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In the global context, countries must reduce carbon dioxide emissions to "net zero" by 2050 to limit global warming to 1.5 °C above pre-industrial levels. China's Nationally Determined Contributions (NDCs) are to peak carbon dioxide emissions by 2030 and achieve the carbon neutrality target by 2060. To monitor the achievements of the NDCs, establishing an annual-based accounting mechanism is necessary to record the carbon stocks in China, especially for Blue Carbon. The paper aims to present China's first national-scale systematic Blue Carbon accounting for mangroves, salt marshes, and seagrasses, covering the accounting subjects of physical and monetary assets, as well as relevant indicators for investors. It focuses on the design of the accounting method and system, the selection of data categories applied to this system, and the application of China's Blue Carbon accounting based on this accounting system. Taking Blue Carbon accounting as a starting point, this paper analyses the restoration prospects of these ecosystems and their application potential for NDCs in China compared with the terrestrial ecosystems. The results indicate that mangroves are the most cost-effective type of ecosystem, even compared to terrestrial forests. Thus, the paper provides policymakers with a new perspective on the decision-making of carbon sequestration relevant decisions, aiming to promote the monitoring, restoration, and expansion of China's coastal blue carbon ecosystem through the establishment of a sound Blue Carbon accounting system, and to help achieve the carbon neutrality goal in China's NDCs through regular and systematic monitoring of its national Blue Carbon inventories. • China's coastal blue carbon ecosystems are carbon sources rather than carbon sinks. • Mangroves are the most cost-effective coastal blue carbon ecosystem compared to salt marshes and seagrass beds. • The Blue Carbon of mangroves is more cost-effective than the Green Carbon of terrestrial forests when meeting China's Nationally Determined Contributions target of increasing forest stocks. • Establishing guidelines for Blue Carbon data requirements will lay a scientific foundation for formulating strategies and policies to cope with global climate change. [ABSTRACT FROM AUTHOR]

Quantifying fossil fuel CO 2 (CO 2 ff) in the atmosphere provides a benchmark method to monitor anthropogenic carbon emissions. Radiocarbon (14C) in atmospheric CO 2 ff has been widely studied using the 14C in plants to document regional CO 2 ff patterns. However, annual CO 2 ff variations, reflecting spatial distributions based on plant samples, are still scarce. In this paper, the spatial distribution and temporal CO 2 ff changes in the Guanzhong Basin is established using Δ14C measurements from maize leaves collected in 2011 and 2012. With regard to spatial distribution, samples collected around Xi'an City showed lower Δ14C values (more CO 2 ff), while sites located near the perimeter of the basin showed higher Δ14C values (less CO 2 ff). This is likely due to the concentration of anthropogenic activities in the center of the Guanzhong Basin. The observed CO 2 ff mole fractions generally matched with PKU CO 2 inventory and the ODIAC CO 2 inventory data in the spatial distribution trend. However, it seems that thermal power plants were not well captured by the PKU CO 2 inventory. Our results provide useful information for the improvement of the inventory and verification of regional carbon cycle models. • The Δ14C in maize leaves for 2011 and 2012 were analyzed in Guanzhong Basin. • Spatial distribution of CO 2 ff mole fractions in Guanzhong Basin were studied. • The spatial pattern of observed CO 2 ff matches with the CO 2 inventory. [ABSTRACT FROM AUTHOR]

Terrestrial ecosystems have received considerable attention as a significant sink for organic carbon at regional to global scales. Previous studies were focused on assessment and quantification of carbon sinks for one ecotype, and few have worked on the interconnection of terrestrial sinks. In this paper, we synthesized the data from China's second national soil survey and direct measurements from 54 lakes. Meanwhile, we investigated the controlling factors of carbon accumulation dynamics in soils and lakes. Results showed varied spatial distribution of soil and lake organic carbon in different regions, and three storage modes were found. The storage mode of watershed collection was observed in the region of the Qinghai-Tibetan Plateau, while the northeast China and Yunnan-Guizhou Plateau revealed another storage mode of autochthonous deposition, and the mode of human activities affection was represented by the East Plain and Mongolia-Xinjiang Plateau. The spatial difference throughout China was regulated by various climate patterns, geological conditions and anthropogenic interference. Our results provide insights into carbon storage modes in various regions, and also inform strategies for enhancing global carbon sequestration and future mitigation policies towards global climate change. • Climate, topography and human activity regulate regional soil and lake carbon storage. • Three carbon storage modes based on relationship between soil and lake carbon. • Suggestions to enhance carbon sequestration through soil and lake management. [ABSTRACT FROM AUTHOR]