Ecotoxicity of nanomaterials in relation to the freshwater blackworm, Lumbriculus variegatus
Little, Simon Robert
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Nanotechnologies are increasing being applied within consumer products, science, medicine, engineering and industrial processes. Due to their small size and high reactivity, nanoparticles (NPs) possess a potentially unique risk towards humans and the environment. Although the aquatic environment is predicted to be the final recipient of nano-wastes, little is known regarding the potential toxicity of NPs towards aquatic species. Within this thesis, the toxicity of two reference nanoparticles: silver (NM-300K) and titanium dioxide (NM-104) were investigated in relation to the freshwater oligochaete, Lumbriculus variegatus in artificial water and sediment. Greater toxicity was observed for NM-300K towards L. variegatus in both short-term (96-hour) water and long-term (28-days) sediment exposures. Sub-lethal NM-300K aquatic exposures (0.2 mg/L) led to an inhibition of L. variegatus swimming behaviours designed for the escape of predation as well as increases in the antioxidant enzymes, superoxide dismutase (SOD) and catalase (CAT). Increases in SOD and CAT indicate the onset of oxidative stress, however, no oxidative damage (as measured by lipid peroxidation) was observed. The inclusion of Suwannee River humic acid (5mg/L) as a natural organic matter (NOM) source generally reduced NM-300K toxicity in aquatic exposures – improving swimming behaviours and limiting SOD and CAT activities to those recorded in control exposures. Although NM-300K displayed greater toxicity than NM-104 in sediment exposures, 100% L. variegatus mortality was only observed at extremely high, potentially environmentally irrelevant concentrations (1333.33 mg/kg). The results of this thesis demonstrate the importance of water and sediment NP toxicity testing in relation to L. variegatus using traditional and newly emerging endpoints and variations to abiotic conditions.