反硝化细菌法结合痕量气体分析仪/同位素比质谱仪分析水体硝酸盐氮同位素组成

摘要

建立了反硝化细菌法结合疫量气体分析仪(TraceGas)/同位素比质谱仪分析水体硝酸盐氮同位素组成的方法.对反硝化细菌生长、培养条件和方法的精密度及稳定性进行了分析,并利用标准样品USGS34研究了样品反硝化孵育时间、TraceGas捕集N2O气体时间对δ15N测定的影响.结果表明:恰当的氧气量才能培养出有效的反硝化细菌；本方法精密度及稳定性较好,同一制备时间内硝酸盐δ15N的SD在0.09‰～0.14‰之间,6个月内SD为0.12‰；样品反硝化孵育3～24 h可以得到稳定的δ15N; TraceGas捕集时间为500 s时得到的δ15N校正值与真实值最接近.应用本方法对养殖场污水和灌溉井水的硝酸盐δ15N进行了测定.%A method based on denitrifying with TraceGas and Isotope Ratio Mass Spectrometry (IRMS) has been developed for the determination of nitrogen isotopic composition of nitrate in water samples. Bacterial growth, culture conditions and the precision, stability of method were investigated. The sample incubation time and trapping time by TraceGas affecting δ15N were examined using standard reference material USGS34. It is very important to obtain bacterial growth success by controlling the volume of oxygen in the culture. The method has good precision and stability with the standard deviations (SD) from 0. 09%o to 0. 14%o in the same sample preparation time and 0. 12%o in 6 months. The values of δ15N were almost the same from 3 h to 24 h for the sample incubation time course. 500 s was the best trapping time by TraceGas for the smallest difference between corrected values and real values. The δ15 N yaiues of nitrate in the livestock wastewater and irrigating water were measured by this method.