Browsing by Author "Ondiaka, Mary Nelima"

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    Prediction of behaviour kinetics and toxicity of engineered nanomaterials in aqueous environment using neural networks
    (Stellenbosch : Stellenbosch University, 2016-12) Ondiaka, Mary Nelima; Musee, Ndeke; Stellenbosch University. Faculty of Engineering. Dept. of Process Engineering.
    ENGLISH ABSTRACT: As the global market for engineered nanomaterials (ENMs) continues to grow, the release of ENMs into the environment expose fauna and flora to new diverse stressors. Consequently, a novel approach is required in the monitoring and mitigation of the pollution from ENMs. In this approach, modelling is likely to play a significant role in estimating the release, bioavailability, and toxicity of ENMs in the environment. Many laboratory tests have established the toxic effects associated with the acute and chronic exposure of various organisms to ENMs. However, most of the information generated from these tests and reported in the scientific literature is unstructured and uncertain. A further complication is that unlike with other pollutants, extrapolating experimental findings to assess the environmental risk of ENMs is difficult, owing to their diversity, lack of standardized test protocols and unknown allowable environmental concentrations. Dissimilar ENMs would require case-by-case risk evaluation, a process that would be expensive and time-consuming. Focusing on nTiO2 as a model ENM, and algae and Daphnia magna as indicator organisms, this dissertation presents learning from a database derived from information gathered from the scientific literature. More specifically, an ensemble model trained using multilayer perceptron neural network (MLP-NN) predicts mass coverage of organic adsorbates on nTiO2, as well as the hydrodynamic size of nTiO2 particles. These two response variables represent the behaviour kinetics of the particles in aquatic conditions. Also, the toxicity of the particles was predicted from selected characteristics of nTiO2 and assay water, as well as some biological factors. The neural network models could subsequently be interrogated to establish the effect of the various predictors of the behaviour of the particles associated with their environmental risk. This approach lays a foundation for the data mining of ENMs that would facilitate the use of available data to estimate the ecological impact of nTiO2, as well as other ENMs.