基于稳定同位素自然丰度技术的土壤氧化亚氮产生与排放过程研究进展

氧化亚氮(N₂O)是主要的温室气体之一，并且对平流层臭氧层分解起到重要作用。土壤中N₂O的产生和排放过程复杂多样，对其进行精准溯源与过程区分有助于制定减排策略。稳定同位素自然丰度技术利用N₂O的同位素值δ15Nbulk(N₂O中15N在整体水平上的同位素特征值)、δ18O(N₂O中18O在整体水平上的同位素特征值)以及δ15Nsp(N₂O分子内15N的位点特异性同位素值)，可以示踪N₂O来源、指示N₂O产生的微生物作用途径，在N₂O转化过程溯源中已取得重要进展。而同位素分馏效应是稳定同位素自然丰度技术应用的理论基础，其中微生物过程及其导致的同位素分馏是需要重点关注的问题。本研究概述了同位素分馏效应在N₂O的产生、排放过程中的研究进展及其主要影响因素，梳理了同位素特征值δ15Nbulk、δ18O和δ15Nsp在分析N₂O来源的研究进展，并且提出了影响准确区分过程的因素。因素包括单一产生路径的同位素特征值范围广、不同产生路径的同位素特征值范围的重叠、反应底物同位素组成的变化以及与N₂O还原相关的分馏因子的可变性等问题。明确了今后需加强δ15Nsp等N₂O同位素特征值分馏效应的测定，利用组合同位素特征值及先进手段进行全面的N₂O溯源研究。图2参80

Stable isotope natural abundance techniques in the studies on nitrous oxide production and emission processes: a review

Nitrous oxide (N₂O) is one of the potent greenhouse gases and also plays an important role in ozone layer decomposition. N₂O production and emission processes in soil are complexed. Therefore, accurate source partitioning will help to constrain emission budgets. The application of stable isotope natural abundance technique have stimulated significant progress in N₂O source partitioning and promoted identification in various N₂O microbial production processes, which make use of various N₂O isotope signatures δ15Nbulk(the average of15N), δ18O(the average of 18O) and δ15Nsp(site preference of 15N in different positions of N₂O molecule). However, some factors also add uncertainties to N₂O source partitioning, such as the range of isotope signatures, changes of isotope composition, and various fractionation factors associated with N₂O reduction. It is also noteworthy that microbial processes and related isotopic effects are critical. In this review, the isotopic effects during N₂O production and reduction and related factors are summarized; advances in approaches for N₂O source-partitioning are concluded, including isotope natural abundance and isotopomer methods. The review focused on the progress of isotopic signatures δ15Nbulk, δ18O and δ15Nsp value in constraing N₂O sources. In the future, the measurement of isotope fractionation, a combination of isotope signatures and advanced methodologies are advised for better studying N₂O sources and pathways. [Ch, 2 fig. 80 ref.]