Assessment and Optimization of the Structure of Urban Carbon Metabolism System in Guangzhou: Integrating the Cross-Media Transfer Process

Optimizing the structure of the carbon metabolic network is essential for enhancing network performance. However, a knowledge gap remains in systematically evaluating the network structure and comprehensively identifying the key nodes and paths, particularly in a carbon metabolism system that involves the frequent transition of carbon element across the air, water, and soil mediums. Hence, taking Guangzhou, China, as a case study, we constructed a cross-media metabolism network model based on material flow analysis. Subsequently, the general structural characteristics and key nodes/paths of the network were investigated through the integration of trophic structure analysis, contribution analysis, and stability analysis in ecological network analysis. The results primarily suggest that the connections among nodes in the carbon metabolism network have become looser, and the metabolic system structure was in a medium state with some defects from 2010 to 2020. Sectors of construction and transportation, as well as carbon flows from the agriculture sector to the construction sector and the energy conversion sector to the transportation sector, were identified as the key nodes and paths influencing the structural characteristics. Subsequently, twenty-one optimization scenarios were developed, with the results suggesting the advantage of collaborative regulation of key nodes/paths (e.g., increasing the carbon flows both from the agriculture sector to the construction sector and from the energy conversion sector to the transportation sector by 50%). This work may provide useful guidance for the structure optimization of the carbon metabolism system.