基于15N稳定同位素技术的斜生栅藻对硝氮和氨氮吸收研究

硝氮(NO3--N)和氨氮(NH4+-N)是水体中无机氮的主要形态。利用15N稳定同位素技术研究了斜生栅藻(Scendesmus obliquus)对NO3--N和NH4+-N的吸收特征。结果显示,在相同浓度条件下,斜生栅藻对NH4+-N的吸收速率显著高于对NO3--N的吸收率,在180min的试验中,对15NH4+-N的吸收速率为0.62～1.15μmol/(g·min);对15NO3--N的吸收速率为0.08～0.15μmol/(g·min)。在NO3--N和NH4+-N2种形态氮源同时存在的混合组中,斜生栅藻对NO3--N的吸收速率0.12～1.00μmol/(g·min)]显著低于NO3--N作为唯一氮源的单一组0.78～1.23μmol/(g·min)],表明NH4+-N的存在对藻类吸收NO3--N有抑制作用。在14NO3--N和15NO3--N同时存在时,斜生栅藻优先吸收14NO3--N,产生同位素分馏效应,但不同形态氮对藻类氮吸收的影响远远大于同位素的影响。

The study on uptake of nitrate and ammonium by Scendesmus obliquus based on 15N stable isotope technique

Abstract: Nitrate (NO3 -N) and ammonium (NH4+-N) nitrogen are the main forms of inorganic nitrogen in waters. This paper studied the uptake characteristics of NO3 -N and NH4+-N by Scendesmus obliquus based on 15N stable isotope technique. The result shows that the NH4+-N uptake rate was significantly higher than NO3 -N uptake rate at the same nitrogen concentration; The NO3 -N uptake rate in the mixed nitrogen group in which both NO3 -N and NH4+-N presented was significantly lower than that in the single nitrogen group in which only NO3 -N presented, indicating that the presence of NH4+-N inhibits the uptake of NO3--N. The result also shows that when 15NO3--N and 14NO3--N existed simultaneously, Scendesmus obliquus took up 14NO3--N preferentially which produces isotope fractionation. However, the effect of different form of nitrogen source is far greater than the effect of isotope fractionation.