Gasbench Ⅱ-IRMS升级N_2O预富集装置测定海水硝酸盐的氮氧同位素

N_2O preconcentration device upgraded for Gasbench Ⅱ-IRMS analyzing N and O isotopes of seawater nitrate

本研究研制了由气压棒、气体控制阀、不锈钢管冷阱、石英毛细管冷阱、杜瓦瓶、化学阱等构成的N_2O预富集装置,通过扩展GasbenchⅡ功能控制冷阱的升降,改造气体回路、进样针和样品盘,实现N_2O的预富集以及GasbenchⅡ自动进样与IRMS联机测定.通过将海水中的硝酸盐经化学方法转化成N_2O,建立了海水硝酸盐氮、氧同位素的分析方法.研究表明,所建立方法对海水硝酸盐氮、氧同位素的分析具有很好的精度,硝酸盐δ^(15)N、δ^(18)O及峰面积的相对标准偏差分别小于1%、3%和5%.对采自南极普里兹湾海水样品中硝酸盐氮、氧同位素的分析结果与文献报道值吻合,也与海水硝酸盐氮、氧同位素组成的变化规律相一致,证明所建立的技术方法可成功运用于海水硝酸盐氮、氧同位素的分析.

;The preconcentration device for N2O analysis was upgraded and assembled by a series of components, including air pressure bar, gas control valve, stainless steel cyro trap, fused silica capillary cyro trap, dewar, chemical trap and etc. The function of Gasbench Ⅱ was extended to control the lifting of cyro traps while the gas circuit, sampling syringe, and sample plate were altered to realize the online determination with N20 preconcentration device ,Gasbench Ⅱ and IRMS. Nitrate was chemically converted to N20 to build the method for analysis of N and 0 isotope in seawater nitrate. Our results showed that the developed method has a very good precision. The standard deviation of δ^15N, δ^18O and peak area of nitrate was less than 1%,3 % and 5 % , respectively. The N and 0 iso-topes of nitrate in seawater collected from the Prydz Bay, Antarctica, were measured with this method. The values of δ^15N, δ^18O of nitrate obtained were agreed well with literature reports. The profiles of δ^15N, δ^18O of nitrate in the Prydz Bay showed the typical characteristics of the ocean. The developed technique for analyzing N and O iso-topes of seawater nitrate was feasible.