分类： 地球科学 >> 地理学 提交时间： 2021-06-04 合作期刊: 《干旱区科学》
摘要： The soil type is a key factor influencing N (nitrogen) cycling in soil; however, gross N transformations and N2O emission sources are still poorly understood. In this study, a laboratory 15N tracing experiment was carried out at 60% WHC (water holding capacity) and 25ºC to evaluate the gross N transformation rates and N2O emission pathways in sandy loam and silt loam soils in a semi-arid region of Heilongjiang Province, China. The results showed that the gross rates of N mineralization, immobilization, and nitrification were 3.60, 1.90, and 5.63 mg N/(kg•d) in silt loam soil, respectively, which were 3.62, 4.26, and 3.13 times those in sandy loam soil, respectively. The ratios of the gross nitrification rate to the ammonium immobilization rate (n/ia) in sandy loam soil and silt loam soil were all higher than 1.00, whereas the n/ia in sandy loam soil (4.36) was significantly higher than that in silt loam soil (3.08). This result indicated that the ability of sandy loam soil to release and conserve the available N was relatively poor in comparison with silt loam soil, and the relatively strong nitrification rate compared to the immobilization rate may lead to N loss through NO3– leaching. Under aerobic conditions, both nitrification and denitrification made contributions to N2O emissions. Nitrification was the dominant pathway leading to N2O production in soils and was responsible for 82.0% of the total emitted N2O in sandy loam soil, which was significantly higher than that in silt loam soil (71.7%). However, the average contribution of denitrification to total N2O production in sandy loam soil was 17.9%, which was significantly lower than that in silt loam soil (28.3%). These results are valuable for developing reasonable fertilization management and proposing effective greenhouse gas mitigation strategies in different soil types in semiarid regions.
分类： 化学 >> 物理化学 提交时间： 2017-11-05 合作期刊: 《结构化学》
摘要： One novel phenoxyacetamide derivative (C22H28N2O3, Mr = 368.47) has been synthesized and determined by means of NMR spectroscopy, high resolution mass spectra and single-crystal X-ray diffraction. The single crystal belongs to the monoclinic system, space group Cc with a = 14.910(3), b = 14.592(3), c = 38.683(8) Å, β = 100.37(3)°, V = 8279(3) Å3, Z = 16, Dc = 1.183 g/cm3, F(000) = 3168, μ = 0.079 mm-1, MoKα radiation (λ = 0.71073 Å), the final R = 0.0508 and wR = 0.0666 for 4120 observed reflections with I > 2σ(I). There are four independent molecules in an asymmetric unit cell. The four symmetry-independent molecules have a variety of different conformations indicating considerable conformational freedom. The bioassay results indicated that the title compound displayed effective activities against glutamine-induced neurotoxicity in PC12 cells and significantly prolonged the survival time of mice subjected to acute cerebral ischemia.
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