~(15)N示踪法测定海洋反硝化速率中~(29)N_2浓度的准确定量

利用15 N示踪法实测南海水体反硝化速率的研究发现,培养水样在长时间密闭放置过程中也会受到外界空气的污染,且其29N2/28N2比值恒定为0.007 35。根据空气背景中29N2/28N2比值恒定的特征,提出基于质量平衡关系校正空气N2污染的方法,通过将样品实测29N2浓度扣除由外界空气贡献的29N2浓度,可获得由生物反硝化作用所产生的29N2准确浓度,进而可计算出准确的反硝化速率。经空气29N2背景校正后,29N2浓度的偏差明显小于未经校正的结果,且29N2浓度与培养时间之间的线性相关性显著加强,凸显出空气29N2背景校正是获取准确反硝化速率的关键。鉴于15 N示踪法已被广泛应用于海洋水体与沉积物反硝化速率的测定中,所提出的空气29N2背景校正方法具有重要的意义。

Accurately quantification of 29N2 concentration in 15N tracer derived marine denitrificaiton rates

¹⁵N tracer technique was widely applicated in measuring water column denitrification rate in water samples,however,the sealed samples could be contaminated by air during a long time storage. Our study suggested that N₂ in air has a constant ²⁹N₂/²⁸N₂ ratio of 0.007 35. According to this feature,a mass-balance calculation was proposed to calibrate the interference from air background. It helps obtain more accurately ²⁹N₂ concentrations produced by biological activity and further the denitrification rates. After the calibration,the deviations of ²⁹N₂ concentrations were much less than those of the raw data,and the linear correlation between ²⁹N₂ concentration and the incubation time was more significant. It is important to calibrate extra ²⁹N₂ signals from air contamination for accurately quantification of denitrification rate,considering the ¹⁵N technique has been widely used in pelagic and beneath denitrification rate measurements.