Phosphorus Metabolism of the Food System in the Guangdong-Hong Kong-Macao Greater Bay Area Urban Agglomeration

Yang Lu^1,2,3,4Wei Huang^1,3,4*Shenghui Cui^1,3,4Jiexin Deng^1,2,3,4Yin Zhang^1,2,3,4Yunfeng Huang⁵Bing Gao^1,3,4*

• ¹Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, China
• ²University of Chinese Academy of Sciences, Beijing, China
• ³State Key Laboratory of Regional and Urban Ecology, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, China
• ⁴Xiamen Key Lab of Urban Metabolism, Xiamen, China
• ⁵Environmental Engineering Department, Jimei University, Xiamen, China

Phosphorus (P) is a vital nutrient for food production, yet a significant pollutant when mismanaged. This study analyzes the phosphorus flow of the food system in the Guangdong-Hong Kong-Macao Greater Bay Area (GBA) in 2020, using a Substance Flow Analysis framework. The research examines natural and anthropogenic inputs, outputs and accumulation of phosphorus. Results reveal that the GBA is heavily dependent on external phosphorus inputs, with a total input of 187.69 Gg. The two largest sources of phosphorus inputs areTwo largest phosphorus inputs primarily go into aquaculture (36%) and food consumption (33%). The phosphorus use efficiency (PUE) in crop production, animal husbandry, and aquaculture were approximately 48.8%, 32.37%, and 10.01%, respectively. However, only 7.89% of phosphorus is recycled, while substantial losses (76% to soil and 24% to water bodies) exacerbate environmental pressures. Spatial analysis highlights distinct patterns between production-oriented cities (e.g., Jiangmen and Zhaoqing) and consumption-oriented cities (e.g., Shenzhen and Hong Kong). Policy recommendations include enhancing aquaculture management, improving phosphorus recycling technologies, and fostering intercity collaboration to create a sustainable phosphorus management framework. These findings provide critical insights for addressing phosphorus-related challenges in urban agglomerations.