Heavy Metal
Uptake and Toxicity in the Presence of
Titanium Dioxide Nanoparticles: A Factorial Approach Using <i>Daphnia magna</i>.
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Abstract
Unintentionally
released titanium dioxide nanoparticles (nTiO<sub>2</sub>) may co-occur
in aquatic environments together with other
stressors, such as, metal ions. The effects of P25-nTiO<sub>2</sub> on the toxicity and uptake of the elements silver (Ag), arsenic
(As) and copper (Cu) were assessed by applying a factorial test design.
The test design consisted of two developmental stages of <i>Daphnia
magna</i>, two levels of nTiO<sub>2</sub> (0 versus 2 mg/L) as
well as seven nominal test concentrations of the respective element.
The presence of nTiO<sub>2</sub> increased Ag toxicity for juveniles
as indicated by a 40% lower 72-h EC<sub>50</sub>, while the toxicities
of As and Cu were reduced by up to 80%. This reduction was even more
pronounced for Cu in the presence of dissolved organic carbon (i.e.,
seaweed extract) and nTiO<sub>2</sub>. This outcome coincides with
the body burden of the elements, which was elevated 2-fold for Ag
and decreased 14-fold for Cu in the presence of nTiO<sub>2</sub>.
Although the underlying mechanisms could not be uncovered, the data
suggest that the carrier function of nTiO<sub>2</sub> plays a central
role. However, to understand the processes and mechanisms occurring
in the field due to the presence of nTiO<sub>2</sub> further systematic
investigations considering environmental variables and nanoparticle
characteristics are required