Assessing the risk of metal mixtures in contaminated sediments on Chironomus riparius based on cytosolic accumulation

Sediments usually contain mixtures of trace metals introduced via natural geochemical processes and anthropogenic activities. Kinetics and effects of these metals are strongly dependent both on the composition of the mixture and on the physico-chemical characteristics of the sediment. Relating effects to metal concentration may consequently be advised. However, total accumulation may be a poor predictor of metal toxicity for Chironomus riparius exposed to contaminated field sediments. As an alternative, we proposed to relate effects on Chironomus growth with cytosolic metal accumulation, measured in larvae after a short exposure period. Dose–response relationships were derived for zinc, copper, and cadmium through single-metal exposure data analysed with toxicokinetics and toxicodynamics models. They permitted, on the basis of cytosolic accumulation measures, to predict successfully the effects of mixtures of cadmium, zinc, and copper on the growth of larvae exposed to spiked sediments, as well as to field sediments in which zinc and copper were assumed to be predominant.