In aquatic environments such as streams and rivers, contamination by trace metals such as copper and zinc is a long-standing environmental issue . The risk assessment approaches for many individual metals, such as copper, zinc, and nickel, have seen considerable advancements, particularly with the development of biotic ligand models . However, predicting ecological impacts of metal mixtures remains a challenging task , although a general risk assessment framework has been proposed to address this issue . To effectively understand and predict ecological risks and effects of metal mixtures in natural environments on a broad scale (e.g., a country level), it is crucial to understand the mixture exposure profiles that are likely to occur .