Year

2020

Degree Name

Doctor of Philosophy

Department

School of Earth, Atmospheric and Life Sciences

Abstract

Contamination of aquatic systems with metals is increasing globally, with freshwater ecosystems being particularly vulnerable. However, metal toxicity can vary across orders of magnitude depending on site-specific toxicity modifying factors, e.g. pH, hardness, and dissolved organic matter (DOM), that can influence the bioavailability and toxicity of metals. Dissolved organic matter has been recognised as one of the most influential toxicity modifying factors present in natural freshwaters, with changes not only linked to changes in concentration but also to the quality of DOM. DOM is a product of the surrounding environment (DOM source) and is typically described as predominantly allochthonous (terrestrial origin) or autochthonous (synthesised within the water column). In addition, the nature of these parent materials can vary over time, particularly in ecosystems that experience large seasonal changes (DOM season).

Much of the ecotoxicological data that has been produced on the effects of DOM has been done using DOM isolated from ecosystems in the Northern Hemisphere. The unique ecosystems and climate in Australia mean that Australian DOM is chemically distinct from DOM found elsewhere. Information on the toxicity modifying effect of local Australian DOM on metal toxicity is critical for derivation of water quality guidelines that are protective of local species. This thesis aimed to investigate the effects of Australian DOM concentration, source, and season on the toxicity of copper and nickel to the freshwater tropical microalga Chlorella sp., singly and in binary mixtures, and determine whether metal speciation in the presence of DOM is reflective of the observed toxicity.

FoR codes (2008)

039901 Environmental Chemistry (incl. Atmospheric Chemistry)

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Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.