Comparison Between Twelve Nanomaterial's Accumulation and Elimination Behavior on Microcrustaceans (Daphnia magna)

Nanomaterials (NMs) production and usage have been raising concerns for the last decades. Since such substances are particulate contaminants, their first contact with organisms is a physical encounter ruled by physicochemical processes that can determinate the potential NMs accumulation, toxicity, and trophic transfer. There is still a lack of understanding on the main NMs properties that drive the accumulation and epuration processes. This work aims at studying and comparing the accumulation and epuration profiles of a set of twelve well characterized NMs with the microcrustacean Daphnia magna in equal conditions and to investigate the NMs properties that influence this phenomenon. The NMs set is constituted by 6 TiO2, 3 SiO2, 2 CeO2 and 1 ZnO NMs. The accumulation phase of the study was carried out during 24h of waterborne exposure to 1mg/L NMs suspension. Then, the organisms passed to the elimination phase of 120h in clean media. Samples were taken during the whole accumulation and elimination phases and were analyzed by ICP-OES. Using the biodynamic metal bioaccumulation model, the influx and loss rate constants have been found and compared. Differences have been determined on the accumulation and epuration kinetics of the NMs. These differences appeared to be linked to the NMs physicochemical properties as zeta potential measures can be correlated to the elimination rate constants. Similar observations were made concerning the same NMs and another type of organisms as microalgae, which highlights the importance of the physicochemical properties’ role on the nano-bio interaction. These findings open the possibility of grouping the NMs based on their relationship with organisms for risk assessment purposes.