微扩散法是测定氮转化过程中铵态氮、硝态氮的15N稳定同位素的重要方法。自20世纪50年代Conway提出微扩散法的基本原理后，随着分析技术的迅速发展，微扩散法与质谱仪测定技术相结合，被广泛应用在环境、生态和农业领域中土壤、水体等样品的测定。虽然微扩散法与传统蒸馏法相比优点明显，但其测定结果的准确性、精密性仍受氮回收量、同位素分馏、外源性和内源性的杂质氮污染等因素的影响。如何优化扩散体系，提高测定的准确度是当前微扩散法应用的关注重点。本文综述了影响微扩散法的多种因素，并总结了优化微扩散体系的方法，以期推动微扩散法在我国氮素转化研究中的应用。%Since Conway first outlined fundamental principles of micro-diffusion technique in 1957, it was then adapted to prepare samples for15N isotope measurements. Currently it has been widely developed for nitrogen isotope measurements on ammonium (NH4+) and nitrate (NO3–) in solid and aqueous samples. Compared with traditional distillation method, micro-diffusion technique is advocated because it eliminates cross contamination and requires less operator skill and time. However, the accuracy and sensitivity of this technique is still limited by some factors, including N recovery, isotopic fractionation and blank size. Another main limitation of micro-diffusion is that the results can’t be obtained immediately because diffusion is typically performed for at least one to several days. Thus, how to improve the sensitivity and accuracy of this technique and accelerate the diffusion process have become key research focuses. In this paper, aiming to promote using micro-diffusion technique in research of soil nitrogen transformation, the primary principles and factors impacting this technique were briefly summarized and introduced.
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