Postgraduate Profiles

Pauline Chau

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Thesis: The role of pesticide metabolites and preferential flow in understanding pesticide fate in the vadose zone.

The aim of this thesis is to contribute to a better understanding of pesticide fate and transport in soils paying particular attention to the role of pesticide metabolites as part of that process.

I look at interactions between soil and pesticide properties which may influence the fate of pesticides using classification regression analysis.

Compound Specific Isotope Analysis, a method usually applied to petroleum hydrocarbons, was employed to assess the attenuation of simazine in soil microcosms and was found to be a potentially useful tool for monitoring natural attenuation of simazine, and possibly other triazine herbicides in contaminated sites.

The potential for simazine to leach via preferential flow paths was also investigated in a small-scale field study which showed that simazine could in fact be transported in this way.

A model was then developed to predict the mode of transport of pesticides by using the ratio of pesticide metabolites to their precursors in various decay, retardation and preferential flow scenarios.

Why my research is important

Although the fate and transport of pesticides are generally well researched, little information can be found on the role of pesticide metabolites which can at times be as toxic as their parent compounds.

Compound Specific Isotope Analysis as a method for assessing the attenuation of contaminants in soil and groundwater has only recently been applied to pesticides and is a method still poorly developed for this purpose.

The leaching of a pesticide via preferential flow paths is a concern because it enables pesticides which are considered largely immobile in the soil matrix, to have the potential to be rapidly transported through the soil profile to groundwater, exposing them to downstream sensitive ecological and human receptors.