| 引用本文: | 吴书刚,周卫健,程鹏,侯瑶瑶.2026.碳同位素在示踪城市大气甲烷来源研究中的应用[J].地球环境学报,17(3):762-777 |
| WU Shugang,ZHOU Weijian,CHENG Peng,HOU Yaoyao.2026.Application of carbon isotopes in tracing methane sources in the urban atmosphere[J].Journal of Earth Environment,17(3):762-777 |
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| 碳同位素在示踪城市大气甲烷来源研究中的应用 |
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吴书刚1，2，3，周卫健1，2，4，程鹏1，2，侯瑶瑶1，2
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1.中国科学院地球环境研究所 黄土科学全国重点实验室,西安 710061 ；2.陕西省加速器质谱技术及应用重点实验室 西安加速器质谱中心,西安 710061 ；3.陕西关中平原区域生态环境变化与综合治理国家野外科学观测研究站,西安 710061 ；4.西安地球环境创新研究院,西安 710061
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| 摘要: |
| 大气甲烷（CH4）是仅次于二氧化碳（CO2）的第二大人为温室气体, 其来源结构的不确定性已成为制约城市CH4减排评估的关键科学问题。碳同位素（Δ14C和δ13C）为解析城市CH4来源提供了重要示踪手段。文章系统综述了碳同位素示踪城市大气CH4来源的基本原理、实验方法和应用进展。从原理上看, 化石源CH4不含14C（Δ14C = -1000‰）, 其排放会导致大气Δ14CH4降低, 从而可对化石源贡献进行定量示踪; 而不同生成途径（微生物、热成因、火成因）产生的CH4具有不同的δ13C特征, 可用于定性或半定量来源识别。方法上, 概述了大气CH4碳同位素分析的关键技术流程, 并总结了Keeling-plot、Miller-Tans方法及同位素质量平衡模型在来源解析中的应用。在此基础上, 归纳了城市主要CH4来源的δ13C和Δ14C特征范围, 并提出在城市多源混合背景下, 可构建基于Δ14C一级区分化石源/现代生物源, 并结合δ13C进一步细分现代生物源的双碳同位素分级解析框架, 以提升对城市CH4来源的解析能力; 同时, 综述了美国洛杉矶、英国伦敦、法国巴黎等典型城市的大气CH4同位素观测研究, 表明碳同位素方法在城市CH4来源定量解析中具有重要应用潜力。未来研究应重点提升大气14CH4观测能力, 加强Δ14C与δ13C协同观测, 并完善端元与本底数据, 以支撑城市尺度CH4排放评估与碳监测体系建设。 |
| 关键词: 大气甲烷 放射性碳同位素 稳定碳同位素 来源示踪 城市大气 |
| DOI：10.7515/JEE2024019 |
| CSTR：32259.14.JEE2024019 |
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| Application of carbon isotopes in tracing methane sources in the urban atmosphere |
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WU Shugang1，2，3，ZHOU Weijian1，2，4，CHENG Peng1，2，HOU Yaoyao1，2
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1. State Key Laboratory of Loess Science, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061 , China ；2. Shaanxi Provincial Key Laboratory of Accelerator Mass Spectrometry Technology and Application, Xi'an AMS Center, Xi'an 710061 , China ；3. Guanzhong Plain Ecological Environment Change and Comprehensive Treatment National Observation and Research Station, Xi'an 710061 , China ；4. Xi'an Institute for Innovative Earth Environment Research, Xi'an 710061 , China
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| Abstract: |
| Background, aim, and scope Determining to what extent different sources contribute to the total content of urban atmospheric CH4, the second most prevalent anthropogenic greenhouse gas, is critical for carbon emission mitigation strategies. Carbon isotopes (stable δ13C and radiocarbon Δ14C) are powerful CH4 tracers as they exhibit distinct signatures in different CH4 sources. This review aims to synthesize the principles, methodologies, and applications of tracing urban CH4 sources using carbon isotopes, providing a foundation for further scientific studies in China. Materials and methods The literature on the carbon isotopic composition (δ13C and Δ14C) of major urban CH4 sources (e.g., natural gas, landfills, wastewater treatment plants) has been systematically reviewed, including fundamental principles behind isotope tracing, experimental techniques for atmospheric CH4 sampling and isotopic analysis, and key mathematical models (Keeling plot, Miller-Tans, and mass balance) for source contribution assessment. Results Fossil-derived CH4 (e.g., natural gas leakage) is devoid of 14C (Δ14C=-1000‰), so that its emission causes a measurable dilution in atmospheric Δ14CH4. In contrast, Δ14C values of biogenic CH4 (e.g., from landfills) are close to those of contemporary atmospheric CO2. Stable carbon isotopes appear in a wide range: microbial CH4 is typically more depleted in 13C, whereas thermogenic and pyrogenic sources are relatively enriched. Discussion The literature survey demonstrates that the sole use of Δ14C enables an accurate quantification of the fraction of fossil fuel CH4. On the other hand, using δ13C as a tracer can qualitatively identify dominant source types, as demonstrated by the seasonal shifts in the δ13C content observed in various European cities. Indeed, combining Δ14C and δ13C isotopes warrants a more detailed CH4 apportionment; Δ14C first partitions fossil vs. biogenic CH4 sources, while δ13C subsequently helps differentiate among biogenic sub-sources, like landfills and wastewater treatment. Conclusions Carbon isotopes (Δ14C and δ13C) are indispensable tools for identifying and quantifying the specific emission sources of urban atmospheric CH4. Recommendations and perspectives To advance this field of CH4 tracing in China and support the national carbon reduction goals, we recommend a multi-faceted approach. First and foremost, it is essential to continue strategic investing in developing robust and efficient atmospheric 14CH4 sampling and analysis technological infrastructure to enable systematic and combined Δ14C and δ13C observations in typical urban environments, thereby allowing a detailed characterization of spatial and temporal CH4 emission patterns. Furthermore, establishing a national background monitoring framework for Δ14CH4 at remote, high-altitude sites is critical for providing reference values necessary for accurate calculations of fossil fuel contribution. At the same time, systematic characterization of δ13CH4 for major emission sources is needed to build regionally representative endmember datasets and to better constrain source apportionment. Finally, future studies should further develop hierarchical isotope-based source apportionment frameworks, in which Δ14C is used to distinguish fossil from modern biogenic CH4, while δ13C is used to further resolve biogenic sub-sources, with Bayesian mixing models helping to address endmember and observational uncertainties. Pursuing these research directions will provide robust scientific evidence for formulating more goal-oriented and effective CH4 mitigation policies in China. |
| Key words: atmospheric methane carbon-14 carbon-13 source tracing urban atmosphere |
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