Biokinetic Modeling of Cd Bioaccumulation from Water, Diet and Sediment in a Marine Benthic Goby: A Triple Stable Isotope Tracing Technique.

Aquatic animals are often simultaneously exposed to metals through multiple routes in the natural environment. This study explored a triple stable isotope tracing method to quantify simultaneous cadmium (Cd) uptake biokinetics by yellow stripe goby from water (traced by 110Cd), sediment (traced by 111Cd), and diet (traced by 113Cd) when the fish were exposed to Cd for 24 h. The simultaneous uptake of Cd from multiple routes during 4 weeks was then predicted by the modified biokinetic model. The results demonstrated that the uptake rate constant of waterborne 110Cd, sediment-associated 111Cd, and dietary 113Cd was 3.1 L kg-1 d-1, 2.2 × 10-4 g g-1 d-1, and 3.3 × 10-3 g g-1 d-1 in the fish. Sedimentary Cd was less bioavailable than the waterborne and dietary Cd; however, sediment could become the predominant Cd source of the total Cd bioaccumulation when the partition coefficient of Cd between sediment and seawater ( Kd) is larger than 6 × 104 L kg-1. The simultaneous uptake of Cd from the three routes could be successfully predicted by the modified model. The model revealed that the Cd bioaccumulation generally increased with the increase of ambient Cd concentration in all the three routes. Overall, our findings demonstrated that the multiple stable isotopes tracing method and the modified biokinetic model have a wide generality and applicability for predicting Cd bioaccumulation under multiple routes of metal exposure scenario and may have application to other metals.