溶氧波动对湖泊沉积物氧化亚氮产生和氮物质转化的影响

Effects of diurnal variation of dissolved oxygen on nitrous oxide production and nitrogen cycling in lake sediments

沉水植物光合呼吸作用能够造成浅水湖泊溶氧(dissolved oxygen,DO)浓度的昼夜变化,并可能对湖泊氮物质转化和氧化亚氮(N_2O)排放产生影响.研究了短期DO浓度变化对富营养化浅水湖泊沉积物N_2O产生和N物质转化的影响.结果表明,相对于空白对照组(DO浓度为3.0~4.0 mg/L时),当处理组水体DO浓度昼夜波动为2.0~12.0 mg/L时,水体N_2O浓度和沉积物N物质含量均出现显著变化,其中处理组N_2O浓度显著高于空白对照组,而氮气(N_2)浓度则明显降低.此外,处理组水体和沉积物总氮(total nitrogen,TN)和氨氮(NH_4-N)浓度均显著降低,而硝态氮(NO_3-N)浓度则呈现增加趋势.实验结束后,处理组沉积物潜在氨氧化率、潜在亚硝酸氧化率、潜在硝化速率和潜在反硝化速率都显著上升.

Photosynthesis and respiration of submerged macrophytes play important roles in determining the diurnal variation of dissolved oxygen(DO)concentrations in shallow lakes.This diel DO variation can in turn affect nitrous oxide(N2O)emissions and nitrogen(N)cycling in lakes.Batch experiments were performed to measure N2O and nitrogen concentrations with varied DO concentrations.Sediment cores are collected from a large,shallow eutrophic lake with submerged macrophytes enriched in the lake.Higher N2O and lower nitrogen gas(N2)concentrations were observed at the diurnal varied DO concentrations(2.0~12.0 mg/L)as compared with the relative steady DO concentration(3.0~4.0 mg/L)tests.The diurnal varied DO concentrations in this study showed significant promoted effect on total nitrogen(TN)and ammonia nitrogen(NH4-N)removal.It was found that the major cause of more N2O production and higher TN removal at varied DO concentration was due to higher nitrification and denitrification rates.The results of this study suggest that diurnal varied DO concentration may increase N2O emission and promote N removal from shallow eutrophic lakes.