河口区养殖塘水-气界面N_(2)O扩散通量比较

Comparison of floating chamber and diffusion model methods in determining diffusive N_(2)O fluxes across water-atmosphere interface in estuary aquaculture ponds.

以闽江河口区水产养虾塘为研究对象,于2017年6~11月,采用漂浮箱法和扩散模型法同步原位观测了养殖塘N_(2)O排放通量.结果表明,研究期间悬浮箱法和扩散模型法获得的养殖塘水-气界面N_(2)O通量变化范围分别为(0.38±0.05)~(20.63±5.63)μg/(m^(2)·h)和(2.77±0.52)~(17.23±2.27)μg/(m^(2)·h),随时间推移均呈现“增加-降低-增加-降低”的双峰变化特征.两种方法观测的N_(2)O通量均与水温、水体硝酸盐氮(NO3--N)和氨氮(NH_(4)^(+)-N)浓度呈现显著正相关关系(P<0.05),与水体溶解氧(DO)呈现出显著负相关关系(P<0.05).悬浮箱法与不同扩散模型法测定的N_(2)O排放通量大小排序表现为:模型DMRC01>悬浮箱法>模型DMCL98>模型DMW92a>模型DMMY95>模型DMCW03>模型DMLM86.相比其他几种模型方法,模型RC01与悬浮箱法测得的养殖塘水-气界面N_(2)O通量相关性系数最高.本研究结果初步表明,今后进行东南沿海河口区养殖塘N_(2)O通量的大尺度观测研究时,可考虑选择RC01模型法来代替悬浮箱法进行测定,进而减小人力及物力的投入.

The floating chamber technique(FC)and the diffusion model methods(DMs)are the two primary methods widely used for quantifying the fluxes of CO2,CH4 and N_(2)O across the water-atmosphere interface from aquatic ecosystems,while the comparability of two methods is largely unknown.In this study,FC and DMs models of gas transfer velocity were applied to determine N_(2)O fluxes in the aquaculture ponds in Min River Estuary,southeast China over aquaculture period(from June to November 2017).N_(2)O fluxes measured by FC and DMs changed in the ranges of(0.38±0.05)~(20.63±5.63)μg/(m^(2)·h)and(2.77±0.52)~(17.23±2.27)μg/(m^(2)·h),respectively.The temporal variations in N_(2)O fluxes measured by the two methods were similar,both showing a double-peak pattern during the study period.The N_(2)O fluxes were positively correlated to water temperature,NO3--N and NH_(4)^(+)-N(P<0.05),but negatively correlated to the water dissolved oxygen(DO)concentration in the ponds(P<0.05).N_(2)O fluxes measured by different methods decreased in the order:DMRC01>FC>DMCL98>DMW92a>DMMY95>DMCW03>DMLM86.The correlation coefficient of N_(2)O fluxes between FC and DMs-RC01 was larger than those between FC and other methods.Our results suggested that the DMRC01 model can be used to replace the FC for measuring N_(2)O fluxes in the aquaculture ponds in southeast China,with the lest cost of manpower and logistics.