Document Type

Thesis

Degree Name

Master of Science (MSc)

Department

Biology

Program Name/Specialization

Integrative Biology

Faculty/School

Faculty of Science

First Advisor

Dr. Jim McGeer

Advisor Role

Supervisor

Abstract

There has been an increased use of metal-oxide nanoparticles in both commercial and consumer products. The use of these products and waste generated during manufacture may ultimately be released into the aquatic environment and the potential for these contaminants to cause impacts must be assessed. This study examines the effect of titanium dioxide (TiO2) nanoparticles (NPs) on Hyalella azteca. Chronic toxicity exposures were conducted in 400mL of spiked test solution and contained 20 neonates. Samples collected for characterization of Ti in TiO2 NP exposure solutions were digested using ammonium persulfate as an oxidizing agent and dissolved in 2% HNO3, organisms were digested using 70% HNO3 and 30% H202. Dissolved Ti LC50 was 1404 µg Ti/L, all NP exposure’s had LC50 values above 100 mg TiO2/L. The IC50 value of dissolved Ti on growth was 914 µg Ti /L, while uncoated TiO2 NPs P25, PC105, NM101, and NM105 yield IC50 values of 23.4, 31.2, 16 and 14.5 mg TiO2/L respectively. NM103 (hydrophobic) and NM104 (hydrophilic) yielded IC50 values of 36.4 and 6.5 mg TiO2/L respectively. Testing was done to assess the impact dispersion methods of NPs would have on the toxicity to H.azteca. Organisms were exposed to NP solutions that had been dispersed by a 24h spin or were dispersed by a 24h spin and 5 minute sonication step. Organisms exposed to sonicated solutions showed lower dry weight than those exposed to stirred solutions. H.azteca were exposed to a ‘low’ and ‘high’ cadmium concentration in the presence and absence of P25 TiO2 NPs to determine the potential for NPs to acts a ligand to Cd. There was significantly lower bioaccumulation of Cd in organisms exposed in the presence of P25 TiO2 NPs in both concentrations. These results show dissolved Ti has greater impact on H.azteca than TiO2 NPs and it is difficult to relate physical particle characteristics to biological effect. TiO2 NPs with hydrophilic surface modification are more toxic than those with hydrophobic surface modifications. NP solutions dispersed by sonication are more toxic than those that are stirred. TiO2 NPs acted as a negative vector for cadmium, limiting Cd bioavailability.

Convocation Year

2012

Convocation Season

Spring

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