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dc.contributor.advisorMager, Sarah
dc.contributor.advisorFrew, Russell
dc.contributor.advisorOhlemüller, Ralf
dc.contributor.authorBright, Christina Elyse
dc.date.available2021-03-23T22:15:29Z
dc.date.copyright2021
dc.identifier.citationBright, C. E. (2021). Clarifying the waters: A critical analysis of turbidity and its role in environmental monitoring in New Zealand (Thesis, Doctor of Philosophy). University of Otago. Retrieved from http://hdl.handle.net/10523/10811en
dc.identifier.urihttp://hdl.handle.net/10523/10811
dc.description.abstractTurbidity is widely-used as a water quality indicator to infer the mass of suspended sediment (SS) transported through riverine systems, and is inexpensive, readily available, and can be easily deployed to record continuous measurements. However, using turbidity as a surrogate for SS concentration (SSC) is frequently confounded by the composition of riverine suspended material, and the particle size and shape of sediments. Presented as a series of research papers, this thesis provides a distinctly Southern Hemisphere perspective of sediment, organic matter, organic carbon, and turbidity across southern New Zealand, and offers a critical reflection on the role of turbidity in environment monitoring. The suspended material of southern New Zealand rivers under base flow was mostly comprised of inorganic suspended material, although the total composition also includes variable amounts of organic material (<10%, and up to 50 – 80%). The proportion of organic to inorganic particulate material in southern New Zealand is significant under certain land covers, and contributes a significant proportion of particulate organic carbon flux to the Southern Oceans (0.04 – 2.7 t km-1 a-1). In addition, different catchment morphologies and lithologies have a propensity to discharge different particle size distributions of inorganic sediment. These differences in particle sizes are most likely a function of underlying lithology from in channel attrition. This thesis has also identified that specific turbidity (turbidity normalised to mass concentration of particulates) is a potentially effective metric to indicate a ‘non-standard’ light attenuation response (that is, greater turbidity per mass of SS). Specific turbidity is shown through both in-field measurements and laboratory experiments to be affected by organic composition (particulate and dissolved) and the particle size distribution. Multiple regression analysis of catchment characteristics show that suspended particulate material composition and particle size are linked to discharge and flow behaviour, landcover, and lithology. The application of these findings is applied to monitoring SSC with turbidity across New Zealand by examining the specific turbidity for 77-monitoring stations. It is evident that organic composition and particle size have a notable effect on SS-turbidity ratings across New Zealand, which has limitations for the comparability, and relevance of SS data derived from turbidity when used as a regulatory tool. This thesis shows that although turbidity is pragmatic, its use in SS monitoring is problematic.
dc.format.mimetypeapplication/pdf
dc.language.isoen
dc.publisherUniversity of Otago
dc.rightsAll items in OUR Archive are provided for private study and research purposes and are protected by copyright with all rights reserved unless otherwise indicated.
dc.subjectTurbidity
dc.subjectnephelometry
dc.subjectsuspended sediment concentration
dc.subjectparticle size distribution
dc.subjectTurbidity
dc.subjectSuspended sediment concentration
dc.subjectorganic matter
dc.subjectparticle size distribution
dc.subjectNew Zealand
dc.titleClarifying the waters: A critical analysis of turbidity and its role in environmental monitoring in New Zealand
dc.typeThesis
dc.date.updated2021-03-19T21:31:43Z
dc.language.rfc3066en
thesis.degree.disciplineSchool of Geography
thesis.degree.nameDoctor of Philosophy
thesis.degree.grantorUniversity of Otago
thesis.degree.levelDoctoral
otago.openaccessOpen
otago.evidence.presentYes
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