近日，南京大学王成龙等报道了受放射性碳数据限制的陆地-海洋连续体有机碳转移和积累的全球模式。这一研究成果发表在2024年6月21日出版的国际学术期刊《自然—地球科学》上。

据介绍，放射性碳(Δ¹⁴C)是识别水生生态系统中碳的来源和循环的有效示踪剂。河流颗粒和沿海沉积物中有机碳(OC) Δ¹⁴C值的全球模式对于理解当代碳循环至关重要，但由于采样不足而受到限制。这阻碍了研究人员对全球陆地—海洋连续体的OC转移和积累的理解。

团队研究人员利用机器学习方法和超过3,800个观测数据，构建了河海连续体中Δ¹⁴C值的高空间分辨率全球地图集，研究表明，河流颗粒和相应的海岸沉积物的Δ¹⁴C值可能相似或不同。具体而言，研究识别出四种典型的OC迁移和积累模式：低河流和高海岸沉积物Δ¹⁴C值系统的年老—年轻模式；具有老OC积累的海岸系统接收具有高Δ¹⁴C值和低Δ¹⁴C值的河流颗粒的年轻—年老模式和年老—年老模式；河流和海岸沉积颗粒均为年轻OC的年轻—年轻模式。

区分这些模式及其空间格局对于进一步了解全球碳系统至关重要。具体而言，在全球OC含量较高的沿海地区，年老—年老系统对当代大气二氧化碳(CO₂)的去除基本上是中性或略负的，而年轻—年老和年老—年轻系统分别代表CO₂的源和汇。这些OC含量和同位素组成的空间格局限制了蓝碳溶液的局部潜力。

附：英文原文

Title: Global patterns of organic carbon transfer and accumulation across the land–ocean continuum constrained by radiocarbon data

Author: Wang, Chenglong, Qiu, Yifei, Hao, Zhe, Wang, Junjie, Zhang, Chuchu, Middelburg, Jack J., Wang, Yaping, Zou, Xinqing

Issue&Volume: 2024-06-21

Abstract: Radiocarbon (Δ¹⁴C) serves as an effective tracer for identifying the origin and cycling of carbon in aquatic ecosystems. Global patterns of organic carbon (OC) Δ¹⁴C values in riverine particles and coastal sediments are essential for understanding the contemporary carbon cycle, but are poorly constrained due to under-sampling. This hinders our understanding of OC transfer and accumulation across the land–ocean continuum worldwide. Here, using machine learning approaches and >3,800 observations, we construct a high-spatial resolution global atlas of Δ¹⁴C values in river–ocean continuums and show that Δ¹⁴C values of river particles and corresponding coastal sediments can be similar or different. Specifically, four characteristic OC transfer and accumulation modes are recognized: the old–young mode for systems with low river and high coastal sediment Δ¹⁴C values; the young–old and old–old modes for coastal systems with old OC accumulation receiving riverine particles with high and low Δ¹⁴C values, respectively; and the young–young mode with young OC for both riverine and coastal deposited particles. Distinguishing these modes and their spatial patterns is critical to furthering our understanding of the global carbon system. Specifically, among coastal areas with high OC contents worldwide, old–old systems are largely neutral to slightly negative to contemporary atmospheric carbon dioxide (CO₂) removal, whereas young–old and old–young systems represent CO₂ sources and sinks, respectively. These spatial patterns of OC content and isotope composition constrain the local potential for blue carbon solutions.

DOI: 10.1038/s41561-024-01476-4

Source: https://www.nature.com/articles/s41561-024-01476-4