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

为了解中海咸水湖亚表层水体中硝化和反硝化作用在氧化亚氮（N2 O）积累中的作用，通过培养试验研究了溶解氧（DO）浓度对硝化和反硝化作用的影响.硝化产N_2O活性（N_2O_N）随DO浓度的降低而显著增加。低DO（10-30%饱和度）导致高N_2O_N。反硝化产N_2O活性（N_2O_D）随DO浓度的降低而降低。在低溶解氧条件下，反硝化过程中N_2O的积累量很小，这是由于N_2O被进一步还原为N_2的缘故。从日本神池半咸水沉积物中分离到两株产N_2O细菌：气单胞菌和弧菌。气单胞菌和弧菌的最适生长盐度分别为0-20和10-20 psu。这两个菌株都是嗜盐的咸水区有利。效果 ...更多信息 研究了H_2S对这些菌株产生和积累N_2O的影响。气单胞菌和弧菌积累N_2 O的活性分别在1-5 mgS/L和1-10 mgS/L的H_2S浓度下得到促进。H_2S是N_2O积累的重要因素，本文建立了一种新的、简便的测定环境水样中羟胺的方法。将装有样品水的玻璃小瓶用丁基橡胶塞和铝盖密封，没有顶部空间，然后通过注射器将次氯酸钠溶液注入小瓶中，以将羟胺转化为一氧化二氮。玻璃瓶的顶空用99.9%的N_2用气密注射器制备。气相中的一氧化二氮通过具有电子捕获检测器的气相色谱仪测量。根据溶解度公式计算液相中溶解的一氧化二氮。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