鄱阳湖水体氧化亚氮排放特征及影响因素

Characteristics of nitrous oxide( N_2O) emissions and the related factors in Lake Poyang

于2014年4、7和10月以及2015年1月(分别代表春、夏、秋和冬季)对鄱阳湖13个常规监测点表层水体中氧化亚氮(N_2O)浓度进行测定,并选择合适的模型估算其释放量.结果表明,鄱阳湖全年N_2O平均浓度为32.57±17.35 nmol/L,总体处于过饱和状态,平均饱和度为256.83%±129.05%.鄱阳湖N_2O年平均交换通量为0.83±0.69μmol/(m2·h).鄱阳湖水体N_2O季节性释放规律为春季最高,平均交换通量为1.71μmol/(m2·h),其次是夏季和冬季,秋季最低.从空间上来看,春季北部湖区交换通量显著高于南部湖区.相关性分析表明,铵态氮浓度是影响夏季和冬季鄱阳湖水体N_2O产生的主要因素.结合水域面积初步估算出全年释放N_2O约1.29×107mol,其中春季和夏季是鄱阳湖水体N_2O释放的高峰期,总释放量约占全年的80.40%.全年通过N_2O输出氮素约为361.93 t,对鄱阳湖流域内N_2O分布及质量平衡具有一定影响.

Surface water surveys were carried out seasonally in Lake Poyang from April 2014 to January 2015. Concentrations of nitrous oxide （N2O） in thirteen sampling sites were measured followed by calculation of N2O emission fluxes with interface diffusion model. The N2O concentration in the surface water of Lake Poyang averaged 32.57±17.35 nmol/L with an average saturation of 256.83%±129.05%, which implied a state of N2O-supersaturated. The N2O flux from water to air was calculated to be 0.83±0.69μmol/（ m^2 · h） on the average. The highest N2O flux appeared in spring with an average level of 1.71 μmol/（ m^2 · h） , followed by the summer, winter and autumn in a descending order. In spring, N2O emission rates were significantly higher in the north part of the lake than in the south part. Regression analysis indicated that ammonium in water column had great control effect on N2O production in summer and winter. About 1.29≤10^7 mol N2O was emitted from Lake Poyang annually, of which 80.40% emission was in spring and summer. The N2O-N output of Lake Poyang was estimated in 361.93 t per year, and plays an important role in the N2O distribution in the Poyang basin.