Biodynamics and adverse effects of CuO nanoparticles and CuCl 2 in the oligochaete T. tubifex : Cu form influence biodynamics in water, but not sediment.

The use of copper oxide (CuO) NPs results in the release of these particles into the aquatic environment. Here, the particles settle out and accumulate in the sediment. However, little is known about the biodynamics of sediment-associated NPs in benthic organisms. We compared the toxicity and biodynamics of CuO NPs (7 nm) and dissolved Cu (CuCl ₂ ) in the sediment-dwelling oligochaete, Tubifex tubifex , to gain insights into the relative importance of metal form (CuCl ₂ vs CuO NPs) and exposure route (water vs sediment). Isotopically enriched ⁶⁵ Cu was used as a tracer to distinguish background from newly accumulated ⁶⁵ Cu in worms. For each exposure route, we conducted three experiments: one uptake, one elimination, and one longer-term net accumulation experiment to parameterize uptake and elimination of ⁶⁵ CuCl ₂ and ⁶⁵ CuO NPs in T. tubifex . ⁶⁵ Cu accumulation was detected for both ⁶⁵ CuCl ₂ and ⁶⁵ CuO NPs regardless of whether T. tubifex were exposed in sediment- or water-only setups. Water exposures to ⁶⁵ CuCl ₂ resulted in tail trauma whereas limited effects were seen for sediment exposures or exposures to ⁶⁵ CuO NPs via either exposure route. Uptake rate constants and accumulation of ⁶⁵ Cu in T. tubifex were higher following ⁶⁵ CuCl ₂ exposure than ⁶⁵ CuO NPs, in water, but not in sediment. Thus, the relative importance of exposure route and Cu form for uptake dynamics is not straightforward suggesting that findings on bioaccumulation and toxicity in water exposures cannot be directly extrapolated to sediment.