| 引用本文: | 秦靖迪,罗俊,牛振川,王森,冯雪,梁单,王国卫.2026.北京市海淀区2000—2020年树轮Δ14C和化石源CO2的年际与年内变化特征研究[J].地球环境学报,17(4):1023-1031 |
| QIN Jingdi,LUO Jun,NIU Zhenchuan,WANG Sen,FENG Xue,LANG Dan,WANG Guowei.2026.The interannual and intra-annual variability of tree-ring Δ14C and fossil fuel CO2 in Haidian District, Beijing during 2000—2020[J].Journal of Earth Environment,17(4):1023-1031 |
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| 北京市海淀区2000—2020年树轮Δ14C和化石源CO2的年际与年内变化特征研究 |
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秦靖迪1，2，3，罗俊1，4，牛振川1，2，5，王森4，6，冯雪7，梁单7，王国卫7
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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.中国科学院大学，北京 100049 ；4.西北大学 城市与环境学院，西安 710027 ；5.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 ；6.国家林业与草原局陕西西安国家城市生态系统定位观测研究站，西安 710127 7.西安地球环境创新研究院，西安 710061
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| 摘要: |
| 城市是化石源CO2（CO2ff）排放的重点区域，获取城市CO2ff浓度变化对于制定碳减排政策至关重要。放射性碳（14C）示踪技术可通过树木年轮重建过去大气CO2ff浓度变化。研究以北京市海淀区紫竹院公园的油松（Pinus tabuliformis Carr.）为对象，分析了北京市海淀区采样点2000—2020年树轮Δ14C和CO2ff的年际和年内变化。结果表明：2000—2020年，海淀区树轮Δ14C值由29.3‰±2.4‰下降至-54.3‰±1.9‰，显著低于北半球背景值和京津冀区域背景点（上甸子），显示人为碳排放的稀释作用。重建的CO2ff浓度在2010年达到峰值，为(27.9±1.0) μL/L，随后逐年下降至2020年的(21.9±1.0) μL/L，与北京市CO2排放量显著相关（r=0.83，p＜0.01）。CO2ff峰值出现在2010年，表明碳减排政策在2010年后取得显著成效。分部门分析表明，热电、交通运输、服务业和生活消费是主要影响部门。年内尺度上，树轮早材（3—6月左右）CO2ff浓度总体高于晚材（7—10月左右），平均差值为(1.4±2.4) μL/L，早材偏高与供暖期排放有关；2008年早晚材差值最大（(4.2±0.1) μL/L），响应了北京奥运会期间的减排措施。研究对北京市中心城区过去20年CO2ff浓度的动态变化及原因进行分析，可为城市碳减排政策制定提供科学依据。 |
| 关键词: 树轮Δ14C 加速器质谱 化石源CO2 早材 晚材 北京 |
| DOI：10.7515/JEE2025001 |
| CSTR：32259.14.JEE2025001 |
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| 基金项目:国家自然科学基金项目（42173082）；陕西省杰出青年科学基金项目（2024JC-JCQN-34） |
| 英文基金项目: |
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| The interannual and intra-annual variability of tree-ring Δ14C and fossil fuel CO2 in Haidian District, Beijing during 2000—2020 |
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QIN Jingdi1，2，3，LUO Jun1，4，NIU Zhenchuan1，2，5，WANG Sen4，6，FENG Xue7，LANG Dan7，WANG Guowei7
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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 Applications, Xi’an AMS Center, Xi’an 710061 , China ；3.University of Chinese Academy of Sciences, Beijing 100049 , China ；4.College of Urban and Environmental Sciences, Northwest University, Xi’an 710127 , China ；5.National Observation and Research Station of Regional Ecological Environment Change and Comprehensive Management in the Guanzhong Plain, Shaanxi, Xi’an 710061 , China ；6.Shaanxi Xi’an Urban Ecosystem National Observation and Research Station,National Forestry and Grassland Administration, Xi’an 710127 , China 7.Xi’an Institute for Innovative Earth Environment Research, Xi’an 710061 , China
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| Abstract: |
| Background, aim, and scope Excessive emissions of fossil fuel-derived CO2 (CO2ff) are closely linked to global warming, making it essential to quantify CO2ff emissions. Urban areas play a critical role in CO2ff emissions and serve as core regions for implementing carbon reduction efforts. Radiocarbon (14C), as an effective tracer, can be used to quantify CO2ff concentrations. Tree rings record atmospheric 14C signals through photosynthesis during their growing seasons, making them unique tracing materials for reconstructing past variations in atmospheric CO2ff concentrations. This study collected tree-ring cores from Haidian District (HD), Beijing, to investigate the interannual and intra-annual trends of Δ14C values and CO2ff concentrations from 2000 to 2020, and discuss the influencing factors. Materials and methods As the capital of China and a megacity, Beijing was selected for this study. Tree-ring samples were collected in September 2021 from Zizhuyuan Park (ZZY) in HD. Tree cores (2—3 per tree) were collected at breast height of Pinus tabuliformis Carr. using a 10 mm Haglof Increment Borer. After drying and sanding, cross-dating was conducted to correct for false or missing rings, and earlywood and latewood were manually separated. The samples underwent organic extraction, bleaching, and acid washing to isolate α-cellulose. The α-cellulose was combusted with excess CuO to generate CO2, which was purified via cryogenic trapping and converted to graphite using the Zn-Fe method. The 14C levels of the tree-ring samples were measured using a 0.2 MV accelerator mass spectrometer (AMS). The 14C levels in the samples were expressed as Δ14C, and the CO2ff concentrations were calculated. Results From 2000 to 2020, the tree-ring Δ14C values at the sampling site decreased annually at a rate of 4.2‰±0.3‰, with a mean value of -18.8‰±29.2‰, and were significantly lower than the Δ14C values at Northern Hemisphere background sites (NH) and the Beijing-Tianjin-Hebei (BTH) background site Shangdianzi (SDZ). The reconstructed CO2ff concentrations showed a significant negative correlation with CO2 emissions in Beijing (r=0.83, p＜0.01). CO2 emissions were classified by economic sectors, among which the four dominant emission sectors with the largest emission volumes were the thermal power sector, transportation sector, residential consumption sector and service sector. Pearson correlation analysis was performed between the CO2 emissions of these four sectors and the CO2ff concentration. The results demonstrated statistically significant positive correlations between CO2ff concentration and emissions from the thermal power sector (r=0.73, p＜0.05), service sector (r=0.78, p＜0.01), as well as residential consumption sector (r=0.65, p＜0.05). Although the transportation sector presented a correlation coefficient of r=0.56 with p＞0.05, indicating a non-significant correlation, this sector featured a large total carbon emission base and remained a critical emission source driving variations in regional CO2ff concentration. Analysis of Δ14C and CO2ff during earlywood and latewood growing periods showed that earlywood Δ14C decreased from 28.8‰±2.3‰ in 2000 to -58.2‰±1.9‰ in 2020, while latewood Δ14C decreased from 29.8‰±2.5‰ in 2000 to -52.7‰±1.9‰ in 2018, with similar annual decline rates (4.1‰ and 4.3‰, respectively). CO2ff concentration was generally higher in earlywood than in latewood (mean difference of (1.4±2.4) μL/L). CO2ff concentration increased continuously before 2010 and decreased or stabilized thereafter, with the maximum difference between earlywood and latewood CO2ff reaching (4.2±0.1) μL/L in 2008. Discussion The significantly lower tree-ring Δ14C values in HD indicate substantial influence from anthropogenic CO2 emissions. The CO2ff concentration peaked in 2010 and subsequently declined, demonstrating the notable effectiveness of emission reduction policies implemented post-2010. Sector-based apportionment of CO2 emissions revealed that heating supply, transportation, service industry, and residential activities were the predominant contributors to CO2ff concentration variations. The generally higher CO2ff concentration in earlywood compared to latewood at the sampling site can be attributed to the tree growth seasons: earlywood typically grows in spring and early summer, while latewood grows from mid-to-late July to autumn, allowing earlywood to record CO2 emissions from the heating season. Furthermore, the CO2ff concentrations reconstructed from earlywood and latewood successfully captured the impacts of specific intra-annual events, such as the emission reduction effects during the 2008 Beijing Olympics. Conclusions The tree-ring AMS-14C method is an effective approach for reconstructing historical atmospheric CO2ff levels. Interannual and intra-annual variations in tree-ring CO2ff are influenced by emission reduction policies and specific events.Recommendations and Perspectives This study provides an example for investigating the historical trends and influencing factors of urban atmospheric CO2ff changes. |
| Key words: tree-ring Δ14C accelerator mass spectrometry fossil fuel CO2 earlywood latewood Beijing |
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