Photocatalytic Effects of TiO2 Nanoparticles:
Is there an Impact on the Ecotoxicity of PAHs?
121
Judith Angelstorf , Wolfgang Ahlf , Susanne Heise

1Hamburg University of Applied Sciences, Germany; 2Technical University Hamburg Harburg, Germany

Contact: judith.angelstorf@haw-hamburg.deBackground

Materials and methods

Titanium dioxide nanoparticles (TiO2 NPs) are used in a variety ofBioassay: ISO 10872:2010 - Chronic test of C. elegans

consumer products and expected to increasingly enter the aquatic(Nematoda), endpoints: reproduction, fertility and growthenvironment [1].

Test material:

TiO2 NPs catalyze the degradation of PAHs under UV irradiation. They

 TiO2 NPs P 25 Aeroxide (Degussa AG)

are currently being considered for use in the remediation of PAH-(primary particle size 21 nm; 75% anatase, 25% rutile)

polluted soils and wastewaters [2], although little is known about theDispersion: in ultrapure water using magnetic stirring

effects of potential products of this photo modification process to theand ultrasonic bathaquatic environment.

 Phenanthrene, solvent DMSO

Photo oxidation of PAHs can alter bioavailability (water solubility) andParticle characterization:

intrinsic toxicity of contaminants.

 Dynamic Light Scattering (DLS) and Zeta-Potential
 Scanning Electron Microscopy (SEM).

Main objectives:

1) Assess the solar irradiation-mediated ecotoxicological effects of TiO2 NPs on Caenorhabditis elegans
2) Investigate the impact of TiO2 NPs on the toxicity of phenanthrene

Results
Effects of solar radiation on TiO2 toxicity

Effects of solar radiation and TiO2 on toxicity ofIngestion of TiO2 particles

phenanthrene (combined exposure)

Agglomerated TiO2 particles are taken up into theworm intestinal tract within 96 h exposure to TiO2***(Fig. 4 A and B).

***
**

**

A

B

Fig. 4 C.elegans exposed to 20mg/L TiO2 for 96 h;A)Stereomicroscope images
B) EDX mapping of Titanium with 20 keV

Agglomeration of NPs
Dynamic Light Scattering
Fig. 1: Inhibition of reproduction of C.elegans exposed to TiO2 with andwithout SSR [mean inhibition and SD in %, n=4]; p-Values **<0.01*** < 0,001 (One-Way ANOVA at α = 0.05, post test Dunett).
SSR: 30 min irradiation ,4 h after start of the test, 231 W/m2 at 300-800 nm.

• Mean particle size and SD increase with increasing
particle concentrations (253 nm +/-79 to 718 nm +/-145)• Addition of the test media M9 leads to further• TiO2 NPs significantly inhibit the reproduction ofagglomeration, particle sizes increase by a factor of 1.15

• 30 min simulated solar radiation (SSR)

Fig. 3: Inhibition of reproduction of C.elegans exposed to phenanthrene andTiO2 [mean inhibition and SD in %, n=4]. Grey bars: added single substanceeffects; green bars: effects of combined exposure. SSR: 30 min irradiation, 4 hafter test start, 231 W/m2 at 300-800 nm.

increases the toxicity by a factor of approx. 2Dark: TiO2 NPs increase the toxicity of phenanthrene slightly,

exposure period of 96 h (Fig. 5)(EC50 of 53 mg/L (SSR))

and phenanthrene decreases toxicity slightly, effects
are not significant.

Conclusions
 Reproduction of C.elegans is significantly
inhibited by exposure to TiO2 NPs atconcentrations of 10 mg/L and higher
 Simulated solar radiation increases theinhibition by a factor of approx. 2
 Phenanthrene toxicity is not significantlyaffected by simultaneous exposure to TiO2 orFig. 2: Inhibition of reproduction of C.elegans exposed tophenanthrene with and without SSR [mean inhibition, n=4]; nonlinear
fit of log (x). SSR: 30 min irradiation ,4 h after start of the test, 231
W/m2 at 300-800 nm.

SSR increases the toxicity of phenanthrene by afactor of approx. 2. [EC50 of 1230 µg/L (no-SSR)
and 522 µg/L (SSR)].

• Particle sizes do not significantly change during theeffects are not significant.
SSR: Simultaneous irradiation of C.elegans exposed to TiO2

Effects solar radiation on phenanthrene toxicity

to 1.92

TiO2 and SSR
 Agglomeration and sedimentation of theparticles is observed in the test system
 Agglomerated particles are bioavailable forC.elegans and ingested into the intestinal tract

Acknowledgements
Thanks to Maximilia Kottwitz and Martina Nielsen for assistance in the lab, to Michael Gröger (ITMC UHH) and Jens
Timmermann (TUHH) for help with DLS and SEM/EDX and to the OECD Sponsorship Programme for the provisionof test material. Work was partially funded by Pro Exzellenzia.

NP agglomeration in the testsystem

2000

Mean particle size [d.nm]

C.elegans (LOEC 10 mg/L to 30 mg/L)

0h24 h

1750

48 h

1500

72 h

1250

96 h

1000
750
500
250
0
1

10100

TiO2 [mg/L]

Fig. 5: DLS measures of TiO2 dispersions introduced into the test
media M9 after 0, 24, 48, 72 and 96 h. Average Intensity Meanvalues of particle diameter (10 repeated measures) and SD.

Scanning electron microscopy
Compared to DLS data:• Particle sizes are of the same magnitude(453 nm +/- 58 nm for H2O suspensions;
413 nm +/- 77 nm for suspensions added to M9)• Particle sizes do not increase with increasing
concentrations• Addition of M9 media has no impact on particle sizes

Reference[1]
Gottschalk, F.et al., 2009. Modeled Environmental Concentrations of Engineered Nanomaterials (TiO2, ZnO, Ag,CNT, Fullerenes) for Different Regions. Environmental Science & Technology, 43(24), 9216-9222.
[2]
Dong et al. 2010. Photocatalytic degradation of phenanthrene and pyrene on soil surfaces in the presence ofnanometer rutile TiO2 under UV-irradiation. Chemical Engineering Journal ,158(3):378-383.