Release of radiolabeled multi-walled carbon nanotubes (14C-MWCNT) from epoxy nanocomposites into quartz sand-water systems and their uptake by Lumbriculus variegatus

Abstract Once plastic products containing multi-walled carbon nanotubes (MWCNT) are disposed, UV-light exposure may destabilize their structural integrity, leading to a release of MWCNT into the environment that can possibly be taken up by organisms and cause adverse effects. The aim of this study was to quantify the released amount of embedded 14 C–MWCNT epoxy (E) nanocomposites. Furthermore, bioaccumulation of the released material was investigated in Lumbriculus variegatus . The release of radioactivity (RA) from irradiated (+SSR) E/ 14 C-MWCNT composites was quantified after a series of mechanical treatments and in a quartz sand-water system. Non-irradiated composites served as control group (-SSR). Unlabeled ±SSR-nanocomposites were analyzed by means of electron microscopy. The exposure of blackworms to the released material and the amount of RA in the water phase, the quartz sand, and the faeces was quantified. About 0.1% of the embedded RA was released from +SSR-nanocomposites by mechanical treatment and exposure in the quartz sand-water system, which was about 23 times higher compared to -SSR composites. This corresponds to around 3 mg 14 C-MWCNT m −2 for both approaches. Based on the released mass per composite area, +SSR plates set free a 50-fold higher amount of RA. A detectable amount of 7.3 ± 1.8 ng of 14 C-MWCNT was also found in the water phase of the quartz sand-water systems. Electron microscopy revealed an enhanced surface degradation of the composites after SSR and mechanical treatments. Released polymer particles also contained protruding MWCNT. An amount of 2.4 ± 1.8% of released RA was taken up by blackworms after 2 d and about 66% of ingested material was eliminated again after 24 h. The results of this study show that SSR leads to an enhanced release of mostly E-polymer associated MWCNT from nanocomposites that are bioavailable for sediment-dwelling organisms, although the absolute amount of released material is low. Follow-up studies examining toxicological effects after uptake are essential for the environmental risk assessment of MWCNT and E/MWCNT-composites.