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Arsenate Accumulation, Distribution, and Toxicity Associated with Titanium Dioxide Nanoparticles in Daphnia magna
journal contribution
posted on 2016-08-02, 00:00 authored by Mengting Li, Zhuanxi Luo, Yameng Yan, Zhenhong Wang, Qiaoqiao Chi, Changzhou Yan, Baoshan XingTitanium dioxide
nanoparticles (nano-TiO2) are widely
used in consumer products. Nano-TiO2 dispersion could,
however, interact with metals and modify their behavior and bioavailability
in aquatic environments. In this study, we characterized and examined
arsenate (As(V)) accumulation, distribution, and toxicity in Daphnia magna in the presence of nano-TiO2. Nano-TiO2 acts as a positive carrier, significantly
facilitating D. magna’s ability
to uptake As(V). As nano-TiO2 concentrations increased
from 2 to 20 mg-Ti/L, total As increased by a factor
of 2.3 to 9.8 compared to the uptake from the dissolved phase. This
is also supported by significant correlations between arsenic (As) and titanium (Ti) signal intensities
at concentrations of 2.0 mg-Ti/L nano-TiO2 (R = 0.676, P < 0.01) and 20.0 mg-Ti/L nano-TiO2 (R = 0.776, P < 0.01),
as determined by LA-ICP-MS. Even though As accumulation
increased with increasing nano-TiO2 concentrations in D. magna, As(V) toxicity associated with nano-TiO2 exhibited a dual effect. Compared to the control, the increased As was mainly distributed in BDM (biologically detoxified
metal), but Ti was mainly distributed in MSF (metal-sensitive
fractions) with increasing nano-TiO2 levels. Differences
in subcellular distribution demonstrated that adsorbed As(V) carried
by nano-TiO2 could dissociate itself and be transported
separately, which results in increased toxicity at higher nano-TiO2 concentrations. Decreased As(V) toxicity associated with
lower nano-TiO2 concentrations results from unaffected As levels in MSFs (when compared to the control), where
several As components continued to be adsorbed by
nano-TiO2. Therefore, more attention should be paid to
the potential influence of nano-TiO2 on bioavailability
and toxicity of cocontaminants.