Diuron Sorbed to Carbon Nanotubes Exhibits Enhanced Toxicity to Chlorella vulgaris

Abstract

Carbon nanotubes (CNT) are more and more likely to be present in the environment, where they will associate with organic micropollutants due to strong sorption. The toxic effects of these CNT-micropollutant mixtures on aquatic organisms are poorly characterized. Here, we systematically quantified the effects of the herbicide diuron on the photosynthetic activity of the green alga Chlorella vulgaris in presence of different multiwalled CNT (industrial, purified, pristine, and oxidized) or soot. The presence of carbonaceous nanoparticles reduced the adverse effect of diuron maximally by <78% (industrial CNT) and <34% (soot) at 10.0 mg CNT/L, 5.0 mg soot/L, and diuron concentrations in the range 0.73-2990 μg/L. However, taking into account the measured dissolved instead of the nominal diuron concentration, the toxic effect of diuron was equal to or stronger in the presence of CNT by a factor of up to 5. Sorbed diuron consequently remained partially bioavailable. The most pronounced increase in toxicity occurred after a 24 h exposure of algae and CNT. All results point to locally elevated exposure concentration (LEEC) in the proximity of algal cells associated with CNT as the cause for the increase in diuron toxicity.

Cu and Cr enhanced the effect of various carbon nanotubes on microbial communities in an aquatic environment

“…Meanwhile, some reported bacteria can uptake and accumulate metals in the cytoplasm [34]. Additionally, original Cu 2+ and CrO 4 2− concentrations correspondingly reduced greatly after introducing extra CrO 4 2− and Cu 2+ . This may be due to simulated microbial growth.…”

“…1), and even were not detected at 40 days. It is obvious that CNTs sorbed amounts of metals in the solution (initial concentrations of Cu 2+ at 40 and CrO 4 2− at 45 mg/L) (Fig. S1), and sorption varies with different CNTs.…”

“…S1), and sorption varies with different CNTs. In the neutral aqueous solutions (approximate pH 7), different species of Cu (Cu 2+ and CuOH + ) and Cr (CrO 4 2− and HCrO 4 − ) exist together (calculated by Visual MINTEQ). Generating other species may be a potential reason to cause the decrease of Cu 2+ and CrO 4 2− .…”

“…Many previous studies have been focusing on the toxicity of nanoparticles, including CNTs, to gain a better understanding of their potential adverse effects on humans or other organisms [2][3][4][5]. However, the majority of studies on toxicological effects of CNTs have been conducted in pure cultures.…”

Competitive adsorption of heavy metal ions on carbon nanotubes and the desorption in simulated biofluids

“…Hu et al found that sodium pentachlorophenate adsorbed on CNTs and synergistic toxicity presented [38]. The synergistic toxicity of 4-nonylphenol [39] and diuron [40] with CNTs was also reported. Beyond CNTs, the synergistic toxicity of other nanomaterials and pollutants were found, again indicating the importance of such investigations [41,42].…”