Urban boundaries and emission performance: CO2 and air pollutant synergy in China ——New practice from Guangzhou City

Abstract

Urban areas are pivotal in mitigating climate change and improving air quality. However, complex and ambiguous urban boundaries have significantly hindered the implementation of synergistic gas control strategies and policies. This study proposes and defines four types of urban boundaries: Urban Center (UC), Urban Area (UA), Urban Suburban (US), and Urban Administrative Boundary (AB). Using Guangzhou City, China, as a case study, this study identifies and delineates these boundaries based on population characteristics. By employing high spatial resolution gas emission data, this study analyzes the emission characteristics of CO₂ and air pollutants and their performance within these distinct urban boundaries. The results indicate that stationary combustion and transportation sectors are the primary direct or indirect sources of CO₂ and air pollutants. Notably, the top 10% of emission grids account for more than 60% of the total emissions. The UC, UA, and US are more representative of urban areas concerning human activities, whereas the AB should be considered a region rather than an urban area. The urban gas emissions are far cleaner than it actually is. The actual gas emissions of Guangzhou City are 55.7% (CO₂), 34.1% (SO₂), 42.5% (NO_X), 40.9% (CO), 45.8% (PM₁₀), and 48.5% (PM_2.5) of the total. The space for synergistic gas management overlaps extensively with the delineated UC and UA, with minimal distribution within the US. This study underscores the importance of clear and rational urban boundaries for effective CO₂ and air pollutant synergistic management policies and research.