Mapping critical loads of cadmium in Chinese soils based on multiple environmental effects

While critical load of cadmium (Cd) is a key guideline for atmospheric Cd emission control, existing assessments often focus on a single type of environmental effect, failing to provide comprehensive protection for the "soil-water-plant" system. By considering the cross-medium migration of Cd and integrating multiple environmental effects, we modified the Simple Mass Balance (SMB) model and then developed a 1 km by 1 km resolution critical load map for soil Cd in China. The modified method better reflects the protection for soil and plants. The median critical load is 0.89 g ha^-1 yr^-1 (10th-90th percentile: 0.0096-28 g ha^-1 yr^-1), with values decreasing from the southeast to the northwest. Areas with low plant productivity and limited runoff, as well as some grain-producing agricultural fields, are susceptible to Cd inputs. Cd deposition in China has led to critical load exceedances, especially severe in the northern regions. These findings highlight the urgent need to establish a comprehensive framework for controlling heavy metal emissions in China. Since critical loads may increase under future climate change scenarios, heavy metal emission control strategies need to be dynamically adjusted.