Impact of city characteristics on its phosphorus metabolism in the bay area: A comparative analysis of cities in the Greater Bay Area of China

Abstract

Multiple types of human activities have greatly influenced anthropogenic phosphorus (P) cycle, causing severe environmental pressure especially for populous cities in the bay area with abundant water resources. The impact of city characteristics on their phosphorus metabolism should be identified to accordingly adjust these factors to sustain a more effective phosphorus management. Using the Greater Bay Area of China which contains 11 cities as a case, this study develops a phosphorus flow analysis model to quantify phosphorus flow amounts characterized by production, processing, consumption, and waste management sectors for each city. Impact of city characteristics on their phosphorus metabolic features illustrated by six indicators are then revealed by multiple regression analysis using variable data of the 11 cities. Results show that in 2016, to satisfy the human phosphorus demand of 59.9 Gg/y in the Greater Bay Area of China, 33.0 Gg/y was discharged into surface water, and 59.3 Gg/y accumulated in the city ecosystem. The average utilization rates of phosphorus in crop production, livestock production, and aquaculture were around 33.0%, 27.8%, and 26.7%, respectively. Cities with dense population or with developed agriculture had high emission intensity of phosphorus loads, while the latter type had a much higher per capita phosphorus pollution discharge of more than 2.5 kg/y. The scale of grain crop production and aquaculture production exhibited significant influence on phosphorus pollution emission features, while the recycling rate of sludge and agricultural wastes decided the whole urban systems’ phosphorus recycling rate to a great extent. This study can provide support to depict the urban phosphorus flow patterns, recognize its most influential socioeconomic and environmental factors, and propose effective phosphorus management measures for cities in the bay area.