Carbon nanotubes (CNTs) are often modified for their different intended application potentials to enhance their aqueous stability or change properties such as their surface charge. Such changes may also profoundly impact their environmental behaviors. We here have modified carbon-14 MWNTs with polyetheyleneimine (PEI) surface coatings to make them more stable in water and give them positive, negative or neutral surface charges. These carbon nanotubes were used to test their sorption by soils and uptake and elimination behaviors by earthworms. Sorption results indicate linear sorption for the regular MWNTs and non-linear sorption for the treated MWNTs thus indicating that the PEI coating influences their interactions with soil. Differences in uptake behaviors were not apparent among the different types of PEI-MWNTs and MWNTs, results that indicated limited absorption in into the organism tissues. However, the elimination patterns were clearly fit by an exponential decay, unlike previous results for un-modified MWNTs. The impact of carbon nanotube treatment to soils on several earthworm biomarkers was also investigated. While a dose-response relationship was not observed, positively and neutrally charged nanotubes consistently impacted the biomarkers, while negatively charged and acid-treated MWNTs had no effect on average. This suggests that surface coatings of carbon nanotubes may influence their toxic effects.
Citation: Environmental Science & Technology
Pub Type: Journals
Nanotoxicology, carbon nanotubes, sorption, biomarkers