Interstitial Water-Overlying Water in Sediments of Baiyangdian Entrance Area in Summer

In order to reveal the interaction of overlying water-interstitial water nitrogen and phosphorus nutrient salt in summer at the entrance region of Baiyangdian Lake, this study sampled six main rivers in the region during July 2019. An analysis of the overlying water and interstitial water quality characteristics and the diffusion flux of applied nutrients at the sediment-water interface revealed the effects of nutrient diffusion on sediments and overlying water. The overlying water analysis showed that the water quality was slightly alkaline in the Baiyangdian Lake. The content of dissolved oxygen (DO) was lower, which provided an anaerobic environment for the release of endogenous pollutants from sediments. The ammonia nitrogen (NH4+-N) ranged from 0.35 to 1.76 mg·L-1, and the content of ammonia nitrogen was the highest in the Zhulong River, which was the main source of water supply. The nitrate nitrogen (NO3--N) content ranged from 0.75 to 1.97 mg·L-1. The total dissolved nitrogen (TDN) ranged from 0.99 to 2.70 mg·L-1, and the content of TDN was the highest in Puhe River. The content of total dissolved phosphorus (TDP) was 0.03 to 0.15 mg·L-1, and the content of TDP was the highest was Baigouyin River, which is near the residential area. The results indicated that the content of ammonia nitrogen in the interstitial water was between 5.24 and 10.64 mg·L-1, which was 10 times that of the overlying water, and endogenous pollution in the former was severe. The nitrate nitrogen content ranged from 0.36 to 0.79 mg·L-1. The total dissolved nitrogen content was between 5.36 and 12.02 mg·L-1, which was 5 times higher than that of the overlying water. The total dissolved phosphorus was between 0.03 and 0.3 mg·L-1. According to integrated pollution index, the degree of interstitial water pollution was much higher than that of overlying water, and the sampling points are seriously polluted. The exchange flux analysis of NH4+-N, TDN, and TDP demonstrated that the diffusion flux of NH4+-N was between 1.71 and 7.43 mg·(m2·d)-1, and the diffusion rate of endogenous ammonia nitrogen to the overlying water was fastest in Fu River, the absorbing river in Baoding. The diffusion flux of total dissolved nitrogen was lower in the Baigouyin River, and the other five sample points averaged 9.11 mg·(m2·d)-1. In summer, the dissolved oxygen was lower and the water-sediment had a larger concentration difference, which led to massive nitrogen nutrient of sediment in anaerobic conditions released to the overlying water in great quantities that caused the serious pollution. The diffusion flux of dissolved total phosphorus showed that the sediment of Pinghe River acted as a "sink" of phosphorus nutrients, and the other sampling points ranged from 0.03 to 0.16 mg·(m2·d)-1, showing the state of phosphorus nutrient released upward to the overlying water. Finally, diffusion flux indicated that endogenous pollutants are crucial sources of overlying water pollutants. In order to effectively control the water quality in the entrance area, desilting the nitrogen and phosphorus nutrient salt of sediment is urgently required.

Short-term effects of grazing intensity on soil stoichiometric characteristics of typical grassland in the agro-pastoral ecotone of northern China.

Grazing is the dominant land use way for natural grasslands. Different grazing intensities could affect soil stoichiometry in grasslands by influencing the selective feeding by livestock, litter input, and microbial community structure. In this study, a grazing experiment was carried out in a grassland of agro-pastoral ecotone in Northern China for three years (2017-2019). The concentrations of total carbon (TC), total nitrogen (TN), dissolved organic carbon (DOC), dissolved nitrogen (DN), microbial biomass carbon (MBC), and microbial biomass nitrogen (MBN) in soils were measured. We analyzed the stoichiometric characteristics of those parameters. The results showed that different grazing intensities (1, 2, 4 sheep·0.2 hm-2) had no significant effect on soil TC after three years. The moderate grazing intensity significantly reduced soil TN in 10-20 cm layer in 2019. The light, moderate, and heavy grazing intensities significantly increased soil C/N at 10-20 cm layer, while grazing intensities did not affect soil DOC, DN and DOC/DN. The soil DOC and DN content showed a decreasing trend with the increase of grazing intensity in 2019. It indicated that continuous high intensity grazing might reduce soil dissolved nutrients. The light grazing inten-sity increased soil MBC, while heavy grazing intensity reduced soil MBC significantly, with the increase of grazing year. Different grazing intensities did not affect soil MBN and MBC/MBN.

Suitability of Black Soldier Fly Frass as Soil Amendment and Implication for Organic Waste Hygienization

Because of its nutritious properties, the black soldier fly has emerged as one of the most popular species in advancing circular economy through the re-valorization of anthropogenic organic wastes to insect biomass. Black soldier fly frass accumulates as a major by-product in artificial rearing set-ups and harbors great potential to complement or replace commercial fertilizers. We applied frass from larvae raised on different diets in nitrogen-equivalent amounts as soil amendment, comparing it to NH4NO3 fertilizer as a control. While the soil properties did not reveal any difference between mineral fertilizer and frass, principal component analysis showed significant differences that are mainly attributed to nitrate and dissolved nitrogen contents. We did not find significant differences in the growth of perennial ryegrass between the treatments, indicating that frass serves as a rapidly acting fertilizer comparable to NH4NO3. While the abundance of coliform bacteria increased during frass maturation, after application to the soil, they were outcompeted by gram-negatives. We thus conclude that frass may serve as a valuable fertilizer and does not impair the hygienic properties of soils.

Physical and Theoretical Modeling of the Nitrogen Content of Duplex Stainless Steel Weld Metal: Shielding Gas Composition and Heat Input Effects

Duplex stainless steels (DSSs) are gaining more and more attention in corrosion-resistant applications and also in the transport and automotive industry. The outstanding mechanical and corrosion properties of DSSs highly depends on the austenite-to-ferrite phase balance (A/F). This phase ratio can shift in a large scale during welding. Thus, the heat input and the shielding gas composition should be optimized. Nitrogen addition to argon shielding is frequently used in DSS welding, because it is a potent austenite former. The dissolved nitrogen content in the heat-affected zone and the weld metal (WM) predetermines the A/F. To determine the effect of heat input and nitrogen content in shielding gas, two different heat inputs and six different gas compositions were used in autogenous tungsten inert gas welding. An improved theoretical model was established in order to simulate the WM dissolved nitrogen content, which calculates it with less error than the initial models. The correlation between nitrogen content and arc voltage was also determined. This improved model delivers the basics for shielding gas selection and the subsequent weld design for optimal A/F for industrial applications.

Mycorrhizal associations differentiate soil respiration in five temperate monocultures in Northeast China

Tree species associated with different mycorrhizal fungi play a crucial role in the carbon (C) cycling of forest ecosystems, while their effects on soil respiration (RS) and the underlying mechanisms remain uncertain. In this study, we used a common garden experiment that included five monocultures (two arbuscular mycorrhizal – (AM) and three ectomycorrhizal-associated (ECM) temperate tree species) to explore the effects of mycorrhizal associations on the RS and the driving factors. Our specific objectives were to (1) compare the RS between the AM and ECM stands, and (2) explore the driving factors of the RS. We found that the RS in the AM stands was significantly greater (34.3%) than that in the ECM stands. The RS was significantly and positively correlated with microbial biomass C (Cmic), fine roots biomass (Broot), or soil water content (W5), but negatively with forest floor mass (Fmass) or soil dissolved organic C content (Cdis). The best-fitted models of RS explained 46.3%, 38.3%, and 45.4% of the variations in the RS for the AM stands, the ECM stands, and the combined dataset, respectively. However, the factors contributing to the RS varied with mycorrhizal groups. The RS of the AM stands was mainly influenced by Cmic, Broot, root C/N ratio, Fmass, and Cdis, whereas the RS of the ECM stands was mainly affected by litter C/N ratio, Cdis, soil dissolved nitrogen content, soil temperature and W5. These findings highlight the significance of shifts in AM or ECM tree abundance due to forest management and global change in forest C cycling.

In-depth molecular characterization and biodegradability of water-extractable organic nitrogen in Erhai Lake sediment.

Dissolved organic nitrogen (DON) constitutes a significant fraction of the total dissolved nitrogen content of most aquatic systems and is thus a major nitrogen source for bacteria and phytoplankton. The present work applied Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to a compound-level analysis of the depth-dependent molecular composition of water-extractable organic nitrogen (WEON) in lake sediment. The study focused on Erhai Lake, China. It was found that a large portion (from 16.33 ± 7.87 to 39.54 ± 5.77%) of the WEON in the lake sediment was reactive under cultivation by algal or bacteria. The WEON in the mid-region of Erhai sediment particularly exhibited a lower bioavailability, having been less affected by the basin environment. The FT-ICR MS results revealed the presence of thousands of compounds in the Erhai Lake sediment samples collected at different depths, with the N-containing compounds accounting for 28.3-34.4% of all the compounds. The WEON molecular weight was also observed to increase with increasing sediment depth. A van Krevelen diagram showed that the lignin-type components were dominant (~ 56.2%) in the sediment WEON, contributing to its stabilization and reducing the risk of sediment nutrient release. The FT-ICR MS results further revealed 204 overlapping formulas of WEON for each core sediment sample, attributable to the presence of refractory components. It was observed that 78.4% of the formulas were within the lignin-like region, suggesting unique allochthonous DON sources. The aliphatic component proportion of all the unique formulas was also found to increase with increasing sediment depth. This indicates that, with the development and evolution of the Erhai Basin, the more labile WEON components were transformed into more stable lignin-like substrates, with a positive effect on the Lake Erhai ecosystem. Graphical abstract ᅟ.

Seasonal changes in the content of dissolved organic matter in arable soils

PurposeThe aim of this paper has been to determine the seasonal changes in the content of dissolved organic matter (DOM) in the soils under agricultural use based on assaying changes in dissolved organic carbon (DOC) and dissolved nitrogen (DNt) as well as determining the factors which can define the DOM in soils.Materials and methodsThe research has involved the soils under agricultural use sampled in the Kujawsko-Pomorskie province (Poland). Phaeozems and Luvisols were sampled from the depth of 0–30, 30–60, and 60–100 cm, November 2011 through September 2013, in November, March, May, July, and September. The soil samples were assayed for the grain size composition, pH, dry weight content, content of total organic carbon, and total nitrogen. Dissolved organic matter was extracted with 0.004 mol dm3 CaCl2; in the DOM extracts, the content of dissolved organic carbon (DOC) and dissolved nitrogen (DNt) were assayed. The research results were statistically verified.Results and discussionIt has been demonstrated that in the first year of research, the content of dissolved organic carbon in the soils was changing throughout the year. The highest differences in the content of that carbon fraction occurred across the soil sampled in autumn and the soil sampled in spring. In the second year of research, an inverse dependence was noted. DOC was migrating to deeper layers of the soil profile; yet, the migration got more intensive in summer. The content of dissolved nitrogen was not changing significantly throughout the year. Higher DNt content in the surface layer, in general, resulted in a higher content of dissolved nitrogen in deeper profile layer, which could have been due to leaching of the nutrient deep down the soil profile.ConclusionsThe content of dissolved organic carbon was significantly related to the content of total organic carbon and total nitrogen. Significant changes in the content of dissolved forms of nitrogen were reported in the profile of Phaeozems due to mineral fertilization and irrigation. The soils where irrigation and higher nitrogen rates had been applied demonstrated a higher content and share of soluble forms of nitrogen, as compared with the soils non-irrigated and the soils where lower nitrogen rates had been supplied.

Effects of naphthalene on soil respiration, nutrients and enzyme activities in the subalpine forest of western Sichuan, China

As a biocide to reduce soil and litter faunal populations in field experiments, naphthalene has been widely used in the study of ecological functions of soil fauna, but the non-target effects of naphthalene bring about enormous uncertainty to its application. In order to understand whether there were non-target effects of naphthalene in subalpine forest soil, soil in the subalpine forests of west Qinghai-Tibet Plateau was taken as study object. The short-term responses of soil respiration rate, nutrient content and enzyme activity to naphthalene were studied in microcosms. The results showed that soil respiration rate was significantly suppressed by application of naphthalene within 0-10 days, and then showed a significant promotion effect. Naphthalene significantly affected the dynamics of soil NH4+-N and NO3--N contents. With application of naphthalene, the highest contents of NH4+-N and NO3--N occurred at the 3rd and 7th day, respectively. But they were observed at the 45th and 52nd day with no-naphthalene, respectively. Moreover, soil dissolved carbon content in the naphthalene microcosms showed a sharp increase and then decrease dynamic at the 3rd day, while small change was detected in the no-naphthalene microcosms. Dissolved nitrogen content in both the naphthalene and no-naphthalene microcosms showed an increase at first and then decreased subsequently during the study period. Similar dynamics were found for the soil enzyme activities in both the naphthalene and no-naphthalene microcosms. The highest activities of urease, nitrate reductase and nitrite reductase in both the naphthalene and no-naphthalene microcosms were at the 45th, 38th and 10th day, respectively. In addition, the interaction of naphthalene treatment and sampling time had significant effects on soil respiration rate, the contents of NH4+-N, NO3--N and dissolved nitrogen, but had no significant effects on soil dissolved carbon content, and the activities of invertase, nitrate reductase and nitrite reductase. In a short time, the non-target effect of naphthalene as a biocide to reduce soil fauna abundance might have an important influence on the soil nitrogen cycling in subalpine forest of western Sichuan.

The influence of PTFE used as basic covered electrode binder on weld metal acicular ferrite formation

Weld metals obtained from covered electrodes agglomerated with polytetrafluorethylene presented ultra-low diffusible hydrogen content and appreciable quantities of acicular ferrite. This article investigates the polymer influence on its constituent formation. The microstructure produced by consumables containing this component presented acicular ferrite quantities higher than expected in the literature for weld metals with the same carbon, silicon and manganese content. This difference could not be related to welding parameters employed. The residual chemical element evaluation indicated nitrogen as being mainly responsible for the microstructural variances observed. The operational characteristics of classic E7018 and polymer-agglomerated electrodes showed the lesser weld metal nitrogen absorption must be associated with two main factors. The dissolved nitrogen of the metallic drops collected during the polymer-agglomerated electrode welding showed most effective shielding atmosphere. The carbon content of the polymer-agglomerated electrode indicated an atmosphere rich in this element. This is in accordance with a best shielding process hypothesis. The metallic drops’ average size, dissolved nitrogen content as a function of size and voltage oscillograms indicated metallic transfer mode changes.

Atomization of UMo Particles under Nitrogen Atmosphere

Generally, the atomization of UMo particles is done under vacuum or argon atmosphere, and the surface modification of these UMo particles is, usually, carried on through a further process. The techniques for surface modification of atomized UMo particles, aimed to control the Fuel/Matrix interaction, involve, in some cases, complex methodologies and often with minor effect due to the limited solubility of third elements in solid UMo alloy. The atomization and surface conditioning, applied in separate stages, may affect the efficiency of powder production process. Then, the main goal of this study is to explore the surface modification of UMo particles in liquid state or during the solidification that follows the centrifugal atomization process. Through the change of atomization atmosphere, could be possible to promote liquid/gas reactions, with a higher solubility of the modifier element in micro drops of UMo alloy, before they become solid particles. This paper presents comparative results of centrifugal atomization of UMo particles, carried out under inert argon and reactive nitrogen atmospheres. Dissolved nitrogen contents, measured by SEM-EDS analyses, reached up to 7.57 wt% at the center of under nitrogen atomized particles, very higher than 0.84 wt% of nitrogen measured at the center of UMo particle atomized under argon. The presence of uranium nitride was partially verified by conventional XRD analysis. Nevertheless, Out-of-Pile interaction test result, reveals decreasing of aluminium contents into UMo particles atomized under nitrogen atmosphere; Just 3.77 wt% of Al was the maximum content detected in the center of these particles, very lower than 29.11 wt% of Al measured inside UMo particles atomized under argon. Finally, it is possible to conclude that the atomization under reactive atmosphere may modify the surface composition and the behavior of UMo fuel particles dispersed in aluminium, for dispersion type nuclear fuel application.

Influência do uso de PTFE como aglomerante em eletrodos revestidos básicos sobre a formação de ferrita acicular no metal de solda

Metais de solda produzidos por eletrodos revestidos básicos aglomerados com politetrafluoretileno (PTFE) têm apresentado baixíssimos teores de hidrogênio difusível e elevadas frações volumétricas de ferrita acicular. Esse estudo investigou o papel desempenhado pelo polímero na formação de tal constituinte. A microestrutura produzida por consumíveis contendo esse componente apresentou quantidades de ferrita acicular consideravelmente superiores à prevista na literatura para um metal de solda com os mesmos teores de carbono, silício e manganês. Tal diferença não pode ser atribuída a variações nos parâmetros de soldagem empregados. A análise dos elementos químicos residuais apontou o nitrogênio como sendo o principal responsável pelas discrepâncias observadas na microestrutura. O estudo das características operacionais de eletrodos classe E7018 tradicionais e aglomerados com polímero mostrou que a menor absorção de nitrogênio pelo metal de solda se deve a dois fatores principais. Medidas do teor de nitrogênio dissolvido das gotas coletadas durante a soldagem do eletrodo aglomerado com polímero demonstrou uma atmosfera protetora mais efetiva. O teor de carbono presente no metal de solda obtido pela soldagem do eletrodo com polímero apontou para uma atmosfera rica nesse elemento. Tal característica é coerente com a hipótese de uma melhor proteção gasosa. O tamanho médio das gotas coletadas, teor de nitrogênio dissolvido em função do tamanho e os oscilogramas de tensão indicaram alterações no modo de transferência metálica.

Dissolved organic carbon and dissolved nitrogen in soil under different fertilization treatments

The objective of the study was to evaluate the effects of long-term fertilization of a sandy soil with differentiated doses of cattle slurry as well as its after-effect action on the possibilities of migration of dissolved organic carbon (DOC) and dissolved nitrogen (DNt) down to deeper layers of the soil profile. DOC and DNt were extracted with borate buffer and 0.004M CaCl&lt;sub&gt;2&lt;/sub&gt; solution. Evaluation of effects of cattle slurry on the content of DOC and DNt was done in comparison with mineral fertilization. It was shown that the use of cattle slurry in the doses of 100 and 200&amp;nbsp;m&lt;sup&gt;3&lt;/sup&gt;/ha caused a significant increase of labile organic matter in the 0&amp;ndash;25 and 25&amp;ndash;50 cm layers of soil. As compared with mineral fertilization the application of slurry increased also the amounts of extracted DNt, but only in the surface layer. The DNt content in the deeper soil horizons did not depend on the kind of fertilization. Concentrations of DOC and DNt in the extracts depended not only on their content in soil but it was also modified substantially by the extractant used.

メカニカルアローイング法による高窒素添加ステンレス鋼の作製と局部腐食特性評価

High nitrogen containing stainless steel was prepared by mechanical alloying (MA) method from SUS 447 powder. The SUS 447 powder was ball-milled at N2 atmosphere and then HIP treatment was carried out. The obtained stainless steels were examined by X-ray diffraction (XRD) and scanning electron microscope (SEM). With the increase in the time of MA treatment, dissolved nitrogen content of the stainless steel was increased, and ferrite phase changed into austenite phase. The evaluation of corrosion behavior was carried out by the electrochemical corrosion test. For the stainless steel with MA treatment without nitrogen, it was found that the pitting potential in sulfuric acid solution including the chloride was very noble. And clear pitting corrosion was not observed for the stainless steel with MA treatment with nitrogen. The results of electrochemical corrosion test indicated that localized corrosion was suppressed by the MA treatment.