Risk Assessment and Management of Pyrite Cinder in Roadbed Applications

Environmental risk assessments for the resource products of solid waste generally rely on oversimplified model frameworks. These frameworks often overlook the complexity of pollutant release mechanisms and the diversity of regional environments, making it difficult to accurately characterize the environmental risks of solid waste resource utilization across various climatic zones (arid, semi-arid, semi-humid, humid). Integrating the source strength index decay model with the pollutant instantaneous migration model, and introducing Monte Carlo simulation techniques, this study aims to explore the resource utilization pathway of pyrite cinder in road construction and its potential environmental risks in different climatic zones. Results show that the potential hazard index (PHI) of four heavy metal pollutants (arsenic, manganese, nickel, and cadmium) in pyrite cinder ranges from 3.3 to 14.2, indicating significant potential hazards. After migration and transformation in groundwater, arsenic has an exceedance risk (exceedance probability of 27%), with the exposure concentrations (0.034 mg·L^-1) 3.4 times higher than the Class Ⅲ limit specified in Groundwater Quality Standard (GB/T 14848-2017). The study finds that increased rainfall intensifies the leaching risk of heavy metals, which can be effectively managed by adjusting the mixing ratio of pyrite cinder in roadbed subbase layers. The mixing ratio should be controlled below 30% in humid climatic zones and no more than 40% in semi-humid climatic zones. Traditional assessment methods are insufficient in evaluating pollutant release potential and peak risks. It is urgent to accelerate the establishment of a comprehensive risk assessment and control standard system for solid waste resource utilization, and implement differentiated management strategies for different regions.