水体颗粒物对有机氮转化的影响

以多泥沙河流黄河为例,采用微宇宙实验模拟研究自然水体中有机氮的转化过程和添加人工富集的黄河优势菌种条件下的有机氮转化过程.结果表明,自然水体条件下颗粒物对有机氮的转化有明显的促进作用,转化速率常数随颗粒物含量的增加而增加,用一级动力学拟合有机氮的转化过程发现,当有机氮的初始浓度为5 mg/L,颗粒物含量分别为0、5、10 　g/L时,转化速率常数分别为0.286、0.333、0.538 d^-1,用Logistic模型对硝化过程进行模拟,硝化速率常数K₄分别为0.001 8、0.003 8,0.005 0 L·(d·μmol)^-1.在添加人工富集微生物条件下,微生物初始数量一致,体系有机氮的转化速率常数和硝化速率常数K₄均随颗粒物含量的增加而增加.水体颗粒物对有机氮转化的影响机理是：①颗粒物含量不同的水体其初始微生物数量不同,颗粒物含量越高,微生物数量也越大;②颗粒物对微生物生长有促进作用,微生物亦主要存在于颗粒物表面,且颗粒物的存在使水体有机氮主要存在于颗粒相,有机氮的转化主要发生在水-颗粒物界面;③颗粒物的存在增加了微生物与有机氮的接触几率,促进了有机氮的转化.

Effect of Suspended Sediment on the Transformation of Organic Nitrogen

Microcosm experiments have been carried out to study the effects of suspended sediment on the transformation of organic nitrogen contaminants under different conditions, including with and without spiking bacteria to the water-sediment system. When with the natural water and sediment as cultivation media and without spiking bacteria to the water system, the presence of sediment could stimulate the transformation of organic nitrogen, and the transformation rates were correlated well with the sediment concentration. When the initial concentration of organic nitrogen in the water system was 5 mg/L, and the suspended sediment content were 0, 5 and 10 g/L, the first-order transformation rate constants of organic nitrogen were 0.286,0.333 and 0.538 d(-1), respectively; the nitrification rate constants (K4) were 0.001 8, 0.003 8 and 0.0050 L x (d x micromol)(-1), respectively, when fitting the nitrification process with the Logistic kinetics. When spiking the water systems with the same initial bacteria density, the first-order transformation rate constants of organic nitrogen and nitrification rate constants (K4) increased with the sediment content. With the natural water and sediment as cultivation media, the mechanism regarding the effects of suspended sediment on organic nitrogen transformation includes the following aspects: (1) The initial amount of bacteria increased with the sediment content in the water system. (2) The growth of bacteria was promoted by the sediments, and bacteria tended to attach to the sediment. In addition, most of organic nitrogen was attached to the sediment phase and the transformation of organic nitrogen in the water system mainly occurred at the sediment/water interface. (3) The presence of sediment increased the contact chances between bacteria and organic nitrogen, thus stimulated the transformation of organic nitrogen contaminants.