Research on the carbon profit and loss correlation mechanism of sponge city construction life cycle in urban built up areas

Climate change and rapid urbanization have changed the urban eco-hydrological cycle. Understanding the carbon profit and loss correlation mechanism of sponge city construction life cycle helps identify the eco-environmental benefits. This study constructs a set of carbon accounting methods under the concept of sponge city, which mainly consists of basic database, carbon emission accounting, carbon neutralization, uncertainty and sensitivity analysis module. Taking a typical urban built-up area in Xi'an City as an example, the main sources of carbon emissions from sponge transformation projects are material production and construction, and the sponge transformation project created a carbon source of 95 kg CO₂/m² during the two phases. Carbon neutrality mainly includes building energy saving and green space carbon sequestration, and the latent capacity is 219.92 kg CO₂/m²·year in 50-year accounting period, besides, the static investment payback period for carbon emissions is about 25 years in environmental economics. Based on the Analytic Hierarchy Process (AHP) + Data Quality Indicator (DQI) method combined with Monte Carlo simulation (MCs), the relative standard deviation (RSD)=0.17 is a relatively reliable result. The most significant influence on the results is the electricity factor in the parameters sensitivity analysis.