Toxicity of manufactured nano-ZnO to Lemna minor

The rapid development of nanotechnology has led to a rise in the large-scale production and commercial use of engineered nano-ZnO. Engineered/manufactured nano-ZnO are applied in a broad range of products such as drugs, paints, cosmetics, abrasive agents and insulators. This can result in the unintended exposure of human beings to nano-ZnO and will inevitably result in the release of nano-ZnO in to the environment. Thus, it is necessary to assess the risk of nano-ZnO to the environment. In this thesis the toxicity of nano-ZnO was analysed using the aquatic, primary producer lesser duckweed (Lemna minor), and the mechanism of toxicity was analysed. Both short-term (one week) and long-term (six weeks) toxicity of nano-ZnO (uncoated) were determined. Results show that the toxicity of nano-ZnO added to the aquatic growth medium increases with increasing concentration and that toxicity accumulates with exposure time. A study of nano-ZnO dissolution reveals that the main reason for nano-ZnO toxicity on Lemna minor is the release of Zn ions. Nano-ZnO dissolution is pH dependent, and toxicity matches the release of Zn2+. Functional coating materials are commonly added to nano-ZnO particles to improve specific industrial applications. To test if coating materials contribute to nano-ZnO toxicity on lesser duckweed, the effect of silane coupling agent (KH550) coated nano-ZnO on Lemma minor was investigated. Results show that coating can decrease the release of Zn ions, which reduces toxicity to Lemna minor, in contrast to uncoated particles. Another commonly hypothesized reason for nano-ZnO toxicity is the formation of Reactive Oxygen Species (ROS) on the particles surface. As part of this thesis, the ROS formation induced by nano-ZnO was studied. Results show that nano-ZnO catalyse ROS formation and this can negatively affect duckweed growth. In conclusion, this work has detailed potentially toxic effects of nano-ZnO on Lemna minor. This study has also provides references for future research, and informs regulatory testing for nanoparticle toxicity. Specifically, the outcomes of this study emphasize the importance of exposure time, environmental parameters and coating material when analysing NPs toxicity. Firstly, impacts of longer exposure time should be studied. Secondly, environmental parameters such as pH and medium-composition need to be considered when investigating NPs toxicity. Lastly, coating of NPs should always be considered in the context of NPs toxicity, and similar NPs with different coatings require separate toxicity tests.

Monstrative acts and becoming-monster: on identity, bodies, and the feminine other

Using two examples of literary monsters, the Creature in Mary Shelley’s Frankenstein (1818), and Grendel’s Mother in Beowulf, this thesis demonstrates the bearing fictional identities have on “real” bodies, through an examination of two further literary texts, David Henry Hwang’s play, M. Butterfly (1986) and J. M. Coetzee’s novel, Disgrace (1999). Western definitions of Being have historically divided body and mind, favouring the mind as formative of subjective experience and denigrating the body as secondary and impure. This thesis demonstrates that this mind/body binary is symptomatic of the masculine ontological imperative to disown the body and its effects on Being, simultaneously ridding itself of the feminine it believes is its irrational opposite. Using recent feminist reviews of the canon, which emphasise the body’s importance to ontology and demonstrate the conceptual association between the feminine and the corporeal, this thesis links performative identity practices to theories of monstrosity, explaining how fictional qualities adhere to monstrous bodies by proposing a new theoretical category, the “monstrative.” The monstrative is a performative force that makes the Other into a living sign of Otherness; however, unlike earlier theories of Othering, the monstrative accounts for the Other’s being other to herself. This thesis also attempts to read the misrepresented body of the Other as a possible site for more empowered identity performances, where the monstrous “I” is interpreted as a potentially positive model for identity practice, through the conceptualisation of identity as a process of Becoming rather than Being. The transferal from a noun to a verb not only emphasises the performativity of identity, but also suggests fluidity and multiplicity in identity practice, which always already indicates a monstrosity at work. Thus, while monstrative acts constitute bodies as monstrous, Becoming-monster is an empathetic response to the Other’s monstrosity.