New development in natural abundance determination of 15N (δ15N）in ammonium nitrogen
Ammonium nitrogen (NH4+-N)is a major Nitrogen source for plants and microbs and a main form of active nitrogen input into environment. The natural abundance of 15N（δ15N）plays an important role in estimation of nitrogen source and its transformation in terrestrial ecosystem, water ecosystem and atmospheric sedimentation.
The current method inδ15N determination is quite complicated, time consuming and need big samples.
Under the guidance of Prof Yunting Fang, a doctorial student Dongwei Liu in our institute has developed a new method in δ15N determination. In the new method, hypobromite（BrO-） oxidation was combined with hypoxylammonium reduction, transforming NH4+ into N2O and then Stable Isotope Ratio Mass Spectrometer（PT-IRMS） is used to measure δ15N and calculate ammonium nitrogenδ15N in the sample.
The advancement of the new method :1) Easy to operate. Ammonium nitrogen extraction from samples is omitted.2) Sample solution can be small(less than 4 ml) and thin（0.6 ~ 2 nmol. 3）Safe. Toxic and volatile reductant triazoic acid and denitrifying bacteria are no more used.