不同磷条件下塔玛亚历山大藻氮的生态幅

藻类氮的生态辐是指在一定氮浓度范围内藻类能生长和繁殖的浓度范围。它由藻类生长的最佳氮浓度、氮适宜生长范围和氮耐受限度构成。为了定量计算藻类的氮生态幅,在室内培养条件下,研究了低磷(0.48μmol/L)、中磷(0.97μmol/L)和高磷(1.45μmol/L)3种不同磷起始浓度条件下不同氮对塔玛亚历山大藻细胞数和最大比生长率的影响,依据Shelford耐受性定律建立了塔玛亚历山大藻生长的氮耐受性模型,并得到了藻类生长的最佳氮浓度、氮适宜生长范围和氮耐受范围的定量表达。结果表明,在低磷、中磷和高磷条件下,当氮浓度小于适合藻类生长的最佳氮浓度时,藻类细胞数和最大比生长率均随着氮浓度的增大而增大;当氮浓度大于适合藻类生长的最佳氮浓度时,藻类细胞数和最大比生长率均随着氮浓度的增大而减小。藻类生长的氮耐受性模型与谢尔福德耐受定律较为吻合,定量得到在低磷、中磷和高磷培养条件下塔玛亚历山大藻的最佳氮浓度分别为30.36、62.07和77.85μmol/L;氮适宜生长范围分别为18.30—42.42、37.71—86.43和41.52—114.18μmol/L;氮耐受限度分别为6.24—54.48、13.35—110.79和5.19—150.51μmol/L。研究显示不同磷起始浓度条件下,藻类的氮生态幅也不相同。

斜生栅藻在不同磷条件下氮生态幅的研究

为获得斜生栅藻(Scendesmus obliquus)的氮生态幅,研究根据中华人民共和国地表水环境质量标准磷浓度界定,利用谢尔福德(Shelford)耐受定律进行曲线拟合对斜生栅藻在低磷(0.02 mg/L)、中磷(0.2 mg/L)和高磷(0.4 mg/L)三种不同磷浓度下氮的生态幅进行定量表达,获得三种磷起始条件下斜生栅藻生长的最佳氮浓度、氮适宜生长范围和氮耐受范围。研究表明,在三种磷条件下斜生栅藻生长的最佳氮浓度分别为1.02、8.91和18.05 mg/L,对应的最大比生长速率分别为(0.142±0.006)、(0.314±0.002)和(0.346±0.007)/d,氮适宜生长范围分别为(0.52—1.52)、(4.48—13.34)和(11.72—24.38)mg/L,氮耐受限度分别为(0.02—2.02)、(0.05—17.77)和(5.39—30.71)mg/L。这表明富营养化水体可能引起斜生栅藻的大量生长、繁殖,也暗示了斜生栅藻能作为高氮水环境的一个良好指示生物。

Effects of flux on crystal structure and luminescent properties of nitroxides phosphors

Yellow-green-emitting Sr Si2O2N2:Eu2+phosphors were synthesized with Sr2Si O4:Eu2+as precursor.The effects of flux and the concentration of Eu2+on the crystal structure and luminescent properties of the phosphors were investigated.Results suggested that the optimal content of flux Na2CO3 was 1 wt%and the optimal doping concentration of Eu2+was 0.05 mol.The emission spectra showed the most intense peaks located at 535 nm which corresponded to the 4f65d→4f7 transition of Eu2+.The excitation spectra showed that these phosphors could be effectively excited by near-ultraviolet and blue light,whichwas consistent with the widely applied output wavelengths of near-ultraviolet and blue-white light-emitting diode(LED)chips.When the influence of flux on the luminescent properties of Sr Si2O2N2:Eu2+phosphor was analyzed,the X-ray diffraction(XRD)patterns indicated that the flux could help the crystallization of the phosphors.No other phases except the triclinic structure of Sr Si2O2N2 were formed.The thermal stability and the emission intensity of synthesized Sr Si2O2N2:Eu2+phosphor were examined and compared with commercial YAG yellow phosphors.All results indicate that the yellow-green-emitting phosphor is a suitable candidate for the fabrication of white LEDs.