Rapid urbanization decelerates regional net anthropogenic phosphorus input: Evidence from the Chengdu-Chongqing urban agglomeration in China.

Mitigating the pressure of regional phosphorus (P) inputs driven by human activities is essential for the prevention and control of non-point source pollution as well as for effective environmental management. This study emploied the net anthropogenic phosphorus input (NAPI) model and the coupling coordination degree model (CCDM) to quantitatively analyze the spatiotemporal evolution of phosphorus inputs and urbanization levels in the Chengdu-Chongqing urban agglomeration (CCUA) in Southwest China from 2011 to 2022. By integrating urbanization, socioeconomic and land use data, we identified key driving factors and specific indicators influencing changes in regional phosphorus inputs and their components. Compared to 2011, urbanization levels increased by 16.60% in 2022, while regional phosphorus inputs decreased by 21.52%. P input from human food and livestock feed was the main component of NAPI during the study period (54.27%-61.28%), followed by fertilizer application (37.46%-44.62%). The shift in industrial structure towards the tertiary sector (explanation rate 20.8%) and construction land expansion (explanation rate 17.7%) were identified as key drivers of phosphorus input changes. Additionally, urbanization has a more significant direct standardized path coefficient on P inputs (-7.30) than socioeconomic (0.44) and land use factors (0.37) based on Partial Least Squares Path Modeling (PLS-PM), suggesting that regional phosphorus inputs decrease with increasing urbanization levels. These findings provide new insights for the formulation of effective phosphorus management strategies in rapidly urbanizing areas, and are conducive to the sustainable management of urbanization progress and ecological environment.