Content Of NH4 Research Articles

Effects of different soil water holding capacities on vegetable residue return and its microbiological mechanism.

With the gradual expansion of the protected vegetable planting area, dense planting stubbles and increasing labor cost, the treatment of vegetable residues has become an urgent problem to be solved. Soil bacterial community structure plays an important role in vegetable residue return and is susceptible to environmental changes. Therefore, understanding the influences of different soil water holding capacities on plant residue decomposition and soil bacterial communities is important for biodegradation. During the whole incubation period, the weight loss ratio of plant residue with 100% water holding capacity was 69.60 to 75.27%, which was significantly higher than that with 60% water holding capacity in clay and sandy soil, indicating that high water holding capacity promoted the decomposition of plant residue. The degradation of lignin and cellulose was also promoted within 14 days. Furthermore, with the increase in soil water holding capacity, the contents of NH4+ increased to 5.36 and 4.54 times the initial value in the clay and sandy soil, respectively. The increase in napA and nrfA resulted in the conversion of NO3- into NH4+. The increase in water holding capacity made the bacterial network structure more compact and changed the keystone bacteria. The increase in water holding capacity also increased the relative abundance of Firmicutes at the phylum level and Symbiobacterium, Clostridium at the genus level, which are all involved in lignin and cellulose degradation and might promote their degradation. Overall, these findings provide new insight into the effects of different soil water holding capacities on the degradation of plant residues in situ and the corresponding bacterial mechanisms.

Transport and distribution of residual nitrogen in ion-adsorption rare earth tailings

A large amount of nitrogen remains in ion-absorption rare earth tailings with in-situ leaching technology, and it continually ends up in groundwater sources. However, the distribution and transport of ammonium nitrogen (NH4+-N) and nitrate nitrogen (NO3−-N) across tailings with both depth and hill slopes is still unknown. In this study, the amount of NH4+-N and nitrate nitrogen (NO3−-N) was determined in tailings, and a soil column leaching experiment, served to assess the transport and distribution following mine closure. Firstly, a high concentration of NH4+-N in the leachate at the initial leaching stage was detected, up to 2000 mg L−1, and the concentration of NH4+-N clearly diminished as time passed. Meanwhile, the NH4+-N contents remained relatively high in soil. Secondly, both the content of NH4+-N and NO3−-N varied greatly according to vertical distribution after leaching lasting several years. The amounts of NH4+-N and NO3−-N in surface soil were much smaller than those in deep soil, with 3–4 orders of magnitude variation with depth. Thirdly, when disturbed by NH4+-N, the pH not only diminished but also changed irregularly as depth increased. Fourthly, although the amount of NO3−-N was smaller than that of NH4+-N, both their distribution trend was similar with depth. In fact, NH4+-N and NO3−-N were significantly correlated but this declined from the knap to the piedmont. Based on these results, it is suggested that mining activity could cause nitrogen to be dominated by NH4+-N and acidification in a tailing even if leaching occurs over several years. NO3−-N derived from NH4+-N transports easily and it becomes the main nitrogen pollutant with the potential to be a long-lasting threat to the environment around a mine.

Effects of freeze-thaw cycling on the engineering properties of vegetation concrete

Vegetation concrete has been widely applied for the ecological restoration of bare steep slopes in short-term frozen and non-frozen soil regions in China. However, field experiments conducted in seasonally frozen soil regions have revealed decreases in the bulk density, nutrient content and vegetation coverage. This study aimed to clarify the evolution process and mechanism of the engineering properties of vegetation concrete under atmospheric freeze-thaw (F-T) test conditions. The physical, mechanical, and nutrient properties of vegetation concrete were investigated using six F-T cycles (0, 1, 2, 5, 10 and 20) and two initial soil water contents (18 and 22%). The results revealed decreases in the acoustic wave velocity and cohesive forces and an increase in the permeability coefficient of the vegetation concrete owing to F-T action. X-ray diffraction tests indicated that the decreased cohesive force was closely related to the overall decrease in the content of gelling hydration products in the vegetation concrete. Additionally, the contents of NH4+–N, PO43–P and K+ in the vegetation concrete increased, whereas that of NO3−–N decreased. The loss rates of these soluble nutrients increased, indicating that the nutrient retention capacity of the vegetation concrete had decreased. Specifically, the decreased nutrient retention capacity was mainly related to the disintegration and fragmentation of larger aggregates due to F-T action. This study provides theoretical support for future research on improving the anti-freezing capability of ecological slope protection substrates in seasonally frozen soil regions.

Nitrogen removal performance and bacterial flora analysis of a nitrification‑sulphur autotrophic denitrification coupled with permeable reaction wall (NSAD+PRW) treating rare earth mine groundwater

Rare earth elements (REEs) are strategic resources for the development of modern society. However, their mining can cause nitrogen pollution in groundwater. In this study, a nitrification-sulphur autotrophic denitrification-enhanced permeable reaction wall (NSAD+PRW) was constructed to treat groundwater in rare earth mines and the feasibility of its engineering application was demonstrated. The results show that a maximum removal rate of 100 % was achieved for NO3−-N. The average removal content of NH4+-N was 27.15 mg/L and the highest TN removal content of total nitrogen (TN) reached 145.49 mg/L. The removal rates of most REEs exceeded 99.88 %. The composite filler provides a good environment for microorganisms, which also produce extracellular polymeric substances (EPS) to protect themselves during nitrogen removal. In addition, some nitrifying bacteria (Rhodanobacter and Nitrospira) and denitrifying bacteria (Thiobacillus, Sulfurovum, and Ferritrophicum) with high adaptability to rare earth mine groundwater were found. In conclusion, the results of this study provide an important reference for nitrogen removal from groundwater in rare earth mines with high engineering application significance.

From urine to food and oxygen: effects of high and low NH4+:NO3- ratio on lettuce cultivated in a gas-tight hydroponic facility.

In situ production of food, water and oxygen is essential for long-duration human space missions. Higher plants represent a key element in Bioregenerative Life Support Systems (BLSS), where crop cultivation can be based on water and nutrients recovered from waste and wastewater. Human urine exemplifies an important waste stream with potential to provide crops with nitrogen (N) and other nutrients. Dynamic waste composition and treatment processes may result in mineralized fractions with varying ammonium (NH4 +) to nitrate (NO3 -) ratios. In this study, lettuce was cultivated in the unique ESA MELiSSA Plant Characterization Unit, an advanced, gas-tight hydroponic research facility offering controlled environment and continuous monitoring of atmospheric gas composition. To evaluate biological and system effects of nutrient solution NH4 +:NO3 - ratio, two crop tests were run with different NH4 + to total N ratio (NH4 +:N) and elevated concentrations of Na+ and Cl- in line with a urine recycling scenario. Plants cultivated at 0.5 mol·mol-1 NH4 +:N (HiNH4 +) achieved 50% lower shoot biomass compared to those cultivated at 0.1 mol·mol-1 NH4 +:N (LoNH4 +), accompanied by higher shoot dry weight content and lower harvest index. Analyses of projected leaf area over time indicated that the reduced biomass observed at harvest could be attributed to a lower specific growth rate during the close-to-exponential growth phase. The HiNH4 + crop produced 40% less O2 over the full cultivation period. However, normalization of the results indicated a marginal increase in O2 production per time and per projected leaf area for the HiNH4 + crop during the exponential growth phase, in line with a higher shoot chlorophyll content. Mineral analysis demonstrated that the biomass content of NH4 + and NO3 - varied in line with the nutrient solution composition. The ratio of consumed NH4 + to consumed N was higher than the NH4 +:N ratio of the nutrient solution for both crop tests, resulting in decreasing NH4 +:N ratios in the nutrient solution over time. The results provide enhanced insight for design of waste processes and crop cultivation to optimize overall BLSS efficiency and hold valuable potential for improved resource utilization also in terrestrial food production systems.

Mechanisms and effects of novel ammonifying microorganisms on nitrogen ammonification in cow manure waste composting

It is essential to reduce nitrogen losses and to improve nitrogen conversion during organic waste composting because of environmental protection and sustainable development. To reveal newly domesticated ammonifying microorganisms (AM) cultures on the ammonification and nitrogen conversion during the composting, the screened microbial agents were inoculated at 5 % concentration (in weight basis) into cow manure compost under five different treatments: sterilized distilled water (Control), Amm-1 (mesophilic fungus-F1), Amm-2 (mesophilic bacterium-Z1), Amm-3 (thermotolerant bacterium-Z2), and Amm-4 (consortium: F1, Z1, and Z2), and composted for 42 days. Compared to control, AM inoculation prolonged the thermophilic phases to 9–19 days, increased the content of NH4+-N to 1.60–1.96 g/kg in the thermophilic phase, reduced N2O and NH3 emissions by 22.85–61.13 % and 8.45–23.29 %, increased total Kjeldahl nitrogen, and improved cell count and viability by 12.09–71.33 % and 66.71–72.91 %. AM was significantly associated with different nitrogen and microbial compositions. The structural equation model (SEM) reveals NH4+-N is the preferable nitrogen for the majority of bacterial and fungal growth and that AM is closely associated with the conversion between NH3 and NH4+-N. Among the treatments, inoculation with Amm-4 was more effective, as it significantly enhanced the driving effect of the critical microbial composition on nitrogen conversion and accelerated nitrogen ammonification and sequestration. This study provided new concepts for the dynamics of microbial in the ammonification process of new AM bacterial agents in cow manure compost, and an understanding of the ecological mechanism underlying the ammonification process and its contribution to nitrogen (N) cycling from the perspective of microbial communities.

Effect of Biochar with Phosphorus Fertilizer on Soil Nutrients, Enzyme Activity, and Nutrient Uptake of Alfalfa

Biochar is widely used in agricultural production practices as a soil conditioner that can be used both alone and jointly with chemical fertilizer. However, there are few studies on the effects of the combined application of biochar and phosphate fertilizer with different particle sizes on soil and plants. In this experiment, pot experiments were used to study the effects of biochar with different particle sizes on soil nutrients, enzyme activity, and Alfalfa nutrient absorption under two phosphorus levels (according to diameter, the biochar was divided into C1:>1 mm and C2:<0.01 mm). This study showed that the combined application of biochar and phosphorus significantly improved soil nutrients, enzyme activity, and Alfalfa nutrient absorption. Among them, the C2 treatment significantly increased the soil available phosphorus content and phosphatase activity (P<0.05), whereas the C1 treatment had a significant effect on ammonium nitrogen, nitrate nitrogen, urease, and catalase activities (P<0.05). Moreover, the differences in nutrients and enzymes among biochar treatments with different particle sizes were affected by soil phosphorus levels. At the P0 level, there was no significant difference in ammonium nitrogen and nitrate nitrogen contents between the C1 and C2 treatments. At the P1 level, the contents of NH4+-N and NO3--N in the C1 treatment were 24.19% and 18.68% higher than those in the C2 treatment (P<0.05), but there was no significant difference between the C1 and C2 treatments. Phosphorus addition significantly increased the N and P contents of Alfalfa above ground and in the ground (P<0.05), but there was no significant effect on the nutrient content of Alfalfa between different particle sizes of biochar. In conclusion, biochar and phosphate fertilizer can be used as an effective means of soil improvement. In addition, when using biochar for soil improvement, the impact of particle size on soil nutrients and soil enzymes should be considered.

Overexpression of PsAMT1.2 in poplar enhances nitrogen utilization and resistance to drought stress.

Ammonium is an important form of inorganic nitrogen, which is essential for plant growth and development, and the uptake of ammonium is mediated by different members of ammonium transporters (AMTs). It is reported that PsAMT1.2 is specially expressed in the root of poplar, and the overexpression of PsAMT1.2 could improve plant growth and the salt tolerance of poplar. However, the role of AMTs in plant drought and low nitrogen (LN) resistance remains unclear. To understand the role of PsAMT1.2 in drought and LN tolerance, the response of PsAMT1.2-overexpression poplar to polyethylene glycol (PEG)-simulated drought stress (5% PEG) under LN (0.001mM NH4NO3) and moderate nitrogen (0.5mM NH4NO3) conditions was investigated. The PsAMT1.2-overexpression poplar showed better growth with increased stem increment, net photosynthetic rate, chlorophyll content, root length, root area, average root diameter and root volume under drought and/or LN stress compared with the wild type (WT). Meanwhile, the content of malondialdehyde significantly decreased, and the activities of superoxide dismutase and catalase significantly increased in the roots and leaves of PsAMT1.2-overexpression poplar compared with WT. The content of NH4+ and NO2- in the roots and leaves of PsAMT1.2-overexpression poplar was increased, and nitrogen metabolism-related genes, such as GS1.3, GS2, Fd-GOGAT and NADH-GOGAT, were significantly upregulated in the roots and/or leaves of PsAMT1.2-overexpression poplar compared with WT under drought and LN stress. The result of this study would be helpful for understanding the function of PsAMT1.2 in plant drought and LN tolerance and also provides a new insight into improving the drought and LN tolerance of Populus at the molecular level.

Leaching is the main pathway of nitrogen loss from a citrus orchard in Central China

Due to the high application rates and low utilization efficiency of inorganic nitrogen (N) fertilizer, conventional citrus orchards tend to cause N losses and extensive pollution. In order to address these issues, it is essential to identify the leading cause of N loss by citrus orchard N mass balance. In the present study, a two-year field experiment was performed on 4 different treatments (CK: no N fertilizer; CF: conventional N fertilizer; NR: 70% of conventional N fertilizer; OM: NR with organic manure) to quantify the pathways of N loss in citrus orchards in Hubei Province, China. Our findings revealed that leaching (17.0%) was the dominant N loss pathway in the conventional citrus orchard of central China, followed by runoff (2.9%), NH3 volatilization (2.3%), and N2O emission (0.5%). Reduced N fertilizer rates (−30.0%) led to a significant reduction in gaseous N loss (−34.9%), runoff N loss (−20.3%), and N leaching (−13.0%) via the reduced content of soil NH4+ and soil NO3-. Interestingly, the presence of organic manure reduced 15.2% of runoff N loss, 3.8% of N leaching and 6.9% of total N loss via reduced soil NO3-, but increased 39.6% of gaseous N loss via increased soil DOC. On the other hand, the low N fertilizer rates suppressed N uptake of citrus by reducing the content of soil NO3-, while organic manure promoted N uptake of citrus via the increased content of soil DOC. Overall, using organic manure as a substitute provides a better solution to fertilization for the citrus orchards in central China compared to reducing N fertilizer rates.

Supercritical water gasification of chicken manure continuously supplied into the reactor

The article presents the research results of the chicken manure gasification in supercritical water. The experiments were carried out using a tubular flow reactor at a pressure of 25 MPa, a temperature gradient along its vertical axis (390–600 °C from top to bottom), and a chicken manure flow rate of 6.9–9.6 g/min, including experiments with the addition of NaOH (2.4 wt%). Data were obtained on the yield and composition of carbonized residues, volatile and liquid products, as well as the content of toxic substances (phenols, N-containing aromatics, and polyaromatic hydrocarbons (PAHs)) and mineral components in effluent collected at the reactor outlet. It is shown that an increase in the residence time of reagents in the high-temperature region of the reactor (HTR) improves the gasification efficiency. Using gas chromatography – mass spectrometry, it was revealed that phenol, pyridine, pyrazine, pyrrole, aniline, indole, quinoline, and their alkyl derivatives predominate in the composition of water-soluble products. The total content of phenols in effluent decreases from 1.3 to 1.1 g/dm3 when increasing the residence time of reagents in HTR, and does not depend on adding NaOH while the total content of N-containing aromatics decreases from 1.0 to 0.7 g/dm3 when adding NaOH. The content of PAHs, which is dominated by naphthalene, increases from 0.5 to 2.1 mg/dm3 in effluent when increasing the residence time of reagents in HTR. According to capillary electrophoresis data, increasing the residence time in HTR and adding NaOH result in increase of the content of NH4+ ions in effluent from 9.8 to 10.9 g/dm3.

Prediction and sensitivity analysis of chlorophyll a based on a support vector machine regression algorithm

Outbreaks of planktonic algae seriously affect the water quality of rivers and are difficult to control. Based on the analysis of the temporal and spatial variation characteristics of environmental factors, this study uses a support vector machine regression (SVR) algorithm to establish a chlorophyll a (Chl-a) prediction model and conduct Chl-a sensitivity analysis. In 2018, the average Chl-a content was 126.25 ug/L. The maximum total nitrogen (TN) content was 16.68mg/L and high year-round. The average NH4+-N and total phosphorous (TP) contents were only 0.78 and 0.18mg/L. The content of NH4+-N was higher in spring and increased significantly along the water flow, while TP decreased slightly along the water flow. We used a radial basis function kernel SVR model and tenfold cross-validation method to optimize parameters. The penalty parameter c was 1.4142, the kernel function parameter g was 1, and the training and verification errors were only 0.032 and 0.067, respectively, indicating a good model fit. Based on a sensitivity analysis of the SVR prediction model, the maximum sensitivity coefficients of Chl-a to TP and WT were 0.571 and 0.394, respectively, and the contributions were 33% and 22%, respectively. The next highest sensitivity coefficients were those of DO (0.28, 16%) and pH (0.243, 14%). The sensitivity coefficients of TN and NH4+-N were the lowest. According to the current water environment pollution conditions, TP is the limiting factor of Chl-a in the Qingshui River, and it is also the main prevention and control factor of phytoplankton outbreak.

The Potential of Bacterial Strains of Luteovulum sphaeroides W22 and W47 for Producing δ-Aminolevulinic Acid to Improve Soil Quality, Growth and Yield of Saline-Irrigated Rice Cultivated in Salt-Contaminated Soil

The present study aimed to identify the abilities of the δ-aminolevulinic acid (ALA) producing purple non-sulfur bacteria (PNSB), Luteovulum sphaeroides W22 and W47, to reduce the Na+ concentration, and to ameliorate the soil fertility, nutrients uptake, growth and yield of rice on the salt-contaminated soil. A two-factor experiment was conducted following a completely randomized block design. The factors were the frequency of applying saline irrigation (zero, one, two, three and four times) and the ALA-producing PNSB supplementation (applying only W22, only W47 and mixed W22 + W47). The results revealed that supplying the PNSB mixture not only reduced the proline content but also increased the plant height, number of panicles per pot, percentage of filled seeds, contents of NH4+, PO43−, total N, P uptake and grain yield. The mixed PNSB application also reduced the Na content and the total Na uptake in plants. L. sphaeroides W22 and W47 decreased the proline content by 31.3% and increased the grain yield by 27.2% in the condition of applying 5‰ saline irrigation four times.

Solid-liquid phase equilibrium for the system ammonium polyphosphate-urea ammonium nitrate-potassium chloride-water at 273.2 K

Based on the dynamic method, a quaternary system of ammonium polyphosphate (APP)-urea ammonium nitrate (UAN, CO(NH2)2-NH4NO3)-potassium chloride (KCl)-H2O and its subsystems (APP-[CO(NH2)2-NH4NO3]-H2O, KCl-[CO(NH2)2-NH4NO3]-H2O and APP-KCl-H2O) were systematically investigated at the temperature of 273.2 K. Each ternary phase diagram contains one invariant point and three crystallization regions. The crystallization regions are: (1) (NH4)3HP2O7, (NH4)4P2O7 and ((NH4)3HP2O7 + (NH4)4P2O7) for APP-[CO(NH2)2-NH4NO3]-H2O diagram; (2) KCl, KNO3 and (KCl + KNO3) for KCl-[CO(NH2)2-NH4NO3]-H2O diagram and (3) (NH4)3HP2O7, KCl and ((NH4)3HP2O7 + KCl) for APP-KCl-H2O diagram. The quaternary phase diagram of APP-[CO(NH2)2-NH4NO3]-KCl-H2O has no quaternary invariant point but includes four solid phase crystallization regions, i.e., (NH4)3HP2O7, (NH4)4P2O7, KNO3 and KCl, in which the KNO3 region occupies the largest area. The maximum total nutrient content (N + P2O5 + K2O) existing as ionic forms in the APP-[CO(NH2)2-NH4NO3]-H2O, KCl-[CO(NH2)2-NH4NO3]-H2O, APP-KCl-H2O and quaternary systems is 44.70%, 32.86%, 45.56% and 46.23% (mass), respectively, indicating that the maximum nutrient content can be reached using raw materials of the corresponding systems to prepare liquid fertilizer. In the quaternary system, the content of NH4+-N ascends with the increase of the total nutrient content, while the contents of NO3--N and CO(NH2)2-N increase with elevated total N. This work can help optimize the operating parameters for the production, storage and transportation of liquid fertilizers.

Optimum Strength and NH4+:NO3- Ratio of Nutrient Solution for Romaine Lettuce Cultivated in a Home Hydroponic System

Concentration of nitrogen, one of the major elements, and ratio of two nitrogen forms (NH4+ and NO3–) in the nutrient solution affect the quality and food safety of fresh vegetable produce. This study was conducted to find an appropriate strength and NH4+:NO3– ratio of a nutrient solution for growth and development of a Romaine lettuce (Lactuca sativa L. var. longiflora) ‘Caesar Green’, a representative leafy vegetable, grown in a home hydroponic system. In the first experiment, plants were grown using three types of nutrient solution: A commercial nutrient solution (Peters) and two strengths (GNU1 and GNU2) of a multipurpose nutrient solution (GNU solution) developed in a Gyeongsang National University lab. Plants grown with the GNU1 and GNU2 had greater shoot length, leaf length and width, and biomass yield than Peters. On the other hand, the root hairs of plants grown with Peters were short and dark in color. Tissue NH4+ content in the Peters was higher than that of the GNU1 and GNU2. The higher contents of NH4+ in this solution may have caused ammonium toxicity. In the second experiment, eight treatment solutions, combining GNU1 and GNU2 solutions with four ratios of NO3–:NH4+ named as 1, 2, 3 and 4 were used. Both experiments showed more growth in the GNU2 group, which had a relatively low ionic strength of the nutrient solution. The growth of Romaine lettuce showed the greatest fresh weight along with low tissue NO3– content in the GNU2-2. This was more advantageous in terms of food safety in that it suppressed the accumulation of surplus NO3– in tissues due to the low ionic strength of the GNU2 subgroup. In addition, this is preferable in that it can reduce the absolute amount of the input of inorganic nutrients to the nutrient solution.

Effects of Successive Planting of Eucalyptus Plantations on Tree Growth and Soil Quality

The ultra-short-cycle successive planting of Eucalyptus plantations has caused environmental and social problems, and changing the rotation cycle is a very good option to solve this issue. However, the effects of successive planting on Eucalyptus growth and soil quality after changing the cultivation period are unclear. This study evaluated the effects of successive Eucalyptus planting on growth, soil nutrients, and bacterial and fungal community structure with an eight-year cultivation period. Eucalyptus plantations with different succession generations (first, second and third generation) were selected, and tree height and diameter at breast height were measured. Ten indicators of soil nutrients in different soil layers (0–20 cm and 20–40 cm) were measured, and soil bacteria and fungi were sequenced in high throughput. Results show that there is an upward trend in tree growth after three successive generations, reaching the highest timber yield in the third-generation plantation. Soil nutrients also showed changes, in the 0–20 cm soil layer, with decreased TN, NH4+-N, NO3−-N and AK and increased AP, particularly for OM and TP content. In the 20–40 cm soil layer, the content of NH4+-N and NO3−-N increased slightly and the soil’s OM, TP, and TK content increased significantly. The diversity of bacterial and fungal communities in different soil layers increased significantly, and the community structure composition changed. Bacterial and fungal community structures were mainly driven by pH, NH4+-N, TP and AP factors and by OM, NH4+-N, TP and TK factors, respectively. Thus, successive plantings of Eucalyptus plantations with a cultivation period of eight years is conducive to the growth of trees. Some nutrients of the soil were returned, and the soil microbial diversity increased. Successive planting has brought efficiency and economic benefits while maintaining the soil’s fertility.

Nitrogen fractionation in mica metapelite under hot subduction conditions: Implications for nitrogen ingassing to the mantle

Nitrogen partitioning between its main hosts is investigated using partly devolatilized natural quartz–muscovite–chlorite schist (mica schist), with NH4+-rich muscovite, under conditions corresponding to hot subduction: 3.0–7.8 GPa, 750–1090 °C, and oxygen fugacity (fO2) about the NNO (Ni-NiO) buffer. At these conditions, mica schist transforms into an eclogitic assemblage, while muscovite (C2/c) recrystallizes successively into two high-pressure white mica phases. The resulting phases are phengite (P3112) and a phase intermediate between the dioctahedral and trioctahedral mica series (C2/m). During dehydration and decarbonation reactions at run P-T conditions mica schist releases an H2O-CO2 fluid containing 0.3–14 rel.% N2 and < 0.1–3.7 rel.% NH3. The contents of NH4+ determined by Fourier transform infrared spectroscopy (FTIR) decrease from 1600 to 2000 ppm in primary muscovite to ∼1500 ppm in phengitic muscovite at 6.3 GPa and 1000 °С and to 610–990 ppm in the intermediate between the dioctahedral and trioctahedral mica phase at 7.8 GPa and 1070-1090 °C. Ammonium in the analyzed metapelite shows incompatible behavior (DNH4Mica−Fluid=0.05–0.15) at ≥ 5.5 GPa and temperatures and fO2 common to hot oxidizing slabs, which is expected to cause its efficient outgassing from subducting metasediments depleted in volatiles. Nitrogen partitioning under hot subduction conditions at sub-arc depths is generally controlled by devolatilization of measediments, phase transitions in N-bearing micas, and changes of fluid composition near the second critical point.

ВИКОРИСТАННЯ БІОЧАРУ І МІСКАНТУСУ ГІГАНТСЬКОГО (MISCANTHUS GIGANTEUS) ДЛЯ РЕМЕДІАЦІЇ ҐРУНТУ, ЗАБРУДНЕНОГО НАФТОПРОДУКТАМИ

The dynamics of changes in the chemical composition of soils contaminated with oil products during the vegetation of Miscanthus giganteus, as well as under the conditions of adding biochar (biochar) were studied. The possibility of using the culture of Miscanthus giant and biochar for soil remediation under conditions of oil pollution was analyzed. It was shown that the introduction of biochar into the soil enriched it with nitrate nitrogen, which was actively assimilated by giant miscanthus plants during the growing season. The absorption of nitrate anions by plants was especially active in the second series of the experiment, when the soil + biochar was contaminated with diesel fuel. It was established that the content of NH4+ ions in both series of the experiment increased until the end of the growing season. Obviously, ammonium nitrogen is absorbed to a lesser extent by M. giganteus plants, compared to nitrate. The increase in ammonium content can be additionally caused by the activity of soil microbes in the rhizosphere of plants, which contributes to the accumulation of ammonium nitrogen in the soil. It has been shown that miscanthus plants actively absorbed water-soluble forms of phosphorus, especially in the period from June to September. The application of biochar was a significant source of phosphorus, although its release into the soil is a rather slow process. It was determined that additional amounts of potassium were added to the soil with biochar, which was actively used by the M. giganteus culture. The minimum amounts of potassium in both series of studies were absorbed by plants of E groups, where the content of diesel fuel in the soil was the highest. The introduction of petroleum products had a minor effect on the value of exchangeable acidity. The addition of biochar contributed to the shift of the acid-base balance in the direction of alkalinity, but after the end of the miscanthus vegetation (September), a decrease in the pH of the saline extract of the soil was noted. It is shown that the most noticeable decrease in the concentration of diesel fuel in the soil was noted under the conditions of adding biochar and after growing miscanthus, which can be effectively used for the remediation of lands contaminated by oil products.

Soil characteristics controlling nitrous oxide emissions of tropical peatlands

Emission of nitrous oxide (N2O) from peatlands contributes very significantly to the world global warming, although the factors controlling N2O emissions from peatlands are not yet clear. This study aimed to determine peat characteristics controlling N2O emissions in peatlands. N2O emissions and several soil characteristics (pH, electrical conductivity, height of water table, water-filled pore space, decomposition degree of peats, bulk density, organic carbon, total nitrogen, and concentrations of ammonium and nitrate) were observed in peatlands with different crops and land-uses: lettuce, spring-onion, albizia, shrubs-peat, and burned-peats. Correlation-regression analyses were employed to quantify peat properties influencing the rates of N2O emission from peatlands. The results of the study showed that N2O emissions varied based on the type of crops/land-uses, in which peats used for crop cultivation had higher N2O emissions than others. The results of the analysis also revealed that N2O emissions of peat were controlled by variables related to water contents and the contents of NH4 + and NO3 −. In peats with relatively similar NH4 + and NO3 − contents, N2O emissions were determined by variables related to water contents (height of water table and volumetric water contents). The result of this study shows the need for water and peat fertility management for the mitigation of N2O emission from peatlands. Thus, managing the availability of nitrogen by using biological fertilizers to reduce the amounts of inorganic nitrogen fertilizers is required to reduce N2O emissions without decreasing crop yields in peatlands.

The Effect of Drying–Wetting Cycles on Soil Inorganic Nitrogen Transformation in Drip-Irrigated Cotton Field Soil in Northwestern China

Drip irrigation under plastic mulch is widely used and leads to periodic drying–rewetting (DW) cycles in Xinjiang, Northwest China. However, the effect of different wet and dry alternation types on soil inorganic nitrogen transformation is not clear. Studying these issues not only provides reference for the formulation of fertilization and irrigation systems but is also of great significance for reducing non-point source pollution. An incubation experiment was conducted in 2018 in Baotou Lake farm in Korla City, Xinjiang, with drip-irrigated cotton (Gossypium hirsutum L.). The treatments were designed comprising three parts: (1) DW intensity (Q100, Q90, Q80, Q70, Q60); (2) DW frequency (P3d, P5d, P7d, P9d, P11d); and (3) soil wetting time (P1m, P3m, P5m). The results revealed that the contents of the NH4+ and NO3− decreased with the increase in the DW intensity and were highest in the Q100 treatment. The rate of net N mineralization decreased with the increase in the DW intensity. The highest rate (7.02 mg kg−1 d−1) was found in the Q70 treatment in the wet to dry process and 3.03 mg kg−1 d−1 in the Q60 treatment in the dry to wet process, respectively. The contents of the NH4+ and NO3− were higher with the higher DW frequency (P3d). The rate of net N mineralization decreased with the increase in the DW frequency and was highest in the P3d treatment in the wet to dry process and the P5d treatment in the dry to wet process, respectively. The soil wetting time was longer with the content of NH4+, NO3−, and N mineralization (P5m). The rate of net N mineralization was higher with the longer soil wetting time in the wet to dry process and the shorter soil wetting time from the dry to wet process. These results demonstrate that a reasonable DW intensity, DW frequency, and soil wetting time could not only effectively promote nitrogen transformation and the absorption of nitrogen but also reduce the nitrogen losses under drip irrigation.

Dissolution Characteristics of Ammonium and Nitrate in Soil with Bottom Ash from Biomass Power Plant

Recently, biomass power plants are increasing as an alternative energy source to reduce the carbon emissions from fossil fuels. The amount of waste from biomass power plants increases and bottom ash is generally buried in soil. However, there is little research on the dissolution characteristics of nitrogen, a macronutrient in soil, using bottom ash (BA). To evaluate nitrogen dissolution in soil with BA, we mixed BA with soil, collected leachate for 5 weeks, and measured NH4+-N and NO3--N concentration in leachate. As a results, BA reduced the leaching of NH4+-N and NO3--N by up to 18% and 38%, respectively. The decrease of NH4+-N leaching is judged to be the result of increased NH4+-N adsorption due to the high pH of the bottom ash, and these results are often confirmed in other biochar. The NO3--N leaching also decreased, but it is not related to the adsorption capacity of BA, so further research is needed. These results suggested that BA reduces the contents of NH4+-N and NO3--N in the soil effluent, which can be used as an important indicator for using bottom ash in the soil.The amount of NH4+-N and NO3--N dissolution in soil using bottom ash from biomass power plant (average and standard deviation; 3 replicate). (left) Accumulation of NH4+-N; (right) Accumulation of NO3--N.