摘要
^(15)N稳定同位素技术已经广泛应用于土壤、水体氮循环研究中,不同形态样品的^(15)N丰度是该类研究的关键数据。样品储存是实验过程中最基础也是极其重要的一步,储存过程中的不确定性可能影响样品^(15)N丰度。以不同气态和液态样品为对象,研究储存容器、温度、时间、样品前处理等因素对样品^(15)N丰度的影响。结果表明:对于气态样品,铝箔气袋稳定储存N_(2)O样品的时间很短,在第10天^(15)N丰度就明显发生变化;而螺口顶空瓶+丁基塞和钳口顶空瓶+丁基塞稳定储存时间可长达200 d左右。对于自然丰度的土壤浸提液,NO_(3)^(-)的^(15)N丰度在4℃和-20℃下可稳定储存10 d无明显变化,储存30 d则明显变化;而NH_(4)^(+)的^(15)N丰度在-20℃下可稳定储存60 d后才有明显变化,但在4℃下只能稳定储存10 d。对于^(15)N富集的土壤浸提液,NO_(3)^(-)的^(15)N丰度在稳定储存160 d后发生变化;但其NH_(4)^(+)的^(15)N丰度在-20℃下仅能稳定储存30 d,4℃下仅能稳定储存10 d。对于自然丰度的河水样品,其NO_(3)^(-)和NH_(4)^(+)的δ^(15)N值在4℃或-20℃下稳定储存10 d后均发生变化。储存条件会显著影响气态和液态样品的^(15)N丰度,这些研究结果为^(15)N稳定同位素研究中样品储存提供了科学依据。
【Objective】^(15)N isotope techniques have been widely used in investigating soil and water nitrogen transformation.The ^(15)N isotopic composition of NO_(3)^(-),NH_(4)^(+)and N_(2)O are key data for this type of study.These gas or liquid samples are usually stored before their concentrations or before ^(15)N abundance are determined.Nevertheless,improper storage processes may induce changes in these samples.However,the effect of storage conditions on the ^(15)N isotopic composition of the gas or liquid samples has not been well defined.【Method】The influence of storage container,temperature,sample pretreatment,time and other factors on the ^(15)N abundance of gaseous and liquid samples were studied in this paper.【Result】The stable storage time of N_(2)O samples in aluminum foil air bags is very short,and its δ^(15)N values significantly changed after 10-day storage.Also,the δ^(15)N values were stable in a screw-top vacuum vial+butyl septa and clamp headspace vial+butyl septa for about 200 days.For soil extracts with natural abundance,the δ^(15)N values of NO_(3)^(-)kept stable for about 10 days when refrigerated at 4℃ and frozen at -20℃,but its δ^(15)N values of NH_(4)^(+)remained stable for about 60 days and no more than 10 days when frozen at -20℃ and refrigerated at 4℃,respectively.Besides,for ^(15)N enriched soil extracts,the ^(15)N abundance of NO_(3)^(-)was stable for about 160 days,while the ^(15)N abundance of NH_(4)^(+)was only stable for about 30 days in -20℃ and less than 10 days in 4℃.For river samples,δ^(15)N values of NO_(3)^(-)and NH_(4)^(+)were only stable for about 10 days no matter whether the samples were refrigerated at 4℃ or frozen at-20℃.【Conclusion】Our results highlight the importance of storage conditions on ^(15)N abundance of gas and liquid samples,and provides scientific guidance for proper storage conditions when adopting ^(15)N isotope techniques.
作者
何梦秋
温腾
张金波
HE Mengqiu;WEN Teng;ZHANG Jinbo(School of Geography Science,Nanjing Normal University,Nanjing 210023,China;State Key Laboratory Cultivation Base of Geographical Environment Evolution(Jiangsu Province),Nanjing 210023,China;Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application,Nanjing 210023,China;Key Laboratory of Virtual Geographic Environment(Nanjing Normal University),Ministry of Education,Nanjing 210023,China)
出处
《土壤学报》
CAS
CSCD
北大核心
2022年第3期797-807,共11页
Acta Pedologica Sinica
基金
国家重点研发计划项目(2017YFD0200100)
国家自然科学基金项目(41977084)资助。