State of the art and future directions in groundwater contamination risk assessment

[Background] Rapid global socio-economic development has intensified the resource crisis and contamination of groundwater, rendering groundwater contamination risk assessments critical to contamination prevention, control, and remediation. [Advances] Through a systematic summary of domestic and international studies, this study reviews the development of theories on groundwater contamination risk assessments and the formation of the theoretical system. Based on the source-pathway-receptor assessment system, this study presents a summary of the research methods for the assessments of contamination source load risks, groundwater vulnerability, and contamination hazards. Groundwater contamination risk assessments have evolved from unidimensional qualitative assessments to quantitative process models highlighting contamination mechanisms and consequences. To enhance the reliability of these models, modern technologies such as hydrogeophysics, geological stochastic methods, and machine learning have been incorporated. Primary issues in current research include the inadequate analysis of the superposition effects of contamination sources, undefined dynamic transport mechanisms of compound contaminants in complex aquifer systems, incomplete assessments of receptor risks, and high model uncertainty. Exploring the transport mechanisms and processes of various contaminants in changeable geologic environments has become a critical scientific issue to be addressed urgently. [Prospects] Given the multi-source contamination, complex geologic conditions, and semi-artificial ecosystems in mining areas, conducting fine-scale process assessments of groundwater contamination risks in the areas serves as an essential foundation for ecosystem management and restoration of mines. Future research should focus on the full-cycle hydrogeologic monitoring of contamination through the fusion of multi-source data, the dynamic transport and risk responses of contaminants in complex aquifer systems under natural and anthropogenic influences, and interdisciplinary risk assessment and decision-making. This study will assist in enhancing the identification and prediction accuracy of groundwater contamination risks, achieving scientific groundwater management, and ensuring the safe and sustainable utilization of water resources. © Editorial Office of Coal Geology & Exploration.