title: 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.
authors.affiliation: EMPA-Swiss Federal Laboratories for Materials Science and Technology, CH-9014 St. Gallen, Switzerland.
authors.forename: Fabienne
authors.initials: F
authors.lastname: Schwab
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Bucheli
authors.forename: Louise
authors.initials: L
authors.lastname: Camenzuli
authors.forename: Arnaud
authors.initials: A
authors.lastname: Magrez
authors.forename: Katja
authors.initials: K
authors.lastname: Knauer
authors.forename: Laura
authors.initials: L
authors.lastname: Sigg
authors.forename: Bernd
authors.initials: B
authors.lastname: Nowack
mesh_terms: D000327:Adsorption; D001682:Biological Availability; D048408:Chlorella vulgaris / Q000187:drug effects* / Q000378:metabolism; D004237:Diuron / Q000737:chemistry / Q000633:toxicity*; D006540:Herbicides / Q000737:chemistry / Q000633:toxicity*; D037742:Nanotubes, Carbon / Q000737:chemistry / Q000633:toxicity*; D045332:Photosystem II Protein Complex / Q000378:metabolism
chemical_list: D006540:Herbicides; D037742:Nanotubes, Carbon; D045332:Photosystem II Protein Complex; D004237:Diuron