Uptake of Cadmium Adsorbed on Particulates by Gills of Goldfish (Carassius auratus)

Goldfish (Carassius auratus) were exposed to mixtures of constant dissolved cadmium (0.01 mg/L) and cadmium adsorbed on gibbsite particles at concentrations of 0, 0.025, 0.050, 0.075, and 0.100 mg/L. The gills of the fish were excised after a 5-day exposure experiment and both cadmium and aluminum in the gills were measured. The gills were also examined with a light microscope for surface adherence of the particles after the exposure. The evidence collected demonstrated that the concentration of cadmium in the gills increased with increased concentration of particulate cadmium during the exposure while the dissolved cadmium remained constant. The ratio of cadmium to aluminum in the gills was apparently higher than that in the solution, indicating the stripping and translocation of cadmium from the particles. A multistep uptake process is proposed and the bioavailability of particulate cadmium to fish gills is discussed.