Studies on nitrous oxide from oxidation-reduction boundary layer in brackish lakes

为了了解Nakaumi湖微咸水中硝化和反硝化作用在亚硝酸氮(N2O)积累中的作用，通过培养实验研究了DO浓度对Nakaumi湖水中N2O积累的影响。硝化作用产生N2O的活性(N2ON)随着DO浓度的降低而显著增加。低DO(10-30%饱和度)导致较高的N2ON，与硝化作用相反，反硝化产生N2O的活性(N2OD)随着DO浓度的降低而降低。在低DO条件下的反硝化过程中，由于N2O被进一步还原为N_2，几乎没有积累N_2O。从日本新日湖的咸水沉积物中分离到两株产N_2O的细菌，气单胞菌和弧菌。气单胞菌和弧菌生长的最适盐度分别为0-20和10-20PSU。这两个菌株都是嗜盐细菌，对微咸水地区有利。The Effect…研究了更多的H_2S对这些菌株产生和积累N_2O的影响。当H_2S浓度为1~5mGS/L和1~10mGS/L时，气单胞菌和弧菌对N_2O的积累均有促进作用。针对H_2S是N_2O积累的重要因素，建立了一种用次氯酸盐测定淡水河湖等环境水样中羟胺的新方法，并用气相色谱测定。在装有样品水的玻璃瓶中，用丁基橡胶塞子和无顶空的铝盖密封，然后通过注射器向玻璃瓶中注入次氯酸钠溶液，将羟胺转化为一氧化二氮。玻璃瓶的顶空是用气密性注射器在99.9%的氮气中制备的。用带有电子捕获检测器的气相色谱仪测定了气相中的一氧化二氮。根据溶解度公式计算了氧化亚氮在液相中的溶解量。较少

In order to understand the role of nitrification and denitrification in the accumulation of nitrous oxide (N_2O) in the hypolimnetic water of brackish Lake Nakaumi, the effects of dissolved oxygen (DO) concentration on these activities were investigated by incubation experiments. N_2O-producing activity by nitrification (N_2O_N) increased markedly with decreasing concentration of DO. Low DO (10-30% saturation) induced high N_2O_N. In contrast to nitrification, N_2O-producing activity by denitrification (N_2O_D) decreased with decreasing concentration of DO. Little N_2O was accumulated during denitrification under low-level conditions of DO, because of further reduction of N_2O to N_2.Two strains of N_2O-producing bacteria, Aeromonas sp.and Vibrio sp.were isolated from the sediment in brackish Lake Shinj, Japan. The optimum salinities for growth of Aeromonas sp.and Vibrio sp.were 0-20 and 10-20 psu, respectively. Both strains were halophile favorable for brackish water areas. The effect … More s of H_2S on the production and accumulation of N_2O by these strains were studied. N_2O-accumulating activities by Aeromonas sp.and Vibrio sp.were accelerated at 1-5 mgS/L and 1-10 mgS/L of H_2S concentrations, respectively. H_2S was an important factor for N_2O accumulation.A new and simple method for the determination of hydroxylamine in environmental water, such as fresh rivers and lakes using hypochlorite, followed by its gas chromatographic detection, has been developed. A glass vial filled with sample water was sealed by a butyl-rubber stopper and aluminum cap without head-space, and then sodium hypochlorite solution was injected into the vial through a syringe to convert hydroxylamine to nitrous oxide. The head-space in the glass vial was prepared with 99.9% grade N_2 using a gas-tight syringe. The nitrous oxide in the gas-phase was measured by a gas chromatograph with an electron-capture detector. The dissolved nitrous oxide in the liquid-phase was calculated according to the solubility formula. Less