183 research outputs found
Iron oxidation affects nitrous oxide emissions via donating electrons to denitrification in paddy soils
No full textPaddy soils are important source of nitrous oxide (N2O), which production is mainly regulated through redox processes and electron transfer. Ferrous iron [Fe(II)] oxidation coupled to denitrification is ubiquitous in paddy soils, which could affect N2O production via donating electrons to denitrification. To clarify the effects of Fe(II) oxidation on denitrification and N2O emissions, a flooding experiment was conducted in two paddy soils with contrasting Fe(II) levels. The soil with high Fe(II) concentration emitted less N2O than did the other soil with low Fe(II) concentration. Nitrate addition decreased Fe(II) concentration and stimulated N2O production in both soils, suggesting that Fe(II) oxidation is coupled to denitrification. The stoichiometry of electron transfer between nitrate reduction and Fe(II) oxidation demonstrated that the percentage of electrons contributed by Fe(II) to denitrification accounted for 16.2% and 32.9%, and the ratios of the electrons donated by Fe(II) to the electrons accepted by nitrate for N2O production were 43.7% and 130.7% in the two soils with low and high Fe(II) concentration, respectively. The ratio beyond 100% implies that the electrons donated by high Fe(II) concentration exceed the electron demand for N2O production, which lead to the further reduction of N2O to N2. In conclusion, Fe(II) oxidation coupled to denitrification affects N2O emissions via electron donation, and Fe(II) in a high concentration bears great potential for efficient denitrification and low N2O emissions from paddy soils
Enzyme activities and organic matter mineralization in response to application of gypsum, manure and rice straw in saline and sodic soils
No full textSoil organic matter priming and carbon balance after straw addition is regulated by long-term fertilization
No full textStraw incorporation is crucial to soil organic carbon (SOC) sequestration, thus improving soil fertility and mitigating climate change. The fate of straw C and the associated net SOC balance remain largely unexplored, particularly in soils subjected to long-term mineral and organic fertilization. To address this, soil (δ13C: –19‰) that had been continuously cropped with maize for 31 years and subjected to five long-term fertilization regimes, including (i) control (Unfertilized), (ii) mineral fertilizer (NPK) application, (iii) 200% NPK (2 × NPK) application, (iv) manure (M) application, and (v) NPK plus manure (NPKM) application, was incubated with or without addition of rice straw (δ13C: –29‰) for 70 days. Straw addition largely primed SOC mineralization. The priming effect (PE) was considerably higher in 2 × NPK (+122% of CO2 from soil without straw addition) but lower in M (+43%) relative to the unfertilized soil (+82%), highlighting the importance of fertilization in controlling PE intensity. Fertilization increased the straw-derived microbial biomass C by 90–577% and straw-derived SOC by 34–68% compared to the unfertilized soil, primarily due to the increased abundance of Gram-negative bacteria and cellobiohydrolase activity. Straw-derived SOC was strongly positively correlated with straw-derived microbial biomass C, suggesting that dead microbial biomass (necromass) was a dominant precursor of SOC formation. Consequently, fertilization facilitated microbial utilization of straw C and its retention in soil, particularly in the M and NPKM fertilized soils. The amounts of straw-derived SOC overcompensated for the SOC losses by mineralization, resulting in net C sequestration which was highest in the NPK fertilized soil. Our study emphasizes that NPK fertilization decreases the intensity of the PE induced by straw addition and increases straw C incorporation into SOC, thus facilitating C sequestration in agricultural soils
A multi-layer steganographic method based on audio time domain segmented and network steganography
No full textLabile organic matter intensifies phosphorous mobilization in paddy soils by microbial iron (III) reduction
No full textCarbon budget and greenhouse gas balance during the initial years after rice paddy conversion to vegetable cultivation
No full textReply to: "A global survey of alternative splicing of HBV transcriptome using long-read sequencing" (Letter)
No full textWe read with delight and great interest the latest work by Professors Chen, Lu and their colleagues that confirmed some of the major findings reported in our recently published article, in which multiomics approaches were applied to study HBV-host interactions.1,2 Specifically, through the use of a third-generation sequencing (Iso-seq) technique that enabled the direct sequencing of long transcripts, the authors not only identified known HBV transcripts, but also discovered many previously under-characterized splicing products of HBV RNAs. Among them, of particular interest were the isoforms that resulted from RNA splicing events, A2,446T2,447/G489 and A2,446T2,447/T2,902, which were found to account for 7.3% and 3.5%, respectively, of all the spliced HBV RNA transcripts. These newly obtained data1,3,4 had thus directly substantiated the existence of the major RNA splicing events and products, based on which we showed that the translated products, HBxZ and HpZ, restricted HBV gene expression and replication, and likely contributed to the self-restrictive nature of HBV infection.2 While highlighting the fruitfulness of embracing and applying more novel techniques to investigate HBV-host interactions, these discoveries have unequivocally proven the extra coding potential of the HBV genome, which was under-appreciated.No Full Tex
Comparison of N2O and CO2 concentrations and fluxes in the soil profile between a Gray Lowland soil and an Andosol
No full textWe measured N2O and CO2 fluxes from the soil surface and in the soil through a depth of 0.3 m, and their concentration profiles through a depth of 0.6 m in both a Gray Lowland soil with macropores and cracks and an Andosol with undeveloped soil structure in central Hokkaido, Japan. The objective of this study was to elucidate the difference of N2O production and flux in the soil profile between these two soil types. In the Gray Lowland soil, the N2O concentration above 0.4 m increased with an increase in soil depth. In the Andosol, there were no distinctive N2O concentration gradients in the topsoil when the N2O flux did not increase. However, the N2O concentration at a depth of 0.1 m significantly increased and this concentration was higher than the concentration below 0.2 m when the N2O flux greatly increased. The N2O concentration profiles were thus different between these two soils. The contribution ratios of the N2O produced in the top soil (0-0.3 m depth) to the total N2O emitted from the soil to the atmosphere in the Gray Lowland soil and the Andosol were 0.86 and 1.00, respectively. It indicates that the N2O emitted from the soil to the atmosphere was mainly produced in the top soil. However, the contribution ratio of the subsoil to the N2O emitted from the Gray Lowland soil was higher than that of the Andosol. There was a significant positive correlation between the N2O flux through a 0.3 m depth and the flux from the soil to the atmosphere in only the Gray Lowland soil. These results suggest that N2O production in the subsoil of the Gray Lowland soil could have been activated by NO^[-]_[3] leaching through macropores and cracks, and subsequently the N2O produced in the subsoil could have been rapidly emitted to the atmosphere through the macropores and cracks
Development of a low cost micro fuel cell complete with power conversion
No full textThe objective of the report was to design and fabricate a low cost micro fuel cell stack (μPEMFC). The author reviewed the components and technical considerations to take note in the design of the PEMFC which will affect the performance. Five main areas to tackle were the material selection, mechanical strength, electrical conductivity, sealing of the fuel cell and geometrical considerations.
A low cost μPEMFC was developed with the bipolar plate combination of stainless steel porous metal foam and stainless steel plate. The porosity of the stainless steel porous metal foam reduces additional machining process and simplifies the design by eliminating the need to incise flow channels. A prototype was fabricated using the Computer Numerical Cutting (CNC) machine and the fuel cell was operated in the dead-end mode. The size of the fuel cell was approximated to be that of a D-size battery for portability purposes.Bachelor of Engineering (Mechanical Engineering
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