Assessing Ecological Risks of Particulate Copper in Aquatic Ecosystems: A Challenge to the Traditional Assumption of...

Suspended particles are ubiquitous in the aquatic environment, however, traditional ecological risk assessment mainly focused on dissolved chemicals, overlooking the bioavailability and hazard of contaminants adsorbed on these particles. This study addressed this oversight by assessing the ecological risks associated with particulate copper (Cu), a prevalent trace element adsorbed on suspended particulates in various aquatic environments. The highest concentrations of particulate Cu were found in freshwater systems, with progressively lower levels found moving towards coastal areas, and remote ocean. Also, a significant decrease in the particulate Cu to dissolved Cu ratio was evident from inland to oceanic waters, with the ratio averaging 18 in freshwater systems, 2.6 in coastal areas, and 0.062 in remote ocean. According to the species sensitivity distribution of four classes of aquatic organisms, the hazardous concentration for 5% of the species was determined as 6.77 mg/kg for particulate Cu, while its predicted no-effect concentration was derived as 67.7 mg/kg by dividing a commonly used assessment factor of 10. By comparing the measured environmental concentrations of particulate Cu and the derived predicted no-effect concentration, 37% of the detected samples exhibited high ecological risks, raising our concerns about their adverse effects in aquatic ecosystems. These findings will contribute to a refined understanding of trace metal contamination in aquatic environments and emphasize the need for more research on the toxicity, hazard and risks of contaminants, particularly those adsorbed on the suspended particles.